Rack and Pinion or Ballscrews?

"Company X is trying to sell me on ball screws, claiming that anything else is inferior."

I have heard people say that many times before, at trade shows and when consulting with them about what type of CNC Router they should buy. Is there any truth to that statement? I guess that depends on what you mean by truth.

Like any machine design, a ball screw driven system is only as good as its designers. Rack and pinion allows for a lighweight design, with low rotational mass on the drive system. The typical ball screw drive system does not.

These days, many CNC Router manufacturers are employing a "rotating nut" design in the engineering of their machines. This design allows for low rotational mass. One company which uses this design is CNT Motion Systems. They use auto-lubricating ball screw design on their X axis, and helical rack-and-pinion on their Y axis. They have been making CNC Routers for a very long time, and make a fine machine. I will personally vouch for that. Why would they mix ball screws and rack-and-pinion on the same system if ball screws were so far superior to rack-and-pinion?

On October 21, 2002 Design News magazine released an article entitled "Re-evaluating the Rack-and-Pinion". This article sheds some new light on this ongoing feud between rack and pinion and ball screws. It is a very technical, in-depth article. So, for those tech-savvy readers, I encourage you to read this article. For those who are intimidated by this sort of thing, but are looking to buy a cnc router, the article basically says this: Depending on how your machine is designed, and due to the newer technologies out there, it is quite possible that rack-and-pinion beats ballscrew, both in cost, accuracy, and performance. Granted, this does not apply in every case. But you should not be duped into believing that you are better off with a slower, ball-screw driven machine, when you can buy a rack-and-pinion driven machine for the same cost and get exponentially greater speeds.

The bottom line is this: The most important thing when purchasing cnc routers is not the type of drive system it has. CNC Routers are getting to be like automobiles now:Everybody needs them, everybody makes them, everybody sells them.

The most important thing is to develop a relationship with the company that sells and supports the machine. What kind of reputation do they have? How long have they been working with CNC routers? What support medium do they use to take care of the customer after the sale? Do they have user's groups, phone support, remote assistance and support via the internet?

After all, once you've paid your 50% down, you want to know you can trust these people to take care of you, 'cause "you ain't gonna get it back." My advice is to go visit the factory of your potiential CNC router vendor in person. It may cost a few dollars, but it will ease your mind. You'll know who you are buying from, and you'll know how they operate. That way, after they have your deposit, you won't be so terrified that you made the wrong choice. You'll know you've made the right choice.

For those of you who have already bought a CNC Machine, but are having trouble getting the support you need and have exhausted your options with the factory... Or if you are in need of a retrofit for your existing control system on your older machine, email CNC Experts at info@cncexperts.com . CNC Experts can service and/or perform retrofits and upgrades on the following machines: MultiCAM, CAMaster CNC routers, WartHog CNC Routers, Digital Tool cnc routers, VyTek machines, and others.

Can Drawing Software Be Used With CNC Routers?

Drawing software, or illustration software, such as CorelDraw and Adobe Illustrator, is sometimes used as the first step in creating a design for use with CNC Routers. This can be a very practical solution for some router users, such as sign shops, and those cutting more "artistic" shapes. It is also practical for many who use CNC laser cutters and engravers which communicate to an HPGL driven machine via a Windows printer driver.

In this case, all the user has to do is use a simple CAM software to assign depths, speeds, and information about the tool being used to cut the job, then output to G-Code.

Drawing software, however, is not always practical for those with very geometrically shaped parts, as drawing software is based on Bezier curves instead of lines and arcs. No blanket rule can be set, as the needs of every customer are different.

For this reason, it is often recommended to use a CAD/CAM software package which has all or most of these capabilities in one program. A good example of such a software is EnRoute, a Scanvec/Amiable product.

How Would My Sign Shop Benefit From a CNC Router?

Sign shops can benefit greatly from the practical benefits of CNC Routers. Bundled with the right software, a CNC router can be used to do any or all of the following:

1. Cut channel letter faces and backs
2. Cut routed signs from wood, high density urethane foam, and other materials.
3. Cut letters from foam, acrylic, pvc, aluminum, brass, etc.

The average sign shop typically does not have $60,000 to spend on a CNC router and software. The truth is, a complete CNC router solution can be found for a sign shop between $18,000 and $25,000.

The most a reasonable sign shop owner would want to pay for a CNC router system, even if he wanted all the bells and whistles would be $45,000 or so. However, a system like this would be more than most would ever use. Most people would simply be throwing away between $15,000 and $20,000.

A system for around $25,000 would include signmaking software, the machine, a vacuum hold-down system, and everything else needed to go into the sign business with a CNC router.

Below are a couple photos of items cut using a CNC Router.

Plastic Part cut on CNC Router

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Routed Sign cut on CNC Router
Made from HDU (High-Density Urethane Foam)

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The Letter "R" Routed from HDU (shown unpainted)

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What is a postprocessor?

The term postprocessor, sometimes referred to as a "post," basically means a translator.

Picture a job foreman who speaks English. He needs to instruct his worker, who speaks Spanish, how a certain project should be done. So, he uses a human to communicate his instructions to his worker.

Think of the CAM software as that job foreman. The machine is the worker. The postprocessor is the translator.

In more technical terms, the postprocessor contains the instructions needed to translate design and toolpath information from a software's native language into the language a CNC machine uses to accept instructions.

What is CAD/CAM Software?

When a software claims to be CAD/CAM software, this means the software has the ability to do all of the following:

1. Create a design from scratch.
2. Apply toolpath information to the design (such as cutting speed, depth of cut, etc.)
3. Using a postprocessor written for the machine's controller, send that toolpath information to the machine in the language that the machine understands. (Typically this "machine language" is some form of G-Code or HPGL. You'll learn more about this later.)

In other words, CAD/CAM software stands alone and does not require any other software between itself and the machine's controller.

What about CAM? What does that mean?

CAM stands for computer-aided machining. If a software claims to be "CAM" software, it usually means that it is used to act as a bridge between some CAM software, which designs a part, and the CNC machine that produces the part.

What does the acronym CAD Stand For?

CAD stands for computer-aided design. Typically this abbreviation is used when discussing CAD software. One well-known example of such software would be AutoCAD. Many people use AutoCAD or similar CAD software to design parts and shapes to be cut using CNC Routers.

What is a CNC Router?

I know it may seem strange that we would even address this question here. But we're going to.

For those of you who are just getting your feet wet, a CNC Router is a computer-controlled machine that cuts things. You create a design in a CAD program, and the router will cut it out, automatically.

Here is a picture of a basic CNC Router:

First -- The Purpose of This Blog

The purpose of this blog is to discuss trends related to CNC Routers as well as assist those who need help getting started into the world of CNC Routers. Things in the industry are changing rapidly. It seems everybody wants to sell you their idea of what you need.

In reality, what you need is to be able to educate yourself, with the help of those who have experience, so that you can come to your own intelligent conclusion regarding decisions like these:

1. What CAD/CAM software should I use to drive my CNC Router?
2. What price range should I be looking at?
3. Of all the bells and whistles offered out there, which options do I really need?

These are just a few of the questions I intend to answer in this blog. Perhaps you have questions. Feel free to post comments with anything you would like to share.