howdy do yall
or is that all yall
i can never tell
I was wondering, what would be involved in getting EMC to run steppers like servos?
basically I am thinking to wrap the existing stepper module in a "virtual servo"
so you can drive it like a DC motor and get position information from an encoder rather than leaving it open loop
SWPadnos_ is now known as SWPadnos
* Valen zaps the room Frankenstine style MUWHAHAH!
tomp is now known as tomp3
cutting with the lathe is fun, too bad I have almost no idea what I'm doing
removing all the bits that dont look like the end product
that's my goal anyway
getting some 1um linear scales to use on our mill today
as the encoder
should have enough resolution that the servo loop will run nicley
I have some scales for my lathe
and got a price of $360 for a set of ballscrews
that we are going to manually anti-backlash with some valve springs or belvile washers or something
that doesn't sound too bad
so hopefully we can have a "0ish" backlash system
gaah feels like using PWM to limit he current wont work to well, say i have a motor with a very high inductance, a small PWM pulse wont do much on that, on the other hand a motor with very small inductance a small pwm pulse will do alot right?
fry the controller
well not nesicarily fry but it will pull lots more current
basically the PWM frequency you run needs to be somewhat matched to the inductance of the motor
ie low inductance high PWM freq and vice versa
the inductance smooths out the current flowing
ye, thats what i figured, so a fixed pwm current wont work :/
it will for a given motor
most motors are pretty much the same
well enough that 3khz+ PWM will give a decent smoothing
first thing i was thinking was to use timers, one timer that checks ADC until a threashold value, disables the enable pin, fires another timer, that continiously checks until the current is low enough and turns it on again .. or if its all manageable in one timer
what are you really trying to do?
running a stepper with an AVR
the goal of the whole project
Valen, learning how it all works and make a microstepping controller =)
just PWM it at 20Khz or so it'll be fine
you can use the hardware PWM modules then (i presume the AVR's have them)
ye, 5 or 6 output pins
easy peasy then ;->
the higher the frequency the better lol
but then i have to take into account reference voltage ... for max current the motor can run at, and the current limiting per step :)
until you melt the silicon, but then most steppers are pretty low power anyway
Valen, noticed the motor screams at to low frequencies :)
cool word no ;->
what are you using for current sense?
its a current sense resistor and i put that throught the ADC of the AVR
if its for current limiting thats typically regarded as too slow
Valen, ye i figured that also but the AVR people insist it shouldnt be a problem
what you would usually do there is have that output go to a comparitor (possibly via an amp) and then into an and gate in line with your AVR
so ive been looking at doing hw chopping with opamps/comparators
its also handy that it'll keep it protected if the AVR faults
ye loads of problems to solve =)
Personally driving steppers i wouldn't worry about cycle by cycle current limiting
if its for a personal project i wouldn't bother with current limit at all
Valen, wel for microstepping i have no choice :)
just map the current Vs voltage for your motors
either its high torque full stepping or its high/low torque halfstepping :)
run it open loop
you can still micro step, you just measure the voltage vs current for your motors "offline" and put that in as a table into the AVR
you mean never sense the voltage just adjust the curves of the PWM according to the max current of the steppers?
so if i got motors that has max 1A i just hardcode the curve for that you mean? :)
at low speeds (when the micro stepping matters) it should work pretty well
otherwise you need to factor in the back EMF from the motor spinning
comes down to what you like more, hardware or software ;->
alot of stuff to take into account :)
software i know :)
as ive programmed for many years :)
might be easiest to do that then
like i said, when your doing the microstepping its not going to matter to much
and factoring in back EMF is pretty easy
stick it in a drill and attach a scope
see what the volts per RPM you get is
you can then subtract that from the measured voltage to get the "true" voltage
its not as "good" as doing it all the right way but hey its pretty easy ;->
does the allegro chip etc do that kind of thing ? ..factor in that ? :)
whats the allegro chip? the current sensor?
nah the stepper chips
that is a full translator and h-bridge and everything
if they do the microstepping, they probably do proper current sensing
but i should be able to calculate the curves fromt he reference voltage also right ? :)
ye, they have a 3 bit or so ADC
they almost certainly do that because they wont know the motor your running
using software i could hook up a small memory and make a program to set up the chip to the motors running on it from the PC :)
so it loads the settings each time it starts and runs with them :)
I wish that hostmot2 knew how to drive "brushless DC servo motors" directly
cos that is a stepper motor driver right there ;->
so i could use the REF voltage to a comparator to cut the power to the coils if exessive current flows throught the coils for safety and do the rest in software right? :)
hadcoded values in code for current and PWM duty cycles, just pushing that to the controller for each step and voila :)
sounds ALOT simpler =)
Valen, you know how a chopper works also ? .. does it turn down the voltage after it reaches its destination current or does it not ?
is the same say 24V applied each time i pulse the coils ?
sorry was repairing a speed controller for somebody
not going to make post today dang
i dunno what exactly a "chopper" is
i think thats what is refered to as this whole thing lol
Another way you can do it if you want a more analog approach is a kind of "servo" system
basically if you are putting a current sense resistor in it at all and want current limiting
you can get the AVR (through some small filtering caps) to output an analog voltage
then you run that into one input of your comparator and the other input via an amp from the sense resistor
so you are effectively using the comparator to do the PWM for you
(the output from the comp goes into the FET driver)
MrSunshine: you need a D FlipFlop and a clock signal as the easy way to get some hysteristis (cant spell that damn) into the system so it doesn't float
Otherwise you put the output of the amp into a difference amp and run the fet in analogue mode
old school style that one ;-> with a modern twist using the micro to generate the analogue voltage rather than a counter of some kind
Valen, thats what i was thinking for a hw only chopper .. chopper is the current limiting .. cutting the current at a limit and then turning it on again when its fallen far enough
im out doing yard work so wont be very active :)
moved into a house where theres TONS of stuff to do :)
pjm__, useful lump near you 260399234970
MrSunshine: I reckon its probably easiest to just do open loop control with a decent map of current Vs Voltage (for a software guy) with a RPM correction. Every step after that is basically leading you closer to an analogue controller,
At the power levels your talking about a straightup analogue amp based controller should be pretty simple to throw together just using some decent FET's and a heatsink
I should prolly blog this mill conversion i guess
a thought on stepper performance! If you could give more than one max_acceleration parameter (high for the first part of a rapid move when the step motor makes its best torque than drop to a lower acceleration as the torque drops off)
cvs server seems down
there was a hardware problem last night. I'm not sure what the status is now (though I confirm that it does seem to be down)
my machine preforms better at a lower max_velocity ,as when it reaches the top of its velocity at higher ipm settings it can no longer keep up do to torque loss and in order use these setting my max_acceleration must be so low
yeah. I think DeskCNC uses a torque curve for that reason
there's a more general problem in that accel limits can be dependent on position as well - consider a rotational joint on a robot
you can file a feature request if you like
skunkworks, yes, finally
got stuck in Miami for an extra day (horror! :) )
watch out for the swine flu... ;)
Miami, not Mexico
though I have no idea how many people from Mexico were on the cruise
or Spain - that seems to be the other hotspot
this is cool: http://maps.google.com/maps/ms?ie=UTF8&hl=en&t=p&msa=0&msid=106484775090296685271.0004681a37b713f6b5950&ll=32.639375,-110.390625&spn=15.738151,25.488281&z=5
uh - couple in kansas
luckily, they're "perfectly willing to isolate themselves" ;)
"Hey honey, we're supposed to stay home all week. can you think of anything to do?"
