In this series, we are going to look at sliding guides – what are they and how to use them. We’ll start with an introduction and then move onto other topics as the series progresses. In a nutshell, sliding guides are used anytime you have a part or object that needs to move in a predictable and defined path. There are three qualities that a sliding guide must possess, regardless of type:
- Support the load you need to move
- Require a small and stable moving force
- Be accurate and stable during a long term, high speed motion
Each of the above requirements has specific design concerns and technologies associated with it. First, controlling friction and wear is always an issue with sliding guides as both have a direct impact on supporting the load and calculating the force needed to move it. The materials that are used in constructing the guide are also an issue – fancier and more exotic materials usually have a higher cost, but may be necessary. Finally, anytime you add motion to a design, you have to look at dynamic loads and moments, while keeping in mind the expected lifetime of the guide.
Linear Bushing Image from MISUMI
There are three main types of sliding guides for linear motion: linear guides with round shafts, linear motion guides, and gib guides with either flat gibs or triangle rails. Each has advantages and disadvantages, and selecting the appropriate one for your application is usually a simple matter.
Linear guides can utilize a single shaft if rotation is not a main concern during your motion. Heavy loads can easily be supported on larger diameter shafts, and you can quickly add a friction reduction mechanism. Examples of this solution include linear bushings, jig bushings, and miniature ball guide sets.
The next solution, linear motion guides, are excellent for low friction requirements and have a superbly accuracy for your high demand applications. They can also be designed with a high rigidity if deflections are an issue. Examples include linear guides, slide ways, and slide tables.
Linear Guide Image from MISUMI
Sometimes your design needs a wide range of performance levels, and in this case, a gib guide is a good choice. They have a low part count, which can translate into a lower cost and an ultra high performance. Choices include guide rails and air bearings.
Air Bearing Image from Bombay Harbor
Motion doesn’t always need to be straight, either. Most types of linear guides can be formed to fit a curved profile, allowing the same great benefits as straight paths. As with any curved motion, you have to be careful with the drive mechanism, but usually a standard or ultrasonic motor can be adapted to fit the task. The nice thing about rotary motion is that you usually don’t have to worry with inertia as the motion is typically turning the same way. Also, advanced ball bearing designs can be used to provide great performance at high speeds.
Regardless of your design requirements, remember that there are a variety of different slides available, each having unique benefits. Additionally, guides don’t always have to be straight – there are solutions for rotary motion as well. Hopefully, this introduction has you thinking about how you can use sliding guides. In the meantime, keep an eye out for part 2 of this series!
Can’t wait until part 2 of this series, or have specific questions you would like to have answered? Comment below, or visit us at www.misumiusa.com!