Alignment Problem

[mwpfeifer]

Having some kind of an alignment problem and need some suggestions as to what I may be missing. I have been working on some simple trays using the Pocketing tool path in Partworks. My material size is 13 x 19 x 1.4 and the pocket size is 12 x 17.75 x 1.15. I’m using the center of the material as the X/Y zero point and the pocket is centered in the material. Using a laser center finder I zero the spindle X/Y position on the center of the material. I’m using a 1.25 dia bowel cutter with a 40% stepover.

When I preview the tool path the pocket is centered in the material but, when I run the cutfile the pocket is shifted approximately 0.125 in the +X and +Y direction. This happens every time I run this file. I have reviewed the code and haven’t found any offset in the X/Y. Any ideas as to what might be causing this offset?

[beacon14]

Are you sure the laser is properly calibrated to the router bit?

[mwpfeifer]

Yep, the laser is dead on. The dot is stationary when I rotate the spindle.

[Gary Campbell]

Michael...
Can you post a picture? I am assuming you chuck the laser in the collet? Unless the laser is in the collet, it will change position as the axis goes up/down.
Gary

[mwpfeifer]

Gary,
Yes it's in the collet. I guess I'm not understanding what you are getting at regarding the axis going up and down. With the +X and +Y edges of the pocket being off by an 1/8" and only cutting 1.15" deep the Z axis would have to be tilted off vertical enough that it would be visually noticable. I have verified the the Z axis carriage is within < 0.1 degrees of vertical measured with a Wixy digital angle indicator and the Y axis beam is level. (My machine is a 48" Buddy). What would you like me to take a photo of?? (Yeh, I know... don't end a sentence in a preposition! I can still hear my English teacher yelling at me!)

[Gary Campbell]

Michael..
A picture wont help if the laser is in the collet.

With the info you have posted, I could only fling a few wild guesses as to the cause. I will tell you that we have not great luck with this type of cutting, until we switched to a slightly oversized blank which was pocketed AND profiled in the same file. Since implementing that method, we have no errors or problems.
Gary

[mwpfeifer]

Gary,
Your right, that method does seem to result in more accuracy but since I don't have vacuum hold down I wind up wasting more wood to shavings.
Hopefully someone else has had this problem and found a solution.

[Gary Campbell]

Michael...
Try going back into the drawing file and make a pocket toolpath 1/8" deep inside the outer border of the tray (on the table). that should give you the centering accuracy and will also help hold the part in place.

You could also place a piece of mdf located by dowels on the table and then cut it out to acommodate the tray. You can remove and replace it as needed.
Gary