View Full Version : Calibration values for gears on new machines

11-24-2000, 12:20 PM
Just got working on my new machine and found out from Shopbot that they have shipped different toothed pinion gears. Check your values under VU. If your machine is moving too far or not enough you need to change the Values.

For 20 tooth gears
x&y= 127.3240
z= 1018.5920

For 18 tooth gears
x&y= 141.4711

I have 20 tooth gears on x & y and 18 tooth on Z.

John Forney
ps. refer all questions to Shopbot

01-03-2002, 05:40 PM
anyone know what the calibration should be for my new prt96 counted the teeth on a pinion and there seems to be 25, the manual only goes upto 22tooth pinion.
many thanks for your help.
great site this!

01-07-2002, 09:52 PM
My PRT96 shopbot has the gearhead stepper motor set-up and 25 teeth pinions. I have it set at 152.789 for both X and Y and 733.386 for Z and accessory

Ted Hall, ShopBot Tools
01-08-2002, 11:58 AM
For standard PRT tools that have been shipped in the last 6 months or so, the correct Unit Values are:

X = 183.347
Y = 183.347
Z = 916.733

Use the [VU] Command to enter these values.

These values are the default values in the current version of the software. If you delete your ShopBot.ini file, a new one will be created and these will be the values that are included.

FYI -- Unit values tell your software what the gearing ratio (in Steps per Movement Unit [e.g. inches]) should be (for historic reasons, x & y are 1/4 the number of steps per inch, while the z and a value are the full steps per inch).

Further FYI -- When you install new software, the ShopBot.ini file is not overwritten ... thus whatever values you have already set will remain in place. However, it is always useful to have the values for your tool written down, since you may need them if you ever need to re-install the software from scratch.

TESTING YOUR UNIT VALUES is easy. Once you've installed them, just have your tool move a known distance (e.g. MX 10, MY 10 or MZ 4) and measure how far the carriage actually moved. If you have the right unit values it will be dead on, if not, it will be far enough off that it will be very obvious.

Over the years, we have fussed somewhat with the gearing ratio because of changes in the motor-gearhead unit, and changes in the microstepping drivers. Some applications also benefit from different gear ratios. Unfortunately, this adds a little confusion, but once you have this number correctly set, it's not something you will need to think about again.

01-12-2002, 12:29 PM
Ted and Mayo many thanks for reply now calibrated perfectly.