In my first post a few months ago, I mentioned how my company has grown and matured to the point that I am considering adding a CNC machine to the shop. I also discussed the incredible weight a decision like that brings to the mind of a small shop owner. A CNC machine is not a “genie-in-a-bottle” that will solve all of our problems, so I want to make sure I don’t treat it as such. But, on the flip side, I don’t want to be so paralyzed by the fear of making a decision that I never leave the reasearch and analysis stage.

Today, I want to discuss what my business is looking to get out of a CNC machine and how those needs translate into actual machine specs.

My company specializes in custom furniture and cabinetry. The cabinetry, primarily residential remodels, accounts for 2/3 of our revenue, and custom furniture accounts for the remaining 1/3. It is pretty obvious how a CNC machine will help the cabinetry side of our business. I do not have to be convinced of the machine’s value in cutting up sheet goods quickly and accurately. The unknown factor, and where a CNC machine could really shine for us, is in how much we would be able to utilize it for the custom furniture we design and build. Everything I have read says that, once you have the machine, you will end up using it for far more than you realized, and this may very will be the case for us, since we do such a wide variety of custom work. I have also been told that you will be able to use your increased capabilities to land a wider variety of jobs. But, before we get to carried away, lets focus on the most important aspects of the machine and how they will serve our current needs.

Table Size

The majority of the sheet goods that we cut up are 4×8, but there have been a few dozen times that we have ordered 5×8 or 4×10 sheets of MDF or melamine, which mostly occurs when we are making built-in bookcases for 9′ and 10′ tall ceilings. For this reason I will be purchasing a machine with a 5×10 table size. Many machines are available with a 12′ long table, but the only thing that we have ever cut that is 12′ long is the occasional sheet of laminate, so that is not important enough to warrant the extra cost. Now, if your shop is constantly processing 12′ sheets of laminate, your answer may be slightly different.

Router Size

I want to make sure that the router head is powerful enough to machine solid wood components, like a 1.75″ thick table top. This translates to a 9-12HP router head, which will be able to cut through solid wood panels and table tops at the necessary speeds to optimize cutter head longevity.

Vacuum Pumps I will admit, this is one aspect of the machine I don’t yet fully understand. I do know that bigger is better, but what is the optimal volume in cubic meters? If you oversize the pumps, then you will be wasting money on your electrical bill. But, if you go with an undersized pump, you will be fighting with small parts moving during processing. Add into the equation the fact that vacuum size changes depending on your elevation above sea level, and this is one spec I will probably just trust my rep to answer for me.

Vacuum Pods – Z Clearance The use of vacuum pods are “imperative” for the machining of solid wood components. Without the ability to use pods, solid wood parts have to be held down to the spoil board using another method, such as clamps or screws.

Using pods then brings into play the Z-axis clearance of the machine. If the Z clearance is to short, by the time you set a pod to the table top, lay the work piece on the pod, and add a cutter head to the router, you may not have enough room to do the necessary machining to the work piece. Any machine we purchase will need to be pod-ready and will need to have enough Z-clearance to machine a variety of solid wood components.

These are just a some of the details to consider when choosing a CNC machine. In the next installment, I will take a look at the rest of the specs that I feel are necessary, and some that I have decided aren’t worth the cost at this moment in time.