Frequently Asked Questions
1. What is a roller screw?
Creative Motion Control roller screws transfer an electric motor’s rotational motion into linear motion. The rolling elements consist of threaded rods which orbit around the shaft. These threads are in constant contact with the threads on the OD of the shaft and on the ID of the roller nut, resulting in incredible force density, very high load capacities, high speeds, and long life.
2. What industries/applications are good fits for roller screws and roller screw actuators?
Roller screws and roller screw actuators are a great fit when you are looking for high force, clean, quiet, linear motion in a very compact package. They can operate with incredible precision and at very high speeds as well.
Here is a sample of industries/solutions currently being served:
• Special Purpose Machine Tools
• Automotive
• DOD/Military
• Factory Automation
• Pressing
• Crimping
• Tube Bending
• Thermoforming
• Wood Processing
• Oil & Gas
• Entertainment
• Test Equipment
• Transportation
3. Why is CMC’s patented Grooved Roller Bearing so much better?
The Grooved Roller Bearing (GRB) design was borne out of CMC’s roller screw expertise. The GRB is essentially a zero-lead roller screw that benefits from all of the advantages that roller screws have over ball screws — more contact points provide more force in the same physical space (higher force density). This is critical in roller screw actuators because the bearing is the force-limiting component in the drive train — bigger bearings just won’t fit into the space available. Therefore, the whole actuator’s capabilities max out based on the bearing’s capabilities. CMC’s patented GRBs used in the CPD-series actuators actually have greater force capacities than the roller screws, so we are able to take full advantage of the roller screw’s high load and life capabilities in our CPD actuators.
4. Where are your roller screws, bearings and actuators manufactured?
CMC roller screws and roller screw actuators are designed and manufactured in the US.
5. What are your ‘normal’ manufacturing lead times?
Our standard actuator lead times are 8-9 weeks and our standard standalone roller screw lead times are 12 weeks.
6. What is the easiest/quickest way to get a quote?
Send us an email with your requirements and we’ll get you a quote ASAP. Send it to sales@creativemotioncontrol.com
7. Do I have to work through a distributor?
CMC has dozens of high-tech distributors in the US and around the globe who do a great job supporting their customers, but there is no restriction on working directly with CMC. If you would like to work direct, just send us an email at sales@creativemotioncontrol.com
8. Does CMC sell motors, gearboxes, drives, HMIs, cables, etc?
In a package including our actuators and/or roller screws, yes.
9. Do you provide drive programming services?
When selling a complete integrated package (actuator, motor/gearbox/drive, cables, etc), we also do the programming of the drive so that your stroke profile, end-of-travel sensors, and end of stroke are pre-programmed for you. We don’t offer generic programming services outside of our integrated packages.
10. How do I select the right motors, drives, gearboxes…?
CMC actuators can be fitted to pretty much any motor or gearbox of your choice. You can source these components separately, or you can purchase an integrated package from CMC that includes all of these components. If you source them separately, the catalog has the information you need to model your stroke profile in the motor selection software and determine the appropriate motor/gearing combination to achieve your desired stroke profile with the actuator or roller screw selected.
11. Do you ship actuators with motors and/or gearboxes pre-installed?
Yes. If you purchase the motor/gearbox from CMC, we will always install it prior to shipment. If you purchase them separately, you can ship them to us and we’ll install them during our installation process.
12. What happens if there’s a problem with an actuator or roller screw that I purchased?
If you are having an issue with a CMC roller screw or actuator, please send an email to info@creativemotioncontrol.com with a description of the problem. We will discuss the issue with you to see if there are any steps that can be taken in the field to identify and correct the problem. If that’s not possible, we will issue an RMA for you to ship the unit back to the factory. We will, at no charge, disassemble and carefully inspect the unit when it arrives and provide you with a detailed report of our findings, at which time you can decide whether you want to proceed with the required repairs or consider a replacement. Of course, if the unit is under warranty and the issue was caused by a defect in materials or workmanship, the unit will be repaired free of charge.
13. When would I need a CMC roller-screw-driven actuator instead of a ball screw actuator?
Roller screws can handle more loads in smaller footprints, can move the loads faster, and will last much longer than ball screws. In Creative Motion Control’s CPD actuators, the combination of CMC’s roller screws and CMC’s patented thrust bearings (see #5 above) give the CPD actuators significantly higher force density than anyone else in the industry.
