Dialing In a Buddy

[Forum Admin]

Reflections on motivation will be considered off topic and should go private.

[myxpykalix]

Art,
Have you tried taking a piece of wood or mdf and making a long cut in the X and then in the Y to see if the consistency of depth is the same in both directions all along this path? That might rule out whether or not your table might be out of plumb.
Have you called tech support, they would be the best source of help on this.

[acb]

Didn't do it precisely that way, Jack, but I started with a fresh surfacing run on my whole spoilboard. Then I made my depth measurements relative to a shallow "surfacing" pocket on top of the test material to level out any material variations. That's why I'm fairly confident I was measuring actual cutter Z-movement.

(As mentioned above, I was less rigorous in the X and Y, as I measured those pretty much as an afterthought... it was my depths consistently coming up short that had me really curious.)

Anyway, being off half a percent with the generic unit values didn't surprise me all that much. What I was curious about was how much variation other folks had observed, as an informal sample of variance over a larger population of machines... and whether folks had dialed-in their global unit values without (or with) any non-obvious side effects.

[ljdm]

I only noticed my x and y were off when I did some full sheet projects for the first time. 1/16" over 96" wasn't noticeable on smaller jobs like 10" x 12" plaques, etc. Had me scratching my head for days until I talked to SB support, when they had me try to adjust the unit values. Still don't know why or what was off to need to adjust the value, just know it fixed it.
Hate to get you going again, but, if the z is consistently off the same percentage, try adjusting the z value. Now don't go beserk at the suggestion, mic the actual z travel vs the SB reported distance, if its off by a certain pct, try adjusting the z value accordingly. There are no side effects that I know of, except that it might cause more accurate cuts.

[acb]

Well, that was more or less my original question, Lou... whether it was better to adjust globally using the unit values or cut-by-cut. Because I did compare the measured-versus-SB values; that's where I started. Was I unclear about that?

Anyway, now I'm confused: if SB recommended you change your unit value and you did and it worked for you, why do you recommend I do it the other way? (Not going "berserk," just asking. Hope that's ok.)

[ljdm]

Not sure what you mean by "the other way". I thought I said to change the values. My recommendation is - if the actual travel of the z,x,or y is off by a certain percentage, .1 at 1',.4 at 4', .8 at 8', adjust unit value accordingly. Best bet,if unsure about changing values, call support, tell them how much it is off at certain distances, they can figure the calculations for you. Measure at longest distances of travel possible, for best accuracy in measurement of error. As far as adjustin globally or cut by cut, global is best. If the unit value is correct at 1" travel, it will be correct at 96" travel. Email your phone number if a call will help.

[acb]

OK, so when you said z-value you meant the unit value. My mistake, I though you were saying to adjust the cut. Got it now.

[cubicdissection]

I just have to say I'm amazed more and more by this forum every time I visit it. This guy comes in with an attitude and you continue to help.

Shopbot forum....you make me want to be a better man *sniff*

[kevin_morin]

Art, when we began testing a new Buddie48 PRS for repeatability we used a dial indicator inverted under a centering point bit chucked in the spindle.

This confirmed that we could develop a few thou hysteresis if we used an XY move then Z up and down followed by an XY return and a Z up down. After a few cycled moves we found about 0.002-0.004" hysteresis in repeatability of the Z axis movements.

I thought that was just the motors and drivers loosing a fraction of a step of resolution over repeated operations?

What did you do, if you did finally resolve this matter, to solve your problem/question that lead to this thread?

cheers,
Kevin Morin