I'm planning to make a small mill from scratch
about mini-mill sized
[00:00:50] <sed_> http://www.jrkerr.com/boards.html
Amplifier capable of driving 6 amps continuously at up to 48vdc. Built-in thermal,
overcurrent and undervoltage protection.
ahh, I'm using steppers.
* bill2or3 scrolls down
you reading the pdf or the page?
at those prices, you're better off with Geckos
and you can throw in a G-Rex with the extra cash
oh? where are Geckos?
[00:04:22] <SWPadnos> http://www.geckodrive.com
G320 for servos, G201 or G202 for steppers
whats the differance between servo and sttepper?
the G-Rex does extremely fast pulse rates, so you don't need the step multipliers in the G340 or G212/G210)
servo = DC motor that just runs when voltage is applied
stepper = dual-coil motor that needs external controls to change the currents through the two phases
(ie, internally vs externally commutated motors)
which one is gooder?
depends on the application
for the most part, servos are better
they're more expensive for small motors though, so for smaller apps, steppers can be a better choice
Mariss (the owner/engineer at Geckodrive) uses the rule of thimb that steppers are generally better for <200W, servos for >300W, and it depends between 200 and 300
sed, I asked a ton of (probablly annoying) questions here and my decision was "use steppers"
but you're valuing cost over everything
and you havea very small mill / project
I want to drive the knee on my mill for the z axis
a Bridgeport (or a near-BP-sized Jet), is at the end of the stepper viability range
you eed a servo, or a huge stepper for that
when you get into larger machines, and higher speeds, servos become more cost effective, because they work the opposite of steppers
that's true, my design objectives are pretty low-end.
a servo can be overdriven for short periods of time, to get through a hard spot, so you can rate a servo for the amount of torque you expect to need
and you'll have headroom for short bursts of extra power
a stepper is a constant power device above its corner frequency (usuallly in the couple hundred to 1k RPM range, I think)
that means that as you go faster, you have less torque available
there's nothing you can do to increase the torque at high speeds
sure there is - you increase the voltage
time to go home, bye.
yes - that gives you a higher constant power, but for a given supply voltage, you'll still have a constant power device, so torque will decrease linearly with speed
and, you'll be dissipating lots more power in the motor, so heat becomes a big issue
all you have to do is not go too fast... they sure are nice and cheap.
right - for slow / low power apps, they're fine
[00:14:37] <sed_> http://puga.mauibuilt.com/shop/DSCF0091.JPG
thats my mill
a BP-sized machine doesn't necessarily qualify
what's the total weight on that machine?
thousand pounds??? if that
ok - what's the table size
um 8x30?? small
has like 24" of travel on X
the knee is not that hard to crank
they usually aren't - the 10TPI screw helps ;)
at least on a bridgeport
think its 8
1.25 per rev
so that would make it 8
well - a bridgeport knee+saddle+table is around 900 pounds, and has a 10TPI screw
that's before you add a vise or a workpiece
thats as heavy as my mill in total with the stand Im sure
heh - probably
to run a BP knee, you should have at least a 40 in-lb servo, and 50-60 is preferable
(a 40 gets hot in normal use)
[00:21:15] <sed_> http://puga.mauibuilt.com/shop/DSCF0085.JPG
thats my lathe
I probably shold have cleand up before I took the pictures
a stepper would need to be 1.5-2x the torque, so figure 75 in-Lb, or 1200 oz-in
your mill has probably 1/3 the weight to move, but 8/10 the drive ratio
so you probably need a 600 oz-in stepper or more for the knee
how much do they cost about??
I'm a servo guy ;)
so how much would a 40 in-lb servo cost??
loads, if you get it new, like $1200
the mill cost less
you only need half that though, so something in the $600 -700 range (new)
ebay has servos in that range pretty frequently
I would like one I could attach the hand crank to..
you'd generally use a belt drive to couple the servo to the crank, so you could probably have a handle after the gear
1" bellt do it?
note that a knee drive without feedback is probably a bad idea, unles syou really overspec the stepper motor
overkill, the best elts are Gates GT2, and 15mm width would be plenty for you
har dto find the pulleys online though (or at least, hard to find both belts and pulleys at teh same place)
I think I have a source localy
just bought some cogged belts for a polisher
GT2 seem to be harder to find for some reason
could be the patents and stuff
If I lived in the real world I would just wait for some old ebay CNC I could retro fit
plenty to choose from right now
My Friend got a working Maho 400 for like $2500
there are a lot of good deals (now that I already bought a mill)
well time to go home, thanks for your help
sure - see you later
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[Global Notice] Hi all. We just experienced a brief connectivity loss on a main rotation server. Looking at the problem now. Apologies for the inconvenience!
