Experiments in aluminium (6082) cutting on an eShapeoko

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superfrog
Posts: 19
Joined: Tue Sep 08, 2015 6:50 pm

Experiments in aluminium (6082) cutting on an eShapeoko

Post by superfrog » Mon May 02, 2016 5:27 pm

Hello people,

As Blighty is blighted by clouds and random drizzle and it is a bank holiday (causation/correlation?), I have spent the afternoon playing with my eShapeoko.

I have been trying to cut aluminium for a couple weeks and not getting great success at rates that do not involve waiting for the heat death of the universe before finishing a longer cut; I have finally had some success.

As a first try a couple weeks ago, I was using 2 flute carbide end mill ( the cheap chinese type) 1/8" diameter, 22mm long flutes, running at 24kRPM. I could do clean slots at .2 mm deep at 500mm/min. My test pattern was a 4mm wide pocket done as a slope .2mm along the way, turning along the required radius and doing the same on the way back. The chips did not look great. I also managed spiral plunge to reach a 4mm hoie diameter with 0.04mm per revolution, an there the chips were dust. All in all, a bit disappointing. My attempts at more aggressive cuts all but one finished with aluminium welded to the the tool, and requiring gentle heating with a blowtorch to remove the blockage with a wire brush (not the recommended way, maybe, but it works and does not damage the carbide much). The same bits perform well in wood and acrylic/perspex (MDF at 1200mm/min 3.5mm deep, acrylic at 800mm/min at 2.5mm deep, 21kRPM in both cases)

I received better tools for Al last week, and I was keen to try them. They are 3 flute, 45deg flute, carbide, 4mm diameter, noticeably sharper and pretty cheap too (about £2.50 a pop). After an afternoon of frustration, I finally managed to get feeds and speeds that give good results at a halfway decent speed. At 21k RPM, dry, climb cutting unless otherwise mentioned.
Spiral downcut along a 1mm radius, .4mm per revolution (leading to a 6mm hole), perfectly fine, could go harder.
Using a HSM inspired path, going forward one step, doing a full circle to remove material, and doing that again until the end, I managed 3mm deep cut, at a feedrate of 500mm/min with a forward step of 0.5mm (so about 12% tool engagement). Anything much above this was giving me tool blockage after 15 or so mm It feels like I could probably have gone to 4 or 4.5 mm deep without too much problem. The chips look lovely and the tool does not clog. This followed by a finishing conventional cut pass along the same external path, and with a accrued depth of 0.1mm gave pretty good finish.
For the honest bit about it, each 0.5mm currently takes a 6.8 mm path to finish. This is a roughly 14 times slowdown. The cut is 15 times deeper, so on paper it is near draw. Feedrate is a bit faster, with this type of cut, but I can't go anywhere near the correct one (similar mills are advertised as 1800-2100 mm/min for side milling, I suspect with active cooling). I could improve actual speed by reducing the radius of the cutting pass, and will try this as a next step (a 0.5 radius would lead to only a 7 ish times slowdown), will try this next.

I also found, by chance/don't ask, that the same cutting profile will effortlessly cut 12mm deep in MDF, with excellent finish and could probably do deeper and use more aggressive steps (I would not put it past its ability to do 18mm MDF in one cut with feed at 1500).

Would it be a good idea to update wiki with these data points ?
eShapeko #377: "Uncle Bob" 500x1000 deluxe frame, with nicely coloured plates.
Arduino Due + GAUPS 1.1 + 4xDRV8825 at 30V running G2
800W ER11 "Ol' Sparky" Chinese spindle + VFD

WillAdams
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Location: Pennsylvania --- south of the Turnpike, East of US-15
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Re: Experiments in aluminium (6082) cutting on an eShapeoko

Post by WillAdams » Mon May 02, 2016 5:40 pm

Excellent idea!

Done.

