DIY CNC Router Build
Hacking the Cricut
About 10 years ago I discovered CNC routers and wanted one on my bench sooo badly! Normally I can convince my wife to hand me the checkbook for a trip to my favorite tool store fairly easily, she asks me to do a particular project and I always reply “yea honey, gonna need a new tool for that though”, but even I flinched at the $6000 price tag for a table saw sized CNC machine at the time. So I did my research and cobbled together a pretty decent machine for around $300, most of the cost was for the controller, the rest of the machine was built from plywood, home store drawer slides, and threaded rod. It wasn’t fast or as accurate as a commercial machine, but it worked like a champ at milling designs in wood and Styrofoam for signs and silicone mold making.
Fast forward 5 years and I score a defective Cricut Expression cutting machine off eBay for 20 bucks including shipping. A Cricut is nothing more than a CNC machine designed to be easy to use by anyone, I made a simple fix to the machine and I’m off cutting vinyl signs and stickers like a madman. Never being one to waste a good thing, I bought a half dozen more defective Cricuts off eBay for practically nothing and stuck them up on the shelf for another project that was brewing in the back of my mind. Meanwhile, I got wind of a couple of new software programs that could be used with the Cricut to cut any design you wanted without resorting to buying expensive pattern cartridges. Early versions of “Sure Cuts A Lot” and “Make The Cut” would work with the early Cricuts via it’s USB port as long as you had a cartridge in the machine. Unfortunately ProvoCraft, the makers of the Cricut, didn’t see that fitting into their business model of selling cheap machines that relied on expensive cartridges to do it’s job, they went after the software creators with a vengeance. They won in court but lost a boatload of business in the process, they pissed off their customer base, and even Walmart quit selling their consumables, at least in my area. Luckily the Cricuts I have are all early versions and I have early versions of both software packages as well. So, let the Cricut hacking commence!
I’ve had five Cricuts sitting on the shelf waiting to be cannibalized, three of the 12″ Expressions and two of the 6″ Personals, for this project I’m going with the Expressions. What I plan to do is marry the 3 units together into one to create a “12 x “12 cnc machine based on the Cricut control circuitry. The Y axis on the Expression is actually 16″ so if I do it right I should easily get a 12″ x 12″ platform, probably closer to 14″ x 14”. Instead of using a router on the finished frame I plan to mount a 2 watt laser I have in my toy box that I’ve been playing with on my existing CNC machine. I don’t want to leave it there because that machine was built 10 years ago and while it’s still a pretty decent machine it’s a bruiser because I built it to run a trim router, quite a bit of overkill for a laser. I’ve already got the three Expressions disassembled so let the FrankenCricut build begin!
FrankenCricuit: Test assembly
Ok, so the preliminary test assembly is completed, the Laser head with cooling fan is mounted, now time to get the electronics ready. Click picture for larger view.
FrankenCricut: Not Exactly a Go
Ok, so things didn’t exactly go as planned. I got the Cricut electronics all hooked up and ran it through a few test runs before turning on the laser. I ran it from Sure Cuts A Lot (SCUT) and it worked just fine, even the relay interface for the laser worked as planned, it looked like I was going to have a winner on my hands. The problem: once I powered up the laser everything worked great except the machine ran too fast for my 2 watt laser. The laser worked just fine on my older/slower home built CNC, but on the Cricut even at it’s slowest setting, the laser would only scar the surface of the wood. I tried to figure out a way to slow the Cricut down but all the control for speed is coded in the software, and short of trying to hack the control chip on the motherboard there was no way to accomplish the task. Hmmm, what now. The whole idea of this build was to show that it could be done on a limited budget using a low powered laser. The existing 2 watt I have is a standard high power diode which was $135.00 on eBay, with the driver and housing. To go to a higher powered system and do it right, you have to use a Co2 tube laser which starts at $300.00, then you have to get a power supply for it, then with optics and water cooling you’re up to a grand in cost, after that your CNC would only be usable for the one purpose. I want mine to be multipurpose with interchangeable heads for milling, and in the future, plasma cutting. So on to plan “B”, a CNC machine using a standard control board running Mach 3 CNC software on a Windows XP box. My old machine was a DOS box running TurboCNC which works fine but I figure that if I’m going through all the trouble to build a new router I might as well bring the computer into the 21st century, so stay tuned as I continue my CNC build.
