Once thought of as little more than a cheap substitute for ball screws and only suitable for limited use in less demanding applications, lead screws (sometimes called lead screws, power screws, acme screws or translation screws) have evolved and now offer many significant advantages over alternative technologies
Once thought of as little more than a cheap substitute for ball screws and only suitable for limited use in less demanding applications, lead screws (sometimes called lead screws, power screws, acme screws or translation screws) have evolved and now offer many significant advantages over alternative technologies. In fact, many of the lead and acme screws available today are considered the go-to choice for many specific motion control functions.
Unlike ball screws which run on ball bearings, these screws have no internal moving parts. They rely on sliding friction between the nut and screw and feature deeper helical recesses with an acme or triangular thread and a mating nut to translate motion. As a result, these screws are generally less expensive and offer more flexibility than ball screws which are typically harder to modify or customize to specific applications. This advantage is just the tip of a growing lead screw iceberg of benefits however.
Here are ten reasons you might want to be using lead screws in your next linear motion application.
1. Cost Effectiveness – we already established that these screws are easier on the budget than ball screws, but that understates the relevant facts a bit. Because they can be easily tailored to meet the specific performance requirements of a given application – they can essentially be “right sized” – they cost anywhere from 25 to 85 percent less than ball screws. Thus, cost is a significant differentiator between the technologies. This often requires a greater investment in life cycle testing in the design phase but the long term cost savings (which can be passed along to your customer) make the product more competitive in a fiscally constrained market.
2. Customization – precision lead or acme screws offer increased customization options in terms of lead sizes and diameters. For example, hundreds of options are available that make it possible for you modify the screw to precisely accommodate your design, rather than having to make your design fit the envelope of the screw, which is often the case with ball screws.
3. Custom Nut Designs – provide engineers with enhanced design flexibility. Should cost or design constraints require a more integrated package, custom nut designs can be achieved by combining several different components into a molded nut. Lead nuts can be fabricated from various materials that are rated for different life cycle requirements. Lead nut materials can meet specific environmental conditions including operating pressure-velocity and temperature and can be molded or machined in complex shapes and sizes.
4. No Additional Lubrication – Unlike ball nuts, plastic lead nuts will operate without additional external lubrication thanks to the use of materials that help to reduce friction (less than 0.10).
5. Better Operation – because there are no moving parts, lead or acme screws are quieter and less likely to cause vibration which can lead to increased wear and tear on the assembly – in turn leading to increased maintenance requirements and downtime. This helps make the newest breed of Helix screws especially well suited to precision applications such as medical equipment.
6. Vertical Appeal – designed to be self-locking at low leads they are particularly useful in vertical applications.
7. Environmentally Friendly – because they are less likely to suffer from particulate contamination and they can incorporate a "dry" PTFE lubricant.
8. Energy Efficient – Many screw designs can be operated without the use of electric brakes help to reduce the consumption of power. All ball screws will back-drive and require a brake to secure the load to ensure that the system operates safely and accurately.
9. Low Maintenance Requirements – these screws are ideal for applications in environments where maintenance will be difficult or impossible. They also offer increased reliability over long service life and can be manufactured from materials that are resistant to corrosion.
10. Anti-backlash Technology – Precision is a critical requirement in most linear motion applications and backlash, the gaps and spaces found in the helices of many nut and screw combinations, can make achieving that precision challenging. Screw assemblies can be designed to minimize this issue with various anti-backlash technologies. Anti-backlash screw assemblies deliver accurate and repeatable linear motion that rivals ball screws.
There are times when a ball screw is the appropriate choice but due to the advanced manufacturing and engineering technologies employed by Helix Linear Technologies, those times are fewer and farther between.