Same freshman, new problems

[sevendale]

First of all the help on this forum is inspirational. Ask me about drawing in Autocad. My question has to do with my Z '0' setting: I set Z at the top of my part, ran a few parts with SAFE Z set at .5. After a few ups and downs the bit was coasting way above the table so I sent it home where it measured 2 1/2" above the part! The screen said 1", so how did I add 3 half inches? And why did it go to 1" when I specified 1/2"? Anyone deal with this before?
Thanks

[signsbyjay]

Rob,

Sounds like you are losing steps, how well is your machine grounded?

I speak from experience, thought I had it grounded, but I was wrong, you can not over ground.

Jay

[dana_swift]

Rob- Is your SB3 set for "relative"? That sounds like what is going on.. set it to "absolute". See if the problem goes away-

D

[seana]

Rob check you unit values
I think you said that you have an older prt that was a pr before upgrade.
Do you have ball screw on the z instead of rack and pinion?

Sean

[sevendale]

OK, Jay, I'll doublecheck that wire and add one if I'm not sure: more is gooder. Dana, I believe I'm working in absolute, It shows that on the screen, but I'll try to learn how to change that (my training consisted of there's the gas, there's the brake, take er for a spin). Sean, it's an older pr that just stayed that way working from version 2.38 and partwizard version 1.010. Ball screw yes, and offline from Paul I got suggestions about measuring all my movements to determine my accuracies, which I will now do.
Lastly, You folks are a great help! Thanks!

[sevendale]

So I cut off the grounding wire and redid it cleanly. I doublechecked units: absolutely and measured parts from cuts: as drawn. I even bypassed partwizard and converted a dxf to sbp and set my &Zup to .25 and my z depth for -.1875.
It cut the first few parts, but then it gradually drifted up til it just coasted over the table not cutting anything.......losing steps in Z? Help!?

[Gary Campbell]

Rob...
Any chance the bit is loose?
Router/Spindle?
Collet size? Mic bit?
Z plunge speed?
Gary

[bob_dodd]

your z speed should be .5 or .75" per sec. any faster it'll loose steps
check the set screws in the coulping between the stepper motor & screw , make sure coulping is not moving on shaft
remove motor make sure screw moves smoothly

[sevendale]

Gary & Bob, Excellent reply thanks. I will ask you how to set Z speed in a bit, but first: it's an ol strut built machine so I ran Z up and down and watched. Yup; it's losing steps badly. X and Y seem fine so far but back to Z. I took it apart. The rails are strut, and scarred from years of misuse; the bottom wheels are sticky and drag. I'm going to drill the verticals so I can move the left to the right and right to left exposing fresh corners for the wheels to ride on. Then I'll try to find fresh wheels. The motor is smooth as is the screw, unfortunately I unscrewed the whatayacallit that the screw pushes and a bunch of little steel balls fell out in my hand. I caught them all and saved them then carved out a lot of gunk from the whatayacallit and cleaned it. So if y'all ain't tired of me yet could you take turns with these questions?:
1) The 2 letter commands to set Z speed are?
2) Can I pour those balls back in there and if so what kind of lubricant do I need?
3) Who has those ~1" wheels?
4) Is there an actual manual for this ol thing?

By the way, Gary: portercable 1/2" and 1/4" collets tightened and stable, seems to be the Z rails and wheels. And last this on screen:
MOVE Z = 2 [0.20] JOG Z = 0.25 [0.25]
5) Does that mean my Z is running too fast?
Wo that's a lot! Any help helps. Thanks, I'm off to find parts, back soon.........

[sevendale]

OK now I'm really going, but I tried to set my Z speed...... M S 2,.5 that's what I typed: it worked! XY now (I hope) will move at 2 and Z will move at .5 not 2 where it was before. I can't test it yet, but it shows those parameters on screen. This is fun, sortof.