If you want, you could get an account --- send a PM to the group wikiadmin (or wikiadmins?) incl. your e-mail and someone will manage to make an account for you.
Shapeoko 3XL #0006 w/Makita RT0701 Router w/0.125″ and ¼″ Elaire precision collets
Nomad 883 Pro #596 (bamboo)

DRobs86
Posts: 148
Joined: Fri Jun 05, 2015 4:19 am

Re: Experiments in aluminium (6082) cutting on an eShapeoko

Post by DRobs86 » Mon May 02, 2016 9:57 pm

I found that at least some of those cheap chinese endmills advertised as carbide are probably not carbide. I cant mill 6061 aluminun with them without chipweld. I have no problem however with quality carbide end mills.

sgth0mas
Posts: 101
Joined: Sat Dec 12, 2015 5:57 pm

Re: Experiments in aluminium (6082) cutting on an eShapeoko

Post by sgth0mas » Mon May 02, 2016 10:03 pm

DRobs86 wrote:I found that at least some of those cheap chinese endmills advertised as carbide are probably not carbide. I cant mill 6061 aluminun with them without chipweld. I have no problem however with quality carbide end mills.
Even high end bits with high polish mirror finishes can encounter chip weld...so i wouldnt only go by that as an indicator of carbide quality.

DRobs86
Posts: 148
Joined: Fri Jun 05, 2015 4:19 am

Re: Experiments in aluminium (6082) cutting on an eShapeoko

Post by DRobs86 » Tue May 03, 2016 4:59 am

True. I was also going by the 90 cents per endmill price. Lol.

superfrog
Posts: 19
Joined: Tue Sep 08, 2015 6:50 pm

Re: Experiments in aluminium (6082) cutting on an eShapeoko

Post by superfrog » Tue May 03, 2016 12:14 pm

This is a good point, maybe I should get a couple bits from APT and compare. They do look like carbide and feel like carbide density wise. There are so many grades of carbide that it means little anyway.
I have been trawling the internets for bits in the past couple months, trying to snatch a good deal when possible.
My current results are, all from Amazon/Ebay:
1/8" 1 or two flute, from £7 (make it 10USD) per 10
4mm 60 deg or so 1, 2, 3 flutes £7-£10 (10-15USD) per 5. I found one place that will sell 10 two flute for under £10. Have yet to try them out.
4mm 45 deg endmills for Al, foudn one place that will sell them for £2.50 (4 USD) from Hong Kong. Local shops have them starting from £4, less of a difference.

For anything fancy, the price of the local shops against the price of the China/Hong Kong shops is not different enough to warrant the increased risks.

The biggest problem was that the inconsistent labelling makes it really hard to find anything through a search.

As to cutting aluminium experiments, I consistently welded the cutter trying to do a 3mm deep, 5mm wide pocket with a 4mm 45 degree bit at 500mm/min. What is a bit frustrating about this whole experimenting is that you never know whether you are getting a weld because surface speed is incorrect, feed is too high, feed is too low or poor rigidity of the machine is causing tool to deflect and grind rather than cut. I should probably try the same experiment with conventional milling cuts rather than climb milling cuts, but I like the climb then conventional on springy machines.
eShapeko #377: "Uncle Bob" 500x1000 deluxe frame, with nicely coloured plates.
Arduino Due + GAUPS 1.1 + 4xDRV8825 at 30V running G2
800W ER11 "Ol' Sparky" Chinese spindle + VFD

superfrog
Posts: 19
Joined: Tue Sep 08, 2015 6:50 pm

Re: Experiments in aluminium (6082) cutting on an eShapeoko

Post by superfrog » Thu May 05, 2016 9:03 pm

As an update, with the same 3flute 45degcabide bit a 21kRPM, 3mm deep pocketing with 0.33mm tool engagement at 750mm.min sounds better on the machine (but is about the same removal rate). The chips are absolutely lovely.

The same at 1000mm.min clogs the tool. I am wondering whether I am just hitting the limits of material removal with this 3 flute end mill.
eShapeko #377: "Uncle Bob" 500x1000 deluxe frame, with nicely coloured plates.
Arduino Due + GAUPS 1.1 + 4xDRV8825 at 30V running G2
800W ER11 "Ol' Sparky" Chinese spindle + VFD

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