SWPadnos is now known as SWP_Away
Hi fenn. You becoming a day person now or just not sleeping at all?
i have a 25.5 hour schedule
i try to skip the "wake up at 10 pm" part of the cycle as fast as i can
i have some responsibilities now so i guess i'll have to try to stay on regular hours
Really. You able to elaborate?
great fun last night!
so my sound was ok?
les_w: great !
no distortion ;P
I managed to route digital direct to paltalk
* jepler looks at the screenshot of "weave"
the weave stuff reminds me a little of the dovetail gcode I am making
I may write it up as a little expert system c program to generate the code
enter dimensions, type of dovetail, etc
I have a swivel so I can lock the spindle at 30,45,60,90 degrees
I don't understand why he doesn't just generate g-code for that path
i lost the link
oh let me look
there's a jpeg attachment to the last mail from Colin Wildsmith
[14:38:00] <fenn> http://fenn.freeshell.org/weavesnapshot1.jpg
holy cow look at his rapids
nice blend huh
* fenn cackles
yeah, well little c programs to generate special g codes are pretty easy
Eveb I can write them!
I also find it easy to write programs to generate g code
well, I had better get to wiring
converting to optocouplers
runaway. run away! r u n!!!!!
OH SHIT A-L-P-H-A HERE! RUN RUN FOR YOUR LIVES!!!!!!!!!!!!!!!1
you better fear me!
it be much easier to just /kick you
abuse of power...
sad sad sad.
A-L-P-H-A and your point is?
just take your abuse like a good beeeyatch.
and I have an alias for it.... dont tempt me
Jymmm, what ever happened to that machine you had?
what do you mean?
the one with sooo many initial problems...
did you get them all resolved?
that gantry thing.
AS best to be expected, yeah. Better if I had geckos of course.
what cha been making with it?
my mill hasn't been turned on in like 6 months.
it's sitting there... doing nothing.
Signs, have pics, but haven't posted them yet.
nor my lathe.
let me see.
let me see what I have available, gimme a few. you sw the parrot, right?
I haven't seen anything... I haven't been in here much.
Jymmm, just put them up on flickr or something
I'll check them later... as my blood sugar level I think just dropped... as I'm suddenly feeling really tired
then again, I've been up for like 4 hrs, without eating anything yet
A-L-P-H-A chk your msgs
[19:15:30] <Jymmm> http://static.flickr.com/33/61765799_f610fa36cb_m.jpg
what are you using to draw things?
art or cad wise?
various tools, depending on the situation... Corel mostly of editing vector graphics
Jymmm: Thanks for suggesting that onsrud(?) tool for cutting plexiglass. I finally got back to that project last night, and the results were very good.
jepler Yeah? let me see
jepler and which one did you order?
Jymmm: I don't remember which one. "O" cut, 3/16, something..
jepler you have pics?
jepler: They have about 8 different 3/16" 'O' Cut bits. I'd liek to compare the bit with a pic of the results.
Jymmm: I don't have a picture of it, but maybe I can put one online this weekend
jepler: Ok, cool. Maybe you can get the PN at the same time.
jepler: See, I had done the research, even talked to the Sales Engineer, but was still reloctant to buy =) So you were the beta bitch in this case - But all they make are tools for (mostly) plastics.
jepler also what spindle RPM
Jymmm: 2400rpm, feedrate 13ipm
jepler: eeeeeew, I can only go down to 8000RPM
But they did say it SHOULD work.
jepler no melt over at all?
say jymmm how much does a spindle with 1/4" collet cost?
