Issues milling aluminum

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Jim
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Issues milling aluminum

Post by Jim » Tue Mar 24, 2015 4:14 pm

I have been using my S2 for a bit now successfully milling different woods and some plastics. Now I am wanting to mill some parts in aluminum, but I am having some issues and I am not sure how to proceed.

For starters, I am trying to mill some simple holes, about 0.18" using a 0.125 bit. I am using a DeWalt DWP611 spindle. The problem seems to be that it never completely cut through the material (even though it coded to). If I make multiple passes, I can eventually get through.

I have tried a few different versions of parameters, with the latest being:
  • Pass Depth: 0.007" (roughly 0.2mm)
  • Step Over: 30%
  • Spindle Speed: 16000 (lowest setting without a Super-PID)
  • Feed Rate: 44.83 in/min
  • Plunge Rate: 0.47 in/mm
I think at least one of the issues I am having is clearing the chips due to the hole size in relation to the bit size.

If anyone has any insights that would be great.
Jim

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WillAdams
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Re: Issues milling aluminum

Post by WillAdams » Tue Mar 24, 2015 4:19 pm

In metal you want to use peck drilling --- if your CAM program won't simulate that, you'll need to edit the code by hand to do so.

You'll also want to clear the chips from the hole so as to not dull the endmill recutting them.

Post the specifics of your workflow and maybe someone can help more.
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MeanderBolt
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Re: Issues milling aluminum

Post by MeanderBolt » Tue Mar 24, 2015 5:42 pm

Aluminum is one of my new materials. I have been cutting it for a few weeks now. A single flute endmill at 500mm feed speed. I am using the 660 which only has one speed (30,000) so that's where I sit. Also, I am doing .1mm passes. I am going to try going deeper, but so far that's as far as I have gone. I have done holes as both profiles and pockets with success. I am using Cambam which will set up spiral profiles so it is always woking it's way down. I have been using the endmills from Drillman 1 on eBay with a lot of success.
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Jim
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Re: Issues milling aluminum

Post by Jim » Wed Mar 25, 2015 3:15 pm

@WillAdams: This is the first thing I have tried, and it entails a simple profile cut to make the hole (since the hole is larger, albeit, not by much, than the bit). So, in this case are you suggesting I peck drill first, then profile cut? I am using Cut2D and yes, it will peck if I am drilling. It will also do ramp cuts for profile and pocket cuts too.

You asked for me to post the specifics of my workflow, which is fine, but exactly what do you mean by that? Are you wanting to see my g-code file? Or simply what the spirit of my g-code file is trying to do? Are you asking for specifics about my setup, bits, etc.? Happy to oblige, just need to know what you are looking for.

@MeanderBolt: Thanks for the info. I noticed though that the link you sent me was for end mills for specifically cutting plastic. Is that what you are using for aluminum too? I will also check out that vendor's other bits too.

Thanks,
Jim
Jim

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WillAdams
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Re: Issues milling aluminum

Post by WillAdams » Wed Mar 25, 2015 3:20 pm

Yes, I believe drill operations should always be done first. Do whatever is necessary to clear the chips --- can't afford to waste energy on re-cutting them.

By workflow I meant something along the lines of:

CAD --- drew parts in <X>, exported in <Y>format
CAM --- imported files using <Z> settings, set tool to <###>dim. performed <pocket|profile|drill> operation w/ <abc-xyz> settings
exported to G-code
sent G-code to machine using <foo-bar>

Unfortunately, we need to think outside of the box when selecting endmills --- they're manufactured for industry and intended for industrial machines, so we need to do things such as use single-flute endmills intended for plastic when cutting harder materials so as to reduce our effective spindle speeds.
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Jim
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Re: Issues milling aluminum

Post by Jim » Wed Mar 25, 2015 3:42 pm

Since I am drilling a simple hole in this case, I skipped the CAD and just went straight to the CAM, which is Cut2D. I drew an appropriately sized hole (0.18") and told it to do a profile cut using the parameters I mentioned in my original post.

I then exported the CAM to a g-code file and used Chilipepr to do the (attempted) cut as I am using a TinyG controller.

My end mill, currently, is a Dremel 194 High Speed Cutter, which is a 1/8" cutter.
Jim

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WillAdams
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Re: Issues milling aluminum

Post by WillAdams » Wed Mar 25, 2015 3:46 pm

First, biggest and easiest improvement, get a ``real'' endmill.
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Gadgetman!
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Re: Issues milling aluminum

Post by Gadgetman! » Wed Mar 25, 2015 4:16 pm

Just a little question...

Does the hole need to be exactly 0.18" ?
According to my calculator, that is 4.572mm...

I would have 'peck drilled' holes with the diameter of the endmill to reate a 'pilot hole', then use a 4.5mm drill in my drill-press.
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Jimf
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Re: Issues milling aluminum

Post by Jimf » Wed Mar 25, 2015 4:25 pm

The dremel bit has to many flutes to mill aluminum at 16,000rpm. Ideally you want a 1 or 2 flute endmill to cut aluminum at that speed.

Also I can't tell from the picture if that dremel bit is designed for plunge cutting operation. Some bits don't have the necessary front facing cutter and clearance for plunge op. This make it difficult or impossible to "drill".

Search for ebay seller drillman1 and order some end mills. He has high quality ones for good price.

Jim
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Re: Issues milling aluminum

Post by Jim » Wed Mar 25, 2015 8:54 pm

@JimF: OK, I will track down a real end mill, especially one designed for aluminum. You wondered if the Dremel version is designed for plunging. Not sure if it is designed to what you are expecting, but yes, the flutes "extend" to the bottom of the bit for cutting on the bottom, as opposed to Dremel's solid carbide bit which is literally flat/smooth on the bottom. While I normally use a carbide end mill with my cuts lately, it broke and I didn't have anymore, so I used this HSS one that I had on hand (and claimed it cuts non-ferrous metals--but probably not in this kind of setup...)

One of the prior posters also mentioned Drillman1 on eBay, so I will check him out.

Thanks
Jim

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