Slop in 7.2:1 upgrade motors...

[harryball]

I just can't see how this can be normal...

I noticed, with the power on and everything fully engaged, there is a slight click click when I pull back and forth on the Y axis. The gantry actually moves, it sounds and feels like backlash in the gear box. I've checked and the pinion (which is practically new) is not moving in the teeth but actually turning just slightly.

Not sure what to do or check. When I get the second Z installed the load is going to be even higher on this motor.

Advice on what to check, inspect, investigate?

/RB

[stevem]

The gearbox has backlash, just like the regular gearboxes. These are not "zero backlash" gearboxes. You will probably get .010" to .015" movement of the axis with the steppers holding position.

[elcruisr]

I have the same motor/gearbox combo and have nothing like what you are describing. Are you sure the lock screw is fully engaged on the shaft? Almost sounds like a loose pinion gear to me.

[harryball]

I thought the same thing, but it IS backlash in the transmission. You can place a screwdriver on the transmission and put your ear on the screwdriver handle (old mechanics trick for listening to engines) and when you push/pull the gantry the clicking is from inside the transmission. I can also move the X axis motors but no where near as much.

I'm going to drop the motor and directly check the backlash. I suppose there is nothing I can do about it? .015 seems small but when I'm cutting letters .25" high on these little plaques that's 6% of the letter height. It might explain why nothing I can do will eliminate the chatter I'm getting on these small parts.


3969

/RB

[ljdm]

There is definitely backlash in the gearbox. I don't know exact amount, but there is slight movement each way. Guess this is normal.

[cnc_works]

I think that .015 is excessive, but I definitely have 4 or 5 thou play in my PRT gearboxes.

I wonder if that play has anything to do with the edge chatter that I can minimize, but never get rid of. It is at its worst at 45deg to the axis where the steppers hand off to each other in an arc or a circle.

Donn

[harryball]

To clarify the photo above, the cut is along the X axis while the Y Axis is holding position. It seems that the Y axis is moving (chattering) while the X axis is working down the table.

/RB

[gabepari]

RB- That could be the material moving. Next time your cutting those, put your hand on the material, as close as you feel comfortable to the cutter, see if you can feel the material vibrating.

Gabe

[zorlack]

Just out of curiosity, what kind of material is that?

[harryball]

It is ABS plastic.

After I pull the motor and check it if I don't find anything that seems "extreme" I will use some screws to secure a small peice and try again. I'll have to slow the cut down and check things closely for any movement.

/RB