Swiss Cheese

Slowly perfecting my processes, in this case for what is called a profile cut, where the object’s outer border is defined and the CNC router cuts the shape out.

I’ve been using a 1/8″ upcut solid carbide router bit – the 46100 from Toolstoday.com for the job so far, but knowing that it is not the correct router bit for the job.  What I should be using is something like the 46184 1/8″ solid carbide compression bit, or the 46180. (46237 and 46227 are also interesting bits, being 1/16″ diameter, which would be needed if doing nested work in 3mm MDF.)

Few reasons.

1. An upcut bit produces a lot of tearout in MDF.  While I can easily fix this with a quick sand of the top surface before removing the sheet, it would be preferable to avoid that step.

2. The upcut bit, especially at speed and with a large depth of cut, tries to lift the material being cut.  MDF is not a stiff structure, especially in a nesting situation which really turns the board to Swiss cheese.  It becomes almost impossible to stop the board being lifted, so I had to increase the number of passes from 2 to 5, and even then had a few lifting problems.

Not a fault of the router bit, I’m just using it as I don’t have another one of that diameter (or smaller) to work with 6mm thick boards in a nested layout, especially where I need grooves cut in the workpiece that are 5.9mm wide so they can slot together.

I’m cutting at 80mm/sec, and with about a 2mm depth of cut (DOC).  I know the CNC machine and the router bit can easily handle a lot more DOC, but my holddowns cannot keep up.  If I had a vacuum table, or even used a fair amount of double sided tape, that would be much less of an issue.

To stop the individual pieces being cut loose and walking into the cutter, wrecking them, I added tabs to each piece generally 2-3 per piece, 4mm wide and 1mm deep.  These are easily cut and sanded away at the end of the job.

It is important to ensure the cut goes all the way through in that final pass.  I have been using 0.5mm, but am thinking 1mm would work better.  Certainly, that means the router bit is cutting all the way through and partially out the other side, but that is why the tabletop has a sacrificial layer added.

What I made this time is the tropical fish (Angel Fish)……..

CNC-1 CNC-2 CNC-3and a stegosaurus!

CNC-4 CNC-5

It is very addictive!

And just for a sense of scale, here are both projects photographed alongside a bottle of wine (not so easy to see sorry!)

CNC-6

Now I just have 148 designs to go!

Plans from MakeCNC

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