Re: [CAD_CAM_EDM_DRO] part holding

At 10:30 AM 9/4/2004, you wrote:

>Hi Doug:
> Is this your routine for production jobs only, or do you do one off jobs
>the same way?

Production only. No need to keep the program for parts that are obviously
singles to begin with.

>My personal habit has always been to program my one off parts in smaller
>chunks too, but I just run the programs one after another, rather than
>stringing them together with sub calls.

With my controller it is easier and faster to do the sub calls. Again
we're talking about building a program for future production. Being new to
the CNC game I find it much easier to get small processes and their results
in finished metal in small easy to see, easy to evaluate and easy to alter
chunks. When making the prototype, I do those small chunks - sub routines
- in their own program and complete the cut on the prototype. When it
works right, it is only a few key strokes to open the parent program and
include the sub call. At that point that part of the full program is
finished, and I proceed to the next small chunk by creating a new
program. That new program, when finished and working properly, will be
added to the parent as a sub call.

One of the things I like about this method is the ability to block any sub
call in the parent. Doing that allows me to see the graphics for the
remaining subs all put together in one part. If the part is all a single
program, it is very difficult to view individual pieces of the finished
part on the graphics screen.

>I'll typically run the programs straight out of Mastercam with only the
>verification utility in that program to verify that my program is OK.
>I run an optional stop routine after every cutter, so I can check the tool
>height offsets by dropping the rapid and feedrates in the control and I stop
>the feed just above the job to see if I'm in the ballpark.

I think I accomplish the same thing using the sub routines. Tool changes
can be in the sub or the parent. If several subs use the same tool, the
tool has been aligned and checked in each sub as the sub is being built.
All subs use the same part zeros. If any of those zeros change, they
change in the sub only. If a tool change is made, it is put in the sub and
checked while the sub is under construction.

>If my cutter is roughly in the right X-Y location and at roughly the right
>height, I assume everything is good, and have at 'er.
>I'll be programming the next bits while the roughing is going on, so I can
>constantly keep the machine cutting.

Here you have a great advantage over me. My controller uses DOS. Linux
became available shortly after my system was installed. DOS doesn't have
the capability to run and program at the same time. I also do all this
with the conversational programming utility on the controller - fill in the
blanks & hit the button. The mill does not run from conversational,
however. When the conversational looks right, I hit F10. That saves the
conversational part of the program and posts to the .CNC file. At this
point there are 2 files on the system for each part, the file read by the
conversational program and the .CNC file. Takes much longer to write
about it than do it. From conversational, to .CNC to chips is only a
matter of seconds.

>Typically I'll invest less than 15 minutes in the first program, just to get
>the ball rolling, and I never dry run it.

With an increase in confidence I may forego the dry runs as well, but
probably not. With the conversational programming I can set the feed rate
very high. Setting the feed rate on the first line automatically changes
the feed for following lines. The feed can be slowed to a crawl or stopped
from the key pad. The cut is visible on the table as well as the
monitor. Running through the sub is fast too as it usually contains only a
few cuts. There are usually repeat to depth cuts too. I generally put the
repeat to depth line in after making sure the original lines work. That
way the sub only has the original cut and takes far less time to run and view.

>Of course, my production jobs are never run this way; those get the full
>meal deal, so I can take full advantage of the fixturing and the
>toolchanger.

Again you have the advantage. I have two tool changers - my left hand and
my right hand. Works ok with the power drawbar. That is taken into
consideration when building the program too. I try to cut down on the tool
changes.

>I do have some tricks to keep the unexpected at bay:
>First, I always set the top of the job to be Z=0.

I do the same.

>Whenever possible, on one off work, I leave myself 0.100" of clamping stock
>and squeeze the block in the vise, if I have both inside and outside
>contours to cut.

I use the vise when practical, but would rather spend a bit more set up
time and use clamps when use of the vise would require removing and
replacing the part, particularly when it would have to be done more than once.

>My individual programs are always dirt simple, typically one or two cutters,
>doing one or two operations.
>Holes are always done as a separate program, and my first operation is
>always a facing pass at Z=0.

It sounds like we do basically the same thing. If I understand you
correctly, you do several stand alone programs, and then run them one after
the other from the keyboard, either with key strokes or with some function
of your controller that allows you to run sequential programs. I do the
same thing without the ability in the controller to run more than a single
stand alone program. The parent program running sub routines accomplishes
the same thing, however.

>I mostly build injection molds and production tooling, so most of my work is
>one or two off.

I do one offs, but would prefer small production runs instead. Hopefully
my one offs may also be semi production in that a customer will call for a
single part. Load the blank, load the program, press the button, and go
watch TV. :-) Speaking of mold making, I have an old guy coming in next
week that has years of commercial mold making experience under his belt
from programming to finished part. He's older than me, and I'm about the
same age as dirt. He's going to help out in the shop on a part time basis
and do piece work. Looking forward to it.

Hey, cheers to yourself as well. Appreciate the response.

Doug C.
Houston, Tex.