Ball-Screw vs. Rack & Pinion

Unbeatable Accuracy and Durability with Ball Screws

Traditionally, lower-cost CNC routing systems were driven by a CNC rack and Pinion system while high-priced aerospace and metal working mills were Ball Screw driven. With that in mind, drive system technology has come a long way over the years, allowing companies to introduce the Ball Screw system into the CNC Router industry to make machines more accurate and more reliable. But what makes Ball Screws so much better?

The rack and pinion drive system works by using a circular gear (the pinion) that engages with a linear gear (the rack) to convert rotational motion into linear motion. The key components include the rack with teeth that bolt onto the side of the frame and the pinion that meshes with the rack to make the machine move.

There are many reasons to consider a ShopSabre CNC system driven by Ball Screw over a system using a less sufficient drive system like Rack and Pinion. Here are the three main reasons why Ball Screw is the way to go.

Improved Wear and Tear Levels

Ball Screw systems create improved wear and tear levels. The Ball Screws on our CNC router tables consist of a sealed bearing with many re-circulating ball bearings evenly spaced and constantly lubricated as it moves through a channel design. The channel is cleared by wipers ahead of time to prevent any debris or dust from penetrating the inner bearing.

Rack and Pinion does not have this technology and is simply a gear and track that mesh together with no lubrication (metal-on-metal contact). You must apply grease manually to the track which will become contaminated by dust, dirt, and other debris from cutting. This reduces the lubrication and increases the wearing of the gear and its track.

Time, Dust & Dirt

Over time, this begins to wear down the gear/track, and the teeth become further apart (increasing backlash), eventually changing the overall accuracy of your table. This is caused by the fact that a Rack and Pinion system must stop on the same points (tooth) over and over.

Our ball screw design does not have this issue because the ball screw’s many ball bearings have an unlimited amount of contact surfaces to stop on, therefore wearing this system much less and allowing your system to hold a tighter accuracy for much longer.

Improved Overall Accuracy

The second reason to consider Ball Screw is the overall accuracy of your machine can be at risk with a Rack and Pinion design. Gears from the factory cannot produce the resolution or tolerances of a ball bearing. Many of the “Repeatability and Resolutions” advertised by Rack and Pinions cannot physically be maintained because the gears do not see those tolerances.

Even the most advanced Rack and Pinion systems retailing for well over $100,000 do not hold the same tolerances of a ball bearing. This is why when you look at any industrial machine, you will find that the most crucial axis (Z Axis) runs a ball screw. When depth and cutting tolerances matter they trust the best technology.

Our CNC machines with re-circulating ball bearings are used on all Linear Guide Rail systems and are a trusted technology from high-end CNC Routers to high-end aerospace and metalworking milling centers.

Your CNC router should have this same technology incorporated in it so you can go to work with the most advanced and accurate system possible.

When ShopSabre CNC mounts these drive systems, we take the backlash and whip risks out of them by fix mounting the long axes, therefore routing only the ball nut as designed to give you smoother motion, higher speed, better-cutting forces, and of course better accuracy.

Rack and Pinion System Differences

Unlike a Rack and Pinion drive, these large contact pads and ball bearing drives on EVERY axis allow the cut forces to be evenly distributed throughout the bearings, guide rails, and frame design. This allows you to eliminate the backlash that is required in Rack and Pinion which will translate into smoother cutting edges and better finishes.

For MDF doors, this is a critical technology as it is very noticeable in the difference between many Rack and Pinion to Ball Screw produced cuts. The technology of Ball Screw removes the wobble, dog walking, and inaccuracy that many lead screw and Rack and Pinion drives have.

With Rack and Pinion, you have two motors on the Y axis (long axis) with independent gears which allows for your machine to eventually wear unevenly because no two gears will ever wear identically. Keep in mind you won’t likely work in the middle of your table every time; therefore, if you have more work done on one side of the machine or the front or back, you will add additional wear to that location and the Rack and Pinion system thus creating uneven wear patterns.

Gear Rack Wear and Tear

As you use your machine and gear rack, the gear on one side may become smaller than the gear on the other side of the machine which can result in a dog walk, wobble, or inaccuracy. The reason you will not have this with a ShopSabre CNC Router equipped with Ball Screw technology is that ball bearings do not wear out like a gear and do not change tolerances from the cutting, the debris, and the work.

Helical gear racks have angled teeth that result in smoother, lower-friction movement, better performance, and less wear on associated components compared to straight gear racks.

Overall Cut Forces and Machine Movements

The third thing to consider is overall cut forces and machine movements. Ball Screw drives allow the machine to apply maximum cut forces to the head and allow your bit to cut more materials at higher speeds without bending, breaking, or twisting.

A Rack and Pinion CNC machine will not allow for even cut forces because the CNC router head will apply additional cut forces to the closest gear and motor forcing the other motor to adapt its speeds to keep the gantry straight as it applies more torque into a gear many times not much bigger than a wedding ring. This will result in concerns of missing steps, gear fracturing, or pinion stress.

Many competitors priced competitively do not have an intelligent enough machine control system to perform the task of fixing this. In the end, you will find yourself slowing your cuts down or re-cutting inaccurate parts. The Rack and Pinion design requires both gears on each side to run the exact same start and stop with cut forces applied against it otherwise any delay in motor reaction could turn into a difference in accuracy between the left and right side.

ShopSabre Ball Screw CNC machines do not have this concern because of the resolution, cut force abilities and quality of our components. We are so confident in our Ball Screw Design we have had a full-grown man pull against our gantry as the machine moved from one end of the table to the other and then went back and hit the same cut after the person let go. The machine is built with many of the largest components in class, so accuracy is no issue for a ShopSabre CNC.

If you are not convinced, we do manufacture a lower level of CNC Router machines that utilize the Rack and Pinion drive systems. When quality matters, use the best in technology – Ball Screw Drive Systems!

Choose a design that has been proven by high-end CNC systems in the $100,000 price range. Anyone can build a CNC system that cuts the first day, but ShopSabre CNC designs a machine that will continue to hold tolerance and perform essential cuts even 10+ years down the road.