PNCconf error

OK, back from more testing.

John, you were right, scale was a little off. I increased to 2 microsteps, and went from 5 TPI, to 25 TPI.

Tested Y and Z axis with indicator with 1" +/- travel, using cheap enco indicator. Started at 10'/min velocity and 1"/sec acceleration. Went up to 100"/min and as much as 5"/sec. No missed steps. Indicator was on 0, at the end of every cycle.

Went back to the X axis, and even at 10"/min velocity and 1"/sec acceleration it was missing lots of steps in the middle of the table. I think this is indicating a problem with the amount of torque needed to turn the X ballscrew???

Anything else I should check???

If not I guess I'll be pulling the X stepper and trying to reduce the "drag", by backing off of the loading on the thrust washer/bearing on that ballscrew.

BTW, I tried clicking on the Run button on the X axis, and it worked even though it didn't show being "active", when the jog buttons were active. The Run button showed being active on the Y and Z axes.

thanks,
Ken

Four wires, plus ground (5).

I can shut everything down, and pull the connectors on X and Y, and reverse them. Try a quick test.

thanks,
Ken

OK, quick test is over.

Reversed wiring on X & Y axis steppers. Same X axis (now Y in test/tune) is missing steps. Y axis is still working fine.

Next test is to switch steppers, I guess. Make sure the stepper isn't weak??? Both X,Y steppers rated 1600in/oz. Z rated 1200in/oz.

Then, I'll back off on the thrust washer/bearing. Hopefully without increasing backlash.

thanks,
Ken

Next test.

I pulled both stepper motors and moved the stepper motor that was missing steps on X axis to Y axis. Working perfectly, no problems.

Decided to go ahead and back off the thrust washer/bearing on X axis. Heated nut to loosen thread lock, completely removed the nut and thrush washer. X axis was still difficult to move. Never was this difficult before installing stepper, unless I overtightened the thrust washer. I screwed the ball screw in about an inch, so that it was no longer contacting the table. When I bumped the table it slid no problems, ways are lubricated, and table locks are off.

The ball screws were installed when I bought this mill on both X and Y axis. However, they were not mechanically fastened to the table. Seems like once the ball screw was moved away from contact with table it moves much easier. I've got to figure out how to fasten the table to the ball screw, without binding the ball screw???

thanks,
Ken

andypugh wrote:

customcutter wrote:

The ball screws were installed when I bought this mill on both X and Y axis. However, they were not mechanically fastened to the table. Seems like once the ball screw was moved away from contact with table it moves much easier. I've got to figure out how to fasten the table to the ball screw, without binding the ball screw???

A picture is worth a thousand words. Your choice

Some of us make a living as mechanical designers, and I used to, let's have a look at the situation.

Andy, I thought of taking a pic. I can't send pics on my phone to my e-mail (don't ask me why Verizon techs can't figure it out either) have to send them to someone else, and have them send it to my e-mail. Then I can finally post them.

The original design was for the collar on the ballscrew to go through the end cap and rest on the inner race of the bearing. It likes about .020 of going through the end cap. I placed a washer between the collar and the end cap. Then when I tighten the thrust washer it tightens everything up.

I pulled everything apart and noticed some very small burrs on the shoulders of the washers. I cleaned it up with some 150 and 320 grit sandpaper and polished on a hard Arkansas stone. Put a little way oil on it and everything "feels" good right now. Reassembled everything and waiting on the thread lock to set. I'll try it in the AM. If it doesn't work, I can either turn a collar to extend from the shoulder on the ball screw to the inner bearing race, or I can try to mill out the pocket that the ball screw extends through so that the collar can set directly against the inner race. I doubt that I have an end mill the correct size for that. Don't know if I can clamp the end plate in a 4 jaw on the lathe. Maybe I can figure a way to clamp it on a rotary table I bought a few months ago. Just have to indicate it in.

thanks for the assistance.
Ken

Did I say

Just did a quick check on the X axis and everything is working fine. No missed steps on the default 100"/minute, 2"/sec.

I'll check and see if I spot any backlash after I have some breakfast.

Thanks to everyone and to this site! You guys have the patience of Job.

Ken

BigJohnT wrote:

Just an observation from my previous machines but I ended up with maximum acceleration about 10 to 20 times maximum velocity (speaking in the same units). For example if my maximum velocity was 2 IPS my maximum acceleration would end up being 20 - 40 IPSS. Dunno why, just a ratio that I noticed...

John

Note PNCconf does velocity in units per MINUTE and acceleration in units per second per second.
so in Johns example

120 inches per MINUTE would be about 20-40 inches per second per second

Chris M