Motor fault

[brian]

while running a program I get the motor fault and have to reset the control box.I know that none of the stops are being hit but it keeps happening forcing me to reset,rezero the bit and edit the file to where it quit.
Today the program quit twice,just after 100,000 lines of code.What would cause this to happen,lack of RAM etc.
I have the bot well grounded so I don't think it could be static

[Brady Watson]

Sounds like a static problem to me. Do you have a bare copper wire running through your DC hose? It should go from the dust foot thru the hose and connect to the metal frame of the DC. Static can trigger an input, like input #3 (which is the input for your proximity switches)

-B

[brian]

Brady
I was playing around with the z axis today(power off)and I noticed a rough feeling in the linear movement.It's down towards the farthest the z axis will go,right about were it was showing a motor fault.A few months ago I put a heavier spring on the z axis to counterbalance the spindle.I removed it and put the original lighter spring back.I still notice the section were there is some impedence.I investigated farther and still cannot tell what is causing this problem.
Could the bearing be too tight??
I can't see any physical reason why this is happenning.I cleaned the gears as best I could without dismantling the axis.

Any guesses?

Thanks Brian

[rnels]

Brian,

I was having the same issue after putting in a 12 inch Z. Was getting motor faults at the lower Z. I modified the springs by adding an eye bolt and spacer. Lowered the spring until there wasn't as much tension on the lower Z. That took care of my problem. Need to raise it back up for indexer turnings as the higher Z doesn't have enough spring.

Good luck!

Randy

[Brady Watson]

"Any guesses?"

Yes...your spings are either too light or too strong and the motor doesn't have enough power to either A) Lift the Z quickly without stalling (spring too light) or B) move the Z all the way down to the bottom, overcoming the force of the springs (springs too strong)

-B

[brian]

Thanks

Brian

[dowty]

Brady,

Thanks for the information I recently encountered a similar problem. I am running an older PR with a R&P Z axis doing quite accurate on cutting files with limited or no z moves, but seemed to run into a heap of z loss when I recently tried to cut a 3d circle.
This circle has heaps of z comes. Just quickly added an extra spring and noticed a difference. Not accurate yet. . . But this brings me to my question on how everyone deals with the loss of spring tension? Do you shorten them by hand, go out and purchase new ones? Just wondering the best advice before I take it upon myself?

[Brady Watson]

David,
I never had a problem with spring tension on my PRT or Alpha using the hardware that ShopBot provided with the tool. I am wondering how people are having issues with spring tension on their tools using the factory offerings. The ONLY purpose of the springs is to counterbalance the weight of the spindle/router to equalize the force that the stepper needs to apply to move the tool in a + or - direction. The Z axis should use the same amount of force going up as it does going down, without considering the force needed to plunge into the material. If there is excessive force required to overcome a spring that is too strong at the bottom most area of the stroke, then there is that much less torque available to plunge into material before the stepper stalls. Conversely, if you try to raise the Z axis too quickly and there isn't sufficient spring tension to assist it, the stepper will stall. The earlier PR & PRTs used a constant force flat spring (coil) that worked well when new, but over time they lose their spring. You can replace these OR buy the appropriate coil springs & hardware (spring yoke, bolts etc) directly from ShopBot and convert it. It is important to get the right springs on there...

-B

[sam_harbold]

I have an older PR machine and the Z axis is very inconsistant. My Z uses a ballscrew and I have unplugged the motor and can run the router from top to bottom with just my thumb and index finger. The full range is smooth and no resistance but the Z is still not accurate. I was told that I was running the Z too fast .50 jog and .25 move. I have changes to .20 jog and .12 move but no difference. I can Zero the Z axis then move the z to zero and it can be out as much as + or - .06. The springs are the original springs shipped with the unit. Will increasing or decreasing the tension inprove the accuracy of the Z?

Sam

[Brady Watson]

Sam,
What direction is the Z out...Does it walk down into the material, or does it park higher up than original Zzero setting?

The PR with that little Z motor is limited...and you have to make provisions for this since it lacks the torque to plunge into the material and keep it's position. It would be worth your while to look into a replacement motor for the Z axis that has more torque (less than 2A).

-B

[sam_harbold]

Brady

The amount and direction that the Z is out is inconsistant. Sometime after zeroing the Z then moving to 0.00 it will plunge into the work piece and at other times it will stop before touching the work piece. That is why I am confused as to increase or decrease the tension on the springs. Also I have upgraded to the prt control box about 2 years ago when the upgrade was offered. This is just for information as the problem existed before the upgrade.

Sam

[dowty]

Brady,
Just a quick question . . . I still need to get some more information on my part, but what I was wondering was. . . since I have an old PR model that I purchased used and then purchased an R&P Z. Might my problem lie in the control box not delivering enough power to drive to new Z versus the ball and screw Z that it shipped with?

[Brady Watson]

If you are using a ShopBot PRT type stepper on it (like XY uses), I don't see it being a problem. A geared stepper is best for torque and resolution. As long as the stepper's amp rating is less than 2A, you should be fine.

-B