Toby V's CNC Machine and Process

Here is another excellent example of a customer putting together a CNC machine kit and revising/adding to fit his needs. Specifically, this is the blackToe version 4.0 CNC machine kit, put together by Toby, a Neuroscience Ph.D with a post Doctorate at Harvard focusing on electrophysiology of the biological neural network in the retna. He used this knowledge to create computational models of artificial neural networks to test new hypothesis. Now, he is mainly focusing on the business aspect with his current occupation and spending time at home with woodworking. With his knowledge and willingness to delve into the CNC world with my kit, I was, obviously overjoyed, at the opportunity to get feedback and see what additions and modifications he would make to the machine.

You will see some great imporvement to the overall machine. The machine, as most like it, can move. There are four sets of wheels, two at fixed orientation and two that can swivel, but that's not all. The wheels that swivel can be swung out of place and set on a pair of friction points. The helm of the machine is equiiped with a nice setup including a monitor, e-stop button, ketboard, mouse and other controls tidily at the front of the machine, all in my favorite material... wood. The vacuum hose ends at the top vacuum hose mount and Toby connected the two vacuum mounts with a red pipe, which gives the head of the machine a nice appearance. I have been meaning to do a review on the PinchBlox clamping system in a clamping tutorial, but toby has beat me to the punch and is using these great low profile clamps. All of the electronics are housed under the table and check out the fan and A/C HEPA filter idea. Very cool! With all of these modifications, I hope the users will benefit from Toby's experience.

Toby's Write-up:

I just finished construction of my first CNC system – a blackToe 2x4’ version 4.0. I really leaned on Patrick and the forum contributors to get me through. I am a total newb and it is killing me not to be playing with it, but I wanted to let the community know of some of the alterations I made to the standard unit.

Table- I really wasn’t ready to lock into a single location in my shop, so I wanted a sturdy, but movable table. I figured I could use the space under the table to store all the electronics, so the only connection my table would need is power and vacuum (computer is using wireless). Using sturdy 4x4” posts and 2x4”s for framing the whole unit was placed on a movable tool base (~$60 Rockler). The infrastructure came together nicely and was very solid. I created a torsion box out of ½” MDF to the table size of 56”x27”. As it turns out, you need a couple inches of overhang on the long side to accommodate the rails and x-axis mechanisms, so I trimmed off one side and simply added a new cover for the newly exposed edge. The torsion box was screwed to the table and then I added the ¾” birch plywood top cut to exact dimensions. To make the internal part of the table into a ‘dust-free’ cabinet, I sealed it up with MDF and included doors for access. I drilled out some air holes on the back and powered two large computer fans to draw air through a replaceable 3M filter. Once air is inside the cabinet, the best exit for it is to cascade over the motor drivers and leave the cabinet toward the bottom of one end.

Holddown- OK so my design goals here were pretty simple: I wanted a system that was easy to implement, cheap, and wouldn’t put road hazards out there for my precious end mills. I mean, I am a rookie after all and I think there is almost certainty that I will attempt to drill out of bounds. The actual table surface itself is ¾” birch plywood. I inserted about eight ¼” threaded inserts into the top. Over this, I placed a ¾” sacrificial MDF sheet. I used counter sunk screw holes to insert nylon hex top bolts to thread into the inserts and hold the sheet down on the table. The nylon heads are just below the surface area of the MDF. Then I routed three t-slots into the MDF lengthwise about 7” apart from each other. This requires a t-slot bit, of course, and hand router. Once this sheet of MDF is thoroughly perforated, I will use the CNC tool to cut the slots and might get more creative.

Now here’s the hold down part. I used the pinch clamps but ditched the brass screws they come with and used inverted nylon bolts and nylon thumbscrews to hold these in place. Turns out there’s not much you can’t reach with only 3 t-slots cut into the sacrificial layer and the holding power has been flawless in all my tests so far. This system can be quickly rearranged for large or small boards. Oh yah, there’s nothing above the original table that would fowl an end mill.

Electronics- Sure I wanted the big, red emergency stop button, but I wanted a little more control over the CNC. For example, I have placed a common outlet and switch on the front of the table (rt side) that controls power to the entire device. This way, I can turn it all on from one switch and off at the end of a session. And you can’t have too many outlets, so I included a couple up front. The computer is internal to the table; the keyboard/mouse combo reside under one end and can slide under the top for fewer dust issues. The 18.5” monitor was purchased new for less than $100 at Best Buy.

I wired up X and Y axis limit switches and wired them together to stop the machine if they are reached. Even though I used shielded cable for these, I still had a lot of noise on the system. I solved this with putting a 1kOhm resistor in line on the signal.

The e-stop controls the three axis by default, but I was most concerned with the business end of the CNC, so I wanted to be able to control this up front manually- and within Mach3. I purchased an on/off combo switch with a light. The light tells me power is going to the system. I took up two inputs on the breakout board and tied them to the on and off switches. Then I configured Mach3 to constantly watch these inputs via a script. When it seems the ‘On’ button depressed it turns on the spindle and off for red. One of the byproducts of this exercise is that now Mach3 also turns the spindle on and off at the appropriate times, for example, at a tool change. For mach3 to control the spindle, I wired an Output on the breakout board to a low cost solid-state relay that I wired to an outlet box where the router is plugged in. A person could also plug in the vacuum here so turn on only when the spindle is moving. If there’s interest in how to do the electronics here, I’d be happy to spell out the parts and configuration.