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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > Has anyone machined Steel with their CNC Router?
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  1. #1
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    Has anyone machined Steel with their CNC Router?

    I am keen to make a CNC router mostly for working with Aluminium but would like to be able to do the odd bit of steel machining. All for hobby purposes so don't need production quality or speed.

    I know this will be a difficult task so I am curious to know if anyone has pulled it off? and if so what configuration of machine was used - fixed or moving gantry, ball screws or lead screws, linear bearing used?, servo motors or steppers etc.

    Brett

    PS I know this forum is under the woodworking section but most of the CNC router experts seem to be here...

  2. #2
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    Hi, here's a fixed gantry CNC mill that will mill steel.....note the heavy construction........anything less than this is what you get with DIY aluminium extrusion framework designs, only fit for wood, plastics and possible with the right design some aluminium.

    If you are intending majoring in the aluminium field, with maybe a bit of the odd steel or brass job, go for a column mill design.

    With any CNC you will need ball screws, linear ways and water cooled high speed spindles, and without any doubt a Gecko G540 controller.............anything less and you're dreaming.

    You're definitely in dream land for a new model out of the box if you don't have a budget that starts at $3,000 for disposable income you won't miss.

    Once you're into it there's no going back, and an "investment" in the very best DIY build will get you cents on the dollar if you give it up.

    Starting at $2,000, you can go on EBAY and buy a ready to go (with modificatons) smallish gantry router, that with a bit of persuasion can handle some aluminium, but you won't find one "pre loved" any where near half this price.

    I'm sure if you post a work envelop expectation, more advice would be forth coming as to what you could achieve with serious DIY input and a little cash flowing from time to time.

    There are many bits and pieces on EBAY that you can tack onto a frame once you have got started........you'll save a heap in labour if you go DIY.
    Ian.

  3. #3
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    Milling steel

    Mine will mill steel, stainless and anything else.

    It is a scratch build, portal mill, 1600 mm wide table, linear guides, BP M head as spindle (driven by hitachi VFD).
    All steel, welded assys with drilled/tapped/pinned as appropriate.Multiple preloads.
    The head is about 50-60 years old.

    Mass about 2000 kg. Took 13.000 work hours. 2 redesigns, and needed to learn to weld and turn and do 2 lathe cnc refits.
    2 m wide. 1.8 m deep.

    Now moving to bigger ballscrews (from 0.750") to 32 x4 mm, and ac brushless servos.
    And redoing the head quill with a large 25x4 mm ballscrew.

    Parts cost was commensurate, approx 15k.
    It runs fine with 3 Nm steppers and gecko 251, and 48V lab PSU, at 2kW or 50 amps, the servos are not really needed.
    They are there for production purposes (guaranteed in-spec machine movement), and as a demo.
    300 or so pieces to do.

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  5. #5
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    I think we have to be realistic in the cost and physical size to achieve the end result.

    Personally, although the bamboo wood router was sturdy and did cut steel, in my opinion it is only suited for wood.
    Ian.

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    I was expecting to see big heavy steel machines but not a bamboo one! That is impressive.

    In terms of work envelope I am thinking about 600mm x 400mm x 150mm. Any smaller and I think I might be better of getting a small milling machine.

    Brett

  7. #7
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    The experiment was not intended to claim my bamboo machine is a professional or even well suited tool for milling steel. It was indeed designed as a wood router.

    However, I wanted to challenge the over and over repeated paradigm "it can not be done, forget it". Of course it can.

    If the machine is just rigid enough (say, at least 3-5000 lbs/inch) and backlash free one can make the occasional steel part with a good quality bit, even with a high speed spindle (I mean mild steel, not hardened or tough alloys). Not as efficient and precise as on a Bridgeport or similar equipment but surely good enough for many purposes. The lack of proper coolant and chip catching is the main reason I don't like doing that.

    Similar for brass. Other than many opinions I read here I found it much nicer to machine than the sticky aluminum. If it only was not so darn expensive.
    Box Joint and Dovetail CAM software here: WWW.TAILMAKER.NET

  8. #8
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    My build (nearing end of design) is based on the idea of being able to mill steel on a 3x4" gantry machine. I have gone through 10 major revisions. Weight of the machine has gone from a few hundred to over 2000. The table bed has gone from plywood+MDF top to poured concrete, to a 1400 lb granite surface table (which I have now) with the x beams bolted to it. The gantry is two 3" x 5" x 3/8" steel beams with lots of welding. I will be at least partially filling the beams with epoxy granite. I expect the 3 foot gantry + Z to weigh near 300 lbs. I have switched from 960 oz/inch steppers to servos. Ball screws have gone from 1610 size throughout to 2510 for the longer runs. The proposed spindle is currently automationtechnologies.com 4.5 KW water cooled (not totally sure it's good enough).
    I still expect the machinists to sneer at this design! Should this discourage you? NO! I am building it because I always wanted one. Do what you want! But do your homework. You have to become comfortable with beam deflection calculations.

