Cut size not equal to part wizard-toolpath size

[bob_schroeder]

Hello - just got my PRS Alpha BT with spindle running and ran my first part file. The cut size is smaller than the part file size and it wasn't off consistently from X to Y (size of part wizard file is 25 x 2.75 but when it was cut it was 20.75 x 2.25).

I'm using the 1/4 inch Onsrud bit. The toolpath is using a 1/4 inch end mill and I even deleted all the toolpaths and recreated them, ensuring I was using the 1/4 inch end mill tool.

I'm using a profile toolpath, cutting on the outside and a 2d clearance cutting on the inside that's also too small.

I then decided to cut 1/2 inch squares that were 1/2 inch apart. They were cut at 7/16 wide and 3/8 inch apart.

This is baffling me. I've looked through the doucmentation over and over and reviewed my drawings until I'm blue in the face! Any suggestions are greatly appreciated!

[srwtlc]

Bob,

Check to be sure that you have the proper unit values loaded for your PRS Alpha BT (look at the unit values with VU) or reload them with UR or from the menu Utilities/Reset and load for your size machine.

Either ShopBot_PRS_BT32alpha.sbd or ShopBot_PRS_BT48alpha.sbd

Unit values appear to be 2482.8171 for X and Y and 2979.3805 for the Z.

You can also check to see if the machine is moving the commanded amount by measuring off the carriage somewhere. Clamp a block to one part and move the tool say 10, 20, or 30 inches and see if the measurement is the same as the input distance.

[fleinbach]

See here for unit value info

http://www.talkshopbot.com/forum/sho...9028#POST59028

[bob_schroeder]

Thank you Scott and Frank. I've verified the unit values and they are as you stated and accoring to Frank's screen shot for the PRS BT Alpha. We also updated to the 3.5.4 version of the control software based on ShopBot's support team's recommendation. It's still smaller. I'm sure we're doing something wrong or have a setting wrong somewhere else. I don't think we should have to come up with our own unit values - right? We have an email into support asking what else we can do. If anyone has other suggestions, we'd love to hear them as we'd like to cut some pieces on Sunday.

Thank you everyone!

[scottcox]

Maybe check the proportion values on the Part File Execute Fill-In Sheet?

These should be defaulted to 1.0, but a different value could cause your problem.

[bob_schroeder]

Thank you everyone who responded. ShopBot support sent us a new settings file as our pinion gear was different than what was configured in the original settings file.

Having cut our first accurate square, we're officially Botters now! YEAH!