Think before you take the CNC plunge

WOODWEB technical advisor Brian Personett offers some food for thought to those thinking about purchasing CNC equipment. November 15, 2000

For those of you who are looking at getting into CNC equipment, here are some things to think about when justifying the cost of the equipment, particularly routers and P2Pís. These are somewhat hidden costs that the machinery people often neglect to tell you about. If this is your first foray into automated equipment, they may well be things you would never think about.

First and foremost--do you have enough power in your building? If you only have 200-amp service you may well be looking at installing new service. Whatís an additional 200-amp panel going to cost you? What about getting it installed? Also, do you have 3 phase? If not, you are either going to have to get 3 phase service or a converter. If you live in a rural area, you may well be forced into the converter (if you havenít already fallen over dead with a heart attack when your rural power company gives you the price for installing 3 phase). It really depends on your local company (it didnít cost us anything back when we got our 3-phase service).

You will also want to find out how much dust collection your machineís manufacturer requires. Donít skimp here. If these machines do anything well, itís make dust. Poor dust collection will cost you dearly in both tooling life and the life of the machine itself. You are most likely going to be running some high tech (expensive) router bits, and proper dust extraction is a must. Also, if you have a machine with an electrospindle (or even some standard routers), it will rely on the dust collection for cooling. Does it really make sense to save a couple grand on the dust collector when you'll soon be replacing routers at 10K a pop?

Where will the machine actually set in your shop? Will you have adequate room to work once the machine is installed? Will you have room to get all around the machine to perform routine maintenance? What about the floor--will it handle the weight and motion? Your machine may weigh in excess of 4 tons, with a head weighing 1200 pounds and moving at 40 meters a minute.

Of course there is software. I won't go into a great deal of detail here--this stuff has been discussed ad nauseum all over the Internet. However, I'll point out that if you are going to purchase a router or P2P, you will need two pieces of software in addition to the machine's operating software. You will need some kind of CAD package, anything that will generate an accurate DXF file (Corel Draw is not an option), and a post processor.

You will use the CAD package to do complex curves, angles, most of the ďgoofy stuffĒ. You can probably do all this stuff with your machineís software, but the math can sometimes be overwhelming.

The post processor takes the DXF file from your CAD package and actually writes the G-code for your machine. Some machine-supplied software has a built-in post processor (I believe Weekeís WoodWop does).

There are people out there not using either of these. However, in my opinion your machine will never operate anywhere near its capacity without them. You may say "I just want to make straight square cabinet parts--I donít need any of that stuff" and thatís fine, but donít forget your son or daughter will probably want some of those cool dinosaurs and I canít imagine trying to write a nest like that by hand. So use whatever CAD package and post processor you want, but if you are considering the addition of a router or P2P, start exploring your options.

The last thing I want to touch on is tooling. In my experience the machinery dealers donít do well offering tooling solutions. Go to the tooling manufacturers, tell them what you are doing and ask for their assistance. There are endless options depending on your specific needs. In my experience most of the tooling companies around today make decent tools. Company A may make a better 3 flute hogger than company B, but company B makes a much better compression bit.

Know going into this that you are going to spend a few bucks. Itís not out of the realm of possibility that you will spend $1000 to $1500 or more to put tools on your machine. Do some research, see what other people are using, try some different company's bits, experiment.

Buying your first piece of CNC equipment can be quite overwhelming. When we signed on the dotted line, I had so much going through my mind I wasnít sure I could find the car in the parking lot when we left. After the salesman got done with us I was certain this machine would fly me to the moon. Do some leg work before you start talking seriously to the different salesmen. There are forums all over the net where most of these machines have been discussed, both their strengths and weaknesses.

Brian Personett, forum technical advisor

I agree wholeheartedly and would only add that an understanding of what you plan to run on the machine and how it will be run is invaluable when deciding which machine. With our machine we lucked into most of the right choices but I would make a few changes if I had to do it again. The more tool change capacity the better in terms of flexibility in manufacturing, and size does matter!

We found out about the power issue the day the tech arrived. We could not even start up the machine because the frequency of our converter was too high (or low or something) when none of the other machines were running. When we turned on all the other machines (saw, bander, sander, etc.), the frequency was fine. To make a long story short, we had to send the tech back to Stiles, wait a week to have a second converter built dedicated just for the P2P, and fly the tech back to Indiana for another 3 days. Killed 2 full weeks in the process.

Our electrical service provider wanted $20,000 to run 3 phase service 150 yards to our facility. In the process we had to install a new service, breaker box and a bunch of other things. And of course we did it all again 2 months ago when we moved the machine to a new building addition. So I guess the lesson here is to have all these ducks in row ahead of time.