[mrlttlman]

don't know if this is the right form or not but when I am engraving acrylic or wood while it is doing a pocket of a large area the z axis seem do dip down a few thousandths for a few lines . so what is happening on a big pocket is I end up with a deeper line in some areas.

any help would be appreciated

z axis has a 5 start acme screw with antibacklash nut . stepper motor . no play or flex on the slides.

Thanks again
William

[tony978]

don't know if this is the right form or not but when I am engraving acrylic or wood while it is doing a pocket of a large area the z axis seem do dip down a few thousandths for a few lines . so what is happening on a big pocket is I end up with a deeper line in some areas.

any help would be appreciated

z axis has a 5 start acme screw with antibacklash nut . stepper motor . no play or flex on the slides.

Thanks again
William

hi William
you might want to try with the acrylic in use double sided tape to hold it around ware the pocket is and look at your g-code to see if it is a programming problem

-Tony

[mrlttlman]

Thanks Tony,

Its all held down by clamps and vacuum . went through g code all is good. its not repetitive it does it in different spots. I have tried different feedrates and it comes out the same . it also does it in 3d as well .

[tony978]

have you looked into the spindle at all ?

[mrlttlman]

What would I b looking for. Everything is tight on the spindle no movement from the bearings.

[tony978]

it sounds like a power problem wile your running . maybe a overloaded circuit or a high current start load on a device . that might cause the spindle to slow and deflect/ dig in to the parts .

[mrlttlman]

The router spindle is hooked up to a super pid . All electronics are hooked up to a dedicated circuit. Dust collection on another circuit. Maybe it could b noise interference. Found out that the cables for the steppers are unshielded. Could that be the cause? The spindle never drops below 17200 while running. I sat and watched it.

[tony978]

Are you loosing steps ? After the run if you home the machine is it off more then .005"?

[mrlttlman]

it doesn't appear to lose steps. what is happening is while it is pocketing out an area there will be a slight dip in the workpiece about a 1/16 wide while not moving the z axis at all. when I doing a large letter today where it starts comes out beautiful when the z moves to go the other side it looks like it raises a few thousandths then for no reasons dips while doing the pocket and then goes back to normal I would say. The only play I can find in the z axis is on the stepper motor on the shaft but that is normal for the motor I could put so shims in it to get rid of that but I don't think that's it.

[tony978]

Try a run with a small depth of cut and if ya get it still then shin and check for backlash . You could use the comp in the controller for the backlash and see if that fixes it .

[mrlttlman]

I am going to try another pocket . My cuts are only .0137 deep I will slow speed Down to 60 ipm and just to try take off backlash comp since its been on the whole time. Will post when done.

[tony978]

Try at 30 ipm then go up if you get good results

[mrlttlman]

OK will do

[mrlttlman]

OK so I did the test at 32ipm and it can out about the same. While it was doing the last bit of pocketing I increased the feed rate and it actually started to raise up enough about a piece of paper thick I would say. I am going to shim the stepper motor to see if that helps

[ropanach]

Have you checked to see if the vaccum table is plug in some areas, where the spindel is not dipping but the table may be higher?

[mrlttlman]

vacuum table is not plugged and everything is clamped down so nothing is higher or moving. I attached a photo to show what is going on and what I mean. you will notice by the end of the drill bit the dip in the acrylic. still cant figure it out

[ropanach]

It apears that the spindle is not raseing up to your set point, the spindle may be sticking. I use a very light 5 weight oil on my spindle, so I don't have that problem, I cut abs plastic and wood and brass, hope this helps.

[mrlttlman]

So far I shimmed up the stepper motor and applied the lubricant to the screw and ran another sample same thing. I pulled the router spindle and found out on the porter cable 7519 there was a little up and down play on the shaft. is this normal or should it be tight. I think it should be tight.

[tony978]

i would try putting an indicator on the table up to a metal dowel in the router and push up . with the same setup wright a repeating drill cycle with the router off and see if it is coming back to the same z height .

[mrlttlman]

I did that before I tore the spindle apart . I however didn't push up on it and ran program for 10 minutes and it came back dead on. I do believe its the spindle because it keeps happening in various places.