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Thread: low speed milling heads vs high speed spindles for aluminum on small CNC machines?

  1. #1
    Join Date
    Jun 2017
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    Default low speed milling heads vs high speed spindles for aluminum on small CNC machines?

    Does anyone here own both high speed spindles and lower RPM milling heads? I am interested in what people think is best for milling aluminum on smaller / lighter desktop or benchtop mills or CNC routers etc?

    I am more focused on hobby or small shop level devices and not the high end spindles you find on $100,000 CNC machines.

    Hobby users and small businesses are fortunate these days that low cost 2500rpm R8 milling heads and 18,000 rpm 2.2kw CNC spindles are readily available for diy machine builders. The choice is easy for some cutting materials. For example, the milling head is clearly the right choice for steel but... for aluminum, it's not as straightforward.

    The advice I have seen is mostly that the 18,000 rpm 2.2kw or 3kw spindles are better for making aluminum parts but people are still buying small mills. Does anyone here think that a small CNC mill is better than a small CNC router for aluminum?

  2. #2
    Join Date
    Nov 2008
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    Doesn't the decision come down to the size of the tool, availability of coolant and type of tooling?

    If I'm using a manual mill, I'll swap in a nice big, slow rotating fly cutter to flatten a large area. Then I'll put in a smaller endmill for details. If you use a small cnc router, you will be likely to use the endmill that is most appropriate based on the smallest detail you are cutting and then you'll make a lot of passes. If it's a small carbide or coated endmill you will probably want to run it pretty fast.

    Dan
    Measure twice. Cut once. Weld. Repeat.
    ( Welding solves many problems.)

  3. #3
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    Jun 2017
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    I think that sounds fair if you have access to both and choosing for a specific job but if you are buying one machine to cut aluminum for hobby work or a small business, you probably have to choose one or the other.

    Also, most of the small hobby level benchtop mills I have seen only fit a max of 5/8" end mills. That's a little more your typical ER20 or ER16 CNC spindle but the size of the motor might also be a limiting factor in the choice of end mill. Most of the small mills I have seen are 1/2hp or 3/4hp.

    I have been told that you can cut aluminum on either but the job will be quicker with high speed spindle. I have also read that it is linked to the weight of the machine - I.e. Lighter machines need faster spindles.

    I am interested to know if there is any advantage to small desktop CNC enabled mill over a small CNC router with high speed 2.2kw (3hp spindle) if you only cut aluminum and never harder metals like steel.

  4. #4
    Join Date
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    Live Oak, TEXAS
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    I think it depends on exactly what kind of work will be done.
    Routers are great if you're making alot of parts out of large sheets of material.
    Mills are better for multiple sided parts, and multiple set-ups.
    If you're looking at cutting Aluminum and softer material, then a 10,000 Spindle is plenty of RPM's for either a small mill or a router.
    Anything above 10k is really overkill, unless you're running a batch of 1,000 parts +, and absolutely NEED the speed.
    I run 1/4" endmills at 7000 RPM, 25 inches per minute. Smaller endmills get 10,000 RPM. They run great.
    The smallest endmill I've ran at 10k was a 1/32" two flute, in brass and aluminum.
    Last edited by KiddZimaHater; 07-09-2017 at 08:22 PM.

  5. #5
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    Mar 2013
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    I can tell you that over 10,000 RPM is not overkill. When I was programming for a Fadal 4020 I always wished we had a fast spindle. FS Wizard pro says a 1/4" TiN carbide end mill at 30,000 rpm slotting 6061 1/4" deep you can feed at 85 ipm. That requires just 1.59 hp and removes over 5 cubic inches per minute. My home built CNC can't quite make that cut as I only have a 1.5 hp router spindle.

    I also have an R8 5,000 rpm spindle for the machine. Haven't used it for a while as I've been cutting mostly aluminum and plastics. I also have done steel parts using a 1/8" TiN carbide end mill at 13,000 rpm and a 14 ipm feed rate. FS Wizard will help you get better performance from your spindle and your tools. Cutting at conservative feed rates wears out tool faster.

  6. #6
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    Aug 2006
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    Beaverton, OR
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    My mill's spindle will do about 5500 RPM Max. For faster stuff I have a Nikken spindle speeder which will do 20k. They are limited on duty cycle though. For faster yet I have a few NSK Nakanishi Astro-Z high speed spindles. They do up to 40k and have various angled heads and gear reducers to do different setups.


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