I am kinda curious....this may even be a dumb question, but why would the boards limit the performance...the only think I can think of is the encoder feedback
Jymmm is now known as Red70sShow
Red70sShow is now known as Jymmm
les_w you lurking by chance?
it sure is quiet in here....everyone must be out having a better friday night than me
friday before easter
any friday is good though
that is true
what were you refering to earlier when you were talking about performance diffrences
things like maximum step rates, maximum encoder count rates, etc
for step and/or count rates under 10KHz you can get by _very_ cheaply using software counting and step pulse generation and a parallel port for IO
on the other hand, there are boards ranging from $200 to $500 that will step and/or count up to 1MHz or more
if you haven't done the math to figure out what rates you need, you can't possibly decide which is right for you
It just seemed to make more since to go with too much
ok, what boards were you refering to that had higher rates
unfortunately I don't know of any that so steps _and_ DACs for servo
Its the servo thats throwing me off so bad
Jon Elson's USC board ($200) generates step pulses and counts encoders, up to about 300KHz
lots of board, like vital, motenc, and mesa, do DACs and count encoders
the mesa might be able to generate step pulses
Yeah, I called Jon Elson.....He must have other things going on right now or something
I think Elson's board has a connector for an external DAC, so if you are handy with electronics (or pay Jon to do it) you could run the servo with that
His boards was originally what I had in mind
but I cant seem to get one from him right now
why does usc count encoders? that doesnt make sense
fenn: when you are using the steppers, the usc actually counts the outgoing step pulses
but it uses the same hardware, and from the softwares perspective, it is counting encoders
SWPadnos is now known as SWP_Away
03jmkasunich 07HEAD * 10infrastructure/farm-scripts/check_commit: working on new farm scripts
slow day today?
samco is now known as SkunkWorks
This looks kinda interesting... both 6" and 8" http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=35098
[17:41:56] <Jymmm> http://www.craigslist.org/sby/tls/150964066.html
03rayh 07HEAD * 10emc2/tcl/bin/halconfig.tcl: cleanup modify and start axis tune
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03cradek 07HEAD * 10infrastructure/cvs-server/chroot.html: document describing the basic chroot scheme
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can someone please tell me where (what directory) does apt-get install emc2 put all files?
it puts them in several places depending on their purpose
dpkg -L emc2
it's too bad the sherline table is so small
it's too bad the sherline is so small, I think you mean
I wonder if they'd do well making slightly larger machines
jmkasunich: maybe so
their machines are sure useful for making small things, they have that market cornered well
and there is something to be said for machines that can be picked up with one hand, and carried by one person without a hernia
I'm not sure how much bigger you could get and still meet that criteria
weight goes as size cubed
whats needed to set up passwordless (non-interactive) ssh/scp?
my main "want" is to mill circuit boards, so a table at least as big as the blank PCB (4x6) would be nice.
jmkasunich: you have to have a private key on the side that will execute "ssh", and the public key in the authorized_keys on the other end.
jepler you couldn't add a plate?
jmkasunich: just copy a key
you need more X and Y and less Z
more Y mostly I think
* Jymmm has that!
dont need much rigidity for circuit boards
jepler: is it a question of travel, or table surface?
fenn: to mill away the copper? You need plenty of rigidity
plenty is relative
you need nice repeatability, but no force is involved
0.005 deep in copper compared to 0.2 deep in steel are two different worlds
sherline's 5400 is 5" Y travel with a 2.75" deep table.
you only need 4", so that works
is the throat depth >4"?
2000 is 7" Y travel but the same 2.75" deep table.
what do you guys use to hold down the board stock when milling? clamps along the edges? double-side tape? vacuum?
clamps are useless - they don't flatten the board
jmkasunich: I just copy everything cradek does
vacuum seems like it might work, except you lose it when you drill
so all you need is a 4.5x6.5 chunk of 1/4" or 3/8" aluminum plate
drill holes for four flathead screws that fit the tee-nuts
if you want to go first class, make a rectangular bar on the bottom that fits into a table slot so it goes on square
what does "throat depth" mean?
I bet you'd have to attack it with the flycutter to get it flat enough
I have a 5-1/2" face mill ;-)
jepler: how far forward from the back edge of the work can you cut without the work hitting something
anybody want "pc board tables" ?
