CAD CAM EDM DRO - Yahoo Group Archive

Getting Started with Servo CNC

Posted by erikreikes
on 2002-09-09 16:46:51 UTC
Hello All,
I'm in the process of setting up my ShopTask for CNC with Servos.
I found some big servos (around 600 Oz-In) on Ebay for cheap and
decided to go with a servo system. I bought the power supply kit
from camtronics and assembled it and I bought Gecko G320 servo
controllers.

In the process of setting things up I realized that with 500line
encoders and a 2-1 reduction on the drive to 10 turn/in lead screws
that I would be getting (0.1 inch/turn / (2000 steps/rev *
2revs/turn) .000025" per step which seems might fine. By my calcs
this works out to around a max of 15IPM using Master5's max pulse
rate of around 10000 steps/s. Seems kinda slow for a beefy servo
system, but may be acceptable. I'm not sure because of my limited
CNC expreience what is a good number.

Question 1 : What is the recommended way to improve this? I've
noticed that gecko has a soon to be released servo driver with a step
multiplier. Being a computer engineer I could make something like
this fairly easily as a front end add on between the parrallel port
and the geckos, and I may go this route. I also was thinking of
going from a 2-1 reduction to a 1-1 reduction, but I'm not sure if my
torque is sufficient to handle this. Also, if I work up a custom 3
axis pulse multiplier board would anyone else be interested in
purchasing them to help me defray the cost of board spins? I would
estimate it would be in the $40 range with parts to build in low
quantity.

I've decided that as soom as I'm up and running my first project
will be a Stainless Steel chess set (well, first it will be aluminum
to test, but then SS). This involves mostly lathe operations. It
seems to me that Master5 is mostly set up for milling operations. I
use Rhino3D for CAD work and have been fooling around with importing
DXF's into Master5. It seems to always add Z movement even when I
inhibit z in the dialog box. I'm thinking I may have to import dxf,
export g-code, manually edit the code and re-import again.

Question 2 : What extra features does the paid version of Master5
support that would help in my endeavours. I plan on buying it
anyhow, if I like the way it works, but I'd like to know what extras
it has before I order it. Also, any similar programs that are sset
up for lathe CAM? Something like a dxf to lathe command program or
something. I am a bit overwhelmed at the dizzying array of programs
out there.

Vector CAD/CAM seems like a really neat package, but it is a bit
over my threshold of pain at $800.

Question 3 : Are there any used copies of people who have moved on to
something else? Any sales or things like that the list knows about?
Is it really worth the $800?

The servos I have do not fit the Nema 34 mounts on the Shoptask.
I've been trying to thing of a way to elegantly mount them. My first
thought was a servo bolt pattern to Nema34 adapter plate, but in
addition to being kind of kludgey it would be tough to figure a way
to provide access to all the bolts, plus I'd have to do machining on
the existing plates anyhow. My second though is to either modify or
fabricate entirely new mounting plates that fit only the servos.

Question 4 : Has anyone here done a servo conversion on their
shoptask successfully? If so, would it be possible for me to see how
you did the mounting? This is currently the last thing I really need
to get my CNC up and running, and I'd like it to be right.

Question 5 : What is everyone's experience with using backlash
compensation with Acme lead screws while CNC-ing? I know ballscrews
are the way to go, but I'd prefer to leave that sort of upgrade until
I ge t abit more experienced with cnc in general. Will I be terribly
dissapointed with acme cnc performance machining simple things with
moderate tolerances (.001"). Can I compensate by ensuring that my g-
code programs don't take out backlash? FYI the shoptask does have
backlash compensating nuts on the acme leads that gets me down to
aroun .005-.010" backlash on each axis (well, except the Z axis whic
sucks).

Thanks in advance for any and all replies.

-Erik reikes

Discussion Thread

erikreikes 2002-09-09 16:46:51 UTC Getting Started with Servo CNC bsptrades 2002-09-09 18:58:09 UTC Re: Getting Started with Servo CNC wanliker@a... 2002-09-09 19:23:50 UTC Re: [CAD_CAM_EDM_DRO] Getting Started with Servo CNC wanliker@a... 2002-09-09 19:58:29 UTC Re: [CAD_CAM_EDM_DRO] Getting Started with Servo CNC wayne_j_hill 2002-09-09 21:55:36 UTC Re: Getting Started with Servo CNC Erik Reikes 2002-09-10 00:12:16 UTC Re: Getting Started with Servo CNC Fred Smith 2002-09-10 09:30:06 UTC Re: Getting Started with Servo CNC Dan Mauch 2002-09-10 10:55:08 UTC RE: [CAD_CAM_EDM_DRO] Getting Started with Servo CNC Erik Reikes 2002-09-10 14:59:19 UTC Re: Getting Started with Servo CNC Dan Mauch 2002-09-12 09:19:28 UTC RE: [CAD_CAM_EDM_DRO] Re: Getting Started with Servo CNC Dan Mauch 2002-09-13 09:40:18 UTC Multiple Operating Systems mgdcnc 2002-09-13 21:19:23 UTC Re: Getting Started with Servo CNC jeffdavis516 2002-09-14 08:47:10 UTC Re: Getting Started with Servo CNC mgdcnc 2002-09-15 00:10:52 UTC Re: Getting Started with Servo CNC