It's crazy, but I started a CNC lathe conversion, a CNC milling machine conversion, a CNC laser build, a couple of 3D Ord Bots, and now I'm building a CNC router. I'm either going to get an award for the most concurrent projects, or Bart is going to kick me off BuildLog.net for starting too many projects and not finishing them. My excuse for starting projects and not finishing them is that my online business was very busy this year. I had a surplus of revenue and didn't want to pay taxes on it, so I bought the equipment to expand my business so I'd have 2012 deductions, even though my hectic one man business allowed me little build time.
I wanted to design and build my own 2X4 CNC router with an integrated table and dust collection system, and make it beefy enough that I could do some semi-serious machining in aluminum... sort of a cross between a gantry router and a small vertical machining center... but given my abundance of unfinished projects and my lack of time, I decided to BUY a very beefy 2X4 CNC router kit.
The kit manufacturer also sells on eBay (user name: signal-seeker). He doesn't have much of a website, so here's his current eBay ad, and some pictures I'll repost for later when the eBay ad is gone.
http://www.ebay.com/itm/130820766902As you can see, this CNC router kit uses Chinese linear rail and Chinese ball screws, and the rest of the design is aluminum. The materials certainly look beefy, and the design looks fairly beefy too. Probably not as ridiculously beefy as what I'd design, but pretty darn good. It's definitely not the cheapest CNC router kit on the market. Far from it. In fact, it's one of the more expensive for its size, but I can say that it's one of the cheapest to use ball screws and linear rail and the other nice features. This is the manufacturer's "commercial" kit. The same manufacturer also sells a kit that uses linear rod and Acme screws that still looks quite nice. I opted for the beefier commercial version, because I plan to run production on it, and I expect my brother will use it a lot for his new business venture too. Of course, I'm sure that most people who buy a CNC router have some sort of serious justification, whether it works out that way or not.
I'll be picking up the CNC router kit on Saturday.
I bought the CNC router kit without the motors and motor drive and I/O electronics for $2500, which is $200 less than the complete kit in the eBay auction. I plan on using (you guessed it) bigger motors. I also had my own preference in motor drivers that I accommodated at the same time. The stock stepper motors were 270 ounce inch NEMA 23 motors. I purchased a complete three axis stepper motor motion control kit with 1090 ounce inch NEMA 34 motors.
http://www.ebay.com/itm/140894283015I'll need to drill and tap my own mounting holes for the larger motors. I'll laser cut a drill guide with four NEMA 23 clearance holes, and concentric NEMA 34 tap hole drill guides. I'll make it with two sets of NEMA 34 mounting holes, 45 degrees apart, in case I need to mount a motor at an angle because of clearance issues. I hope the larger motors fit the router table without much grief. That was a bit of a leap of faith.
The motion control kit was purchased on 29DEC12 and should be here in about a week or so. There's no evidence that it's shipped yet.
I went a bit nuts and bought a Chinese 3 HP water cooled spindle.
http://www.ebay.com/itm/200773029466I'll never use that much power on a gantry router. The machine is just not stiff enough. I probably should have bought the 1 HP or 2 HP version and saved some weight. The added mass is just more to accelerate when moving the gantry. My thinking was to get a 3 HP sealed water cooled spindle, use maybe 1/2 HP, and it should last a good long time. After receiving the spindle, I had other thoughts. If I was doing it over, I'd probably get a 2 HP spindle. I might make some slightly aggressive cuts for roughing cuts, where a little bit of deflection could be tolerated as long as it didn't start to chatter as that tends to shatter carbide tooling. I'd make lighter finish cuts where I needed to maintain precision. As it is, I expect to layout my jobs so the heavier cuts are in the direction of the longer axis, which I'm calling the X axis. Based on the design, I expect the machine to be more rigid in the X axis, and less rigid cutting side-to-side which would tend to distort the gantry from a rectangle into a parallelogram. If that seems like a problem, I'll probably mount an aluminum plate across the back of the gantry to stiffen it against such bending. If I did, the Y axis may be the stiffer axis, given that the X axis stiffness is riding on one bearing block on each side of the gantry. Too many variables to guess. I'll have to wait and see after it's built.