IOW, distance from centerline of tool to the column of the machine (or other obstacle)
jmkasunich: jepler won't actually buy a mill... he can mooch for free
what do you put under the board to keep from drilling the table?
cradek: well yeah probably
another piece of circuit board would also work
so the stack is table, tape, perf, tape, board?
seems like the tape would cause a lot of non-flatness
different tapes so the right thing comes apart when you pull
jepler: Lets say a drill press, "throat depth" is how large of a piece of material you can drill before it hits the back support (as example)
I agree, but it works surprisingly well
you have to apply the tape carefully
I bet decent aluminum plate is flat enough without even flycutting it
yes, could be, if it's in good shape
(not rectangular bar, that is extruded and tends to be wonky, but plate is pretty good)
"good shape" = new
they make that new? I'm such a scrounger
a 6x6 piece of 1/4 plate is something like $12 from metal express
for some things I scrounge, for some I buy
when a customer is paying for it, I usually buy
I looked up the 6x6x1/4 a few days ago to do a quote
screwing it to your larger mill's table and cutting everything but the t-slot bars would give you a nice flat fit
leave two bars to go in the slots
(makes it easier to install, no real sacrifice in accuracy)
I would probably make the bar a separate piece
but same idea, the part you cut away becomes flat
mill a slot for the bar
yeah, either way
use 1/4" or 3/16" x slot width for the bar
depends on whether it starts "flat enough"
that way I can just take a skim cut to make the thing flat
otherwise it takes multiple passes
I forget you don't have cnc...
and I have older machines, if I make a single pass without moving Y, no errors from slop in Y
besides, why make a lot of passes when one will do?
I can mill a 4x6 plate flat in about 2 minutes
btw a flycutter wont make a flat surface
it will be slightly curved because the mill isnt perfectly square
btw, a flycutter won't make a flat surface _IF_ your machine isn't square
btw, nothing can make a _flat_ surface
just a matter of how close to flat you want/need to be
your machine won't be perfectly square
get out the blue and the scraper...... ;-)
I'm sure that's true
anyway, unless this plate is an inch thick, holding tighter than a thou or so is silly, it will bend that much when you screw it down
i'm used to working with crappy equipment
does the sherline come with a flycutter?
so i'd face it off while it was on the table to make sure it's flat and parallel anyway
and how big can it cut in one pass
you can get a small one
if I was doing it, I'd flatten one side of the plate on my big mill, and square the edges
then mill the slot for the bar, and drill the screw holes
screw it to the table
and flycut the top on the sherline
also, mill the back edge on the sherline, so its parallel to X
then you can either mount a "fence" on the back edge, or just hold something there when mounting a board
I was thinking more of something flat
I have some parallels, 1/2" x 1" x 6", ground all over
I'd use one of those
[20:59:13] <Jymmm> http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=789
if I wanted a permanent fence it would be 1/8 alum, screwed into the edge of the plate
mine are ancient, belonged to my dad
probably 40+ years old
for $20, they could be mounted on his table
the problem with a permanent fence is chips getting down in the 90 degree groove between fence and table
with a removable one, you wipe the table clean, then hold the "fence" against the table with one hand, push the board against it with the other, and then lower it onto the tape
if you do a permanent fence, put a 1/16" x 45 degree chamfer on the table edge first
someplace for the chips to go
sorry... I menat get a big flate plate, pin it so the parallels sit solid, place the blank PCB againest it
you can scrape out most of them, and the tiny ones left do no harm in the groove
this is one of those cases where a pic is worth 1000 words
I don't follow you
jmkasunich you have a base plate, maybe with a grid of holes. You put in pins/pegs that the parallels will fit on to. then you have a perfectly sqaure edge to place your stock againest.
like a lip of sorts.
the holes in the table and the parallels need to be very good fit on the pins
he does have a cnc mill
a cnc mill doesn't mean precision
you want a 0.0005 fit
so hole diameter and pin diameter and hole spacing all need to be better than that
jmkasunich he's (better) not making nuclear reactor parts
ok, maybe he doesn't need 0.0005
but since my method can give him 0.0005 squareness with no precision parts, might as well take it
actually, there is another approach - just mill the fence out of the solid
I just figured reuse existing shit when you can =)
IOW, flycut the entire plate down 0.060" except where you want the fence to be
...and hope that there isn't one tiny sliver of swarf under the stock =)
i dont see how this fence stuff helps align the two sides of the pcb
the fence takes care of alignment in one direction only
yeah but you're not using the same datum surface on the pcb stock
(and it ensures parallelism
yes you are
when you flip it over?
one edge (back edge) is the datum
flip from side to side, back edge is still back edge
by "two sides" i mean front and back
so you'd need 3 fences to align it
one fence gets you Y and parallel
all thats left is X
which can be done by offsetting
or you could rotate it 90 degrees when you flip i guess
then you lose everything, X, Y, and parallel
* fenn considers chicken-scratching
if you have ONE straight edge on your board stock, and a fence on the table, you can do the flip and only have to align one axis
gotta go away for a while
fenn: good idea using the same registered edges
i cant figure out what jmk is saying