Urgent Help on corner not square!

[bstern]

Need to do about 5 hr of cutting tonight but having some strange problems.

I cut 3/4 melamine.
Using 3/8 in compression spiral.
I use CR to cut a rectangle climb mill to onion skin.
Then cut conventional with the same command at full depth.
On shopbot corner #2 on the climb mill it cuts the corner too soon
for about 1 inch then pulls away to the correct cut.

It is always corner # 2 always, no matter what corner I start on. only on climb mill pass. You can see the onion skin part square is as can be.
This happens on the first cut with no kerf or with kerf.
No slop in the Y car.


I have been using the same code for years without this problem.
I slowed down the cut to see if it would help but no help at all.
I back loaded to the last software update, no help.

Any sugestions would be apprecated.

4 3

1 2

10091

[nat_wheatley]

Are you cutting these parts individually, or as part of a nest? I've had similiar results when nested parts weren't spaced far enough apart. The outward deflection on the 'climb' pass would cut into adjacent pieces in select areas.

[bstern]

yes, its part of a nest but it happens when the part is at Y0 with no other part next to it. It only goes for about 1 inch. its hard to see in the picture.

[navigator7]

Any suggestions would be appreciated.

Just a fresh set of ideas to mebbie give you a push start....
o Junk on the ways?
o Worn cutter? Sloppy collet?
o Is the material moving?
o Have you zoomed in to your drawing? (Select all and look for something that is not supposed to be there)
o Backlash?
o Try cutting some foam to replicate the problem and not eat up expensive material?
o Reverse the path?

[bstern]

Checked all that.
Have found a work around for now but still need to find out whats going on.


Making first climb cut out a ways and increased my spacing on my nest.

[sailfl]

It looks at a quick glance that you have a low spot on your bed which doesn't allow the bit to go all the way down at that spot or the material is being lifted which could also cause that problem.

[cabnet636]

set z zero on the bed in one corner, then check the other three

[bstern]

Definitely not a Z problem.

If you look at the picture, the upper part that has the scallop is the first cut that is done climb mill. the lower part is the 2nd pass at conventional. this cuts fine and square.

it does this on all parts on all areas of the spoilboard. I start on corner 4 and the problem is always on corner 2.

Still have not found the issue.

[srwtlc]

Have you tried the same cut path with a file generated from another program eliminating a canned cycle (CR) problem.

Can you see it happen while air cutting? If not, then it would seem to be something mechanical flexing or tool deflection.

[Gary Campbell]

Bob...
I am with Scott on this one. Try a cut using cad/cam generated cut path using same climb/conventional parameters. This will eliminate a software error, which I thinks is one possibilty.

If that doesnt eliminate the problem, then your problem is mechanical. You say "no slop in Y car". What were the dial indicator readings? How much movement at what load rate?

[ken_rychlik]

I vote for slack.

It is to consistant and there are two forces happening at the same time for cornering. It may be a little each of x and y.

Kenneth

[bstern]

That sound like a great idea.
I will try that tomorrow. I should have thought of that already!

What I meant by no slop was that pushing and pulling on the Z car in the
Y direction showed no slop in the motor/pinion gears i could detect.
The actual deviation in the cut is about is about .05. This would make it obvious if it were slop in the gears or motors. (i think)
What is interesting is that the start of the groove is inside the rectangle being cut.
There has always been some z flex/bit flex in the cutting. I use this to my advantage by cutting climb first, with the bit pulling to the outside then finishing with conventional that may pull the bit to the inside. This has always trimmed away the flex. Since this pass is not cutting much it cuts to size very well. But this problem "cuts the corner" so to speak. Its like it does not flex for the first inch of the cut on that side on that pass. But this is inside the rectangle being cut. So it makes no sense to me that it would be flex.

I know I am missing something. Thanks for all your help and suggestions.

[gundog]

Make sure your X motors are both locked up good. I had a problem where I was having one of the X motors dropping out and I got results like that and egg shaped circles.