14. When would I need a CMC roller-screw-driven actuator instead of hydraulics?
Replacing hydraulics with electric actuators generally requires similar force density and high-speed capability of the hydraulics. Therefore, the only solution is a roller screw actuator. But you get a lot more benefit with a CPD actuator than just force density; the dramatic reduction in maintenance is often reason enough, but on top of that you get higher precision, lower noise, a much simpler changeover to different parts/processes, more flexibility in your stroke profiles, and far simpler commissioning. In addition, you remove the risk of hazardous waste spills of hydraulic fluid from leaks which can be extremely expensive and time-consuming.
All of those are great reasons, but TCO (total cost of ownership) may be the most exciting. As the cost of energy continues to grow, electric actuators that only need to draw max current when the actuator is exerting max force compared to the constant max draw of the hydraulic power plant often pay for themselves in power savings over the first several years of use.
15. How do I select the right size actuator?
Many times, engineers and distributors will size an actuator simply on the basis of the maximum load of the application. This often leads to unhappy customers with actuators that do not last as long as they would like. Selecting the appropriately sized actuator for a given application requires an analysis of the load/stroke profile (the level of load throughout the length of the extent and the return strokes) along with the duty cycle and a minimum life expectancy. Contact CMC at sales@creativemotioncontrol.com and we can help with this analysis.
16. What features set the CPD actuators apart from the competition?
CMC’s CPD advantages include:
• Higher force density (more load in a smaller space)
• Longer life
• ZERO maintenance if an oil-filled actuator is selected
• Unlimited gear reducer/increaser options
• The highest static force capabilities in the industry
• Available customizations
• Standard internal anti-rotation
• IP65 compliance with the Outdoor Exposure option
•100% MADE IN THE USA by Creative Motion Control
17. Why would you use an oil bath vs. grease lubrication?
CMC recommends using oil only if using grease is not practical for some reason (actuator is deployed in a remote location with no option for maintenance, in a machine where you just can’t access it, the stroke profile demands it, etc.).
Technically, an oil bath is a little bit better lubrication system than grease. So, with all other things being equal and you’re operating in a lab, you would select oil. However, oil brings some issues with it that grease doesn’t. First and foremost: leaks. Leaks don’t often happen, but they can happen and when they do the actuator often has to be shipped back to the factory for analysis and repair. You might be ‘down’ during that time, or in the best case incur the transportation and repair costs. Often this happens towards the end of life where the actuator might be operating perfectly, but one of the seals gets brittle and fails. Again, the actuator often has to get pulled from the line and sent to the factory for repair. With grease, you’ve avoided all of that downtime and repair cost. The tradeoff is the requirement for re-greasing, which is a pretty simple process usually required every three to six months.
98% of the roller screws and roller screw actuators in operation in the world are grease-lubricated. As long as there are no offset loads or impact loads introduced, CMC actuators have proven to outlast the predicted operational lifespan of the actuator by a pretty big margin when using grease as the lubrication.
18. How do I know how big of a motor I need to do the job?
The CPD catalog has a page titled “Motor Selection” which provides the basic calculations needed to get you in the right ballpark in terms of torque and power required for your application. You can also send us an email at sales@creativemotioncontrol.com and we’ll help with the calculation. To select a specific motor, the stroke profile needs to be modeled in the motor selection software to ensure that the motor specifications are adequate for the application.
19. What are some typical applications that are a good fit for CMC’s roller screw actuators?
Pressing, crimping, bending, riveting, welding, automation operations, valve and blade control, clamping, stamping, broaching, drilling, and positioning. Many of our products are used on application-specific machine tools. Industries include automotive, broaching, thermoforming, injection molding, pressing, defense, mobile equipment, metal/tube bending/cutting/forming, wood processing, simulation, robotic welding/fastening/joining, food processing, oil & gas (including explosion-proof).
20. How do I figure out what the life of the actuator will be?
The basis of the life calculation for a roller screw is fairly straightforward: it is based on the loads throughout the stroke and the amount of travel the roller screw will handle at those loads. So “life at max load” (a specification often listed in catalogs) is simply the total distance that a unit can travel at that max load before pitting emerges on the rolling contact surfaces of the roller screw. However, this statistic is not very useful per se, since if you operate at max load, the life of the actuator would be relatively short. Instead, an accurate life expectancy requires a more complex calculation based on the actual loads throughout the stroke and applied to the duty cycle.
HOWEVER, it’s important to understand that for an actuator, this calculation needs to be performed using the max continuous load capability of the actuator, NOT the dynamic load capacity of the roller screw. Solely referencing the dynamic load capacity of the roller screw can give the reader the impression that the actuator has more force/life capability than it actually does. You can send us an email at sales@creativemotioncontrol.com and we’ll help with the calculation and get you life expectancy numbers for different sizes of CPD actuators.
