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    Registered GingerNinja's Avatar
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    Default 1900 x 600 Router concept

    Been toying with the idea of getting a CNC router for a while and been working on this concept until now. My workshop is limited in size and this router will be used predominantly for hobby machining MDF,Hardwood and drag knifing plastic base for use in snowboard building with a little bit of aluminium machining.

    The working envelope will be 1900 x 600 x 200.
    20mm Chinese rail and blocks on al 3 axis
    CNCRouterparts rack and pinion for Y axis, SFU1610-3 ballscrew for X, SFU1605-3 balscrew for Z. I am after very fine resolution Z height and less concerned with the Z speed
    Considering the whole electronics package from CNCRouterparts + Nema 23 - 420 stepper motors

    The frame will be 2"x4" steel frame stitch welded together with 2"x2" supports to minimise the distortion..
    The gantry will be 0.625" aluminium machined series 5 tool plate plus a 8020 8016 Aluminium cross member that the Z carraige will ride on.
    I anticipate to use a porter cable or Bosch router for spindle.

    A Vacuum base will be used for hold down still to be designed.

    I have access to a 4x8' CNC router during the build so will epoxy pour the Y axis rails mounting surface and machine a datum edge to align the rail on.

    From other members experience would this setup be suitable for occasional aluminium work or is the gutfeel that it will be too flexible on the Gantry cross member and should be replaced with a 3" x 6" steel beam instead?

    Any thougths on simplifying or improvements that can be made before i firm this design up?

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    Default Re: 1900 x 600 Router concept

    One of the problems with trying to answer questions of the type you are asking is that we don’t know what your expectations are. Plus a phrase like machine a bit of aluminum means different things to different people.

    So the first thing to understand here is that routers are not milling machines so don’t expect milling machine capabilities machining Aluminum. That being said perfectly acceptable results are had in aluminum on routers everyday, you get the best results from a more rigid machine.

    So a few comments in line below.

    Quote Originally Posted by GingerNinja View Post
    Been toying with the idea of getting a CNC router for a while and been working on this concept until now. My workshop is limited in size and this router will be used predominantly for hobby machining MDF,Hardwood and drag knifing plastic base for use in snowboard building with a little bit of aluminium machining.

    The working envelope will be 1900 x 600 x 200.
    This is a very manageable size for a first build. You need to be careful with the Z axis design to maintain rigidity.
    20mm Chinese rail and blocks on al 3 axis
    CNCRouterparts rack and pinion for Y axis, SFU1610-3 ballscrew for X, SFU1605-3 balscrew for Z. I am after very fine resolution Z height and less concerned with the Z speed
    First off which is your gantry? The message implies that your X is, if so that is not a convention I like to follow.

    In any event there is no real good reason for rack and pinion on such a small machine. Properly mounted ball screws will work fine.

    I do have to wonder why you want the fine resolution? You have to remember that this is a router type machine and thus getting good repeatability first should be high on your list of priorities. Even if you strive to produce a rigid router you will still have flex and twist to deal with. All you will get out of high resolution leadscrews is a slow machine.
    Considering the whole electronics package from CNCRouterparts + Nema 23 - 420 stepper motors
    Don’t jump the gun here, make sure your mechanical design is nailed down first.
    The frame will be 2"x4" steel frame stitch welded together with 2"x2" supports to minimise the distortion.
    Welding introduces distortion the only thing you can do is to minimize it. I like that it is welded though but do realize that the ladder frames like your renderings show can twist this you need a leveling arraingement. Feet if you will. More importantly these frames can walk under operation so you may want to bolt the machine down. I’m assuming you have a bench or table to mount this to, if not consider a complete frame with legs.

    I would not rely upon just butt welding the tubes in place. Put in plenty of gussets and corner plates to stiffen up the machine. I’d probably stick with 2x4 rungs on that ladder frame also. The reason is to stiffen up the side rails some. It might also help with material purchases if you can get everything out of one stick of material.
    The gantry will be 0.625" aluminium machined series 5 tool plate plus a 8020 8016 Aluminium cross member that the Z carraige will ride on.
    Is that 8016 a typo? Even for a 2 foot span you likely would want 8040 sized extrusions at a minimal. You need to remember that deflection isn’t just up and down, the beam gets pushed back and forth too. The small span is great in that you don’t need a huge beam for light work. At the same time you gain considerable advantage from a larger beam.
    I anticipate to use a porter cable or Bosch router for spindle.

    A Vacuum base will be used for hold down still to be designed.

