Strange output

[carlhopkins]

This is the first time with any issues, PRT Alpha 120 x 60.
*While cutting (6) rectangles, I noticed the “final” step down did not occur on (3) sides, same side of the pieces. Making it look as a rabbit on that side.
*Then on another program one of (3) pieces was 1” short.
*Then yet another program another just (1) of (6) had the step down problem.
I have notice before parts not looking as I thought they should and find it to be in my drawing, by not placing a part correctly.
I looked back to the drawings and could not see anything out of place. I draw and then copy the parts but thought maybe it might be the operator but not this time.
Could this be caused by static? I did notice some static around. I live near Atlanta and we have a cool front moving through. If so what should I do?
Thanks in advance for your help.

[dana_swift]

Carl, create a short test file that exhibits the problem.

First logical question, are the 3 sides the last three cuts in the file? Does the router move to correct Z on later cuts. The bot isnt smart enough to know how to do that by itself.

Then examine the SBP file to be sure that it commands the bit to move to the final depth.

If not- the problem is in the toolpath generation somewhere. Are you using partworks, partwizard or some other thing?

If the SBP file does command full depth, there is a list of things it might be:

First check zzero before you run the file. I would command "MZ 0" and be sure the bit is on the surface. Then run the file, command "MZ 0" again. has the bit shifted up in the collet? (Put the zzero plate away first or you will damage both it and the bit)

Also that will test that the zzero routine is in fact setting the bit at the surface of the material.

There was a bug in PartWorks where generating tabs would generate wrong Z profiles, the latest update available from Shopbot has this bug fixed, in case your 3 sides include tabs. That may be your problem.

Hope that helps-

D

[carlhopkins]

Thanks Dana
I am using Part Wizard 2. The drawing file is from Progecad STD. I did make one change from what I have been doing, I set the Z to machine bed.
I will see if I can recreate. The Z looks to be fine in the program.
I did loose the "Z" depth a couple of times also. The first was when I first started up, this has happened once before but only at start up. FYI I always set the Z and the XY before cutting. The second time was between programs. I reset it and all went well. Thats what makes me think static. I was using tabs too.
I am not using the Bot today but I hope to be soon. Must build, sand and paint for a while.

[dana_swift]

Carl, Although static discharge could cause problems, it is a guess at best. Most problems can be traced to a definitive cause, even though it may not be found for a long time. If static is an issue, the real problem is shielding or grounding.

When you say "Z looks fine in the program" are you referring to having inspected the Part Wizard, or the SBP file?

Losing Z with an alpha is a very unlikely thing to have happen, which is why we pay so much extra for an alpha. It is designed to know when the position does not match the command and correct the error automatically. If the hardware isn't working correctly.. all the design intent is out the window.

I once had a problem with my alpha losing Z, and after getting all kinds of "wild guess advice", it turned out to be the cable to the stepper motor had a intermittent connection. Once that bad cable was replaced the unit has been absolutely rock solid.

Your symptoms sound different than mine, and I don't suspect a bad cable (yet) as cable faults are fairly rare in electronics (i was truly surprised to find it was the case with mine).

One question I have, does the Z console display on the SB3 program show the correct depth during the final pass on the bad cuts? If so.. the bot "thinks" its at the correct depth. That helps narrow down the problem to hardware. If it shows the depth of the actual cut that leads back to the SBP file and tool path generator.

Another thought.. if you run the SB3 (beta version) program in preview mode does it show the cut depth correctly? If so.. that means the problem is on the hardware side. If not its on the toolpath side.

If its on the hardware side I recommend a chat with tech support. They get paid to diagnose those issues, and it appears you may have a shopbot that is under warranty. Once you can prove it is on the hardware side that is the best route.

Good luck, and I along with hundreds of interested botters would love to know what it turns out to be!

D

[woodworx]

I had similar problems at the start and it's just a guess, but i loaded my SB3 program on a computer with 2 hard drives. Some directory files were saved on 1 hard drive and some to the other drive. I removed the 2nd drive and reloaded the software. Much better.

I think the static theory is not going to be your problem.

Re create your vectors/make sure they are cleanly drawn and re-toolpath. Hope it works. Justin