there goes another baby boom
ba-da-bang, ba-da-boom :)
man, you guys were yakking a lot while I was gone. there are more emails on teh EMC users list than CCED and Geckodrive combined
how possible/hard is it do you think to "wrap" the stepper drive such that it appears like a servo to EMC
i am thinking in software rather than hardware
simple. use stepgen in velocity mode, and stick a PID on it
so it can be done in HAL without changes to EMC propper?
that's what the Pico Systems USC does - the step generator hardware is just a rate generator, and you use PID just like on a servo
yes. "EMC proper" only outputs positions, it's up to other things (PID or stepgen) to make the motors get there
I'm just looking around and it seems much easier to get steppers than servos in a decent power/torque range
why not just use stepgen then?
I had my first read through of the manual last night lol, i'm going up from the electronics/ballscrew level now
if you're asking about using steppers with encoder feedback, that's a totally different problem
When i had looked previously everybody seemed to say you couldn't use steppers with encoders
see above ;)
thats what i am talking about ;->
well, it might be possible, but you'd have to write a HAL module to do it
then what ezacterly is the PID getting its information from?
they may have said you don't want to -- different from saying you can't
and you should also have specialized stepper drives
or, your question was slightly different :-)
which don't exist AFAIK
it seemed answered pretty unequivacly ;->
here's the difference between steppers and servos, you can decide for yourself:
if a stepper is out of position, it has already stalled and the part is ruined
I wanted to use the stepper output and such from EMC so that the hardware was off the shelf, and i wanted to use encoder inputs from my shiny new 1um scales for position
if a servo starts lagging, you can ask it for more torque to catch up
what is the actual goal you're working toward, that led you to putting encoders on your steppers? maybe we haven't talked about the right question yet.
yes, everyone wants to do that, and it's not a solved problem
so you're not even talking about encoders, you're talking about scales?
as far as EMC is concerned theres no difference
provided the backlash is "minimal"
as far as control loop, there's a huge difference
no, that's not true - there is a huge difference
its a quadrature input that is theoretically based on position
PID looks at the difference between command and feedback, and outputs a control value to make the two match
and how are the pulses from an encoder different to those from the scale?
one gives the motor position, one gives the axis position
steppers have no "reserve torque", and can therefor never put out any "extra effort" like servos can
hold on, there are at least two questions being answered here
I'll go have breakfast - that'll help
one is the difference between loosely coupled feedback (scales vs. encoders)
they have a torque limit the same as a servo, in both cases you cant excede it
ok, problem 1: loosely coupled feedback
yes that is a given
that problem we are planning on solving mechanically
ok, so zero backlash
yes, otherwise the whole system is screwed
not "almost zero", but zero
ok, problem 1 solved ;)
problem 2: reserve torque
it should be within a count or 2
given that there is no such thing as "zero"
a servo has two ratings, continuous and peak torque
you design for continuous torque, not peak - else your motors melt
yup, and steppers have the same properties if not the same ratings
therefore a servo has extra torque available sometimes, for limited amounts of time
no, they don't
no they are completely different
steppers have a speed/torque limit
steppers are rated at their peak (holding) torque
point is both have a maximum torque that you cant excede
no, that is *NOT* the point
so you are saying you can excede the max torque on a servo?
you are correct, in that you will demagnetize either if you exceed some limit, but that is irrelevant here
you can exceed the *design* torque on a servo, yes
its just a different design limitation, you just have to spec the system to not excede the torque the stepper can output in both acceleration and velocity
because you design to the continuous rating, not the peak
same as a servo, just with different numbers
well, you're not letting me get to the important part
that a steppers peak torque is the same as its continious torque?
no its not
no, that's important, but not the main point
or that when the servo lags you can stuff more amps in to get more torque out
which you cannot do if you are already at max torque
the stepper cogs in that situation
ok, so you've caught everything so far, excellent
ergo both have limitations that you have to take into account
i knew all this stuff to start with
and one limitation of a stepper is that it is already dead in the water once you can detect a position mismatch
not if you are using the stepper like you would a brushless DC motor
which is essentially what is happening
sure, like I said - you need a specialized drive to do this, and I'm not sure any exist yet
and you won't be able to use software to make that happen, the timing is too tight
if you can get EMC to put out stepper pulses, but to treat it like it would an encoder then it will work
you still have to run open loop on the stepper output so you dont "slip"
steppers dont slip unless you are cutting too hard
which is usually taken care of by the driver in a brushless system but provided you keep on the inside of the torque curve that's not a problem
and then you are out of position already, and applying more speed/torque to catch up makes them stall even worse
if you are using linear scales you can correct for a dropped step
or encoders for that matter
sure, you can correct for it in software, but physically, your motor will not lose one step
it will stall, and lose many steps, and not restart until the speed has been reduced
it'll loose some multiple of poles and magnets
or until the torque is reduced to the point it works but in any case you have exceded the design of the system and you have your self to blame
for a positioning system, that's fine - it will eventually get where it's supposed to go
but for a contouring system, the contour will already be screwed up, because presumably the other axes don't all stall
not really relavent, if you exceed the limits of the machine it wont work, thats pretty common
yeah, nobody is arguing that
its not a "magic" thing that makes everything work
I'm hoping to get ~5um accuracy without paying $4000 a screw
the thing is that servo/PID assumes that you can exceed the design specs for short periods
and be able to use off the shelf drives
you cant exceed the specs though
there are two specs, continuous and maximum ...