Even though I'm convinced that the spindle motor is way too big, even for a beefy CNC gantry router, I'm very impressed with the spindle motor's build quality. I haven't fired it up yet, but spinning the spindle by hand was a nearly sexual experience. I've never felt such a smooth spinning armature on a motor of that size. The eBay auction mentioned some fancy German bearings, and I believe it. It has a very high precision feel. It was like a 3 HP dental drill. Expensive servo motors don't feel nearly this nice, and the typical router from Dewalt, Porter-Cable, Bosch, et al, feels like it has gravel for bearings by comparison.
The ER20 collet nut was spot drilled in three places where it was dynamically balanced at the factory. I paid quite a bit extra to get some precision ER20 collets with .0002" average total indicated runout. I bought regular non-precision ER20 collets for my milling machine, but they won't be spinning at 24000 RPM like the spindle on the CNC router. At that angular velocity, a lot less runout can result in significant centripetal forces leading to vibration, and I didn't want to accelerate the spindle motor bearing wear or accelerate the wear on carbide cutting surfaces from chatter or vibration. I'm a bit suspicious of the .0002"
AVERAGE TIR. Average isn't a kosher way to measure TIR, in my opinion. I think it should be measured as maximum runout, but, whatever. The US made precision ER20 collets were sold in sets for over $200, and sometimes WAY more. The Chinese precision collets looked good and inexpensive. We'll see.
http://www.ebay.com/itm/251198551519I've also bought some carbide tooling (Chinese and US, to compare), a 5/24V DC power supply to power the control electronics and logic on the machine side of the optoisolators, etc. I have lots of stuff left over from previous builds, where I bought extra E-stop switches, LCD temperature displays (for the spindle coolant temperature), a small coolant pump, solid state relays, prox switches, etc. I still have some minor stuff to buy, mostly some incidental electronics and the support table/frame and dust collection enclosure. I'll wait to design that, after the CNC router is running on saw horses, but I've already bought most of this project.
Here's the Chinese 1/8" carbide ball end mills I bought.
http://www.ebay.com/itm/140444566452Oh yeah. In my mad dash to purchase as many expense deductible items as possible before the end of the year, I purchased a digitizing probe.
http://deepgroove1.com/probe/probe.htmI've been reading up on how to do digital probing. Apparently, there's a wizard to do that in Mach 3. I'll be using LinuxCNC, and it's done with either gridprobe or smartprobe, which are just some reasonably simple G code. They write XYZ point cloud coordinate data to a file that can then be input to several different programs to create a surface, which can then be output as an STL, or with information added about the cutting tool, G code can be generated to cut the copied surface on the CNC router. A Linux and LinuxCNC compatible solution for generating G code from DXF, STL, etc. is PyCAM.
http://sourceforge.net/apps/mediawiki/pycam/index.php?title=FeaturesI'll probably buy a PC and monitor on Craig's List to run LinuxCNC. $100 or less is pretty cheap for a realtime controller with a nice big graphical display.
I like the Logitech K400 wireless keyboards because they can be carried close to the work and used as a glorified wireless pendant for touching off on the workpiece and other up-close precision work.
http://www.logitech.com/en-us/product/wireless-touch-keyboard-k400But I also bought four of the JogIt! pendants on KickStarter, configured for LinuxCNC, and they should be shipping later this month.
http://www.kickstarter.com/projects/1651082654/jog-it-open-source-controller-pendant-for-emc2-andI'm always overly optimistic about my projects - ridiculously so - but I expect this CNC router to come together fairly quickly. I bought the kit for the router table, and it should assemble in a few hours. It's mostly bolt-together. The Z axis is pre-assembled. Bolt on the stepper motors, wire them to the motor controllers, wire those to their power supplies and the motion control kit is installed. Stock LinuxCNC is good about controlling these stepper motors. Run the stepconf routine, tell it the microsteps and the pitch of the ball screws, and it should be a done deal. You guys can quote this arrogance later in this build log and laugh at me when I run into the inevitable problems. Really, I don't mind.
Then maybe I can finish the more complicated projects - the CNC laser, CNC milling machine and the CNC lathe.
I'll probably post a picture or two of me transporting the CNC router mechanical kit, but then it's all build posts. I think I'll take a tip from some of you other guys and lean more in the direction of a build vlog - heavy on the video, so you can see the build in greater detail with less of my wordiness to suffer through. Of course, I think listening to my voice may be worse.