More CNC progress.

August 24th, 2016

I’ve been coming home and working on the CNC machine as well as at work in breaks. I am still waiting for parts to arrive from China before I can do too much more though.

I spent an evening making motor mounting brackets then when I was done realised I had made them all too small! I also realised I had made one part backwards so I redrilled some holes in the Z axis plate to make things right again. If anyone asks the holes are too add lightness like we do on old racing cars.

Today I cut up some angle aluminium (40 x 40 x 4mm) to make the gantry/X axis frame. I used the metal saw at work to cut the 45 degree angles and it works extremely well. I did the straight cuts at home by hand. This is them laid out to see how things will fit. I cut small brackets to bolt the corners together when the time comes. The gantry is just under 600mm high and I get 207mm of usable Z axis. That will be the absolute tallest thing I can 3D print.

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I laid the Z axis on top of the rails to check the motion and found a problem. Although everything moves smoothly I messed up some measurements and the X axis plate just hits the top of the frame at the sides so I will need to take them back to work and mill 10mm or so off the top of the angle that makes up the sides of the gantry. The X platform base needs to go over the top of the frame to get full sideways travel. If the base hits the frame the tool can’t get to the extremes of the X travel. I am using two bearings side by side to give me a wider base (at the expense of less travel) and am still waiting for the extra bearings to arrive.

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You can see above how the top of the platform is flush with the top of the frame instead of running just over it.

My colleague Rod didn’t believe me you can drill through aluminium with a normal spade bit. I manage it fine. I just use a very slow speed in the drill press and lots of cutting fluid. Lately I have been using Inox as a cutting fluid (since I ran out of other stuff). It actually works very well. It has the advantage of being clear so you can see through it and see what you are drilling. It also smells nice!

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That was the hole in my new motor mount for the Z axis. I need shorter screws to mount the motor and also need to make a spacer to go between the plate and the bracket to get the motor height correct. The top of the gantry frame will need to be milled down a little to provide clearance for this bracket.

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You can see above the flexible coupling that links the stepper motor to the lead screw. The X and Y axis motor brackets will be the same. They are held by the same bolts that hold the lead screw bearing in place.

You can see my planning wasn’t precise. My drawings allowed me to see the basics would work and I knew I would have some tweaks to do as I actually started building. But I am trying to keep the design as simple as possible. I am confident the basic design is going to work now though. Lots of little things to work out still like where to mount limit switches and exactly the best way to make the base plate so it can be changed from 3D printing (which needs a heated bed) to laser cutting to machining.

2 Responses to “More CNC progress.”

  1. Brett Cooper Says:

    Great tip about the use of a spade bit to drill through the aluminium. Thanks

  2. Simon Says:

    It’s probably not good for them but I was using cheap ones anyway so there was nothing lost if it didn’t work.