Jerky moves and lost steps

[gergistheword]

Hey Everyone,
I love my Shopbot buddy and have used it reliably for years but it has become unreliable in the past few weeks. Maybe it's related to an upgrade in control software? I'm using the latest 3.8.36.

When performing certain moves like clearing pockets, the bot will make sudden, quick, short, harsh moves that cause it to lose position.

It's best illustrated with this video I shot today.
https://drive.google.com/open?id=0B1LbWjGsd-6ZM2RhT3dGN0dEQ3c

The point at which it makes the clunky move in this file is repeated MOST times it comes to the same spot. It is expanding the offset for a pocket. I have been forced to slow the move speed WAY down to compensate. The video shows the slowed feed rate of 1.5IPS I needed to use to avoid losing steps.

I have also noticed other odd behavior like moving around corners extremely slowly resulting in burnt wood and cooked bits.

I am forced to hover and watch the machine like a hawk and it has become entirely unreliable.

Has anyone else had this same issue? Ramp settings?

Frustrated.

[Brady Watson]

Post up your VR settings.

ALt + PrtScr the VR sheet, paste into MSPaint and upload.

There is an outside chance it is doing the "v3.8 crawl", but that was supposed to be fixed in an earlier version than you are running...

-B

[Davo]

That spindle is quiet as hell compared to my router...

I wonder the total cost for me to switch over to that

[barrowj]

Davo,

It ain't cheap but so much better, no torque issues, constant power and of course as you say, so much quieter. My first bot had a Porter Cable 3 1/4hp which just screamed so when I bought the one I have now with the 3hp Colombo I can actually talk to my wife while it's cutting. You would not be disappointed.

Joe

[jerry_stanek]

You may want to look into one of the Chinese spindles like this air cooled one

http://www.ebay.com/itm/FOUR-BEARING-ER20-AIR-COOLED-SPINDLE-MOTOR-3KW-INVERTER-DRIVE-VFD-FOR-CNC-/271588716311?hash=item3f3bf2ef17


Or this water cooled one I would check to see if it would fit the same mount as your router

http://www.ebay.com/itm/2-2KW-WATER-COOLED-SPINDLE-MOTOR-ER20-VFD-INVERTER-DRIVE-80MM-DIAMETER-CNC-/252029788256?hash=item3aae256060
they give you the option of more collet sizes

[Davo]

That's cheaper than my router!

[gergistheword]

26247

Here they are, Brady.

Greg

[Brady Watson]

Somehow your first parameter got jacked...Change it (XY Move Ramp Speed) from .05 to .4

Your tool will run a little nicer if you change the following:

3D Ramp Threshold from 100 to 150
Minimum Distance to Check from .15 to .08
Slow Corner Speed from 65 to 45

If you don't want to do any of that, the 'easy button' is to just click on the Reset link at the bottom of the fill in sheet to put them back to stock. My numbers run nicer though...

-B

[gergistheword]

Thanks Brady. I just changed the settings and will aircut the part again to see the changes in action. BTW, I read your blog post on ramp values in the mean time. Great stuff and worth another link in case it helps someone else with similar trouble to understand what the settings control.

Here's the link to Brady's blog post.
http://www.shopbotblog.com/2008/03/a-ramping-the-vr-command-and-how-to-tune-your-tool-for-maximum-performance/

[gergistheword]

Works like a charm. Thanks again, Brady.

[Brady Watson]

Great! Glad you got it sorted.

-B