Aluminium - load on machine

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Aluminium - load on machine

Post by aarvidsson » Sat May 02, 2015 3:00 pm

This might the dumbest question this saturday, but I'm curious as to what you guys say. What is the most demanding (and why?) of a somewhat souped-up Shapeoko 2 cutting 1mm aluminium - feed rate of 400mm/min and 0.2 pass depth with a 1-flute endmill, or feed rate of say, 100 or 200mm/min and 1.05mm pass depth with the same endmill? Would the latter attempt end in spectacular failure?
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Re: Aluminium - load on machine

Post by clockit » Sat May 02, 2015 3:22 pm

trust me, I'm no expert, the only aluminum cutting my S2 does is when it crashes, lol... but, I think the answer is directly related to the type/grade of aluminum that you are trying to machine. I gather from other posts on this forum that some grades are a lot more forgiving than others... I know, you're like 'well, that doesn't help much', lol, sorry, it's all I got... :D

edit for a typo, oops...
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Re: Aluminium - load on machine

Post by Jimf » Sat May 02, 2015 4:09 pm

FSwizard will calculate cutting force if you plug in the numbers. This will give you the optimal feed rate and RPM for the material being cut. Change feed rate button up/down to see how much cutting force is required.

A Shapeoko isn't rigid enough to use the optimum 100% feed rate that is calculated. I would probably choose 25% as a starting point and see how well the CNC cuts before adjusting feed.

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Re: Aluminium - load on machine

Post by WillAdams » Sat May 02, 2015 11:02 pm

We have a bit on the wiki: ... #Aluminium

Increasing the depth of cut would require more of the machine — get some end mills and try some cuts? (Make sure you have spares and wear eye protection — they’re likely to break.)
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Re: Aluminium - load on machine

Post by MeanderBolt » Mon May 04, 2015 8:00 pm

Having now done many jobs in aluminum, I would say keep the speed up, and the depth of the passes small. I did take an 1/8 at one time, and only one time, not by my choice, but of my doing :roll: . The result was not pretty. The single flute endmill was the thing that made it all work smoothly for me. I successfully milled with a 2 flute, but there is a night and day difference between 2 flute and 1. I am using a DeWalt DW660, therefore 30k rpms. I do not slow it down so I can keep maximum strength.

Comfortable milling is currently .15 - .2mm passes at 500mm. When I am doing holes, I have started to slow this down (.1mm spiral) as I have noticed some oddness in depth after a number of holes. I have yet to figure this one out. It's like the opposite of missed steps. After 5 or 6 holes, if I were then to do a profile op, it's like the machine thinks that 0 is a fill millimeter or more below where it should be, so it plows pretty hard into the material. If I were missing steps I would think that it would 0 out above the work piece, therefore air milling. So far, the deepest I have milled aluminum is a half inch (12.7mm). When conventional milling, the bit tends to push out slightly. I have noticed that at the bottom of 1/2 in aluminum (the back side), the cuts are slightly wider than at the top (front) due to this. Normally with wood, it (in my experience) has not been an issue. But it really is with the 6061.
I do plan on doing some strengthening of the machine soon (bolting the X maker slides together) which should afford me deeper, straighter cuts.

Another thing, (which I am about to start trying) is to get the work piece as close to the gantry as possible (without running into the work, or workholding objects). This will allow the machine to go deeper before it starts to flex. This would obviously require a fixture to get the material higher.
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