if you exceed the max torque on a servo it just wont push any harder
and you can exceel the continuous spec for short periods, but never the maximum spec
and the same thing happens your curve is screwed
yeah, or it'll melt and/or demagnetize
yes, so you just design your system not to exceed the specs same as any other
in a servo system you leave some margin over what the max torque on the motor is
you do the same in a stepper
in a stepper the max and cont torques are ~=
sure, so you design to 50 or 80% of the rated torque
in a servo there is a bit more range
yeah, like 5x
like i said, its still not really important, if you don't ask for more torque than the stepper can give it wont drop steps
in that case, you don't need scales
since you will never have an "out of position" event
you do if you have cheap crappy ballscrews
like say ones you can get for $300 from china
scales don't magically change the number of steps per inch
no but they are accurate
they don't vary over their length
or with temperature (much)
if you sufficiently limit the speeds and accels, then you can probably get by just by using the method I first mentioned
which is to use a velocity mode stepgen and PID
I'm pretty sure your machine will grow 3µm because of heat..
you said that EMC wont accept scales for steppers
there, you're making the assumption that the stepper will always move how you tell it, and the scale becomes your true feedback
thats the goal
I said that using scales to correct steppers is not a solved problem
if you can drive the stepper the same as you would a servo it would work no?
but, if you make it so the steppers will never ever ever need correction, by designing the machine to 50% of the stepper specs, for example, then you can do positioning based on scales
that was what i was looking at doing
It seems i can get steppers and their controllers on the second hand market
that doesn't seem true for servos
"encoders on steppers" is usually brought up to describe a system where you correct for lost steps, not for a system where the number of steps per unit changes
you can, but it depends on the sizes
no lost steps = crappy and not going to work
DC servos are reasonably cheap, brushless and AC are quite a bit more
I see DC servos for $450 or so an axis US
for decent ones
hm.. that's pretty cheap
you shop in the wrong place
[13:26:22] <Valen> http://www.magmotor.com/brushed/brushed.html
the bottom one
do you have to buy new?
$330 gets a C40-300
or have a reliable source?
no, but i am yet to find 2nd hand actualy available
(ie, can something like surplus center or ebay work, or do you want to make more pmachines later)
ebay would be fine but there doesn't seem to be anything comparable to those motors on it
and the scrap yards i know of here don't seem to know about these "motars?"
great sp mpw tjere are ass;pads ;p;
[13:29:09] <skunkworks> http://kelinginc.net/DCBrushlessMotor.html
hmm off by one
"great so now there are assloads"
[13:29:26] <skunkworks> http://kelinginc.net/ServoMotor.html
noice, although they eem about half the spec of the mag motors though?
the $149 one is 226 oz-in cont.
though it's only 3200 RPM vs. 4000
ahh i was comparing the peak, i hadn't got to the cont ratings yet
never ever ever ever look at peak! ;)
its a servo system, peak gives an indication of acceleration
true, but you always design to continuous specs, and the peak is a nice reserve
the other thing is those need 40A to hit peak which is 2x the mesa controller i was going to use can put out
yes but wouldn't you rather have 2x the "margin" ?
but it also depends on the driver I'd be using
you're right, the 40A spec is annoying
hmmm can the gecko's do 40A at ~90 volts?
didnt think so
the mags have a 23A peak torque winding
same as the mesa, except the mesa is good for 170v or so
on that winding i run out of volts before i hit top speed, looking at ~2500 RPM on the mag
which is ~500 IPM traverse speed
what is your 2X peak going to be used for? accelleration?
thats about all
and not that much of it more than likley
ouch they know how to charge for the AC stuff ;->
yaknow if you wanted to get "funky" with using steppers as BLDC's without too much added hardware, you could use the scale signal as a "rotational position" and drive the steppers based on that
although it'd work better with a rotary encoder on the back of the shaft
so SWPadnos you reckons the stepper as "servoish" thing might work?
so what happens when you are contouring a part where you are hitting the 2x current continuously?
I don't know how well it will work - a lot of that depends on how crippled you make the design (Relative to the stepper torque ratings)
steppers seem to have torque to spare really
they seem to at zero speed, because that's where they're rated
their cont torque (in ~ the same package) seems to be ~= the peak torque on the servo
yep, and that's because they lose torque at higher speeds, whereas servos don't
although the faster your going the less torque your typically going to need
thier torque drops off quite fast at higher rpm
that's not true
you still need to decelerate
a servo actually does the same, as the speed goes up your controller (typically) runs out of voltage, so you cant hit peak torque at near full speed
servo torque is independent of voltage
no it isnt
it most certainly is
it is dependant on amperage
and when you spin the motor you need to counter its backEMF to get the same amperage
so yes, at speeds where your drive can't overcome back EMF and still provide sufficient current, you have a problem
on the mag motor system i was putting togther you hit the controller limit at ~1200RPM as i recall
you run out of volts at that point
assuming i can get a 160 odd volt controller ;->
anybody know a source for that or will i need to wind my own?
I'd really rather not wind a transformer lol
in that case i will have a shower ;->
so on to another matter, where would i start for the "using scales as a DRO through the parallel port" project
I have seen the thing in the wiki, its just a little deep for a first step lol
going for max acceleration AND using the parport does not make too much sense
they are 2 seperate projects
the DRO is on a lathe
it might get converted to CnC at some stage but its a low priority
at this stage its a "feet wet" type thing
so any idea where to start? ;->
read the documentation
then hook it up
there are lots of examples of hooking encoders to parallel ports in the sample configurations. people do this for simple servo machines and MPGs.
I shall look more into the sample configurations
It was more the pyVCP side of things ;->
I shall muddle through ;->
you can use the regular DRO in any of the guis - you can defer or permanently avoid messing with pyvcp
the gui's and EMC are ok with not having any outputs?
Just don't bring it out of estop ;)
oooh shiny ;->
that sounds like the place to start then
yeah it will track the position fine as-is.
if you use AXIS you'll have a nice etch-a-sketch
so emc wont whine about not having any outputs?
emc still outputs whatever it wants. if those signals never get routed to the real world, who cares?
i mean it needs a dummy output configured, i cant just put the encoders into HAL?
