started with. It can also be used for importing drawings from another CAD program you may have used, to then generate the G code.
Let’ s now talk about the machine. As I said earlier, CNC can be used to control a number of different types of machines. I chose to build a router table of 1300mm long by 900mm wide with about 200mm of vertical spindle height. This is a straight forward 3 axis machine with the Y axis being the movement from front to back, the X axis being the movement from left to right and the Z axis being the vertical movement of the spindle motor( router). I chose a machine like this principally because the majority of the work I want to do is cutting out parts as a profile cutter, plus the occasional 3 dimensional job( such as some molds I recently shaped to make gear doors for my new jet model). With this size table I can cut materials of up to 1 metre long( which is great for
cutting out spars etc.) and still get cutting accuracy better than 0.05mm for those tiny jobs. I’ ll go into the construction details in the next edition of MFW.
Another free bit of software out there is a program called Mach 3. Again, it is free with some limitations( in this case, the number of lines of G code you can run), but when you pay for it, these limitations become unlocked. Mach 3 is a program used on the machine to operate the axis of movement. Again, if you are sparked with interest, download it and try running some of the code you’ ve generated with CAMBAM to see how it works. It has digital readouts to display the movements of each axis, to give you an idea of where they are tracking. At this trial stage it will be fine to run Mach 3 on any computer, but if you decide to persevere further you will need a dedicated computer to run the machine and use it for absolutely nothing else other than running the machine. Mach 3 is a program which works below the levels of the basic windows operating system and can be disrupted by other programs running on the same computer. For instance I spent weeks trying to find why my machine would hesitate whilst cutting circles and found it to be associated with the wireless card I had plugged into one of the PCI slots on the motherboard. Also with Mach 3 it is vitally important to reboot your computer after installing the program and before opening it for the first time, otherwise the main driver will become corrupted and give you headaches to fix it. This dedicated machine doesn’ t need to be anything special. Mine is an old Pentium 4 with a fresh reload of windows XP which I had kicking around here and an old 13” flat screen monitor, all mounted in a cabinet to keep some of the dust out. Mach 3 can be downloaded at: http:// www. machsupport. com / downloads. php Download version Mach3 R3.043.066. Excellent setup and configuration v i d e o t u t o r i a l s c a n b e f o u n d a t http:// www. machsupport. com / videos /
Stepper motors
I mentioned earlier about pulling stepper motors out of old printers and tinkering with them. Unfortunately these motors are nowhere near big enough to handle the loads of a machine this size. If you’ ve never had anything to do with steppers, you can find an excellent You Tube, 2 part video of how they work at: http:// youtu. be / MHdz3c6KLrg Stepper motors do exactly as their name suggests by stepping around the axis of rotation in very precise steps. They need to be controlled by a dedicated driver unit to schedule the steps and the direction they step. By attaching the shaft to a drive source( i. e. A ball screw or rack and pinion system) we can now create the linear movement of the axis we want to move. The size of these motors are generally identified by their holding torque. I used 4 motors,( one each on the X and Z axis and two on the Y axis) rated at 425 oz / in and have found them to be matched perfectly for the size of the machine. As much as I prefer to support local industry, I was not able to find what I wanted in NZ, so ended up buying the motors, drivers, power supply and break out board
Top: Wing Spar assembly cut for Vigilante Sport Jet Middle: Gear door plates. Leaving the tabs in place make it ideal for gluing door hinges precisely in place. Above: Body parts for a tri copter cut from G10 fibreglass material
from China at a pretty reasonable price. Have a look at: http:// www. wantmotor. com / for what they have available as kit sets. Another great source I have used for parts and advice has been Peter Homann at Homann designs in Melbourne. He has a good deal of CNC gear available at very competitive prices. Have a look at his website at http:// www. homanndesigns. com /.