View Full Version : Set up After Transport

05-28-2003, 10:03 PM

We've finally gotten time to set up the shopbot. Just as a review, we purchased a used PRT60-120. We transported the bot to our shop by placing the table on a trailer and the y carriage in the bed, secured of course.

I have a few questions and wasn't satisfied with my archieve search.

We found that the frame had measurable deflection in the middle of the x-axis, so we added legs at that location that exactly matched the factory legs.

One thing that we found right off, is that the y-car was riding up on one side. Following the manual, we adjusted and fixed this.

We were using a machinist level to level the machine but it's driving me NUTS!!! What would you recommend to level the x-axis from front to back and side to side? We don't have an accurate 8' level! We do have a rotary laser that we could mount on a tripod.?

How do we check level on the Ycar since there can be deflection in it as well?

I know that our accuracy will be dependant upon this initial setup and I'm a fanatic about accuracy. But, I seem to be chasing my ass here! Any help or advice will be greatly appreciated! Anyone near Southwest VA that would like to help, let me know!

Chris Robinson

05-29-2003, 02:03 AM
Chris, levelling the table is a total non-issue if you are going to surface cut it later. Sure, get it as good as you can, but don't waste your energy on it. Your main headache is to get everything square.

"Deflection" will always be present, irrespective of how many legs and stiffeners you add. Again remember that you will be surface cutting the table afterwards. Even the high$$$ machines have deflection.

05-29-2003, 08:53 AM

I thought I was chasing my butt!

I did read the manual and online archieves regarding squaring. I also saw the pictures of the squareing blocks. Timm is in the process of making them so he can tack them on this weekend.

I'll let you know how it goes.


05-29-2003, 09:35 AM
With the PRT and its good V-rollers, you also need to make sure that your V-topped rails are straight and parallel to each other. These rails are relatively flimsy before bolting them to the underlying supports, and tensioning the bolts normally deflects the rail to meet the support. (For both the X and Y axes.)

If a pair of x-rails for example, are 1mm out of parallel to each other, the v-rollers simply ride up higher, lifting the y-gantry by 1mm (in theory, because it is a 90 degree v-roller). Luckily, in practice there is some flexibility, and the gantry does not lift for slightly out of parallel rails.