21. What is the maintenance schedule for a CMC CPD actuator?
The only maintenance required for CPD actuators is re-greasing. The re-greasing schedule is dependent on a few application-specific factors. For each application, CMC provides a customized re-greasing schedule and instruction guide to ensure that you have everything you need to properly maintain your actuators.
22. If the loads are extreme, can you use two/four CMC actuators and synchronize them?
Our largest actuator can handle 250,000 lbf, so it’s often possible to use just one actuator. However, in some instances synchronizing two or four actuators is required. The actuators can be electronically synchronized through the driver software or can be mechanically connected. We recommend safeguards be put in place to ensure that the actuators never get out of synchronization as the actuators (and the machine they are mounted in) can be damaged when this happens.
23. How can I buy CMC actuators?
If you don’t have a local distributor that has presented you with CMC’s products, you can contact us directly at sales@creativemotioncontrol.com and we will assist you in either providing the actuator directly or connecting you to a local distributor, whichever you prefer.
24. Does CMC purchase any components of their actuators?
Only the basic commodity components: nuts and bolts, seals, oil, etc. All other components are manufactured by CMC in the United States.
25. Can I get a load cell with a CMC actuator?
Yes, CMC has partnered with a couple of different load cell manufacturers to include these with our actuators.
26. What if I need a custom mount or a custom rod end?
Custom mounts and custom rod ends are no problem — we can always make the mounts or rod ends to your specifications. The added cost is generally small and the increased lead time is just a few days.
27. Can I get custom lengths?
Yes. Standard lengths are in whole inches, but if you need something in between, we can do that. The cost is minimal and the lead time is often not extended.
28. Can you make longer stroke lengths than what is listed in your catalog?
Sometimes, yes. We will work with you to ensure there are no buckling, manufacturing, and/or critical speed issues, but we can make longer units.
29. What if my motor is too big for the space available?
If the actuator is a parallel configuration and the motor is too big to avoid interference, we offer a taller ‘gear tower’ and gear set. There is an added charge, but that charge is much less than moving to a larger actuator to handle the larger motor.
30. Do CMC actuators backdrive?
Yes, CMC actuators will backdrive. We make the actuators as efficient as possible in both directions (generally between 85% and 88% efficient) to reduce the torque and power requirements of the motor to drive them. Customers generally use a motor brake or secondary brake to avoid backdriving if needed.
31. Are the rated forces available in both directions?
Yes, CPD actuators are designed to handle the same force capabilities in both directions.
32. Is the CMC continuous load capacity rating for the entire actuator or just the roller screw?
The max continuous dynamic force specification is for every component in the entire actuator, not just the roller screw.
33. If CMC actuators have superior features and performance, are they way more expensive?
No. CMC’s actuators, though more capable, are competitively-priced against actuators of the same frame sizes. Often customers use a smaller CPD actuator to do the same job, so they end up being less expensive.
34. What if I need a smaller lead on the roller screw?
CMC took a different and more flexible approach to enable different speed/torque requirements. Instead of changing the lead of the screw — which is changing the most expensive component of the actuator — CMC supplies different gear configurations to either reduce or increase the speed of the roller screw shaft. Reducing the size of the motor with gears is a much better approach since it maintains the life expectancy of the actuator. Reducing the lead of the roller screw reduces the life of the roller screw by the same ratio — cut the lead in half and you’ve cut the life in half.
35. What is backlash?
Backlash is the amount of ‘play’ or ‘lash’ that exists in a mechanical assembly of moving parts. As the actuator reverses direction, there is some very small amount of delay in the reaction of the actuator before it begins moving in the other direction. That amount of play is called backlash. The amount of backlash in CPD actuators is between .002” and .003” depending on the size.
The key is that this backlash is extremely repeatable. After reversing directions, the CPD actuator will move to the same spot to within .0008” every stroke for the life of the actuator. This makes it quite simple to model the backlash in the software and ensure incredibly accuracy in every stroke.
36. What is the accuracy of CPD actuators?
Accuracy is usually used as another term for repeatability. See #35 above.
37. What is lead error, and why doesn’t CMC provide a lead error specification?
Lead error is a manufacturing specification for all types of screws — ball screws, lead screws and roller screws. As you can see in our roller screw catalog, CMC roller screws are built to the industry standard G5 accuracy which means the error in the lead of the screw shaft is within .0023mm/300mm. This specification, however, is just a piece of the ‘accuracy’ of an actuator. The repeatability/accuracy, of an actuator is the key specification to determine the error in the travel of the unit (see #35 above). This takes into account the roller screw, bearing, gears, etc.