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What did you do this week?
As part of a weekly series, these topics are a place for users to casually discuss the things they did — or didn't do — during their week. Did you accomplish any goals? Suffer a failure? Do nothing at all? Tell us about it!
Last week I mentioned spending an exorbitant amount of money in a single week and not being happy about 90% of it, well this week the 10% I was happy to spend arrived!
I've mentioned previously that I am (still) in the process of having a detached garage/workshop built at my home as I'd like to work on my cars out of elements, have more room, and had plans to be able to build my own parts (since I tend to like older vehicles where parts are increasingly rare). That plan included intent to build a CNC router, as a CNC mill was not in the budget.
Router vs Mill
A CNC router is a, relatively, lightweight machine largely used to machine large pieces of wood or plastic. Their strengths are in the size of the work area as they are regularly made to accommodate full (4'x8') sheets of plywood in professional settings. Their weaknesses are in vertical range, rigidity, and power. The more rigid a machine the more accurate a cut can be made. The more powerful the machine the tougher the material and larger a cut can be made. Most CNC routers can't machine anything tougher than thin aluminum sheet metal and even those aren't extremely most common. There are a few CNC routers that can machine thicker aluminum, but it's a slower process with shallower cuts and they are limited by a low Z axis maximum. In a router the material stays stationary and the tooling moves.
A CNC mill by comparison is a hulking beast that powers worldwide industry itself. Mills are used for everything from making prototypes to molds to tooling to end use parts and anything in between. Mills come in various sizes and types, but the point is every single thing around you has some connection to a mill of one shape or another. A mill is a large, rigid, powerful machine that can do damn near anything. Downsides are it's heavy, has higher power requirements (3 phase) than a router, parts/tools are more expensive as they need to be made to handle the power, and its work area is much smaller than a professional router. In a mill the material moves, but the tooling remains stationary.
A CNC router, thanks to open source and hobby level projects (X-Carve, Shapeoko, Ooznest), can be built for around $2,500 these days and would be good enough for the mostly aluminum projects I had in mind. It was my good enough choice. That is until last week when an very lightly used CNC mill popped up on the radar. A little bidding, swipe of a credit card, phone calls to a rigging company, and I now have a 2,600lb hunk of iron sitting in my garage.
The biggest mill disadvantage listed above doesn't really apply to my situation as the CNC router I was going to build was a hobby level Queenbee machine that maxed out at around 30"x30" workable area. The mill I purchased has a 11"x32" workable area that I can stretch to about 17"x32". The small loss in Y axis travel is more than made up by overall ability of the machine and I was unlikely to be making anything that was a huge 30" square anyway. Plus the mill has something the router could never dream of, ample Z axis. A router, being much less rigid than a mill, is extremely limited in Z axis travel, typically under 3", and can only handle flat material that can fit under the gantry. In a mill the knee (the bed where the material sits) can move up and down in addition to the tool itself, giving me room to cut the length of the tool plus about 4.5" and the knee can handle material as tall as 16" or so.
Most mills are manual, so the fact that this one is CNC controllable is a big jump over just buying a normal mill. That said the CNC conversion on this uses a proprietary motion controller that only works with the manufacturer's proprietary software. Big no from me. So I'll be putting in some work and hardware to swap it over to run LinuxCNC instead. Will also need to plan a larger space for the mill if I want to be able to utilize all that bed area. The router was going to take up a 3.5' square table, the mill on the other hand needs an area 8' wide and 5.5' deep.
I was trying to get a lathe as well, but that didn't pan out during this sale as someone else wanted it more than me.