[14:32:41] <JymmmEMC> http://www.opera.com/
fire up axis and let them play togther all without any intention of an output
they should have used <blink> some
[14:36:06] <skunkworks> http://www.cnczone.com/forums/showthread.php?t=79408
so SWPadnos, think it'll be happy without any outputs defined?
yes, EMC doesn't care if anything is "listening"
you just need to make sure that the inputs are satisfied, if you want to get out of e-stop
funky I shall put it on my ToDo list for tomorrow
should just be A+B+R/Z for the 2 encoders yes?
yep, and Z is unnecessary unless you want to get more comples and test homing or something
I figure if its there, might as well wire it up
yea it is cleaning up at 0.075" under size http://imagebin.ca/view/5N9foE.html
if you want to be able to set offsets and switch between them, or zero axes, you will have to be out of estop. you can give emc very large following error limits to keep it from giving following errors.
BJT-Work: oops, looks like you were not centered very well
if it has no outputs defined would it give a following error? it has nothing to follow?
that's why you would need to give large following error limits
the top was worn down about 0.060"
the rest was still round
are you going to have to make a sleeve?
BJT-Work what is it?
I'm just using a different size bearing
center of front axle on my tractor
I can't get the OEM bearings so I'm using mcmaster carr bearings for $6 each
heh OEM would probably be $50 if you could get them
[14:46:31] <Valen> http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=47&page=1
that is for real... I needed a screw I thought till they told me the price $30 for a 2" 1/4-20 screw
oh sorry wrong window
what is the best GUI/IDE compiler on Linux? ...like Delphi on Win
ummm you need a language to compile
I don't think anyone here uses one - nobody ever has an answer for this question when it comes up.
i use SPE for python
that contain alot of component to create like simple button, label, prety boxs..etc
the autocomplete is handy
you mean a gui builder?
i need to create very-prety boxes that exist on today linux distribution...
gyu builder yup
wxpython has a guibuilder integrated into SPE
wxglade i think
not that awesome though really
i do it all by hand
are there any component also... like we could make hallo-world in boxes, button, cycleing labelin a minute
all awesome, but i need a way to program
maybe there is a different channel where people would have better answers
it is free to talk all the better right? we do democratic
hmmm. I wonder if they'll deliver my luggage to the restaurant at the address they have, or if they'll actually look at the luggage tags and bring it here
i look for gambas... but they never update since 2007
A4ndy_, Qt Designer is quite nice
A4ndy_: I didn't mean you weren't welcome to talk here, I meant only what I said: that there may be better answers elsewhere
though I haven't used it in quite a long time
the_goat is now known as Herr_Gemutlich
glade has nice looking widgets also, and seems easy to use (though I don't know if they ever implemented real undo)
i also look on dev-c or code::block ... but i wonder how emc2 gui build off
unfortunately, Kylix is no more (it was Borland's delphi product for Linux)
the GUIs are not built with a designer like that
except for stepconf, which was done at least in part with glade
how and why not?
(1) EMC has been around for longer than RAD GUI builders
(2) nobody has bothered
Herr_Gemutlich is now known as the_goat
is it incompatible isue on getting failing RTAI?
GUI and RTAI have nothing to do with each other
so they (GUIprogramming/builder + RTAI could walk together..)
someone said that they had successfully imported the EMC source tree into code::blocks, but I didn't have success in the 5 minutes I devoted to my attempt
RTAI works whether there's a GUI or not
if you want to make a GUI builder for EMC2, there's a lot more to be done than picking a RAD tool and running with it
RAD tools work because someone did a lot of work making components you can easily use
yes. EMC is a longtime roads... but you guys build it better and better, grew
that work is not easy, especially when the components have to talk to something other than other components (like the real world)
if you do find something like Borland C+ Builder for Linux, let me know - I'd love to try it
.... Dev C++ ?
I would be interested for non-EMC reasons
I use BC++ Builder on Windows, and it has been quite useful
of course, it doesn't seem to exist any more, even on Windows
windows.. i go TC, Pascal, DElphi, even TAsm...
but gcc still exist from my dos era...
oh sure. I've been using Borland products since the days of Turbo Pascal on the Apple 2
complete with Z80 accelerator card
i do Zilog80 too u know
from tiny winny memmorys good old days
we used to have fun with the debug monitor in the Exidy Sorcerer
and of course changing the command names in TRS-DOS on the TRS-80
Over on the propeller forum, they are building a CP/M machine
I reckons it'd be a better use of somebodys time to actually split the RTAI/low level stuff more from the display stuff
nuevo retro :)
so you can run EMC headless without X
Valen, look at the code before saying that - there is no RT in the UI code
but still have all the nice interfaces
and vice versa
you can run headless/networked in 3 or 4 ways
yeah that i knows, but the interfaces between the RT section and the UI section is fairly closley coupled as far as i am aware?
all amaze me
whats the interface?
AXIS has some extra HAL coupling, but it can be disabled with something like AXIS_NO_HAL in the ini file
you can use NML, a text interface over ssh, a graphical interface over remote X, or some VNC-type desktop sharing
X and remote desktop defeat the purpose somewhat
can you run the nice frontends over ssh?
using remote X, yes
lol still defeating the purpose
i mean to have an interface between the nice front end and the backend over the network
do you know of another way to run a graphical X app over ssh that isn't X forwarding?
yes, that's NML
which doesn't run on ssh, it's a separate network protocol
havent heard that one
that's how all the parts of EMC communicate with each other
ahh that sounds like the ticket then
EMC was designed from the ground up to have separate IO, motion, and UI processes, separated by shared memory, serial, or networked communications
A+ on design in that case
yep. the NIST boys put a lot of thought into it
I had just never seen it mentioned much around the place
most people don't use it, so there isn't a lot of discussion
in fact, you can have several UIs running, on one or more computers, simultaneously
Be a nice way of getting around the "propriatry driver latency" issues while still having the beefy OpenGL performance people like in front ends ;->
yep, can be
oh, I completely forgot about the program "emcrsh", which is a remote shell with EMC-specific commands
like telnet for EMC
i never seen something grew from begining like this since turbo-pascal7 legally extict
so do dos
well, time for me to do some pating work. see you
thanks for your help SWPadnos
hope i can return the favour some day
time for dinner here, tis 1:30 in the AM
linux never someone left behind
eh, linux is allways there 4 us
since WinXP would extict in time...
to the Vista era ... like Dos to Win98
all over again from 0
do ya'll know of a C++ irc channel ?
nop sorry, i beginner here
go search the web
theres a #c on here
they mught be able to point
A4ndy: thanks, i looked on the web but nothing thought someone here might know
Valen: that should be about the same topic thanks
jepler_ is now known as jepler
tomp is now known as tomp3
Alright! a use for my 32 serial port over ethernet controller... http://www.youtube.com/watch?v=N15X5OeT2oM&NR=1
BJT-Work: i was just looking at a 'new' belt drive system.
it used a belt that could fold onto itself ( its teeth and space was symmetric ).
by using this belt, pretty much like you used in your machine,
they claimed to get rid of 'all' stretch and had upto 4G accell.
the link is on another box, will get it to you.
the motor pinion engaged the belt and had 2 'idlers', one each side, but the 'free length of belt was just that, from ideler to ider
the belt meshed into itself for the rest of the lentgth of travel
JymmmEMC: rgb led ? run by a propeller chip
that's nice, but it should be wireless instead of usb or rs232. http://emergent.unpy.net/01233419381
(I need to improve the light diffusion on mine, though -- his is much better in that respect)
looks like a mood ring
but it's for my computer's mood
but it's for me too, in that if it's red when I get up, my day will be shitty
jepler i like the idea of the python control, its a very analogish intuitive input device ( the color wheel widget )
jepler: Hmmm, I never tried difusing a sphere before. I'm thinking an inner sphere with reflective surface.
