Positioning Rhino model into Shopbot

[blair_clowdis]

I seem to be having an exceptional amount of trouble positioning a Rhino 3D model on my Shopbot. The relationship of the x,y, model from "0" in Rhino has no apparent relationship to the "0" on the shopbot. I can set the "Z" OK with out any problems and the "X" axis seems to be fine. I have the "Y" axis offset about 2 inches from the Rhino "0" point but the shopbot wants to start on the edge of the part instead of the offset amount. Anybody have any ideas?
Thanks,
Blair

[mrdovey]

Blair...

The goal is to have the machine origin coincide with the model origin.

The easiest way to achieve this is to zero the 'Bot to a known reference point on the workpiece (and for rectangular workpieces, the easiest reference point is a corner).

Once that has been done, there are two options:

(1) Use the VA command to relocate the machine origin to the model origin; or

(2) Move the spindle to the intended model zero and use either Z2 or Z3 (as appropriate) to relocate the machine origin to coincide with the model origin.

...Morris

[mrdovey]

A further note about this business of accurately zeroing x- and y-axis to a corner of the workpiece...

At http://www.iedu.com/DeSoto/SuperZero I have a couple of photos of a device I came up with to zero all three axes quickly and accurately to a corner of the workpiece. If you follow the "Details" link at the bottom of that web page, you can find info about use and options that software can provide.

[cnc_works]

Morris, not to hijaak this thread too blatantly, but have you written any code so your device would work with Mach?

Donn

[mrdovey]

Donn...

Help me out, please - what would be different? If you're talking about a ShopBot controller running V2 or V3 controller software, nothing changes.

If you're talking about a "foreign" controller running G/M code, then the answer is a tentative "yes".

I say tentative because 'yea' or 'nay' depends on how that controller/control software deals with probe and/or limit switch activation.

With those same cautions, I've also written a bit of code that might permit a modified version to run on CNC mills/machining centers.

If we're not talking about ShopBot application, though, we should probably move further conversation off the forum.

Harold...

No reticules yet - there's been too much else happening around here. The reticule is just a circular disk of thinner than 0.1" - and the easy way to ensure accuracy to 0.001" is to clamp the block upside down and use the 'Bot to both find the center and scribe/cut the crosshair.

The accuracy of the current device, and the roundness of the hole is good to better than +/-0.001 (I'm told, but have no way to verify, to better than +/-0.0002")

Please someone jump in with more info for Blair!


...Morris

[blair_clowdis]

Morris,
Thanks a bunch. What I'm doing now is moving the Shopbot to a "0" point on the workpiece and "0" the shopbot there. Then I offset the X and Y axis on the Shopbot to try to co-ordinate them with the "0" position of the model in Rhino and "0" again, basically your #2 option above. The X axis seems to work just fine and offset the required amount, but the Y axis always wants to come back to the edge of the part and not go to where it was programmed to be. In other words, if I have the Y "0" offset 1 inch off the edge of the workpiece, the machine will start cutting the model at the Y "0" point instead of moving the 1 inch and then start cutting.

[blair_clowdis]

I think what I'll try doing is moving the model into another quadrant of the Rhino layout window to reverse the Y position locations and see if that changes anything (go from positive numbers to negative numbers). But for now, I'm going to take my wife to the beach and enjoy New Years for a couple of days and worry about it when I get back!!

[mrdovey]

Blair...

After you get back from the beach, I'd be interested in hearing the command sequences you're using from the point where you position the spindle over your workpiece.

Ice and snow are the rule here - I don't want to hear any of this stuff about going to the beach. ;-)

...Morris

[blair_clowdis]

OK, break's over, back on your heads! Morris, just to clarify a little more. I am cutting (or trying to) gunstocks on my shopbot. I am making a wooden pattern and digitizing that into Rhino. Then I surface the points into the gunstock pattern. I have modeled the barrels and actions that I will be using and stored them into Rhino also. I actually take a long solid model and add the action/barrel model to that and then do a Boolean difference to get a negative of the barrelled action. When cutting I put the blank into the fixture and cut the stock pattern into both sides by using an indexer that is part of the cutting fixture. After I cut the stock pattern I then need to put the cutout for the barrelled action into it. I have a point on this model that corresponds to a point on the finished stock in the fixture. In the Rhino model this happens to be +1.5 inches in X and +1.5 inches in Y off the orgin. To center this on the stock I mark the point on the stock that corresponds to the point on the model and then center the shopbot's XY axis on that point. I then move -1.5 in X and -1.5 in Y and rezero the shopbot axis. The Shopbot XY axis should then correspond to the Rhino XY orgin. The X works out quite well but the Y wants to start cutting right away without taking the 1.5 offset into account. Any ideas anyone? Same thing happens when I try to offset the model for the stock, X works fine but Y wants to start right away. I suppose I could compensate for this somehow but I'd rather see things do what they are supposed to do. Thanks again for any help!

[mrdovey]

Blair...

When you've moved the spindle -1.5" in x and -1.5" in y, you say you "rezero the ShopBot axis".

What command (exactly) do you use to do this?

...Morris