Cutting a miter with Carbide Create

[WillAdams (William Adams (Carbide 3D))]

Worked out doing this previously in the Lounge as a part of another project.

Going to work through it here from scratch in the hope of making it all a bit clearer and more useful.

First, we are going to be cutting a 45 degree miter at the end of a 10" (254mm) wide board which is 3/4" (19mm) thick using a #301 1/2" endmill with a 90 degree taper. Origin will be at the bottom left so as to facilitate using the Probe for setting the zero.

We will work this out in 2 programs: BlockSCAD/OpenSCAD (using Imperial measure so it will fit) and Carbide Create (using metric — rounding off for convenience where necessary).

Start by modeling the stock in BlockSCAD:

and Carbide Create:

[WillAdams (William Adams (Carbide 3D))]

Next, we draw things up in Carbide Create so that we can understand the geometry involved, so we add side and front profile and overhead view (the latter is the stock itself) and draw in geometry to cut the miter in the side view so we’ll be able to see where things line up:

[WillAdams (William Adams (Carbide 3D))]

and we also check the settings for MDF — in particular the depth per pass:

rounding that down to 1.25mm should make the math a bit easier:

19 ÷ 1.25 == 15.2

so we would need a succession of 15 rectangles which each gets narrower by 1.25mm which cut from the surface down to 18.75mm (the balance would be cut by the V endmills) — except that we are going to use a #301 endmill which only needs:

26.87 ÷ 8.98 == 2.9922049

(we’ll round)

3 passes

Except that 6.33333 repeating and the inability to accurately represent that would drive me nuts (it’s really a shame that when the Japanese chose a metric measure for type, kyu (q) it was 0.25mm — ⅓ mm would have been far more useful.

Okay,

19 ÷ 4 == 4.75

so we need 4 rectangles offset by that dimension which will allow cutting down to depths which the Advanced V carving toolpaths can then remove.

[WillAdams (William Adams (Carbide 3D))]

But, why bother with the tool change (thank you for bearing with me as I essentially think through all this out loud in public)?

Draw up a proxy for the tool and superimpose a diamond on it and the dupe and we get:

Draw a square from corner to corner and we get one properly positioned:

so it’s just a matter of creating a series of rounded rectangles properly aligned.

[WillAdams (William Adams (Carbide 3D))]

and then we assign a series of V carving toolpaths — selecting all three at once won’t work due to the overlapping:

[WillAdams (William Adams (Carbide 3D))]

Draw in geometry to measure the depth to which the first layer is cut:

and then select the geometry which needs to be cut further and assign an Advance V carving starting at that depth:

which the previews as:

Add one more to arrive at: