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  1. #21
    marbles's Avatar
    Lives in glasgow, United Kingdom. Last Activity: 10 Hours Ago Has been a member for 5-6 years. Has a total post count of 94. Received thanks 8 times, giving thanks to others 32 times. Referred 1 members to the community.
    Great Log Neale, just added a build log myself to the forum. Similar mild steel profile used 60x40x3mm. I seen to have gotten away with just tapping the 3mm for the linear rail but lets see how that pans out. Like yourself i'm happy to modify the design as I go along, which is crucial. Cheers

  2. #22
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 6 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,178. Received thanks 215 times, giving thanks to others 5 times.
    Someone asked me a long while back how this machine performed cutting aluminium. My one and only attempt to cut Al was a bit of a failure, but not really to do with the machine - poor cutter choice, poor chip clearance, and general incompetence were bigger factors.

    However, recently I have been working on a project which involved a fairly complex box-section structure built from steel pieces. The original design suggested tapping holes in the edge of 3mm steel to hold bits together while silver-soldering. Recipe for large number of broken taps, I thought. So I started thinking tab-and-slot, which I have used a few times for wooden structures in ply. However, I would need a large number of accurately placed 3mm slots, plus tabs on the edges of most of the components. Pieces are typically 40-150mm long by 35mm wide. I'll post a picture of the exploded design when I manage to extract it from my Fusion 360 drawing. I didn't fancy cutting this on my mill (manual, not CNC), so thoughts turned to using the router. What, a CNC router designed for cutting wood, to be used for cutting steel? What could possibly go wrong?

    So, with a certain amount of doubt that it would work, I had a go using a 3mm HSS cutter that I had lying around. The cutter didn't last very long, but again I think it broke due to inadequate chip clearance but results were looking promising. So I had a look at an online catalogue (cutwel.co.uk) and found some carbide cutters that looked likely bets. The great thing about these small cutters (I was looking at 2.5mm to get the detail I wanted) was that the recommended cutting speeds were suitable for my 2.2KW spindle (around 7K RPM) and they were specifically designed to cut dry - no coolant or lubricant to muck up the bed of the machine. 3-flute cutters needed around 110mm/min, max DOC 0.5mm, which meant that cutting wouldn't be superfast in my steel but looked acceptable. I worked up to these feeds slowly, also increasing DOC from less than the recommended values because I was terrified of breaking these tiny cutters, even with only 5 or 6mm flute lengths and on a 6mm shank. However, they turned out to be tougher than they looked and run happily at the quoted speeds and feeds. My small components typically take 20-40 mins to cut. I started using bright mild (cold-rolled) steel although I suspect that I was getting a certain amount of work-hardening in the early stages when I wasn't cutting aggressively enough and I managed to blunt a cutter (but not break it); I moved to black (hot-rolled) steel which cuts better. Cutting finish is not perfect but very acceptable for this job.

    So, the answer to the question, "can a machine like this cut aluminium?" is still an unknown, but it can, within certain limits, cut steel.

    And no, this is not the ideal way to cut pieces like this. Commercially, laser cutting would be a quicker and more cost-effective job, but I'm an amateur, I don't live next door to a laser-cutting service, and I can do it myself to make one-off bits and pieces with no real lead-time. It might also help people thinking about going down the welded-steel route to build a machine like this - this machine is stronger than I expected, even though put together by a beginning welder. And Fusion 360 is a great tool for designing and doing the CAM for bits like this.
    Last edited by Neale; 4 Weeks Ago at 11:13 PM.

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  4. #23
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 6 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,178. Received thanks 215 times, giving thanks to others 5 times.
    Just to give a better idea of what I was cutting, and why I thought that CNC would be a better way than milling manually...

    This is the "finished item", as shown in Fusion 360. It's all now cut and waiting final assembly.
    Click image for larger version. 

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    And this is an exploded view. Not quite as good a view as F360 only explodes "components" and some of my components actually consist of several pieces that are not separated here.
    Click image for larger version. 

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    My technique varied slightly as I went along. I started with more-or-less rectangular tabs and slots, with fillets in the internal corners to soften the tool motion while cutting. The resulting corners needed relieving with small files before assembly. Eventually, I realised that I could machine appropriate clearance fillets, so tabs had small semi-circular cutouts at the base and slots were given semi-circular ends. In practice, with a structure like this it is only the flat faces of the tabs and slots which locate; the tabs can slide sideways a little as this position is actually constrained by the way that the pieces butt up against each other. You can see the different techniques in various places in the exploded view.

    As ever, I don't recommend that you try to copy me too closely, but it's an indication of the art of the possible if you are both careful and lucky.

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