Program Shifting Cutting Location

[Designer]

On several occasions lately my BT32 seems to shift the cut location in the middle of a project. It will also randomly cut a path while in the middle of an operation that it should not. I am running Aspire 64 bit version 8.024. I have a 2.2 HP spindle.

Today, while in the middle of cutting a plaque for a friend that consists of a combination of clip art and sign geometry that I generated, it shifted the depth and X,Y location of the clip art with respect to the projects X,Y,Z zero location. It is now scrap.

I checked the tool to make sure it did not move in the collet and it did not move.

I checked the X,Y,Z zero location of the spindle and it is correct.

I checked the preview in the Aspire software and it is correct.

The only thing I can logic out is that somehow the program decided to shift the football clip art cut about X + 1.00 and Y + 1.00 and Z + .25 from its programmed location while it was cutting. From what I can see, the first cut was close to where it should be and then it changed.

My lap top was started just before I started the project. The wifi was off. No other programs were running.

The attached picture shows the football cut. The top of it should have been flush with the top of the board. That is deep the Z shifted.

Anyone have an idea of what I should look for?

[Tim Lucas]

Is your cut file on a thumb drive? If so copy the file to the computer.

Use the Shopbot editor and look at the cut file - if you know what line number you can view the commands and that might lead you to the problem

If your cut speed is to fast you may be loosing steps

[Designer]

Thanks for the response.

The program is on the hard drive.

Speed on the .0625 ball nose tool is 70 x 70.

I have never used the Shopbot editor. How do you access it?

Thanks again.

[Tim Lucas]

27157
You should have a icon like this
If your cut file or Vcarve file is not real big, upload it maybe we can see something for you

[Designer]

I found the editor. The file is too large to upload. I am looking at the code and also at the meaning of the CG, J3, M3, and MS. One of these is at the beginning off each line in the code. I am wondering if it shifted in a relative position at some point. While it was cutting the Z values showing on the readout did not reflect the dept of the cut. For example, the Z values were never greater than -.25 yet it was cutting over -.5 deep. Am I headed in the correct direction? Does CG, J3, M3, or MS denote a relative move? Thanks again for the help.

[Tim Lucas]

I am looking at the code and also at the meaning of the CG, J3, M3, and MS. One of these is at the beginning off each line in the code. I am wondering if it shifted in a relative position at some point. While it was cutting the Z values showing on the readout did not reflect the dept of the cut. For example, the Z values were never greater than -.25 yet it was cutting over -.5 deep. Am I headed in the correct direction? Does CG, J3, M3, or MS denote a relative move? Thanks again for the help.

The CG is a cut command (I think)- J3 is jog to a position x,x,z (3 position) - M3 is move to a position x,y,z (3 position) - and MS is setting the move speed - those are normal - you say that the screen read -.25" but it was cutting 1/2" deep, did it slowly get that way??? I am wondering if the bit slipped in the collet??? but you checked that - Seems like something mechanical, pinion or collet, or the wood moved - I would say recalculate the tool paths and save them to a new cut file then try it again in some scrap wood. let us know how it goes

[bleeth]

CG is cutting a circle. Specifically written for G code compatibility. Your manual has a command reference and info on the SB software that's very helpful to at least get a bit familiar with even if you have no intention of learning enough of it to write and/or edit your project codes.

[Designer]

Tim, it went there is one pass. It was not a slow change. In the picture I attached you can see a hole at the end on one of the top right cuts. That is where I believe it shifted. Basically, the bit drove down to drill the hole, and then came back up, moved to a new X,Y location and started cutting at the deeper depth. The wood did not move. I have it screwed to the spoiler board and the spoiler board is screwed to the table.

I am think I will save the 3D cut path out to a new file and then running it by itself to see if it follows the same cuts as before. The project is still mounted to the table at the same location. I will also compare the new code to the first one to see if there is a difference. I saved the portion of the code in question out to an Excel file and will save the new code there as well to let Excel do a compare. If it does not follow the same path and there is no difference in the code I think I'll contact Shopbot about it to see if there could be a mechanical reason.

Bleeth, I did find information concerning the codes on ShopBot's web site. I saved them to my computer for future reference. Thanks for the info.

I appreciate all of your help.