If you like that one, you should try this LED mood lighting. http://www.parallax.com/tabid/606/Default.aspx.
Take a look at the you-tube
jepler: I think this is cool, Time to make a cnc hot wire cutter think =) Already have all the parts; slides, hotwire, etc, just need to assemble them.
[16:24:25] <JymmmEMC> http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=47&page=1
[16:28:21] <LawrenceG> http://www.bell-everman.com/serbvideo.html
fast belt drive!
tomp3, I like it!
smart to do it like that :)
like the old cowboy joke... wanna see it again ?
thoose servobelt drives are nice..
shoulndt be to hard to create oneself either? :)
only problem is that the motor has to follow the carrier thingie :)
I dont see a problem with that
only thing that would be a issue is belt stretch :)
and it seems that that design isnt bad about that
people should not make videos of the first run: http://www.youtube.com/watch?v=seLQ5Bo_AIc
Eh, learn from someone else's mistakes
I also noticed the pallet take a good lean as it hits :)
machine needs a service afterwards too
lol dont you just hate the gasp of air in that probe one?
* archivist has no sound
think of the sound you would make after you have just stabbed yourself in the leg with a screwdriver
the one before you start screaming
the noise you make as you get ready to get on with some serious screaming
[17:46:26] <Valen> http://www.youtube.com/watch?v=yln_IGDuOCo&NR=1
so looks like it grinds his head on the floor when it starts off
sure does, looks like fun though
MrSunshine: You can do micro-stepping with a UC that has PWM and current feedback via a ADC
trick is use a PI loop to control PWM (and indirectly) current. To avoid having the PI loop track the
sine wave currents, use a park transform to de-rotate the current vector, then re-rotate
with inverse park to drive the PWM. (then the PI loop just works on "DC" values), The I term will compensate
for Back EMF as the motor spins faster.
pcw: Give me a second to formulate a question for you
pcw: I'd like to talk to a hostmot2 board with an embedded system that has a low voltage i/o (1.8v) and a spi bus
pcw: can the cpld on the parport board be adapted to this, and any advice on voltage translation?
cradek, ough :)
this is setting and reading hostmot registers with spi, not like the spi I/O boards
If you dont need to configure via SPI, the CPLD could stay the way it is,
just use some of the parallel port pins with level translators for the SPI interface
pcw: ah, change the hostmot2 to talk spi instead of epp?
is this for ethernet or something?
Just the top level wrapper
* MrSunshine_ thinks that people would do quite awsome stuff with AVRs if they just stuff them with loads more ram and flash :)
wrong channel :P
geo01005: I'm trying to find out the feasibility of hooking a beagleboard to a mesa board. no ethernet involved.
pcw: and if I want to configure the fpga?
that'd involve changing the CPLD?
Configure via onboard EEPROM
If you want to change, re-write EEPROM
(Dont make a config that fails or you have to go back to USB or EPP)
jepler: Cool. Emc on the beagle board?
or something else...
geo01005: don't count those chickens yet, they're not even laid let alone hatched
geo01005: first someone has to port rtai to beagleboard
Thats how we re-write EEPROM now
(bootstrap FPGA config contains simple SPI master for flash EEPROM interface)
FPGA has 'reconfig thyself' pin so after EEPROM has been wriitten you can reload
FPGA with new config
pcw: any direction restrictions I should observe when choosing the parport pins for SPI?
jepler: I didn't expect that you had EMC running on a beagleboard. I understand that is not a trivial thing to make happen.
The data bits go directly to the FPGA (through 100 Ohm resistors) I'd use those
(You would need to disconnect the USB interface if using SPI since the data pins are shared)
pcw: thanks, that pretty much answers the questions I have right now
good evening.i want control with emc only one circular axis , not x,y and z axis.Is possible ?
(I mean just dont communicate over USB at the same time as you would have a conflict)
pcw: It's OK to do USB powered, and even USB enumeration, just don't transmit?
Yes, USB data bus (shared with EPP) will never be driven unless characters are sent to 7I43
(and FT245 shows FIFO data ready)
that means that if I had spi + usb connection I could send firmware over usb then switch to spi
thanks again for the answers -- if this project gets off the ground, I'm sure you can expect more
Yes but the hand-off would need some care
(Also once configured with your SPI interface, you can just tie the USB read strobe high)
Work can be avoided no longer,,,
humm, got an m3; g4p0.2 for spndle spin up that is not working. no error, but no effect???
gene: set S to something nonzero
it is, 500. driving 1/2 forstner bit, don't want chips all over the place, or overheat the bit and its above those 2 lines in the loop
so the spindle does not come on?
or it doesn't delay?
comes on ok, but no delay in the following z- motion
can you pastebin your gcode
so it hits the wood at about 1/2 speed.\
wtf, I've sent it twice, to pastebin.ca, but konquerer is showingh me a link???
wtf, I've sent it twice, to pastebin.ca, but konquerer is NOT showing me a link???
if you an find it, it left here as cartridge-block.ngc
humm, file->properties says it is only 1/2 second longer with 144 of then total.
hm, I don't see it at pastebin.
just paste the line before, including m3, and after here?
yeah, looking at pastebin.ca
or is there a better place?
pastebin.com is one alternative
not sure - I think there are a lot of pastebins
o100 sub #1 #2 #3 #4 #5 #6 #7 #8 #9
s#9 (spindle speed)
o101 while [#6 le #7] (#6=#32 in call, #7=#37 in call)
g1f#4z.1 (raise for move clearance)
g1f#4x#2y#3 (arg1 is #36 in call,arg2, arg3 is #30)
g1f#4z0.0 (back to work surface)
m3 (start spindle)
g4p0.2 (slight pause for spindle spin up)
(first cut is now 2x deeper)
(g1f#1z[#5/5]) (#4 is arg4=#35, #5 is arg5=#38 in call)
looks like it should wait 0.2 seconds. (that doesn't seem very long)
the real next line goes 2x deeper for the first cut.
if you change it to g4p2 you'll be sure to know whether it's pausing or not
yeah I don't see anything wrong
last block for the day, I'm out of well seasoned 5% 2x6 stock
try testing without material on the table
I'll try that for the first run of the next one. Yeah, duh! And my z screw is still rumbling on the downstroke, darnit.
