Basic considerations for selecting ball screws

As an essential part of modern automation machinery, what issues should be noted in the selection, use, installation methods, and maintenance of ball screws?

Today, let's discuss the main parameters that need to be paid attention to in the selection process of ball screws themselves.

• ◆ Nominal diameter. It is the outer diameter of the ball screw. The common specifications for ball screws are 12, 14, 16, 20, 25, 32, 40, 50, 63, 80, 100, and 120. However, please note that among these specifications, major ball screw manufacturers usually only stock 16-50 pieces, which means that most of the other diameters are futures (produced according to the diagram, and the delivery time is generally between 15-60 days). The nominal diameter of the ball screw is basically proportional to the load, and the larger the diameter of the ball screw, the greater the load. Please refer to the manufacturer's sample for specific values.
• ◆ Lead. Ball screw lead, also known as pitch, is the distance that the nut moves in a straight line after each revolution of the screw. Common ball screw leads include 1, 2, 4, 6, 8, 10, 16, 20, 25, 32, and 40. Small and medium-sized lead products are generally only available in stock at 5 and 10, while large lead products are generally available at 1616, 2020, 2525, 3232, and 4040 (the first two digits are the diameter of the ball screw, and the last two digits are the ball screw lead). Most other specifications are produced separately by manufacturers. The lead of the ball screw is related to the linear speed. When the input speed is constant, the larger the lead, the faster the speed.
• ◆ Length. There are two concepts for the length of ball screws, one is the total length of the ball screw. The other is the thread length of the ball screw. Thread length=effective stroke+nut length+design allowance (if protective cover needs to be installed, the compressed length of the protective cover should also be considered).
• ◆ Nut form. There are several types of ball screw nuts, which can be classified into circular flange, single cut edge flange, double cut edge flange, and no flange according to flange form; There are single nuts and double nuts according to their length. When the installation size and performance of the ball screw allow, designers should try to choose a conventional form when selecting it.
• ◆ Accuracy. Ball screws are classified into P and T categories according to GB, namely transmission and positioning categories. There are several accuracy levels for ball screws, including 1, 2, 3, 4, etc. Foreign products are represented by C0~C10 or specific values. The accuracy and price of ball screws are closely related, and the concept of accuracy is combination and maintenance. The lead error of the screw cannot indicate the error of the entire set of ball screws. Qualified factory accuracy cannot indicate that this accuracy is maintained throughout the rated service life. This is related to the production process of the ball screw manufacturer.

The above are the most important precautions, and there are other aspects that need to be noted. You can directly communicate with the ball screw manufacturer, and technical personnel will help you solve them.