zero axis is acting erradic

[outcaststudios]

PRS 48x96, 2hp spindle running shopbot 3.0 on windows machine with all security features disabled.

when i zero out the Z axis it raises itself to 1.00 from the surface.

if i jog the gantry to another position changing all three axis. the gantry will return the Y and X axis to zero just fine but teh Z axis will stay at whatever height i jogged it to.

if i begin a cut it will plunge about an 1 3/4 too deep.


i started with a 20 inch X20 inch X 3" (in the z axis) material

the program previews fine in vcarve.

when it begins to cut instead of the first cut being about a 1/2 inch deep like in the preview it will go 2 inched down on the first cut.

i stop the program. i re-zero the z zero plate to teh top of the 3" thick material again. i run it again and bam. it acts liek teh zero is actually much lower than what i just set.

Gap is set to above model, the thickness of the model is 2.75 inches.

the thickness of the material is measured with a gauge to 3.03

the bit is a 1/2 inch tapered (2º) to a .127 round tip it extends 2.85 inches from the collet to the tip.

the first cut is supposed to be about 1 inch deep.when i run it on the shopbot the first cut is 2 inches deep and its not cutting the rough toolpath at all like the preview in vcarve.

im about to run a screw into teh center of my brain. i have a job and this material is really really expensive and this is the second attempt.

i reinstalled 3.0 , halp? thanks.

[outcaststudios]

also:

imported .stl into vcarve.
used roughing toolpath, previewed accurately.
used finish toolpath,previewed fine.

exported to shop bot and the dimensions are accurate as far as the diameter,but the depth of all the cuts are wrong. its cutting right through and away material that definitely isnt being removed in the preview cuts. chose gap above and below model ,and had same result both ways.

[steve_g]

In VCP job setup, where is the material Z Zero set to? If set to the deck height when you are expecting top of material, bad things can happen!
SG

http://www.talkshopbot.com/forum/attachment.php?attachmentid=29973&stc=1

[outcaststudios]

steve,
thank you for the reply! its set as shown. i zero the the Z axis form the top of the material. in this case the material is 3.03 thick... i examined the two failed cuts and there seem to be an extra 2 inches above the actual model that is being cut. in other words there it seems to believe that the zero is located two inches below what it actually is. in teh past ive had bits slip out of the collet and so i made sure that the bit is exatly 2.85 from the tip to the collets face.still set the same no bit movement! any other ideas?

[jerry_stanek]

Did you zero with the plate on the material? If you zeroed on the bed you will get that

[scottp55]

Not sure what you have for Z, but you've already used almost 6".
Is it possible you topped out, and lost position?
Check your "Home" position in Vectric file, and possibly the VC "Safe Z Pull-Up" to make sure neither is affecting your Z-Zero routine or the machine going to "Home" position once .crv starts.
I have a Z-prox switch, and I've had Z-Zero routine and cutting file come to a abrupt halt with a "stop hit" more than once.
It would have done what you're encountering without the prox hit.

[myxpykalix]

A couple things to check. Do a JH (jog home) and see what happens from anywhere on the table.
Then start at the same place and do a MH (move home) and see what happens. On mine if i do a JH, if the bit is say 1" above material surface it lowers to 0 above surface and jogs home. If i do MH the bit stays at it's height and moves home. Don't know why, but rather then "fix it if it ain't broke" i just deal with it.

I think you need to check your "start position" like Scott shows in his picture. I think what is happening is your bit is "topping out" and you just don't see it or hear it.

Leave your router/spindle off, Take a small scrap the same height as your material. Zzero to that. Move the scrap piece away. listen to see if you are topping out. Run the file and check your bit heights.

[outcaststudios]

guys,
thanks! i am investigating now. i turned the machine on and zeroed to the 3" thick piece of material. as expected the bit rested exactly one inch above. i then ran the gantry 30 inches back and 30 inches over in the x and y axis ,and i rant eh z axis down to the actual table height (4 inches below its safe Z height) i used M3 and returned to home positions for all. the x and y came back fine the z came back to 1.76 inches above the zeroing point of 3 inches. so it read 1.76 on teh z axis int eh control. then i moved the gantry again using the controller to 30 inches away and set the z height to all the way up. i returned teh axis using the menu function of returning them to safe home axis and the x and y returned fine to 0.00 but teh z height whiel it read 1.00 on teh controller was actually .28 above the material that it was zeroed to.

[outcaststudios]

also when the router pulls itself up to the highest point of its travel before it begins a cut, it does shudder a bit,so that tells me something is off.

[outcaststudios]

Not sure what you have for Z, but you've already used almost 6".
Is it possible you topped out, and lost position?
Check your "Home" position in Vectric file, and possibly the VC "Safe Z Pull-Up" to make sure neither is affecting your Z-Zero routine or the machine going to "Home" position once .crv starts.
I have a Z-prox switch, and I've had Z-Zero routine and cutting file come to a abrupt halt with a "stop hit" more than once.
It would have done what you're encountering without the prox hit.

so i checked the home position in vectric and it was set for 5.5 inches. i reset it to 3.25 inches. could this have been the issue? was it trying to pull up to 5.5 plus the 3 inches of material thickness and physically ran out of space which threw off the z height readings?

[scottp55]

If you're Zeroing from top of material with that bit extended the amount you said, it was trying to go up 5.88" PLUS 5.5"
That "shuddering" may have been a hard stop(on a Desktop it's LOUD)
If zeroing from top of material, and no clamps are in the way, .5" Safe Z-1 and Home position should be more than enough.
If doing that, then also set CV(C utter V alues) for .5" as well.
Add up total Spoilboard thickness, material thickness, cutter extension, and Safe Z height and make sure it doesn't exceed the Z specs for your machine.
Oh Yeah....that will throw it WAY off.

[outcaststudios]

yep that was it, cut beautifully after i changed the safe z height! thanks again Scott!
-gregor

[scottp55]

GLAD Gregor :)
Hard for me to forget my VERY first cut:)
My Z limit switch connection was non functioning, and Vectric default Safe-Z was 2", and I only had 4" of Z with a 3" downcut..... so I "topped out".
The bit took off to CHINA, and only my finger on the Spacebar saved me from a permanent aluminum deck Oopsie:)

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