The screw is stationary, the nut is driven in this design.
And it seems like it gets worse as the day warms up
change to a different grease
archivist yeah that item u pointed out this morning is in my village, btw 190303679774 might be the other 1/2 of it?
pjm__, I wonder where the rest is/was
I have a g-gun full of no name lithium chassis grease, would that be better than stp?
depends on bearing design
and reason for noise
may be stiction between screw and nut and resilience in the belt at a resonant speed
two large axial thrust (end ways) designed sealed ball bearings turn the nuts, screw is 1/2" 10 tpi acme, nuts are bronze, all from McMastterCarr
not from ball bearings
good evening.i want control with emc only one circular axis , not x,y and z axis.Is possible ?
pix, sort of, at <http://gene.homelinux.net:85/gene/emc>
and the belt is tight, very tight. had to to reduce the rotational backlash.
I saw the pics yesterday
messsy ain't it? :)
er no comment
motioncontrol: yes, it works fine
I just gave the screw a shot of (non-lithium, it really is no name crap) and the rumble is changing pitch, but only slightly. It will take hours for it to work down to the lower nut.
thenk jepler i declare only in inifile axis_0 = circular ?
motioncontrol: no, not at all
[19:05:34] <jepler> http://linuxcnc.org/docs/html/config_ini_config.html#sub:[TRAJ]-section
"his has no effect on the mapping from G-code axis names (X- Y- Z-) to joint numbers--for “trivial kinematics”, X is always joint 0, A is always joint 4, and U is always joint 7, and so on"
[19:06:34] <jepler> http://emergent.unpy.net/files/sandbox/oneaxis.ini http://emergent.unpy.net/files/sandbox/core_sim1.hal
must be cleanup time on that screw, the grease turned black instantly from the black coating on the screw I assume.
ok thanks jepler i want realize one 4 axis for my maschine, indipendent at my maschine.
gene great machine fotos!
motioncontrol how do you plan to sync these?
thanks, but I should haver taken some of the z axis disassembled, one pix=1000 words you know..
whith digital io
Next time I have it apart, I will do that.
gene, turning black can mean grinding and wear
on my maschine i have fagor cnc, i write in plc one m fuction for start emc partprogram and read in position emc signal for write in plc fagor start program
That screw is coated with some blackening agent, probably wearing away. When this last block is done, I'll run it up and clean the screw
dang Glyptal Red 1201 is expensive at $55 for a 12.
75 oz aerosol
in emc2 using servo3go SERVO, is a "circle movement" job would translate to a "multiple line movement"?
the output of emc's motion controller is time-sampled position, not movement primitives such as "line" or "circle".
or they go curve circle in 1 single task?
in emc2 source, which part of program in .c that would do time-sampled task...?
are they really do "curve" ...not circle really?
directory.map is an overview of the emc directory structure.
to answer your specific question, src/emc/kinematics or src/emc/motion
is it using p id or fuzzy logc?
the motion controller outputs a series of positions over time. it's up to other components (such as PID or step generators in HAL) to move to the new positions
can u explain ? why not using thats such control?
in some configurations, the commanded position from the motion controller is used as an input to pid
so there is PID in HAL if you use servos or servo-like systems, but there is a clear separation of motion planning (control) vs. actuator control
board of servo2go
this is different from using pid to find positions
and fuzzy logic has nothing to do with any of it
the STG board is used as a DAC and encoder feedback device, and generally will use PID to get feedback to match command positions
if you want to write a fuzzy logic controller instead of PID, you can do that
but all it has to do is take the command position and feedback position as inputs, and output some sort of control value to make them match
and what the different between kinematic and motion?
no, it do fine
do perfect already
kinematics is the conversion between cartesian coordinates (XYZ, ABC rotations) to whatever joints your machine actually has
a joint is a single freedom of motion
like a table slide or a rotator
if you're asking "why is THIS file in src/emc/motion and THAT file in src/emc/kinematics", there may not be a good reason except that we are very resistant to renaming source files.
so you can use robots like Puma or SCARA, or hexapods, or whatever other construction you like, while still programming in cartesian coordinates
i was interrest in what a file work of
how pci could do realtime(in servo2go) ...since it a stream kind of
to do that math
is servo2go has kind of southbridge?
I don't know much about servo2go
I know more about mesa
how about mesa? they work alot the same
in the case of mesa, a very short sequence of outb() instructions will cause one of the DAC outputs to change to a new output value
realtime i mean
I thought servo2go was more or less a DAC and encoder interface
another short sequence of inb() will read the number of accumulated encoder counts
plus some generic I/O
seems a shop to me http://www.servo2go.com/category.php?cat=10018
thats is fast
so encoder reading would go directly to PC clock/clock ??
(clock per clock of it)
the card would have a counter that counts up or down, and the PC would read the count
rather than buffer it up on mesa
there is no buffering, it's a counter
sure.. buffered on mesa, yes i see
if there are 100 counts since the last time the PC read the register, then the number will be 100 higher than before
:> Very interresting
and who decide the servo going too fast or not? PC / mesa?
I had to add an m5 at the top of the syb, for some reason the spindle was running before it was told to on the first hole. Odd.
every millisecond (by default, this can be changed), the PC reads feedback positions, calculates a new target position, and runs the PID calcualtions to move to the new position
And the delay had to be 0.8 secs to be effective.
i pc willing to stop on 100 count ..what would it do? going further and get back?
