Loss of position with deeper cuts

[gamisano]

So, since I've owned my PRT 49x96 I have been very carefull not to cut too deep on any 1 pass. The reason is, that if I cut too deep, even 1/8", it starts cutting, but quickly gets knocked off course. I finally just want to fix it so that I no longer have to cut 3/4" materials in 7 or 8 passes. Any advice/suggestions? Thanks for any help.

Guido

[Brady Watson]

Guido,
I can pretty much gaurantee that you have a weak/dead X motor driver. Try dropping both X motors to disengage from the racks, and see if both motors spin. If they do, engage one motor at a time and tell it to move a certain distance, like 12"...all the while helping the side that has the motor hanging to keep the gantry from racking. You should be able to quickly see which motor is not getting full output.

Once you've determined which motor is running weak, you can turn off the control box (always when you do this) and unplug the weak motor cable, and plug into the 5th driver labelled 'A'. Then in the software, type in the VI command & assign the 4th channel to 'X'. This should do it for you.

When you get some down time, send the board back to ShopBot to be repaired, or it would be an ideal time to upgrade to a 4G board.

-B

[gamisano]

Thanks a lot, Brady. I appreciate the input. I'll give it a try this weekend.

Guido

[gamisano]

Brady,

Thanks for the insight. I tested the x motors, and they were both working strongly. Then I decided to check the Y motor, and found that when I held it back with my hands, it would skip, or loose position. After I did that, the motor would no longer turn, it just made a grinding noise. I released the turnbuckle and disengaged the pinion from the rack, and it still wouldn't spin the pinion...same noise. Next I moved the Y cable to the A driver, and it worked. My first cut went .20 which would've made my machine loose position before. I'm going to try cutting deeper next time. I'll let you know how it goes...so far so good though! Thanks again!

PS- I'm assuming that the Y driver is dust at this point dust. Is it bad to run the Y off the A driver? Should I, do I need to upgrade to the 4g setup? IS it worth it?

Guido

[Brady Watson]

Guido,
There is absolutely no problem running the Y on the A channel. The only caveat being that you no longer have a spare driver.

The 4G is well worth the upgrade price. It will take away that 'deisel' sound and give you 2.5X the resolution of your current setup with smooth motion. You will also get a speed boost of 1.5 to 2.5X what you are doing now (about 6IPS+ cut speed) and 8 to 14 IPS jog speeds. It's also fairly bulletproof in the sense that it is tough to blow out a driver. They have a lot of protection built into them.

-B