Controller losing location on 3d cut files

[Dwild14]

Hi

I am trying to cut some 3d finish parts and I am losing accurate location when trying to cut an offset toolpath or a raster toolpath on any angle that is not 90 or 0. I am running fast (8ips on XY and 2.5 on X). Am I just pushing the controller too fast and either the motors (stepper) can't handle that speed or would this indicate that something is malfunctioning. It seemed to lose accurate location either in X or Y. Happened multiple times. When cutting on a 90 degree raster it cuts fine.

Thanks

[Gary Campbell]

Which machine (PRT or PRS) model (Standard or alpha) and controller version do you have?

[Dwild14]

Sorry. Is the Standard buddy. PRS.

[Gary Campbell]

Yes. You are pushing it too fast. Cut your feedrates in half, verify accurate motion and cut quality, then increase in increments til quality falls off. You will also do better, and possibly even faster with your XY feedrates matching or closer to that of what the Z can manage.

[cowboy1296]

I was running my feet rate at 2.6 inches per second and noticed that i was burning my bits, so have stepped up my speed, but 8 seems way out there
.

[Dwild14]

Ok. Out of curiousity, would you anticipate that an Alpha with servos would be able to handle those speeds better?
Thanks

[Gary Campbell]

The ShopBot alpha models use steppers with encoders, not servos. They are many times more capable than the standard models. That said, and this depends on the actual type of 3D file and the actual length of the vectors, they may not always cut a given 3D file faster. In reality 3D cutting is most dependent on the file type and the ability of the Z to react. No matter what speeds you set your XY at, they will always wait for the Z.

Take this simple example of a Times New Roman Capital "A" using a VCarve toolpath. With feedrates set at 1 ips XY and 1 ips Z it will cut in 40% of the time that it does when feeds are set at 2.5 ips XY and .5 ips Z. Slowing the XY down and matching them to the Z decreases cut time. The same applies to 3D files.