Inconsistent z travel

[dowty]

Hi,

Hoping someone can help. Have a PR96 which I have finally been able to put together. Today I got to the point of cutting my vacuum hold-down (4 sections). The first section cut perfectly, but when it got to the 2nd section it didn't cut. I've checked everything I can think of, but no luck. In the 3rd zone it did the diagonal cuts, but shallower, same with the 4th zone. I have a brand new Z axis and new router.Table is level, square, all rails are the same distance from the floor. Can anyone help?

[Brady Watson]

David,
1st, make sure that you are running the latest software release for your PR, which is v2.38, this is available for download on the shopbot website. There were issues with inconsistent Z-heights with earlier versions.

2nd, When you are setting up your machine for the 1st time, you want to surface the entire table top with a large cutter. This will get the table flat and square to the router head. (If you see ridges or scallops when you do this, you need to re-square your Z-axis) Surfacing the table top may take several attempts to get the entire top flat. Once you have done this you can then go and machine your channels for your vacuum grid.

Hope that helps!
-Brady

[dowty]

Brady,
Thanks for your quick reply. I am useing the latest ver.2.38.
I think my problem may lie in the actual z aaxis not being true to the table. What are the best methods for achieving this. I will give it another go tonight. I am just excited to get cutting.

[Brady Watson]

David,
There is an excellent explanation in the Shopbot assembly manual in the section that talks about surfacing your table and dialing in the Z-axis. You can download the latest version of the manual from the shopbot website.

-Brady

[richards]

I use a 1/2-inch shaft to fit a 1/2-inch collet. At the end of the shaft, I attach a cross piece that holds a $15 dial indicator. The diameter of the dial indicator's path is about 10 inches. I lay down a piece of plate glass on the table to get a flat surface and then turn the shaft by hand, checking every 90-degrees. With a little fussing, it's fairly easy to get the Z-axis to within a couple of thousanths. If you don't have a dial indiactor lying around, just wrap some stiff wire around an old bit and bend the wire so that it barely touches the surface of the table, and then adjust the Z-axis until the wire barely touches the table throughout its entire path. (The purpose of the wire or horizontal cross piece is to magnify the error sufficiently so that you can easily fix it. The entire process is the same that you would use with a TS-Aligner, Jr. device to square up a drill press.)

[Brady Watson]

Good idea Mike.

You can also clamp a 4' level to the Z-axis on the same portion the router mounts & then read the TOP bubble. I have used this method many times and my Z-axis is always dead on the 1st time out.

-Brady