When selecting a linear guide system, a number of different factors must be considered. First and foremost, the approximate size and load of the system must be determined. Miniature sized profile guides aren’t capable of moving 1000 lb+ loads for any extended length of time, and a large diameter shaft and pillow block combination isn’t needed for moving a 10 lb medical sample.
Once that is determined, the more specific details of the application’s load and motion must be calculated and specified. Knowing the location of the load and the desired motion is necessary because acceleration, deceleration, and moment loads are frequently the primary factors in the applied load that is felt by the system. Then, the desired accuracy and repeat-ability can be taken into account, and this is where profile guides and round rails diverge.
When a greater degree of accuracy is needed, or in the case of especially heavy loads, profile guides are the better choice. Profile guides combine a variety of mounting types and orientations with a high level of repeat-ability compared to round rail products. Additionally, in the case of heavy loads, profile guides are much better suited to those types of applications. For example, the largest bushing for a round shaft that NB makes has a maximum load capacity of 54.3 kN. By comparison, the strongest profile guide offered by NB has a maximum load of 542 kN, despite the profile guide block being smaller in size than the bushing. This level of strength, unfortunately, comes at a price, which is often the primary disadvantage of profile guides.
The other downside of profile guides is that the accuracy of the mounting surface must also be very high, otherwise, the rail can be warped when it is bolted to the mounting surface. However, there are many applications where round products are better suited. Round rails and bushing are much easier to get simpler to install, and cost-effective as well. Careful consideration of the benefits and drawbacks for both round rails and profile guides can be challenging and time-consuming, but that process can ultimately yield a set-up that is perfect for any specific application.