When choosing a linear motion screw, engineers juggle many decisions. Linear motion screws must meet efficiency needs, load rating as well as any special design constraints, all while remaining within budget.
Get started by taking a step back and looking at the application as a whole. Often, when deciding on which linear motion screw is best for the job, the choice falls between ball screws and acme screws. Each of these types of screws comes with their own unique advantages in linear motion applications.
Ball Screws for Linear Motion
Ball screws are the most efficient means of linear motion. Manufactured to close tolerances, ball screws are a great fit for linear motion applications that require high precision or when no backlash is necessary. They also benefit from a predictable life span, as a properly built assembly has a life cycle of one million revolutions if the load capacity isn’t exceeded.
The downfall of linear motion ball screws comes from their higher costs and lower load capacity compared to acme screws. In addition, the accompanying ballnuts are usually a larger design than the comparable acme nut, due to the additional components that are required for recirculation.
Acme Screws for Linear Motion
When a higher load capacity is required, acme screws are a strong choice for linear motion assemblies. Acme screws are tough, and able to withstand harsher conditions than ball screw assemblies, and additionally, are easier to manufacture, requiring less components and lowering costs. Their low efficiency can be used to eliminate backdriving within a system, which may be useful in certain applications.
However, that low efficiency can also be a downside for certain linear motion applications. More friction is present in an acme screw assembly compared to a ball screw assembly, which requires more torque to operate and lowers efficiency. The acme nuts take the brunt of this friction, as they are designed to be the wear item in the assembly. This results in more maintenance time compared to a similar ball screw assembly.
Linear Motion Screws at Work
Linear motion screw applications are found in many major industries. While each application is a unique case, aerospace and medical industry applications tend to use ball screws, while industrial applications often favor acme screws.
However, the PST Group has previously manufactured acme screws for aerospace applications and ball screws for industrial applications. Each situation is taken on a case-by-case basis, to ensure that each assembly is the best fit for the application.
Examples of linear motion in action include:
- Ball screw assemblies used in commercial aerospace thrust reversers.
- Acme screw assemblies used for wing tip adjustment in the private jet industry.
- Ball screw assemblies used in landing gear for various military and aerospace/flight applications.
- Acme screw assemblies used in swine barns for opening and closing curtains.
Creating solutions for linear motion applications has been the foundation of the PST Group’s business since the 1950’s. We feel confident that our team can help you find the best screw to suit your needs. Contact us to learn more.