I don't understand your question
if there is enough of an error between commanded and actual positions, then a following error occurs and the machine stops
the software looks for that
u said before that if pc read 100 count, mean realworld goes more than that
no, I said that there isn't "buffering" of encoder counts, there's a counter for that
Hello, I have an AXIS problem. When I select "Show hidden files" in the Open (file) window, AXIS locks up. I wanted to see hidden files because my Samba share is mounted on ~/.gvfs.
so the card doesn't store up 100 edges for the PC to read, it adds or subtracts from a counter, and the PC reads the resulting count
i get it
could u tell me which part of file source .c that do adds or subtracts? ... is it motion?
adds or subtracts what?
it's a function of the hardware
sorry ...do inputing encoder
and process it
it is in the hal hardware driver (e.g., src/hal/drivers) to perform I/O to a specific hardware interface
all movement critical there
kirk_wallace: say you make a folder ~/test, and in it make another folder .test
kirk_wallace: if you go to ~/test, then click "show hidden files and directories", does it lock up?
3d cartesian is perfect room for robotic
I'll try ~/test
I don't have a ~/.gvfs (I don't use gnome) but creating a .test directory, everything seemed to be fine
jepler, just replicated the lockup on 2.2.8 seems worse
lost mouse click response but the pointer is moving around the screen
can you tell me what steps you did?
Locked up for me, I'll try to dismount my Samba share and try again.
for me loaded axis, clicked open file, clicked show hidden...dead ish box, not responding to keyboard or mouse clicks, is serving ok
kirk_wallace: my suggestion with ~/test/.test ?
I have no shares or samba
Dismounted share. Then opened AXIS (okay so far), selected open file, changed to ~/test, see no files (okay so far), click veiw hidden, locked up.
im going log off, thanks alot to you all.
I believe you
unfortunately, it won't lock up for me
after starting it but before locking up axis, open up a terminal and execute: strace `pidof -x axis`
(you may have to install strace first)
make it lock up, then show me the last few lines of output (say, 20 lines) using pastebin.ca
looks like I have to power down pulling the power to get control back
archivist: try ssh first
should be ok for strace
or ctrl-alt-f1 or ctrl-alt-backspace
but if you can't get it back you'll have a hard time putting lines of strace on pastebin for me :-/
ctrl-alt-backspace would kill AXIS..
ctrl alt backspace killed it
(I see archivist mentioned using 2.2.8)
mine is 8.04 from the live cd plus upgrades
ok got it back up...try again
I'm a bit slow, sorry. I'll look into the trace and get back. Ctl-Alt-F1 then killall -s 9 axis works for me. I'm using 2.3.0 and axis sim config.
strace -o /tmp/trace.out `pidof -x axis`
^^ will save it to a file in /tmp so you can read it after using ctrl-alt-backspace again
hm, I tested 2.3.0~beta2 on hardy and CVS TRUNK on dapper and still haven't had a lockup..
kirk_wallace: maybe you can get working again by creating a symlink to the share you need
Another funny thing, while at the command line, I "ls -al" and get"d??????? ? ? ? ? ? ./gfs" other dir and file listings seem okay.
e.g., cd ~/emc2/nc_files; ln -s ~/.gvfs/somethhing/something short-name
kirk_wallace: hm that doesn't sound good
Dooh, I used Nautilus to open the share then copied my file to my ./emc2/ngc_files folder (unhidden). This worked okay and gives me time to look into the lockup. Thanks for the help.
archivist: since I can't make it happen here, the nearest useful thing I can think of is that strace debug output..
dam lcd on the box goes mental when the system shuts down
may have to kick it again to get back in but strace was running
* archivist used the power switch
Im guessing it could be deeper and not axis
good night all
see you alex_joni
jepler, no trace.out waiting for me on reboot
if only it would crash for me as well
such a serious block to the system I cant help thinking its somewhere else completely
but surely some other program would tickle it
just looking for one
you and kirk_wallace are in the same boat in that axis is the only program known to cause this problem
axis uses the standard Tk file browser
let me see if I can tell you how to invoke the Tk file browser for yourself
know of any others ?
ubuntu doesn't come with any standard programs that use Tk
something non emc would be best
well, if tkemc does it, then it's probably not AXIS ...
if not, then it probably is axis
since they both use tk
yes that's certainly one to try
though now that I look, there's apparently a hack in axis to get the "show hidden files" button
and run it: wish files.tcl
it hangs me up too
apparently it does for everyone in the world but me :-/
heh - happens here too.
I never noticed the 'show hidden' check box before
has anyone mentioned which OS version they have?
Linux Millie 2.6.24-16-rtai #1 Tue Sep 30 22:54:33 EEST 2008 i686 GNU/Linux
8.04 latest livecd
and the lockup happens after you click "show hidden files and directories"
before you do anything else, or the screen contents refresh?
hi guys, does anybody know an electronic specific Irc channel on freenode?
ok now fired up emc and axis stops the show
the check doesn't actually check either
and the contents dont change in the window
you can go right into axis - file open - then try to check the checkbox.
aha! finally it did it for me too
I just went to my home folder using axis open and clicked on show hidden.
you guys all click the box. I was clicking the words next to it
heh - odd
clicking on the words works?
odd bug of the year
skunkworks: it does for me
well now I know how I'll be spending my evening
thanks all for crashing your computers for me
does here also
What ever you do - DON'T CLICK ON THE CHECK BOX ;)
Don't click on "Click Me"? Sorry, if I caused a fuss.
kirk_wallace: it's a very real bug, and thanks for reporting it when you discovered it
at least we could all reproduce
besides the workaround of clicking on the words instead of the box, I have a fix: http://emergent.unpy.net/files/sandbox/file-open-dialog-crash-workaround.patch
but it requires a recompile, unfortunately
anyway, if I can't figure out a real fix I'll put this in the next version
ive never needed to load a hidden file I can wait for an update
strange. I have an strace from Jaunty if you'd like it
strace aborted though, which I thought was odd
SWPadnos: I'm not sure -- when I asked for the strace, I thought it was probably some file access problem
now I think it's an event handling problem, and strace won't show that very well if at all
well, there is some sort of file access problem
and I can reproduce it, so I can get whatever output I want
there are a bunch of lseek calls at the end of my log
with lots of octal characters instead of usable names
[20:59:28] <SWPadnos> http://www.linuxcnc.org/wiki/uploads/axistrace
, if you want to take a look
SWPadnos: Haven't seen you around much
no, I've been on vacation the last week
net access is expensive from a cruise ship :)
SWPadnos: Cool, where to?
port to port
Nassau, Half Moon Cay (best beach I've ever seen), and Grand Turk Island (fun diving there)
SWPadnos: Your first cruise?
