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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > Small CNC for Steel - 30 x 40 cm table area. Worth attempting?
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  1. #1
    Join Date
    Feb 2019
    Posts
    3

    Small CNC for Steel - 30 x 40 cm table area. Worth attempting?

    Hi All,

    Been looking into CNC's for a while now, and have looked at pros and cons for many option eg, buying a 6040 unit and upgrading it etc. Buying a proper mini mill and converting into a CNC.

    Each time I come back to starting a DIY build to either eliminate the problems incurred with the above or the initial cost of purchase. I know it will cost a considerable amount, but at least I can span this over time.

    What I am looking for is some advice if it's even worth the effort.

    The reason I am looking into the cnc is I do a lot of knife making and some other trinkets etc Many of these are out of stainless steel or a damascus.Softer materials get used for fittings etc, Brass, Bronze, Nickel Silver. I am not looking to mill a knife or anything like that, but more to add highlights or engravings onto the steel prior to heat treatment. The steel is annealed so is able to be worked with basic tools.

    If it is even worth attempting I was considering a welded steel frame with 20mm linear rails, most likely a gantry style design. This is to help with the rigidity, but any suggestions on that would be helpful, as the size is small a moveable table may be a smarter choice.
    A table of 10mm aluminum or steel, with a layer of sacrificial material attached.
    A high torque spindle (water cooled) to manage to cut the steel at a reasonable rate.

    This is not to build a shipping list, but more to provide some of my thoughts on what it might take to get a successful diy cnc for my needs built.

    Thanks for your time.

    Tim.

  2. #2
    Join Date
    Dec 2013
    Posts
    5717

    Re: Small CNC for Steel - 30 x 40 cm table area. Worth attempting?

    You will be far ahead to buy a machine designed to cut metal. Benchtop routers do a fine job cutting wood and plastics, a lesser job of cutting metals. A small milling machine is an order of magnitude better for cutting metal than a benchtop router, and it will also do a fine job of cutting plastic and wood. Mass is your friend.

    Your idea of using a moving table with a fixed gantry will give you a much more rigid machine and would be the way I would build one. For cutting metal the machine frame and gantry needs to be massive compared to the size of the machine for rigidity.

    For metal, the spindle needs a speed range of about 100 to 6,000 RPM. 18K or 24K spindles will not run in the correct speed range. The exception to this is for engraving where you do need high speeds for use with tiny tip size cutters. I use an auxiliary 50K RPM air powered spindle for this.

    Overall it is probably more cost effective to buy a used bench mill and convert it to CNC. If you have the floor space, buying a used full size CNC milling machine and upgrade the controls would be my first choice. You can pick up used ones with bad controllers for really cheap, for scrap price.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
    Join Date
    May 2005
    Posts
    3920

    Re: Small CNC for Steel - 30 x 40 cm table area. Worth attempting?

    Just to get to the point of doing acceptable engravings is going to be a bigger challenge than many first time builders are aware of. Then you talk about a wide array of other materials you want to work some of which may be more demanding than Steels. Stainless steel and even bronze can be difficult to machine. Your best bet is a small machine built very stiff that usage is limited to operations that would normally be handled on a milling machine with a high speed spindle. Thus engraving and milling with very small diameter cutters. At some point cutter diameter and spindle RPM range will come into conflict and your ability to get good quality work done goes out the window.

    Another problem that will raise its head is that this would need to be a precision build requiring access to a machine shop or a lot of hand work. Small cutters will not tolerate large depth of cut changes, vibration and other machine problems that are not an issue in wood. Even things like leadscrews need to be a step above what is common in wood working routers as backlash and other evils can easily destroy small diameter cutters. So while I will not say it is impossible to build a machine suitable for engraving work and small diameter milling in the metals you suggest I have to say it is a bigger project than a lot of home shops can handle.

    It isn’t impossible, but access to a good milling machine and a bunch of machinist tools would be mandatory in my mind. I’d also strongly suggest the use of steel and cast iron in this build. For the moving table one possibility is looking on line for fast iron plate tables. For the frame thick and large cross section steel tubing would be a good starting point and you may want to fill these with epoxy granite. The goal here is mass and stiffness. Even after all of this and the addition of a good router spindle you will still be limited by that spindles low end speed.

    I might add there are modern tool path processes that will allow you to leverage to some extent high speed spindles in metals on “”less”” rigid machines. To the best of my knowledge these techniques would not help with engraving. You still have the problem that the bargain end spindles have very little low end power. So you will need to have very low expectations for milling type operations.

    So in a nut shell it isnt impossible but don’t confuse what you need as the equivalent of a low end router. You need the capability to build what amounts to being a bridge mill. I would say this is a step beyond doing some sort of Mini mill conversion.

  4. #4
    Join Date
    May 2005
    Posts
    1662

    Re: Small CNC for Steel - 30 x 40 cm table area. Worth attempting?

    Quote Originally Posted by Jim Dawson View Post
    Overall it is probably more cost effective to buy a used bench mill and convert it to CNC. If you have the floor space, buying a used full size CNC milling machine and upgrade the controls would be my first choice. You can pick up used ones with bad controllers for really cheap, for scrap price.
    This, even if just to get the bones. Scratch building a truly capable mill would be a fun project unto itself given the resouces (tools+$$$). As the means to an end it will eat up your time and money,
    Anyone who says "It only goes together one way" has no imagination.

  5. #5
    Join Date
    Feb 2019
    Posts
    3

    Re: Small CNC for Steel - 30 x 40 cm table area. Worth attempting?

    Hi All,

    Thanks for the valuable input....Perhaps I should just go back to the milling machine conversion, will need to see what I can find locally within my budget and then spec out the cost of conversion again.

    Cheers,

    Tim

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