I'm pretty sure it was 7200RPM?
i mean so you wouldnt have to whine about your minimum speed anymore
cradek: I wrote down 2400RPM. Whatever it was, it was the innermost ring on that little disc
fenn : I'm using a router, and I haven't seen one that goes THAT slow.
ok maybe you're right - that's the .005" per tooth
Jymmm: no, I didn't see any melted plastic. Just tiny chips -- maybe 1/4 inch? -- everywhere
jepler Very cool! No issues in curves or when it had to slow done in the corners?
Jymmm: it was just a rectangle last night, but the corners were fine
Jymmm: there's plenty of accel on cradek's mill
jepler: Ah, ok. whe I had it goin at 120IPM it was icky =)
aw now this is just sad http://cgi.ebay.com/A111-G-CODE-DXF-cnc-mill-router-plasma-engraver-STAR_W0QQitemZ7586583367QQcategoryZ57122QQrdZ1QQcmdZViewItem
Jymmm: I bet the tool was 63-766
Jymmm: 13ipm << 120ipm
jepler: Well you're doin 2400RPM too, probably the right chipload
Jymmm: the material was .092"-thick plexiglass (clear w/blue film) so I don't know if it's anything like what you are doing
jepler if it had a blue film that's Extruded Acrylic. Paper film is Cast Acrylic
jepler Cast usually has a bit better results. Especially when laser engraded (just fyi)
Jymmm: this is what I'm doing with it: http://emergent.unpy.net/stippler
Jymmm: the onsrud tool is just to cut out the plexiglass to the right size, nothing complicated.
Jymmm: but an edge that transmits a lot of light is important
jepler: Ah, I want to carve/engrave in acrylic, thus my research.
jepler did you flame polish the edge?
Jymmm: I don't remember what I did for the one on the website, the one I made last night, the edges were buffed with "jeweler's rouge"
jepler If you have a clean, smooth, but fristed edge on acrylic, you can flame polish it so it's perfectly clear using a propane blortorch.
Jymmm: I'll have to try that sometime
jepler : http://www.sdplastics.com/plex.html
jepler: It's how you get a perfect finished edge, especial for light transfer
thank goodness for "Adblock Background Image "
oops .. that makes the page unreadable
jepler: Practice on some scraps, and iirc read up on tempering acrylic too, or you'll end up with micro fractures.
jepler fuck it, just VIEW SOURCE
gawd that's annoying
is tempering basically just baking the water out of it?
fenn: No, it's more heating it to 120 deg F for 5 to 10 minutes.
the temp and times are varied depending on the material
i'm not finding anything on google
me neither, I have some stuff here in dead tree format
well then could you explain it a little for the sake of posterity?
You... want me... to explain properties of polymers?
That's like asking Darwin about Gawd
* fenn wonders whats burning..
when you thermoform or fabricate plastics (in this case acrylic) to prevent micro fractures in the material, it needs to be tempered to release the stress in the material itself.
Unlike metals, tempering plastics doesn't take much effort or heat at all.
If you want to play around... grab some acrylic scrap, and hit it with a upside down can of air.
then let the piece sit in sun for a bit and warm up
hey dmessier how's stuff going?
* Jymmm pushes anonimasu to the OTHER window
* fenn is reading about microcontrollers
i'm drooling over the at91 series
fenn get the butterfly, it's $20
waiting forever for my avr's to arrive
hm, the butterflys is just a demoboard..
anonimasu and your point is?
yeah avr can do plenty just on a breadboard
[23:25:57] <fenn> http://www.robot119.com/market/bookpic/2004425162058663.gif
is that weird or what
can anyone tell what this is? http://tinyurl.com/e4hkg
how come you always post quicksrv forwarded links?
* Jymmm dont do tiny urls
too many XSS
tinyurl doesnt bother me but i have quicksrv blocked out (cause they're spammers)
I like to see where I'm goin befor eI get there
just because the real url was like 150 characters
[23:42:11] <bill2or3> http://cgi.ebay.com/3-Xilinx-Stepper-Cutter-403650-031P-2844-Parallel-Ports_W0QQitemZ8759300798QQcategoryZ56084QQrdZ1QQcmdZViewItem#ebayphotohosting
some sort of embedded controller, I think.
i wonder if all tinyurls go throughh quicksrv now..
ah damn thats really annoying
probably a rack mount parallel port for server rooms
like for putting printers on a network maybe?
* fenn shrugs
google finds nothing, I found it in a search for 'stepper'