I now look like I haven't been in a basement for hte last 10 years :)
SWPadnos: Are those places in the US?
we left from and returned to Miami though
which is more or less in the US
hmmm. I should make a smaller strace log
SWPadnos: Yeah, it's too early in the year to make a Yule Log
so that's interesting. clicking the hidden files button causes strace to die with a glibc error (malloc(): memory corruption ...), but axis works correctly
Can someone give me a hint about an IC that can drive a stepper
at about 2 A / 40 V thus delivering a power of almost 80 w
there are two commonly used ones, though I don't know that either goes to 40V
one is by Allegro, the other by IR(?)
I can't remember the chip numbers at the moment
L297/298 is ST
They can drive motors at 80 w (I mean big stepper for plasma cutter tables for example )
yes, but not that way. I think they're 2.5A, 35V
archivist, thank you. I couldn't remember those
I think the Allegro is the 3977 or 3985 or something like that
Allegro datasheet looks useful
I think people had trouble with the chip, but I don't remember the details
A3977 is the driver chip in the board I use
it works well for me
seems from what you say that both of you don't use steppers
I do use steppers
and what motors do u use jepler
somehthing abut microstepping problems on a allegro chip but i dont remember the model
* MrSunshine would give his right nut for 3 strong servo motors and controllers =)
[21:18:54] <archivist> http://www.arceurotrade.co.uk/Catalogue/Stepper-Motors
invite: my motors are small, NEMA 17, 5W
I got the drivers as well from there
Thanks alot guys
2A / 40V doesn't mean you get 80W of power
Im running about 28 volts 2.4 amps
usually with stepper drivers the motor voltage is much lower than the supply voltage
e.g., my motors have a nominal voltage of 2.42V but I use a 27V supply
we only use a high voltage to improver the response
and how much power do you get from them?
(without taking into account reducers)
the motor is rated 75 oz-in = 0.53 N-m
I dont think in terms of power but torque at a speed
presumably that's holding torque
mine being 180Ncm at 2.4 a holding torque
I see no maximum voltage specified for the motos
Is it then chip driver dependant?
aheuh things are getting more and more clear
and they limit the current by pwm
[21:29:00] <jepler> http://www.geckodrive.com/upload/Step_motor_basics.pdf
discusses the issue of maximum supply voltage on page 13.
another mysterious thing that remains
how a small IC like the allegros
can handle as much current without
getting HOT !!
They dissipate almost 5w
generally you'll heatsink the driver chips
they are switching devices, not linear, so they won't dissipate as much as you may be thinking
aheuh so basically they only dissipate when switching
look at datasheet figures like "output on resistance" to gauge power dissipation in the driver
A3977 = 0.57 + 0.43 ohm max = 1 ohm max
so at 2A motor current you'll dissipate 4W in the A3977
not a huge amount, but enough to imply you should heatsink
Another question Does anyone use microstpping and does it really value the détour
I'm not sure what you mean by "détour"
or should I keep with old good 1/2 step
I use halfsteps
worth it (soory french guy)
I run my boards in 1/8 mode, but mostly to show off the high step rate I can do
I wouldn't cross the street for it
:) crystal clear
I'm really gratefull guys
you really eally AND I mean REALLY helped me a lot
SWPadnos: Somebody said that you have tried out the new gecko G251/G250 stepper drivers?
How do you keep a 8ft leadscrew from whipping? Or does it really matter
We're talking a hot wire foam cutter here.
you could rotate the nut instead of the screw. That is what I'm doing on my machine.
how are you doing that?
Ive also seen long leadscrews with supports that move out the way of the nut as it passes
lets see, I have a video on youtube, but I can't get to it here. Youtube is blocked on our campus.
utl or name?
this isn't the video, but just look at my other videos : http://www.youtube.com/watch?v=txx586M2r9s
Jon_geo01005: use a http proxy ;)
I suppose I could. Usually I just wait till I'm home.
You can't really see how it works from the video if I recall.
Some of the easiest designs I have seen is drilling a tapping a thru hole in a stepper motor shaft.
Then the threaded rod just goes right thru the motor.
You can buy them that way.
JymmmEMC, under the walk way rocking assemply and u cups http://www.collection.archivist.info/archive/DJCPD/PD/2001_04_23_Claymills_roof_before_painting/apr20010009.jpg
JymmmEMC, that one is 40ft long but only rotates slowly
another at 30ft but not visible http://www.collection.archivist.info/archive/DJCPD/PD/2001_09_27_Claymills_Open_Day/P1010345.JPG
Hot wire cutter, you could use that really neat dual bipod design :)
Then you don't even have to worry about a lead screw :)
archivist: Why didn't you climb up there and get close-up pics too
I helped free then when they were seized
archivist: I only see the mechanics on one side, how does it move the support when traveling the opposite direction?
lever gets hit and it rocks
Oh, is that what the added "nubs" on the gear wheel are for?
Well, either way, I think a lil too elaborate for this. Maybe belts instead. it's only moving a wire.
on that particular shaft the gear is driving via a slot in the shaft and the trolley moves left right
JymmmEMC: A bipod sort of like this one : http://www.youtube.com/watch?v=DAPTdw_BTF0
tomp is now known as tomp3
Ok, I've seen that before (with a spray can of paint). What are they using for the straps... toothed belt?
I'm not sure. I think that timing belts are a good idea though.
I guess ion the motors, a toothed gear and a tension pulley of some sort.
to prevent the belt from coming loose
Sure. There was a video posted on here a while ago that actually showed a dual bipod hot wire foam cutter, I think it only used wire wound around a pulley.
Jon_geo01005, I have made a config for hte Gecko G540, which contains 4 G250 drivers in it
SWPadnos: I see, I was just wondering how well they work.
they seem great
SWPadnos: What you think... toothed belt or wire on a pulley?
much cheaper than the others.
I happened to be using a very good latency PC for testing, and I had the stepper running at close to 50ksteps/sec
JymmmEMC, without knowing any more than that question, I'd say toothed belt. wire-on-pulley could slip
SWPadnos: bipod http://www.youtube.com/watch?v=DAPTdw_BTF0
SWPadnos: for a cnc foam cutter
SWPadnos: do you remember somebody putting a link up for a dual bipod foam cutter?
Jon_geo01005, no, not really
JymmmEMC, is that what you'd want the wire/belt for?
hmmm. I don't know then :)
SWPadnos: bipod just seems reasonable for a foam cutter
you'd never be able to cut accurately going downward
SWPadnos: weighted of course
unless the hot wire literally cuts the foam like melted butter
ok, weights could make it work
The one I saw had largish weights.
you also have tension on the cutting wire itself
there's no particular reason why the ends will move in a plane
someone did post a video link on here in the last couple of weeks.... it used a bow holding the hotwire tight that was suspended at each end by 2 wires