Introduction: Alex did an internship at an Industrial Design firm where he helped with 3D model making for various customers and projects. After he got really good with Pro-E and SolidWorks, we decided to build a CNC mill ourselves. We looked around at several kits and hobbiest grade projects, but ultimately found a website that offered conversion kits for the Sieg family of mills. We bought one on sale through Harbor Freight and after waiting several weeks for it to come in, we picked it up and started the conversion process (easier said than done).

Hardware: The first problem was that the mill weighs about 700 pounds, so we had to take it apart so that we could move it. Since the machines are shipped from China on a boat, they come packed in grease to keep everything from rusting. It is a real mess to handle. After we got it picked up and put onto our new bench. Then the next step was integrating the stepper motors and the controller. The conversion kit included 2 NEMA 23 steppers and a big NEMA 34 stepper. We bolted them all together and then wired up a motion control box with stepper drivers, a power supply and hooked up an interface card. Now we had the mechanicals all completed.

Software: After that came integration of hardware and software. For this project we decided on LinuxEMC, since it was free and fairly commonly used. The software was actually pretty easy to configure and get going. We tried a commercial piece of software called Mach3, but found the user interface and documentation to be a kludge. The Linux work only took a couple of evenings and then we were off to make our first test patterns (carving the EMC logo default pattern).

Calibration: The next step was adjusting out backlash, which is hidden in the documentation of LinuxEMC. This must not be a feature that most people use, because when you make a change in the configuration from the install menus, it wipes out any information that you have worked to manually insert into the configuration files. But, after a few tries, we got it so that the backlash was less than a few 1/1000ths of an inch.

For our 3D design software, we bought a copy of BobCAD which includes a crude 3D editor and the necessary CAM software to take 3D STL files and convert them into machine movements. There is a steep learning curve on BobCAD, and I'm still in the early stages of it.

Testing: Next came doing some trial projects. I picked some 2.5D signs to make, one was a neighborhood sign saying that dogs had to be on leashes, and the other was a set of numbers to put on a hill for distance measurements (when doing hill repeats). Alex is doing some 3D home projects, like making a radar detector mount for his car. There have been a few broken bits and a couple of unplanned excursions into the XY table. You might notice in the pictures that we decided to bolt a thick piece of wood onto the table to protect it from the most simple programming errors. Also you might notice that the wood has a profile cut out in it where we (Alex) ran the bit into the table and then did a planar relief cut to resurface it so we could use it.

Pictures: Here are a few pictures of the project:

Mill from side
Mill from front

Motor close-up view:

Mill from side
Mill from side

Test item:

Mill from side
Mill test