  9. #9
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    Quote Originally Posted by bmanners View Post
    I was expecting to see big heavy steel machines but not a bamboo one! ............
    Forgot to mention....yes the frame and gantry are made of Bamboo plywood. But lots of it. The whole machine weighs in at 500-600 pounds, gantry about 160 pounds and I am using top notch C5 grade Kuroda ballscrews.
    Box Joint and Dovetail CAM software here: WWW.TAILMAKER.NET

  10. #10
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    Hi, I'll rephrase in case I came across sceptical........no matter what you build, if you never had a machine before, when you finish it you have one, and if it won't cut steel like a mill at least you are that much wiser.

    There have been so many attempts at designing a router to act like a mill, but the dividing line will always be the gantry supports, whether it's for a fixed gantry or a moving one.

    I don't think anyone can 100% accurately determine how much force a cutter exerts on a router framework and in what direction when it is under load.......crossed fingers and hope for the best is a good approach when all else fails in the calculation department.

    There is a lot of technique involved.......cunning design, like the Chinese routers, has shown that a megabuck price tag is not the only option, but in the end the money part of the equation will be the most important item under the Christmas tree, second only to the build time.

    It goes to show you that given the design, eg the bamboo build, nothing is impossible even if not entirely practical.

    I have a preference with horses for courses, and being a metal worker would not consider in my wildest dreams making a machine where wood or any form other than metal was a component.....or plastic for that matter.

    That is not to say it can't or shouldn't be done, it's just that being a metal worker I leave wood working to the carpenters.
    Ian.

  11. #11
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    Quote Originally Posted by handlewanker View Post
    ............being a metal worker I leave wood working to the carpenters...........
    Ha! I am an electrical engineer and use whatever seems fit

    But I am with you. If I would want to build a machine specifically to make steel parts I would probably bite the bullet and build one from steel. Or maybe just buy one.
    Box Joint and Dovetail CAM software here: WWW.TAILMAKER.NET

  12. #12
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    Quote Originally Posted by bmanners View Post
    I was expecting to see big heavy steel machines but not a bamboo one! That is impressive.

    In terms of work envelope I am thinking about 600mm x 400mm x 150mm. Any smaller and I think I might be better of getting a small milling machine.

    Brett
    Hmmmmm, a small mill.....this means you will get the 600mm in the X travel, but not the 400mm in the Y......Z is no problem.

    This also means you will need to go the retrofit path, and that is an almost 50% waste of materials in a mill designed specifically for manual operations when you replace them with CNC components, and still be working with dovetail slides etc.

    With all that work involved, and really needing a router at the outset, it would be better to completely fabricate a router to a common design right from the word go.

    There is no need to re-invent the wheel when the design layout has already been established over many builds to date.

    I strongly favour a fully welded steel structure......the frame materials are readily available, fairly economical, very easy to weld and finish.

    Provided the locked in stresses from welding are ignored as a might happen but not necessarily will happen factor, the build will be within the bounds of the average DIY person having some metal work skills.

    In 50 years of working with welded steel structures, I have yet to see one that was grossly, if at all, affected by welding to any degree.

    A lot depends on how you assemble the frame and the sequence for welding.....the wrong sequence and it will twist like a banana.

    Mostly the stresses will not come out or affect the build if the frame is not machined to any great degree.

    Some machining, yes, but mainly to have flat faces to mount pieces for assembly, and few of them at that.

    The less machining on a welded structure you can have the better it will work as is.

    Drilling and tapping fixing holes will not affect the structure to any degree.
    Ian.

  13. #13
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    Just to put it in perspective, 600mm X and 400mm Y travel is what the large mills (like the HM-50's) at H&F do, that also weigh around 600-900kgs, and cost upwards of $6000.

    And to do steel, you really want that nice, large amount of mass, unless you live many miles from any neighbors and have extremely good hearing protection?

    cheers, Ian
    It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!

  14. #14
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    Hi, I get the feeling that in a router design, if you only have the room to swing a small cat and decide that a moving gantry model is all you can manage, you have to put up with the result that there will be a definite lack of rigidity, and thinking in terms of metal for serious projects is not going to happen.

    If I had any metal aspirations on the cards, I'd go to a fixed gantry model and allow for the extra length in the Y axis or table travel.