Mike

[Gary Campbell]

Bob...
Reading your last post and assuming that the #2 corner as you describe it is located in the lower right (+X, -Y), and since it does this in climb mill mode, I offer the following: (assuming it also happens with a cad/cam designed part)

I am almost convinced it is mechanical and the movement is a result of the force generated by the previous cut in the -Y direction moving back to actual from the climb cutting force of moving in the -X direction. As the bit accelerates out of the ramp it is back on track.

Check the following:
Y pinion grub screws (bend the wrench)
Y pinion to rack is tight
Y eccentric rollers (not likely, but check anyway)
Z extrusion rollers when lowered to near cutting position
X pinions to racks are tight
That all 4 X rollers are touching rack at all times. Loosen X motors, push gantry slowly back & forth in X axis while putting pressure on one front wheel or the other to see if you can see one stop.


It is a good idea to check, adjust and lube all of the motion parts, including ones I didnt mention above on a regular basis. My schedule is about every 20 hrs of cutting.

[navigator7]

Still have not found the issue.
What about the possibility you missed something you've previously considered ok?

For example, a pneumatic hand tool I was using yesterday stop functioning properly.
Took it apart and all looked fine. Still ... no go.
Assembling the unit a second time, a critical roll pin fell apart in my fingers.

[daski]

1. Please confirm that climb cut for you is clockwise around the piece and that conventional is CCW around.

2. it only happens in corner 2?

3. does it happen in corner 2 if you place the blank somewhere else on the table?

4 if you Z2 somewhere else on the table and rerun it does it still happen.

5. Is the bit is always cutting new material, ie it is not cutting a previously cut path full of dust for an adjacent piece. I put pieces 2 bit widths plus 2mm apart. in your case 9+9+2=20 mm or 7/8"



Try running a square designed in partwizard, this will eliminate the CR part of the equation and will reduce the variables.



try cutting 1 pass at 3 mm depth climb then 1 pass 6mm deep conventional. the side forces on the bit should be small enought help rule them out.

It could be ramping issues, but don't know if the sofware handles each corner seperately.

[bstern]

Yes climb mill is clockwise.

Gary has the problem very well laid out.

It is not a z problem at all. Repeat not a z problem.
What you are seeing as the z problem is the difference between the climb mill at onion skin an the conventional cut at cutting depth.
I understand if you just look at the picture, it looks like a Z problem. But it is not.

Gary, yesterday I checked most of what you suggested by putting the Z at cutting depth and pushing and pulling on z in all directions. Also watching the rollers on the gantry while cutting. All showed no signs of play.
FYI: We lube on a regular basis using lithium grease, every 20 to 30 hrs of cutting.

I woke up thinking about this and the Y car pinon has the most probability to be causing the issue. The "extra flex" is always on the x cuts. The cuts along Y look normal. I did not have that much time yesterday. I will remove the Y motor today and remove inspect and reinstall the pinion gear and motor.

I really appreciate all the brain power on my little problem. My shop help has been out for a week and a half and my Dad is in the Hospital for back surgery. Running pretty hard so, I may not be thinking as clearly as normal.
Not that my thinking is all the clear normally!

[bstern]

PROBLEM SEEMS TO BE SOLVED.

After removing and reinstalling the y motor,switching the driver and
checking everything everyone had mentioned, I started thinking about anything that had changed on the machine lately.

I had just removed the air drill on the Z car. Being desperate I installed the frame for the air drill. The flex in the Y direction is back to normal.
Parts cutting well.

It does not make much sense to me. If anything it should help in the X direction. It also cut fine for a week after removing the drill.
We will see in production tomorrow if it is really fixed or just hiding for bit.

Very Big thanks to all who have contributed. I was pretty desperate and all the ideas kept me going.

I used to do allot of troubleshooting. Some times I found, when all the logical stuff does not work, I would just start checking and changing out anything remotely possible. The drill frame was a shot in the dark. It seems to have paid off.

BTY: I finished installing my new boring head. It works great and has speeded production considerably. I now have a total of 8 selectable boring heads. They are in a L shape, 5 along the X and 4 along the Y (1 common). I use 5 along the X axis for my line boring. 1 on the Y for single 5mm drill, 1 for 10mm and 1 for 20mm. I will get a video posted later this weed if I can.