I still have the "jitters"

[georgew]

I still have the jitters on all my diagonal moves. Straight x and y moves no problem but the diagonal moves, x + y, you can see the carrage shudder and it leaves a "scaloped finish" to the piece. Also, the faster I go the worse it gets. I've gone to a faster computer and upgraded to the latest SB software. My machine is an older PRT, about 5 years old. I've adjusted the motor tension, tightned the runners, ect. I've thought about adding a second Y carrage motor but that's a $1000 experiment.

This happens no matter what material I am cutting, even happens on "air" cuts. The machine did not seem to do this when it was new.

Any help is appreciated.

[srwtlc]

George,

You say that your machine is about five years old, do you happen to have the direct drive motors on it? I used to have those and had the same problem. I later switched to the 3.6:1 gearbox motors/control box and things were much better.

I would be a good idea to drop the motors away from the rack and check all axis for freedom of movement, looking/feeling for any kind of binding. Check the Y car hold down bearings to be sure that they're not binding also. Take a close look at the pinion gears for excessive wear too.

Might be a good time to step up to one of the Gecko drive setups.

[Brady Watson]

#1 cause of poor edge quality ---> Worn pinions. On a 5yr old tool, you are definately due.

Take that $1000 & buy the 4G upgrade, as Scott points out. It will be the best $1000 you could spend on that machine...and it will be like having a completely new CNC.

-B

[normand]

If your machine work fine before dont bother upgrading until you find your problem. You will still have the jitters only 2 or 3 time faster.

[richards]

I agree with Normand. If the machine worked properly before and has 'suddenly' developed a case of the jitters, then something has changed that needs to be fixed. Rolling back to an earlier version of SB software will eliminate the SB software as the culprit. Temporarily connecting the old computer - if possible - will eliminate the computer as being the problem. Although I have nothing against upgrading to either the G4 or Dirk Hazeleger's AGek upgrades - in fact, I think that everyone using the pre-alpha machines would greatly benefit from the upgrade - if you have a problem that needs to be fixed, it would be better to fix it before upgrading.

[georgew]

Thanks for the informations. I undid the motors and the carrage moves in both directions very well, no problem there. The pinion gears on the motors are well worn though and that may be alot of the problem. The long rack gears on the frames do not seem to be worn very much. I am thinking that if I change the pinion gears it should help. I do have the old direct drive motors. Are the gear motors the Scott mentioned part of the Gecko upgrade, or is that just the drivers? Also can you get the Gecko upgrade from ShopBot?

After looking at those gears, I guess it's time to change those. Maybe I should be thinking about some of the other upgrades at the same time.

Thanks for the help guys.

[rcnewcomb]

George,

Let me know if you need a hand.

- Randall

[Brady Watson]

Let me reiterate what I have already said:

Step 1 - Replace pinions on at least X & Y @ $15ea. This will smooth out your once smooth tool. The rack doesn't wear an appreciable amount, the pinions do.

Step 2 (optional but money well spent) Upgrade to the 4G setup. It uses your original motors & replaces the control board & drivers with a new board & Geckos. After you have your new pinions, the microstepping drivers will provide about 2.5X the smoothness & resolution + an increase in speed.

-B