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williamsmotower
03-11-2012, 12:05 AM
I'm cutting this part on both sides.. two sided milling.

I have designated the world in the same corner as the cartesian on both drawings, as shown in pics.

I have already cut the back piece. this didn't go completely smooth, as it didn't cut in the center of the box like I thought it should. I had to manually move part on the table x1.000 and Y-.1 then zero cooridinates (instead of just using corner of box.. but I did leave proccessed code alone. I just fudged table position) Then part was cut.

I then flipped part on table, did my same "fudge factor of manually moving table". I then proceeded to cut this front part of drawing and it's not even close to where it should be.

Why are my parts not cutting in center of the designated green box? what am I doing wrong?

BACK

http://img.photobucket.com/albums/v250/williamsmotowerx/back.jpg

FRONT

http://img.photobucket.com/albums/v250/williamsmotowerx/front.jpg

svenakela
03-11-2012, 04:28 AM
To me it sounds like your machine is off center. Do you have any reference point on the stock?

williamsmotower
03-11-2012, 04:43 AM
Yes, just magic marker for reference.

Machine is good. It was off atleast 1.25"

svenakela
03-11-2012, 06:56 AM
I do two sided milling every day. You either must do something wrong when you flip the piece, either in the machine or in Rhino.

mikemill
03-11-2012, 08:36 AM
When cutting a circular two sided part, make tool origin the center of the circle and have a locateing pin to fit one of your holes you can't go wrong then.
Mike

williamsmotower
03-11-2012, 09:14 AM
Mike, luckily I'll be able to still do that. It will take me more time but I can salvage it by drilling through holes and indicating it. This is a fixture to make my 5th axis trunnion.

Sven, is it common practice to have your cartesian right on top of the world?

It may have been a little hard to understand in my first post, but even on my first side of my milling operation it didn't start cutting in the center of my box like it should have. My part cuts correctly, just not the location on the stock material.

I'm doing all of my toolpaths/drawing in the "perspective" view... and change to the other views if I have to.. for instance to do the 180 rotate. After the rotate I picked the same corner, just opposite side and moved complete model to the origin/cartesian as shown in pics.

williamsmotower
03-11-2012, 10:39 AM
I should be calling my cartesian, c-plane in my previous posts.

I am self taught cad/cam/machining.

My understanding is madcam doesn't do anuthing with cplane... only the origin. Is this correct?

williamsmotower
03-13-2012, 01:01 PM
I have it working now... this is what I found that may or may not be true.

In my views in Rhino, my front and right views kept changing the c-plane orientation on me for some reason. I had to keep clicking world top on those two views... even though world top was on my top and perspective view.

I used madcam bounding box for my origin and cplane. after I changed it to my part everything seemed to work fine. (I did end up using center of part)

mikemill
03-13-2012, 01:46 PM
Such are the joys of CNC machineing, the first run is the shakedown, there is always somthing that needs tweeking, and then away you go to make thousands of parts!!!!!!!
Good Luck
Mike