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For my robotic projects I need some aluminium parts. Currently I am looking for a way to build a chassis including simple gear box. So I need relatively high precision. Which options do I have to machine aluminium without investing in expensive tools?

This is what I could think of so far.

  • Design parts in CAD and send them to a third party company for fabrication. The problem with this is that hobby projects almost never need large quantities and piece production can be still expensive.
  • Buy cheap tools to work aluminium by hand. I don't know which tools would fit this task best. Moreover, the results might be inaccurate, which is a problem for designs with moving parts.
  • Find someone with a CNC who let's me machine my parts. This would most likely result in very slow prototyping cycles though.

A method that I can do at home with not too expensive tools would be perfect, but I'm looking forward to every solution.

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    $\begingroup$ Have you considered laser or waterjet cutting? These are pretty low cost. $\endgroup$ – Rocketmagnet Aug 1 '14 at 22:13
  • $\begingroup$ @Rocketmagnet That's a good idea. I'll look into those. However, that would only allow me to machine flat parts, does it? $\endgroup$ – danijar Aug 2 '14 at 9:18
  • $\begingroup$ I never use nor seen waterjet, only heard it, for a 'mid-range' machine that people can likely easy to get hands on, what is the typical workable thickness and accuracy? Is the cut edge round (which is good as not cutting finger)? How much will the edge slightly bend downward, if any, making metal non flat and have bad effect? $\endgroup$ – EEd Aug 2 '14 at 15:31
  • $\begingroup$ @danijar - Once cut, you can bend the metal into shape. If you have laser cutting in mind when you design your robot, there are a lot of parts that can be made this way. $\endgroup$ – Rocketmagnet Aug 4 '14 at 14:27
  • $\begingroup$ @JohnWilliams - It can cut pretty thick metal. You can also adjust the angle of the jet while cutting to produce sloped sides. Check out this picture of a water jet cut fan. $\endgroup$ – Rocketmagnet Aug 4 '14 at 14:29
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In recent years, there is a surge in low-cost desktop-size home/DIY/High School level CNC, milling machine, router and 3D printers (common 3D motions parts, just the 'head' differs).

Hundreds of companies do sell assembled unit and/or kits.

I do not have hands-on experience on this myself and cannot offer solid help. But since many people make/buy/sell them, it sure live up to expectation (software, speed, accuracy) at the DIY/home/hi school level. People does use metal, plastic and even wood and wide range of price and performance

Examples, randomly picked up for illustration, are http://jason-webb.info/wp-content/uploads/2012/01/cnc-mill.gif http://jason-webb.info/2012/01/cnc-machine-first-thoughts-and-project-overview/

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  • $\begingroup$ +1. You might also add a link to reprap.org/wiki/MillStrap which briefly describes and links to more information on a dozen or so desktop CNC mills. $\endgroup$ – David Cary Aug 2 '14 at 15:23
  • $\begingroup$ Most 3D printers or "routers" will not have enough stiffness to cut metals. You also need the right spindle/tools. Some of the stiffer routers may do if you take really light cuts. There are however cheaper Chinese milling machines that can be converted to CNCs. $\endgroup$ – Guy Sirton Aug 4 '14 at 18:05
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Actually, you can perform most milling operations with a file, a micrometer, and patience.

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  • $\begingroup$ A LOT of patience... Also the finish is going to be pretty rough. I guess you can always polish it. $\endgroup$ – Guy Sirton Aug 4 '14 at 18:21
  • $\begingroup$ Yes, a LOT of patience, but less than the average tool addicted machinist believes. The finish only has to be rough if you make it that way. The original question is 'how can I make a few accurate parts without a huge investment?' - answer - buy simple hand tools, and spend a bunch of time. $\endgroup$ – Anniepoo Aug 4 '14 at 18:48
  • $\begingroup$ True. It's not unlike people who make telescope lenses by hand. If you have a way to remove fine amounts of material, you have a way to measure, and you have time you can do anything... $\endgroup$ – Guy Sirton Aug 4 '14 at 21:35
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As John Williams points out you can find desktop metal milling machines that are reasonably priced. However if you want to work with metal make sure the machine you're buying is designed for that.

There are a few major differences between metal cutting and machines designed for wood or for additive processes (3D printers):

  • The cutting forces with metal (even with a soft metal like Aluminium) are very high. If you do not have a stiff enough frame the cutting tool will simply bounce off the surface of the metal (chatter) and will result with very poor cutting, extra heat, and fast dulling of the tool. If you look at the design of metal mills they are generally very solid hunks of metal (steel).
  • The rotational speed of a metal working tool is going to be much slower than e.g. a wood tool. A router designed to cut wood may run at 10K RPM which is way too fast for metal. It may be able to take very light cuts off aluminium but the cutting tool will dull very quickly and the router itself is not designed to take the forces of cutting metal and will also not live for very long.
  • Metal cutting often requires lubrication/cooling that isn't used with wood.
  • There are many different Aluminium alloys with somewhat different properties.

Depending on what you are trying to build you may not need the entire spectrum of machining capabilities. E.g. if you're just trying to locate some objects in 2D you can get a plate and drill holes in it with reasonable accuracy without needing any fancy milling equipment. You can also sometimes substitute adjustability to accuracy/precision, the simplest example is drilling a large hole and using a caliper or micrometer to measure the position before tightening your bolts.

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  • $\begingroup$ We used to have a Taig CNC Micromill. Mostly we cut plastic, but sometimes Aluminium, and it would struggle. We did cut load of aluminium parts, but it was slow going, and we would often have to sit there squirting coolant onto it for hours. $\endgroup$ – Rocketmagnet Aug 6 '14 at 8:55
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Look for a makerspace in your area, in boston there is http://artisansasylum.com/site/ they have various CNC machines, laser cutters, Etc. which with some simple low cost training you are allowed to use.

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    $\begingroup$ Cool, I wasn't aware of those spaces, we even have some in Berlin. $\endgroup$ – danijar Aug 6 '14 at 14:04

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