What are the differences between rolled and ground ballscrews?

The difference between cold rolling screw (rolled screw) and grinding screw is as follows:
1. Different processing methods:
Cold-rolled ball screw is to cut grooves with a certain depth in polished rod material at first, and the groove spacing is equal to the wire spacing you want to process, and then roll them out with a rolling mill. On the basis of press rolling, the grinding screw uses a special cylindrical grinder to precisely process the arc groove with the same shape and size, and the cut groove is at the bottom of the arc groove.

Rolled ball screw is preferred over cutting (turning on a lathe) for lead screws. It involves pressing a round bar between a set of dies that roll the threads into it. It results in a harder surface with superior surface finish for lead screws. Rolled ball screw is also the most common process for ballscrews because it is more economical and sufficiently accurate for most industrial applications. Lead accuracy can be held to better than .003 inch/foot and longer lengths are possible than with ground ballscrews.

If higher accuracy is required, grinding should be considered. The grinding process can hold lead accuracy’s as tight as .0003 inch/foot or better. However, this process is much more expensive and the maximum length of screw is much shorter.

2. Different scope of application and cost:
The precision grade of rolling screw is below the average, which is suitable for ordinary equipment with low precision requirements. It has a short life, high efficiency and low cost. The precision grade of grinding screw is above average, which is suitable for CNC machine tools and other equipment with high precision requirements. It has high precision, long life and high efficiency, but the cost is also high.
3. Different appearance:
The cold-rolled screw rod is formed by extrusion, and the grinding grade is processed by grinding. Turning is not the same as grinding process, and naturally there are process marks after it comes out. Generally, the surface of cold-rolled screw rod is smooth and shiny, and the light reflection rate is high and dazzling. Grinding marks of grinding wheel can be seen carefully on the surface of grinding screw. In terms of appearance, the raceway groove of the turning grade screw rod is smooth, which is shallower than that of the grinding screw rod.