CNC Pt. 14: Upgrades

Which brings us to our next thing: upgrading to a real spindle.



This is the 4/5hp spindle assembly from an X2 mini mill. The cast iron has been chopped down a bit to reduce weight, and the gear drive replaced with a belt drive for reliability and sound. There are a ton of advantages to a real spindle over a crappy router, too many to list, but here are a few big ones:

1: Play. There is almost none, so chatter is cut down drastically. This is better for your finished product and better for your bits.

2: Torque. A trim router has none. A VFD controlled motor maintains most of its torque at any rpm.

3: Collets. Rather than a crappy, 1/4" only 'collet' (which is really a badly designed chuck), this uses R8 collets (I also have an adapter to go to ER32 collets). This means flexibility in what bits I can use, less chance of them coming loose, and less runout.

4: Sound. Routers sound terrible, this has a pleasing hum to it.

5: Motor placement & type. Since it's far enough away from the business end, and mostly sealed off from the elements, this will make running coolant much easier.

CNC Pt. 13: More Tests

With that done it was time for some real tests. First in wood:



Then in aluminum!





There's some chatter in the router, and of course the router has to be run well above the appropriate cutting speed for aluminum. But it gets us by for some messing around.

CNC Pt. 12: T-Slot Table

Next up was the T-Slot table. This was also the first time the machine could really be used for something meaningfull, as all the holes were drilled by program. This was exciting for a lot of reasons, not the least of which that it was drilling aluminum for the first time.

CNC Pt. 11: Enclosure

I didn't realize how far behind I was on updating this project, but much has happened since the last post. The plan was always to make this an enclosed machine, and to make it as quiet as we could manage. The sides were covered with sheet metal, the sheet metal lined with automotive sound deadening material, and the front with a big piece of 0.25" lexan. The lexan is held in place with magnet strip, which also insures perfect alignment without needing pins.





It has become known as "The Evil Dishwasher."

CNC, Pt. 10: First Test

Everything was moved back out into the garage and all the power supply, controller, and computer parts were mounted into a single tidy computer case.



You'll notice the computer we're using is one of those little ViaC3 mini-ITX setups. They're small, relatively cheap, and have everything built into the motherboard.

Mike made a quick model in Lightwave3D and imported it into DeskProto. DeskProto is a tool that creates machine code (in G-Code format) from 3d models. From there it's just a quick trip to the machine's hard drive to run the file. And here it is, our very first test cut, hacked into a 2x4.



It's fair to note that while the machine is far from done, this is a pretty significant milestone. The first goal: a machine that could cut intricate shapes into wood for use in furniture (or whatever) has been achieved. There are several other goals ahead though.

CNC, Pt. 9: Computer

After a great deal of debate, trial, and research, we loaded a computer with FreeDOS and TurboCNC. To sum up the argument, windows based controllers, in my experience, suffer from an endless chain of issues associated with the use of hardware abstraction layers to provide "security." Linux works well, and offers EMC2 (free), but after a few arguments between myself and the system I decided this was a good place for pure simplicity.

TurboCNC reads control code (G-Code), interprets and outputs directly to the controller. Simple, straightforward, constistant, and free to mess around with. Donate the guy some money once you decide TurboCNC is awesome. Same goes for FreeDOS. These guys put a lot of work into their software for our benefit, and should be rewarded.

It took less than 5 minutes to get TurboCNC moving the machine, where we ran a few test files just to see everything work together. Messing around we were able to achieve some pretty good speeds (up to about 140 IPM, not bad for a heavy machine under powering its motors). Also, at 75 IPM the machine feels totally unstoppable. You can push and pull with all your might and it just keeps tracking along regardless. Also, there is no discernible play or flex in any dimension. When the motors are held constant it feels like everything is just welded in place. I do believe this thing is going to work:

CNC, Pt. 8: Wiring

The whole apparatus was then moved onto my kitchen counter for wiring and testing. All the parts for the power supply, which consists of a large toroid transformer (changes 120V household A/C current to 32V A/C Current), a bridge rectifier (converts AC to DC), and a couple of large capacitors (help keep the power source stable). The final output is 30 volts at more amps than I can make use of.

Stepper motors, for those who have never messed with them, are motors with many sets of magnetic coils that can be energized independently. When one set is energized the motor jumps to a certain position. Energize the next set and it jumps again. By this principle we can control how much a motor turns and how fast. It does, however, make for complicated controlling mechanisms.
The motor controller board was another ebay purchase. It is possibly to save a load of money and build your own controller, which is exactly what I have done in the past, but things have changed since then. My (time X money) = constant ratio has shifted a bit, leaving me with the ability to afford a premade controller, and not a lot of time to build one from scratch. Your situation may closer resemble standard college life.

CNC, Pt. 7: Z Axis Motor Mounts

The mounting of the Z axis motor was done using more 1/4" aluminum plate. It was at this point, or somewhere close to it, that we decided that the Z axis plate needed more structure to prevent it from flexing under load. Aluminum L brackets were added, which had the benefit of looking pretty cool.

Reasons to work late

CNC, Pt. 6: X and Y Axis Motor Mounts

Time to mount the motors! All the ball screws needed to be turned down on a lathe so that a standard coupler could be used to attach them to the motor output shaft. This is a very laborious and time consuming process that is probably best left to someone else. Being a masochist, I went ahead and turned them down myself on my mini-lathe. The outer surface, to about 1/8" depth, is extremely hardened steel. To the point that it cannot be cut with a standard bandsaw blade. It's really tough stuff.



The actual motor and ballnut mounts are made from welded steel plate, then ground flat on a plane sander. It is most important to get the mounts to a perfect 90 degree angle, as any adjustment in this dimension has to be done with shims. When completed I only needed a shim under the Y axis ballnut mount, which was cut out of a cheap auto parts store feeler gauge set.