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Fusion 360 CAM Milling

Suggestions for milling strategies

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Roderick Jenkins11/05/2022 16:10:30
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I have decided that it's about time I investigated the 3D milling capabilities of my Denford/Sherline Mach3 converted mill.

To this end I have drawn a simple test piece to be cut from 1" square aluminium alloy:

denford 3d test.jpg

A 3D adaptive clearance should rough it out OK but I am at a bit of a loss as to what to choose for finishing. There are a lot of alternatives even in the free to use version!

360 options.jpg

I'll be using a 3mm ball end 2 flute cutter and the spindle can run up to 10,000 rpm.

Any suggestions including feeds, speeds and step-overs for initial attempts would be gratefully received.

Cheers,

Rod

JasonB11/05/2022 16:36:24
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I would use a 2D contour to finish the main outer diameter. I usually set the adaptive to leave 0.3mm then the contour is done with one roughing pass at 0.2mm stepover leaving the final finish pass to remove 0.1mm

The ideal option for the rest would have been steep and shallow but that is paye foreven with the non free version,

So I would start with a scallop which will give even stepover. 0.2 to 0.3 stepover

This may not cut the flat outer area so a 3D horizontal will finish that off 0.1 or 0.2mm stepover

Go with the full 10K rpm and feed of to give a chipload of 0.02mm to 0.03 so 400-600mm/min. I usually use a4 flute ball nose for this sort of work so I can feed faster

What is the internal fillet radius?

On the adaptive I would use a 6mm 3-flute cutter 10000rpm and 1000mm/min feed 6mm max stepdown, 0.5mm fine stepdown a s you are using a small 3mm cutter to follow up and the adaptive stepover of 0.6mm. Same tool will do the 2D contour

Use some paraffin on the job particularly with the ball

 

Edited By JasonB on 11/05/2022 17:19:08

JasonB11/05/2022 17:07:20
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I think I pointed to most of the boxes that matter. on the simulation I use "comparisson" for colourization as it shows the stock in purple and the finished surface in green, any purple left and you have missed part of the surface. Watch it full screen on Youtube 
 
Figures are for my 5000rpm spindle so you can up the speed and feed keeping the same chipload.

Edited By JasonB on 11/05/2022 17:22:21

Roderick Jenkins11/05/2022 19:21:53
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Wow, All that in less than an hour!

Thank you. I'll give it a whirl and see what happens surprise

Cheers,

Rod

Andrew Johnston11/05/2022 19:43:35
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It's always difficult to interpret CAM options across packages, but of those shown I think the relevant ones are scallop, spiral and radial. I take scallop to mean that the package chooses a variable stepover to maintain a constant scallop height, giving a consistant surface roughness. Spiral creates a spiral path around the object, although it is not clear if the spiral constants are fixed. Radial creates a series of radial paths starting from the centre. To some extent what path is chosen depends upon the purpose of the part and aesthetics.

I've used all three methods but mostly tend to use scallop as it gives the most consistent surface finish. I assume the size of cutter is determined by the internal fillet at the bottom? In general it is not a good idea to use a cutter the same size as the fillet as there will be a large engagement with possible chatter and poor finish. I try and use a cutter that is smaller than the fillet or internal corner. Assuming the cutter is carbide I'd be running at 10000rpm and 400/600mm/min feed as per JasonB. One needs to be cautious on feedrate. Remember that, depending upon the cutter geometry, on near flat surfaces only one tooth may be cutting, even on a multi-tooth cutter.

Andrew

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