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

[blair_clowdis]

Morris,
From the pull down menu I use Zero 2 (X&Y).
Blair

[blair_clowdis]

Do you think the "Value Axis" VA command might be better? Just rezero after I make the move or put in the negative numbers where it says X and Y and let the machine make the move? Probably won't try tonight, temp in the mid teens and shop not heated very well.
Blair

[mrdovey]

Yuppers. At the registration point, rather than moving the spindle -1.5" in x and -1.5" in y, just use

VA 1.5,1.5

To reposition the origin. I would then do

J2 0,0

for reassurance that everything is behaving the way it should.

[hespj]

Blair, what software are you using to create toolpaths, and what type of toolpath?

John

[blair_clowdis]

John,
I send a "stl" file directly to Mill Wizard from Rhino and then use Mill Wizard to create the toolpaths.
Thanks,
Blair

[hespj]

Are you sure that Millwizard's 0,0 is in the same position as Rhino's 0,0? (In other words, has the export/import worked correctly?)

Can you view the tooplpath in Millwizard? Is it starting in the same incorrect place as the ShopBot? Or is it starting in the correct position?

[blair_clowdis]

Morris,
VA command didn't work either.

John,
When I watch the toolpath in mill wizard it is right over the part. In other words it doesn't start 1.5 x 1.5 off the center of the part. I would not expect it to start at the XY orgin anyway. I would expect it to move to the corner of the part and start cutting there.

For instance, if I was using part wizard to cut a square hole starting 4 inches up and 4 inches to the right of the XY orgin (which is usually in the lower left hand corner of the workpiece) the machine would move up and over 4 inches to begin it's cutting. I would expect it to do the same thing with the Rhino orgin but it moves over the 4 inches but not up. It is completely disregarding the Y orgin in my case.

[hespj]

Can you check if 0,0 in Millwizard is in the same location as in Rhino? It's either losing it Rhino to Millwizard or Millwizard to ShopBot. I suspect Rhino to Millwizard.

Email me the Rhino file if you like. john littlesquirlysymbol hesp.co.uk

[blair_clowdis]

John,
I think the orgin isn't going from Rhino to Mill Wizard. I'm exchanging e-mails with an engineer at Rhino and nothing is making sense. I use his macros, transfer the file and nothing changes, still cuts in the same place. Still working on it though!

[hespj]

Got it working with the original file after messing around awhile.

Try exploding the model, or moving it so that Z zero is at the base. I also looked at the model and cleaned up the inside a bit.

Check the dia of the tool is suitable. (One of the reasons I couldn't get it to work at first. I work in mm usually).

Might be worth checking that Rhino and Millwizard have their units set to inches.

Can I do a toolpath for you?

John

[blair_clowdis]

I think what I'll try is putting something like a cylinder on the center of the point I want to use as a co-ordinate system. This will force mill wizard to go to that point and start there (it will be an air cut since there is no material at that point). Then the model will have the proper offset and be cut where I want it. I'll try it this weekend and see how it works.

[Brian Moran]

Blair,

From what I can remember, I'm pretty sure that MillWizard will take your model and centre it in it's block of material. It will take no notice of any origins you have specified for the part in Rhino. To be honest, Cut3D / PartWorks3D will do this as well, both products are designed to make machining of 3D objects as simple as possible, and therefore reset the model origins to match the material setup.

Brian

[blair_clowdis]

Brian,
Looks like that is the case. I made it work by placing a small cube inside the Rhino XY orgin and that forces the machine to pick up at the edge of the cube and start from there. Kind of a crazy way to have to do things, but whatever works

Blair