[rgreever]

Not your program itself, but is the part file that you are trying to run located on a USB drive? If so, that might be the culprit. Sometimes, our SB errors when we forget to take out the USB thumb drive.
My suggestion would be to not have any thumb drives attached to your computer as it's running the SB software. Make sure all toolpath files are being read from a hard drive on the computer.

Also, make sure that the low voltage cable connecting your SB to the computer is not near the high voltage cables controlling your motors/drivers.

Neither of these might be your issue, but I was just pointing out these, as we have experienced weird stuff because of the aforementioned scenerios

[Tim Lucas]

I am think I will save the 3D cut path out to a new file and then running it by itself to see if it follows the same cuts as before. The project is still mounted to the table at the same location. I will also compare the new code to the first one to see if there is a difference. I saved the portion of the code in question out to an Excel file and will save the new code there as well to let Excel do a compare. If it does not follow the same path and there is no difference in the code I think I'll contact Shopbot about it to see if there could be a mechanical reason.

Let us know what you find please
Tim

[bill_l]

Phil,

I had the very same problem occur while cutting a simple V-carve file. Just like me I suspect that when you analyze the toolpath, you will find nothing wrong with it. I encountered this issue shortly after upgrading to one of the 3.8 versions of the control software. I usually start testing newer versions of the software as soon as they are released but I can't remember which exact version I had installed that day. Being a V-carve file it was relatively small and easy to go through line by line. There was nothing that indicated the change in position. I then went back to Aspire and re-posted the toolpath with another name and did a comparison. Here again there was nothing to indicate the change at that specific position. After consultation with support I reinstalled the last version of the 3.6 control software (3.6.46) and keeping everything the same as when the problem occurred, i.e. part still in position and no other equipment including dust control operating, I ran the original toolpath again and it completed without any errors. Next I ran the second comparison toolpath and it completed right over top of the first.

If you encounter this problem again, try doing what I did but with one extra step. Run the original file a second time without changing anything and see if it shifts position again. If it does then install 3.6.46 and run the file a third time to see what you get. I've stuck with 3.6.46 and have never had a problem again.

Bill

[Designer]

I saved the code for the failing cut to its own cut file. Copied it to Excel and compared the original code to the code in the new file. They were identical. I then ran that cut file on the part and it cut in the correct location and depth this time.

I did check my cables. I moved them to different USB ports that are away from each other and did not have a thumb drive in the lap top.

I will also make sure that these wires are away from other electrical wires. I suspect there was either a poor connection to the lap top or they were picking up stray currents from other wires as stated above.

It sure seems like the only logical reason for this is output from the lap top to the CNC being interrupted.

There is one more variable. I did reorder the cuts to place them in an order that grouped them by bit size. Basically, grouped all of the .25 end mill clearance cuts together, .0625 ball nose bit cuts together, and so on. I would think that they are independent from one another and not somehow linked. If I am wrong that could be an issue.

[Designer]

I am lost.

Bill, I loaded the previous version from SB, which is 3.6.44, on my computer. It is much older than what I had originally when I purchased the machine in March of 2015. Sorry to say that I don't know what the previous version was and it is not available in the properties window. From the web site I suspect that I was running 3.8.26. The older version, 3.6.44, will not run.

I loaded the newest version, which is 3.8.0.4 (web states that it is 3.8.4). It runs, but it stops after a few minutes. It did this two times. It stopped at a different point in the program each time. Both times I got a message stating:

"ShopBot No Longer Being Recognized! An error is occurring that could not be corrected. You will need to exit, check all cables, then restart the software. Tool location may no longer be accurate."

I opened the control box and checked all of the cables in it and they were tight. I did note that my USB cable that connects to the control box does not fit tight in my computer in any of the USB ports. It does stay in place, but it is not as tight as I am use to. The light on the PC board that it connects to stays on when I wiggle the plug in the computer though.

At this point I have no idea of what to do. I am think I will swap computers to see it that changes anything. If the problem still exists it may be the USB cable.

Any other ideas would be appreciated.

[Designer]

I may have solved this. I hooked my newer lap top up to the BT32 and it worked without a problem. The CNC even ran faster. I am not sure what the issue with the older computer is though. It may be an almost worn out USB port where the USB from the CNC was not a real tight fit. Time will tell if using the newer PC is the answer. I sure hope it is.

Thanks to everyone for their help.