Raised lines left on 3d work

[brian]

I've been doing some 3d work this week.I first noticed the raised lines on a litopane,I didn't think much of it at the time until they showed up again on a raised panel with a tree carved on it.
The lines are always right next to a raised section in model usually between two raised sections.
On the lithopane I thought it might have been the programs interpretation of the picture but after showing up on work made from a DXF file I know there is a problem some where.
I am using Artcam pro 8.1 and was running a .125 ball nose at 3IPS on X,Y & 1 IPS on the Z.
Has nayone had similar problem or have any ideas what could be wrong.
I'm going to check out the Z axis this morning to see if it runs smoothly and every thing is tight.

Thanks Brian

[Brady Watson]

It's probably backlash in the Z. You might want to order up a new 20T pinion for it. In the meantime you can carefully adjust the v-roller bearings on the Z to slightly move the gear rack attached to the T-rail closer to the motor pinion. The best way I have found to check quickly is to grab the T-rail and wiggle it up and down, listening for 'ticking'. Move the z around with the keypad and try it again a few times.

The other thing are the rails. Make sure they are burr-free. You may need to wipe them down with a sctoch pad or steel wool and in some cases, sand or de-burr using a wizzer wheel with a Roloc Scotch disc. Feel all around for bumps and jagged edges & remove.

-B

[brian]

I check the Zaxis movement and found that there is a bit of an area where movement is a bit rough and is causing it to bind a bit.
I'm assuming as you stated Brady it's a rough spot or burr on the rails.
I will report back if this solves the problem.

Thanks

[Gary Campbell]

Brian..
I don't know if this applies to your machine,(ours is a PRSa) but I found that the Z bottom stop (located at the top of the Z extrusion) was overhanging the rack and binding against the pinion when using short bits. I replaced it with a socket head cap screw and all the bind is gone.
Gary

[brian]

I have a second Z axis (not mounted)and I compared the movement between the two.The one not mounted is by far smoother.I have not adjusted the bearings since I set the bot up.
Could the bearings simply be too tight causing the slightest imperfection on the rail to bind?

Brian