Shopbot not following Tollpath in one direction

[ffaelan]

I'm a new shopbot user with no formal training but have leapt in heads first. The issue I'm having seems so simple and yet we're scratching our heads here. laying out a simple rectangle frame with rectangles cut out in the middle.

two separate files.

One is 3/4" ply with two passes.
and
one is 1 1/8" ply with three passes

on the second pass of each and the third pass on the thicker material the whole toolpath shifts 1/8" in the "x" axis toward the home position.

anyone have any ideas, because we're stumped. though that's not saying much for only having about 40 hours on this machine.

[ken_rychlik]

Sounds like it is loosing a step. You may try a slower move speed. What is the move speed you are running now?

Kenneth

[ffaelan]

4.5 @ 8000 rpm
ffaelan

[erik_f]

Standard or Alpha? 4.5" a second is pretty fast for .375" if it is a standard. I have cut that fast with my standard however. Have you tested your communication speed for the USB connection? If you are running at a higher speed you may not be loosing steps, but loosing communication with your bot. Try slowing down and see if that helps...that will help with missed steps or slow connection speed. Try running the file at 1.5".

[ffaelan]

its a standard
I'm running multiple passes and just using the speed suggestions i got through the chip load calculator and my own math. I'll try to test my usb speed.
thanks
ff

[Brady Watson]

For the heck of it, try running 15,000 RPM and 2.5 IPS. See how this works for you.

Chipload calculators are OK and really only needed when you are cutting exotic materials. Let the material and router 'tell' you where they want to be. If those speeds you posted are correct, you are seriously overloading the spindle/router. It would be like you eating a footlong sandwich in a single bite...and then having 10 more right behind it to eat in a single bite.

Keep it simple. If you are getting burning or melting, reduce RPM or speed up move speed. If you are getting lost steps, poor cut quality (attributed to high chipload), then increase RPM or slow down move speed.

-B

[mjindustry]

How do you check usb speed?

[ron_moorehead]

Hi Jason,

In the control software go to Utilities on the top menu, then select Diagnostic Tools and a new window should open, select the SpeedTest.exe file.

Hope this helps.

[ffaelan]

I ran the speed test and got a 55% average. On a support suggestion I tried running through an external USB hub, but it made no change at all.

[Brady Watson]

OK...looks like there are 2 separate issues you need to contend with:

1) You said you were running 4.5 IPS @ 8000 RPM. Unless you are cutting 2# styrofoam, these are not appropriate speeds.

2) Be sure that you are running the latest control software for your tool AND that you installed the firmware from the UI command in SB3. Also, make sure that your USB cable is 12 feet or less in length. Then plug in the 2.0 hub and plug the USB from the Bot into that. Then re-run the speed test.

-B

[ffaelan]

Hey Brady
So I updated my firmware and plugged in my hub. I don't think its a 2.0 hub is that totally necessary? The shop computer that this runs on is a 3Ghz processor with 2Gb of ram. What are the recommended specs for a shopbot?

[Brady Watson]

The 2.0 hub opens up an enhanced USB port on your computer that is typically not available on a standard 2.0 USB port. It increases bandwidth and speed on most computers. If you are not getting at least 80% efficiency, I would recommend installing a PCI USB card (regardless of whether your machine has a 2.0 port on it & ALWAYS if it is a Dell, which in my experience have problematic USB ports) and then plug a USB 2.0 hub into that.

What is your transmission efficiency percentage now that you have upgraded the control software & firmware? Have you adjusted your cutting speeds & are you getting better results?

-B