Since the committee has decided to prefer equipment owned by MHV over equipment on loan from members, we need to consider purchasing a new CNC milling machine. On this page, we will gather input from any interested members on what, why, and how.
While 3D printers are all the rage today, CNC mills are the other side of the coin, enabling subtractive manufacturing rather than additive. CNC mills enable us to do a number of things that otherwise require quite a lot of skill, time, and specialized equipment:
Custom precision parts for robots, UAVs, project enclosures, and more are all dramatically easier to make with a CNC mill than by hand. Precision also tends to be higher than 3D printing (certainly much higher than our currently RepRap), and the resulting parts can be much stronger.
In short, a cnc mill enables us to make and hack things better.
(Here, let's propose a small number of reasonable options for such a machine, with cost and capabilities.)
This is a reasonably robust commercial mill made from extruded aluminium components - The mechanical assembly is quite good, but as delivered, the wiring is made from cable which is unsuitable for use in a moving environment - expect to factor an extra $200 to replace the wiring.
The CNC6040 typically comes with an 800 watt VFD driven spindle motor that uses 'ER' style collets - I have used up to 1/4“ bits in my mill with no adverse problems. Backlash in the mechanism is not noticeable, and I can comfortably mill with an accuracy of 0.05mm.
I use a dedicated Linux system to run it (a cheap IBM that work was throwing out). The software I use is LinuxCNC, which is open source.
I purchased mine 2 years ago for $1700 delivered to Australia, and have spent probably $200 upgrading it by replacing wiring and installing limit switches. It is not equivalent to a $20,000 unit, but it is *way* cheaper…
There is a machine for sale in Queanbeyan which looks quite nice.
This is a 4-axis machine, good speed and power, decent work area. Comes with a nice enclosure which would both help keep the machine clean, and improve safety. Asking price is $5500.
I have sent a query asking for a few more details (JJS on 10-Dec-13). UPDATE: apparently this item has been sold, but not yet picked up; the seller will contact us if the current buyer falls through.
The new machine would be set up in our new space. Considerations for placement:
We should also plan to make or buy a cover that fits over the machine and keeps it clean when not in use; dust and grit are really hard on these machines.
Another option is to build a 'hutch' over the machine with transparent sides. This can protect the machine from the outside world as well as protecting the outside world from the machine.
We will need a plan to deal with the actual cutting tools, which tend to wear out and break fairly quickly, especially in the hands of inexperienced users. Possibly each user should bring their own tools, but we may also want a small number of community tools that may be used for training or small jobs.
(TP)One thing I found in experimenting with the Roland was that machining can take a long time. Rather than leave work on the mill and prevent others using it, I made a few jigs to allow me to finish a cutting process, take the work off the mill, and come back a week later, put the jig back in registration and keep going. In a multi-user environment a set of mounting plates would be useful. Or a good process to re-register work.
Should we stock some materials known to work well with the community tools? I would suggest, at the very least, we keep training materials such as hard foam, so that anyone who wants to learn can just grab a piece and start cutting.
We should have a dedicated computer whose only job is to run the CNC mill. In this section, let's brainstorm what computer to use for that. We may have one that will serve in the space (does the one currently driving Alastair's CNC and the Roland JWX-10 belong to MHV?), or we may need to build/buy one.
MHV normally funds such equipment purchases by collecting donations from the initial group of users – people who care enough about the new equipment to chip in some money. Place your name below if you're willing to help make this happen.