    With a fixed gantry and a central screw drive you don't have any deflection of the Gantry side supports (which can be massive) as it's only the table that is being moved and that means less inertia from the weight of the gantry, crossbeam and Z axis mass as in a moving gantry one.

    There will also be no deflection from torsional twisting of the crossbeam by the Z axis at it's lowest down position with a fixed gantry too, one factor that reduces the vibration from any cuts more than just engraving.

    Therefore, in my opinion, the moving gantry type only saves some space in the footprint of it's frame length requirement.....IE, in a fixed gantry design you need to have the frame almost twice the table length for it's travel, but if you make the table overhang the frame at either end by 1/6th the table length, you can save 1/3rd of the overall frame length without sacrificing table support by the bearings on the linear slides, and if the table has three bearing blocks per side it will be rock solid no matter what you cut.

    When someone designs and markets a 6040 fixed gantry router, using steel/iron instead of aluminium and for $2,000.....the days of the mill drill retrofits will be over.

    One of the finest toolroom jig borers, the Societe Genovoise, has a moving table fixed gantry all cast iron design, and is a most sought after used model.
    Ian.

  15. #15
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    Some good points to ponder there, thanks for taking the time to respond everyone.

    With an 18 month old boy and another due in a few weeks I won't get much time to play in the near future. Some time to think while walking the pram though

    Seems like some occasional machining of steel can be done on a router provided the router is designed well, uses quality components etc. I need to find the right compromise between work envelope, cost, build time, rigidity and overall size to suit my needs before going any further.

    Thanks
    Brett

  16. #16
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    I know you said router Brett, but do you mean spindle, or are you talking a domestic wood router?

    Because, if your talking wood router, they definitely aren't designed for doing steel in any quantity. Even just engraving steel would be dubious. Not to say you can't do it with a domestic wood router, but it will do it poorly, extremely noisily, and won't last.

    A good strong spindle with as little runout as possible is far more suitable.

    cheers, Ian
    It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!

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    Yeah I assumed a wood router is not up to it. I also expect to need good quality linear rails and ball screws and steel construction....and plenty of time and $$ ;-)

  18. #18
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    Even if you use the very best rails and ballscrews you can get, ultimately the defining factor between being able to push the machine to occasionally do steel, and being able to cope with regular machining of steel, will be the rigidity and the mass of the machine. You can make the machine very rigid, but for example if it's made of aluminium extrusion, it'll be screaming worse than a banshee when doing steel. And will also loosen every nut and bolt too along the way, as it won't have enough mass to dampen the effects of machining steel.

    A lot of hobbyist cnc machines would struggle to do aluminium, but steel is nothing like alu for these machines. I would actually go so far as to say if you plan on doing anything more than extremely smalls jobs in steel on a very rare basis, build your cnc machine to cope with aluminium, this will keep the costs and the weight of the machine down greatly, and plonk down the cash for a small mill like a BF16, which can be had quite cheaply, for steel work.

    As Ian (Handlewanker) pointed out, it is doable, but I personally don't believe it's at all practical, unless money's no object. Even then, I'd still go a mill over a wood/plastic/alu/steel homebrew machine everytime. That's my opinion though anyway.

    cheers, Ian
    It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!

  19. #19
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    Another factor is spindle speed. Usually the feeds and spindle RPMs are a lot slower than aluminum otherwise you're just creating a lot of heat and wasting endmills.

    As to aluminum machining, some alloys are more CNC-friendly than others. I prefer cast aluminum tooling plate, and the faces are blanchard ground eliminating the need to surface (and most CNC routers would not be able to handle a facemill.)

    One option would be to create wood patterns of your frame parts and have them cast of iron at a foundry. This may not be cheap, but it probably would be better than any steel weldment.

  20. #20
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    Re: Has anyone machined Steel with their CNC Router?

    the reason this guy can cut steel on a bambo cnc .... is very simple he using some of the best tooling in the industry. Titanium coatings TiN, TiCN, TiAlN,

    Titanium Nitride coating with its familiar gold color remains the most popular general purpose coating. TiN has the highest adhesion and ductility characteristics of any of the coatings. The excellent wear resistance, thermal stability, and low coefficient of friction reduces built up edge and thus improves thermal transfer of heat away from the tool.

    Titanium Aluminum Nitride, violet bronze in color, actually forms a hard aluminum oxide layer in hot (> 800ºC), dry machining applications. This further reflects the heat back into the chip and away from the tool and workpiece. Greater ductility makes it a good choice for interrupted cuts. Increased production levels at higher feeds and speeds and longer tool life in high heat applications are the primary benefits.

    He milling at 9000rpm TiAlN tooling is designed for faster milling operation .... 9000rpm on a spindle or router is not ideal but with TiAlN a much wise choice over standard hss or carbide.

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