How to calibrate a prt.

[ludlow6]

Made my first cut on a 5x10 prt shopbot. it was a 4" circle. It came out more like a 4" oval. Is there a way to calibrate this machine? I am running part wizard 2. Anyone know where I can find partwizard 3.

[tlempicke]

During the setup of the machine you entered two values, one for X and one for Y. I am not going to repeat what is in the manual here but effectively that tells the machine how many pulses to the motors equals thousandths of an inch. If you set the machine up properly it is really accurate, within about .002 of an inch.

Here is a quick and dirty way to check. Mount an engraving tool in the spindle. Create a drawing for a three inch square with the zero x and zero y in the middle of the drawing. make a short line at x and y so that you will have a cross at the zero point. A piece of scrap with a blob of spray paint on it makes it easy to see what you are doing. Make and x, move ten inches or so and make another. Measure. If it is exactly ten inches you are good to go. If not, since you used ten inches, the math will be pretty easy.

[ludlow6]

I guess one of the problems is I don't have a manual for this machine. I don't remember the software asking me for 2 values in the setup. It did ask me what size bot I was using. It is a 60" by 120" prt. The software I am using is an older version from my older pr96 machine.

Jim

[Chuck Keysor]

A minor suggestion, but when I was calibrating my PRT alpha, I used my machine to mark out a scaled up 3, 4, 5 right triangle. I have a 5 foot by 12 foot bed, so I multiplied the dimensions by 1.5.

Laying out a 4.5 foot by 6 foot by 7.5 foot right triangle makes it really easy to dial in the accuracy of your machine. You can't do that with little geometries of just a few inches. Chuck