(Revised May 2009)
Thinking about building a CNC router table for home use? Maybe you can benefit from my experiences. But know this: my machine is odd, odd in several ways.
The X and Z motors are housed in (of all things) a plexi box which doubles as a cooling tower. The breeze comes from a discarded computer fan, filtered by cut-your-own foam medium. The cables are held out of the way with a plexi scissors contraption. For all the laughs plexi is quite stiff, lightweight, exposes all the things I need to see. And it’s cheap and easy to work. If it bothers you that it’s not shatter-proof you can opt for the polycarbonate version for a few dollars more. Ironically, the cheaper stuff’s better optically and resists scratching better than the “bullet-proof” variety.
Almost all CNC routers are driven mechanically with leadscrews (leed screws). When the screws turn they move the gantry or the trolley or the spindle. Good screws are expensive and require more thinking. At least, I thought they did. So the screws are absent in favor of off-the-shelf racks and pinions (RnP) in all three axes (ax-eez). I didn’t know when I was building that the most popular hobbyist CNC router, the ShopBot, uses RnP. No, I did it because it seemed easier and cheaper. Probably an even greater factor was availability for the eBay crowd (me). Start shopping for leadscrews and you’ll see what I mean. If cost is no object you can have leadscrews tomorrow morning.
If cost is an issue- you can have new RnP- in the morning. That’s just the way it is. Sometimes a far cheaper option works really well. A perfectly adequate lever can sometimes be as close as a fallen limb.
And while RnP is no stranger to the CNC world- the motor pinions are usually not interfaced directly with the racks. Usually a gear-reduction of some kind is designed in. The consequence of this direct-drive is higher gearing which is not a good thing. It just so happens that I got away with it– probably the result of my motor selection which was also an accident. At some point in the future I will add a gear-reduction mechanism, making a good machine better.
I guess it would be safe to say that every thing I did differently was done to make it easier for me, quite often cheaper. And how did it turn out? To this day I’ve never even been in a room with a CNC other than my own. So comparisons are limited to what I see on YouTube. But I’m tickled. It hauls ass and does smooth precise work.
My greatest worry about this project was the fear of dumping a ton of time and money into it and ending up with a novelty, a machine that could only do parlor tricks like cutting my initials in a piece of Styrofoam. Yawn.
So how to avoid that? I wanted to have something that was capable of doing some real work. I wanted it to have enough power to haul around a full-sized router, cut real wood.
Should I get this motor or that motor? It was a pure crap shoot. I absolutely did not know. I got lucky. That’s all it was. Because this thing does great. Plenty of torque, certainly adequate for it’s intended purpose.
I wanted to be able to use quarter inch bits and cut at least 1/4″ deep into hardwood or plexi. It will. And how! But I had several false-starts. I’d drag the stuff out, get scared, put it away. Started to put it all back on eBay where most of it came from. Who was I to build a CNC anything??? That went on for months! And have you noticed? Life’s short!
A lot of the time I was downright angry. I felt like I was getting half-ass answers when I needed detail. Confusing me is not a good way to get in my wallet. I like to feel confident when I buy. I didn’t want them to kiss my ass. Just wanted them to tell me which thing to order and why. For many would-be suppliers that was just too much trouble. Truth is– lots of so-called vendors out there are faking it. They don’t know diddly. That’s why it’s so important to put your trust in the right people.
I can only speak for myself but I suspect that most successful hobby-level CNC router table builders struggled from start to finish guessing at what to get next. Not what to do, but what to get. How do you know if the part you have budgeted for next is too big or too little, too many amps, too little volts? Most of this indecisiveness is avoidable (sort of) because the info is certainly out there. But it’s damned hard and time consuming to get to. And lots of folks simply don’t answer questions in a language that I can understand. That’s why I’ve always said that a really good teacher should be proud. Most people just don’t convey knowledge worth a damn. That’s particularly unfortunate if you’re in a business that caters to information deprived customers with money in their pockets.
I’ve always known that my blog sucked. It has no particular organization, just doesn’t do what I want it to do. And what I want it to do is to serve as an especially valuable resource for guys who want to build a hobby-level CNC router table. Of course, you can use lots of the info to build a mill or whatever.
A couple of days ago I was poking around the Gecko site (Geckodrives.com) and started reading some of the documentation they provide. I immediately felt the need for some graphics. It’s a learning disability but I must have pictures! So I decided to make some pictures for myself based on what I thought Gecko was saying. I’ll invite them to look them over and hopefully get a thumb’s up. So now I’m inspired to make my blog better by trashing it and starting all over again.
As previously stated my CNC works really well. Without being able to say that there really wouldn’t be any reason for anyone to come here for answers. I’d just be another builder hoping for the best.
The first thing any builder should do is to come up with a plan of action, a build sequence. I couldn’t find any such outline when I was building. As it turns out Gecko probably had it posted all along. So I’m going to combine their suggestions with what I’ve learned and see if I can’t get some more guys into “our thing”.
Gecko suggests you begin by thinking in terms of weight. How much weight will you need to haul around in order to work the kind of material you want to work?
That leads to appropriate motor selections which leads to appropriate Gecko driver selections. After that– you know which power supply to buy and so on down the line until you’re finally deciding which project to make first.
It can happen rather quickly and rather inexpensively depending on your definition of the terms. One thing that helps the budget is the avoidance of purchasing errors. You don’t buy motors to push a five pound router through 1/4″ hardwood if you only intend to cut through 1/16″ balsa with a 1/8″ bit. It doesn’t have to be a crap shoot.
So let’s begin at the beginning. Let’s decide what size motors you’ll need. We’ll use my machine as an example. I knew I wanted to push a full sized Bosch router. So there’s the weight of the router, the aluminum plates (or whatever you choose to mount it on).
You will have to pencil in some weights for those things. If your design has all three motors being hauled around (like mine does) you can put down the weights of (3) motors while most guys will only be plugging in the weights of two. If you don’t know- just guess. We can change them later after we do the worksheet.
Since my machine’s already built I can weigh it while your machine (still on paper) must be calculated. But here’s the idea. (Please scroll to top of page and click page 111)
Let me know if I can help. ResourceGuide@comcast.net