    I have access to a 4x8' CNC router during the build so will epoxy pour the Y axis rails mounting surface and machine a datum edge to align the rail on.
    I’m not sure I follow this at all. First off this is the X axis not the gantry right? Second epoxy leveling is generally used to level a surface to avoid machining. If you have free access to a machine that can mill those rails why not mill them then? I guess I don’t follow the reasoning here. If I had such access I’d take advantage of it.
    From other members experience would this setup be suitable for occasional aluminium work or is the gutfeel that it will be too flexible on the Gantry cross member and should be replaced with a 3" x 6" steel beam instead?
    Well in my mind steel wins just about every time! You do need to be aware of how to design with it and work with it as a material. The reality here is that the 2 foot span would do well with a 3x6 steel beam of suitable thickness. In this case thickness would be about screw holding and machining allowances.

    You do end up with trade offs. The steel beam can be machined, drilled and tapped for rail mounting for example thus eliminating the need to mount a piece of flat aluminum on an extrusion. At two feet you likely can settle for capping the ends of the tube to mitigate any potential parallegraming so that isn’t a huge problem. The biggest problem with steel tube implemented gantry beams is that you need to rethink the gantry supports as the common approach for extrusions will not work without extra effort. There are dozens of solutions here though.
    Any thougths on simplifying or improvements that can be made before i firm this design up?
    I’d make sure you have a suitable place to mount it. Ladder framed machines like this really need to be bolted down and leveled. We aren’t talking picnic tables here either. Operated at any reasonable speeds and accelerations and the machine will walk or shake the table it is bolted to.

    By the way you will want good accelerations and speed if you are expecting to do a lot of MDF and hardwoods. In fact being able to achieve the right speeds and accelerations can be very important in hardwoods as some woods burn very easily going too slow. You need speed flexibility in your axises and spindle.

    It looks like you put some effort into gantry design! However remember that forces are basically in every direction and thus the gantry and its supports must be stiff in every direction.

    Even with a little beefing up this machine will never be optimal for daily machining of aluminum. As long as you understand that it is a light weight machine that can handie an occasional aluminum work load you should be OK. If aluminum is to be a good percentage of your usage you might need a bigger refactoring beefing up everything.

    And sure you don’t design yourself into a corner and make a Z Axis that can’t be updated to a three phase spindle at a later date. Many people start off with hand held routers only to update soon after. Consider a spindle upgrade as a future possibility.

    There is no mention of chip/swarf control but that is very important with MDF which is an irritant. The dust gets everywhere too.



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    Default Re: 1900 x 600 Router concept

    Thanks for the feedback Wizard, it is greatly appreciated.

    The coordinate system will follow the "right hand rule" X being left to right (600) and Y backwards and forwards (1900).

    Noted on the ballscrews for all axis. Looking at what others have used on the DIY forum the 1610 variants seems to be the more often used on hobby machines with some doing 1605 on smaller machines. The only reason for looking for a finer resolution for Z was that with 1610 ballscrew and 200 step stepper the resolution is 0.005" and I was looking a slightly better than that. I might be overthinking going for 1605 for Z since others use 0.005" resolution without problems.

    I just looked at the torque curve for the CNCRouterparts 420oz Nema23 steppers and I think I will need to rerun the numbers on my calculations. The 420oz.in torque curve falls below my needs above 900RPM.

    The router will have leveling feet and will be fastened to a table. I did not however consider the momentum that the gantry will instill under movement. I will need to rethink how I mount and counter this movement and potential walking. Having an Aluminium extrusion gantry will reduce the momentum on the table and subsequent walking, using steel for gantry will increase stiffness and reduce vibrations.

    The welded steel frame will get gusset and corner supports added to it but dont want it to be so heavy that its not possible to move it. Currently i'm in a rental property and thus I need to be able to move it without special heavy lifting equipment.

    The 8020 extrusion part number is 40-8016 ( https://8020.net/shop/40-8016.html), its the 80 x 160 extrusion.

    Reason for not milling the steel frame and looking at epoxy cast surface is that the maker space where I go dont allow steel machining on their 4' x 8' router. Thus the thinking of me there was to epoxy cast and use the router to spot drill into the epoxy and creating the location features for the rails on the frame and gantry (if steel) and get around the problem of the beam distortion from the welding operation.

    My expectations from the setup is that I can machine woods and plastic with tolerance of ±0.005" in X/Y and ±0.002" in Z. This will be purely hobby build with a few hours a month use from it and if its possible to machine simple Aluminium shapes from plate with ±0.010" tolerance on it would be an added bonus. Machine also needs to be able to be moved without special lifting equipment and minimal of tear down to allow that.

    I was planning on putting a dust shoe on the spindle for dust control and run it with a dust collection system. After routering a couple of sheets of MDF and having to clean up for months afterwards I learnt my lesson with MDF dust.



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