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View Full Version : Position values don't match sbp file?



blackhawk
01-23-2009, 10:00 PM
I have an upgraded PRT Alpha with Aspire. I recently ran into a problem when running a 3D finishing toolpath. I used an offset strategy in Aspire to create the toolpath. The first time that I ran the file, my part came out incorrectly. I checked the code in the editor and everything seemed correct, so I don't think the problem came from Aspire.

So,I ran my.sbp file again and watched the actual code values and compared them to the red position window as the file progressed. At line 1500, the Y was off by only .003, but then continually got worse as below:
line 2200 was .010" off
line 2700 was .022" off
line 3000 was .049" off
line 4000 was .163" off
line 5000 was .270" off
line 5450 was .169" off (starting to get better)
line 5500 was the last line of code sending the machine back to the 0,0 start point. It truly returned to the exact zero where I started. I know because I measured the position of the Y carriage to a relative point using calipers before starting the file.

I ran the file a third time and the values were getting off identically as before. Around line 5000, I hit the space bar and paused the machine. While paused, I measured my position with calipers again and it was off exactly the amount that the red position window was saying (about .300"). So, the red position box was accurately giving the position of the Y car.

Now this is where it gets weird...I resumed the cut and now the commanded positions started to match the red position window values! So, I let the file run to the end and when it went back to its 0,0 home position, the Y car went to rest past the Y zero point by .300 inches. This is about exactly what I had measured during the pause. So it seems like the pause reset the red position box to match up with the code, but the physical machine position did not change.

I ran several other different files after this with no problems. I also had never seen this problem before now. I can run the bad file over and over and it repeats exactly even if I re-toolpath it in Aspire. I have also re-toolpathed the finish cut with a raster strategy and the raster toolpath works correctly.

It just seems like the Shopbot control can't handle something about the offset toolpath. I was running about 3 IPS, so not anything super fast. Any ideas?

blackhawk
01-27-2009, 09:04 PM
Man, are you guys just going to leave me hanging? Would anyone with a PRT Alpha at least volunteer to air cut this file for me to see if their machine does the same thing? The file only takes about 6 minutes to run.

myxpykalix
01-27-2009, 09:21 PM
Brad,
I have an alpha. Send me the file and give me some directions as to what i need to be looking for or measuring and I can at least try it. No guarantees i will know what to do, nt know what it is supposed to be making. I need to know details like how big it is, ect.

beacon14
01-27-2009, 10:26 PM
I did have a similar situation once, with a file from VCarve Pro which included multiple depth passes and ramped entry into the material. Cuts were consistently shallower than programmed, and repeatably so. I never did figure out what was going on but I changed the ramp settings (I think I made the ramp longer, so less steep) and the resulting file worked fine. There were several other files that were similar that day and only that one gave me any problems.

blackhawk
01-28-2009, 09:20 AM
Jack - I posted some pictures at this link.
http://www.talkshopbot.com/forum/messages/312/37939.html?1232468397
I will send you the file tonight with more info. Thanks.

Brad