Just to give you an idea of what can be done with a 2 watt laser I’ve added a picture to this post of a door sign I did for my granddaughter using my old CNC machine.
FrankenCricut is Dead? Already?
Not being one to continue to beat a dead horse (for too long) I think I may eventually have to give up on the FrankenCricut idea and move on. Last night I fired up the machine on my old reliable Mechatronics 3 axis controller and as I began to calibrate and tune the motor drivers I soon realized another roadblock in using Cricut parts, the Nema 17 hybrid steppers used on the Cricut are obviously driven by a control board that is fine tuned to their specifications because when I hooked them up to my Mechatronics board they whined like hungry puppies when sitting at idle. If I adjusted the current and decay on the controller to a point where they stopped whining then the motors had no torque and would barely move. I never had this problem on the old machine, but it had bigger Nema 23 motors and was built from heavy plywood so resonance was never a problem unless I really over-drove the steppers. In researching the issue it turns out this is a common occurrence and most people just live with it or power down the controller when not actually doing work, I suppose I could live with that but it’s going to come down to how I can resolve the next problem. My controller is not a 4 axis controller and my X axis has two stepper motors, one for each side on opposite ends, as opposed to having just one in between driving both sides. Normally you would slave two axis together (X+A) on a 4 axis controller then run one of them backwards, in this instance I’m not using the Z axis but unfortunately X + Z is not an option. What to do? Well the Nema 17 motors are rated at 1 amp each and my controller is rated for 2.5 amps per axis, so 2 x 1 = 2amps, just under the rated limit for each axis. I think I’ll try wiring both motors to the same X axis, but wire one of them backwards and hope for no smoke when I bring it all back on line. Stay tuned!!
Yep, FrankenCricut Is Dead…
Time to move on, the original idea of the FrankenCricut has finally died. My attempt to run two steppers from the same axis as previously described didn’t work out so well, one stepper would always get ahead of the other and lock up the X axis, so on to plan B. Start over and build it like the first CNC I built ten years ago, only this one will be all metal. I’ll still be using some of the Cricut parts, the rails, trolleys, and the stepper motors, I’ve decided I can live with the motor resonance at idle I had described in a previous post. I already have the X axis done (pictured below). The next picture shows the four holes (circled) on the Cricuts original end support I transferred to a piece of 1/8th” by 3″ mild steel flat stock purchased at Menards. I cut two pieces the same length and tack welded them together so all the holes would line up end to end keeping the trolley rails perfectly parallel, notice in the picture that the rails have alignment pins as well. At the same time I also drilled holes for the stepper motor shaft and attaching screws at one end and screw shaft bearing support at the other. The X axis will now be screw driven but I plan to keep the Y axis belt driven as it originally was. The next step is building the Y axis, stay tuned….
Current State Of The CNC Laser Router
Every time I get the chance to escape the honeydoo list I get a little more done on the CNC.
Click on pictures to see larger view.
This first picture is of the original Y axis trolley.
My version, one for each side.
Assembled Y axis, minus stepper motor and drive belt.
CNC Assembly Complete
Assembly of my new CNC machine is complete, now for the testing. Keep in mind the original machine I built ten years ago from plywood and drawer slides.
Now the new machine….
Homebuilt CNC Test Run
Just a quick update as I’ve run into a bit of a snag, while in initial test’s the Cricut’s Nema 17 steppers worked ok with the laser head but don’t think they’d be able to handle engraving with an engraver or Dremel, they just don’t seem to have the torque. Going to fabricate some larger motor mounts and stick some Nema 23’s on it now instead of having to go back and do it later.
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