How to choose the ideal linear slide for your swiss Artisan diy CNC router
Choosing a Linear Slide
A Linear Motion (LM) system plays a key role in any CNC router. This system, combined with a drive system, is what guides your CNC routers linear motion precisely and minimizes friction in addition to supporting machine components and secondary loads (lateral loads, torque, etc.). The LM system is composed a linear slide (also called a linear bearing) and linear slide guides. There are numerous types of bearings and guides, each of which has their own advantages and disadvantages. Someone who is buying or building a CNC router needs to know what they are looking for with such an important part of their machine.
The quality of your LM system will make or break your machine. If you are buying a brand new CNC router there is not much to worry about. On mid-range and high-end models, linear slides on modern machines are high-quality and are used on almost all new CNC routers built today. For hobby CNC routers or lower-end machines it is very important for you to know how to identify quality systems from the rest. Not every manufacturer will specify exactly what components are installed in a machine; you need to be able to identify those parts yourself. If you are buying a used CNC router it is even more important to know what linear slide is installed so that you can make sure the machine works properly and so that you will know what questions you need to ask.
Replacing a full set of linear slides can cost $10,000 or more, depending on the parts you need. A company may also no longer make or sell the parts you need if you are using an older machine. This could be very damaging if you have a part that must be replaced for your machine to keep working. Whether you are buying a new CNC router or building your own you need to be sure you have the right linear slides because it can be one of expensive parts of the machine to purchase, and the most difficult to build if you are putting your own machine together. You need to be able to identify the parts, be sure that all the parts are working correctly, and know whether or not you would be able to get replacement parts if you need them.
When selecting what type of rail to use make your decision before you even start laying out components for the machine. Mounting fixtures for your rails will be different depending on if you are using a square or round rail. Changing from one square rail to another (or one round to another) is much easier than changing between a square rail and round one. Like with any part, you will get what you pay for when selecting a rail. For example, a supported linear shaft may do a better job than an unsupported round shaft and that may seem good enough at a glance but paying a little extra for a profile rail from a company like HIWIN will give your machine a much better load capacity due to the higher quality of the part.
Another key part to component you can consider is the pillow block. Pillow blocks are mounted bearings that can give you support for a rotating shaft. The bearing should be placed on a parallel line in the axis of the shaft. The two basic types are hydrodynamic (used at low speeds to remove metal-to-metal contact) and hydrostatic (used at heavier loads at varying speeds; no metal-to-metal contact and low-friction coefficient). There are many different designs for pillow blocks including plain-bored, solid, babbitt-lined, and cast iron to name just a few. Be sure to check shaft size and capacity when making your selection.
An at-home CNC router generally has 2 or 3 axes. A 2-Axis machine is what a hobbyist is likely to have for making household items. A 3-Axis machine is more common overall and usually has an 8-foot x-axis (going front to back), a 4-foot y-axis (left to right) and a 6-inch z-axis (up and down). 3-Axis machines are primarily used for flat, two dimensional projects. Making carvings or even furniture out of wood, metal or other materials is a good task for a CNC router enthusiast and could be where you start your hobby too.