There are several things you should know when contacting your local ballscrews suppliers for replacements. You can always ask one of the experts at the ballscrews distributors themselves, but it will help to get the selection right if you know the following information ahead of time.
The information you should know includes the amount of axial force required, the lead accuracy, and the axial clearance and preload requirements. You will also want to know the critical rotational speeds of the shaft and the nut.
Let’s look at each of these factors in more detail.
Axial Force Requirements
Calculating the axial force requirements of the ballscrew first requires knowledge of the load mass, and then the guide system’s friction coefficient. The vertical or horizontal orientation of the application should also be noted along with any special working conditions, all of which will help you calculate the overall working load.
Once you have an idea of the working load of your application, you ideally want your ballscrews suppliers to provide ballscrew options that have a dynamic load rating at least three times that of the working load.
Ballscrew Lead Accuracy
You may need to check the manual or other specifics and information to figure out the lead accuracy you need for your ballscrew. It is basically the amount of fluctuation caused against a thread length of 300mm, with the lead angle accuracy of ballscrew controlled in accordance with the JIS standard JIS B 1192 (ISO 3408).
The accuracy grades run from C0 to C5, which define the linearity and the directional property, and then from C7 to C10 which define the travel distance error in relation to the standard 300mm thread length. There are also numerous higher grades so check any catalogue information for your current ballscrew lead accuracy.
Axial Clearance and Preload Requirements
Ballscrews distributors should have plenty of rolled ballscrew products which usually have an axial clearance in the range of 50 to 100 microns. Selecting the right ballscrew according to axial clearance will help eliminate or reduce backlash.
The ballscrew preload requirements may include a need to eliminate axial clearance entirely or to minimise any displacement caused by the axial load. Preloading usually involves either pitch shifting or the use of spacers which you can ask your ballscrews suppliers about.
Critical Speeds of Ballscrew Nut and Shaft
Critical speed refers to the maximum rotational speed of the shaft as well as the maximum rotational speed of the nut. The shaft’s critical speed depends on the mounting distance and the mounting method, as well as the shaft root diameter.
The critical speed of the nut is determined by the DN value of the nut along with the diameter of the ball circle. Usually, DN values for rolled ballscrews range between 50,000 and 70,000, though there are also products with higher values available through your local ballscrews distributors.
If you require any ballscrews, then contact YB Components who are the UK’s leading ballscrews suppliers in Yorkshire. We keep local stocks of all such parts and more ready to ship out fast and free all over the UK and the rest of the world.