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  1. #1
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    Default Newcastle: Large mill / planer / grinder needed for job

    Hi guys. Daily reader, seldom poster. Most days I come on here I leave with another list of things to buy.
    Decent surface plate and granite square are high on the list at the moment. But I digress.

    I'm currently in the planning stages of a CNC router.
    I've previously built a router from aluminium and plywood. It's a bit subpar, not rigid enough.
    So I'm going to build another one from steel.

    I'm planning to use thickish RHS steel with linear bearings mounted to it. Linear bearings need quite a flat surface, which RHS is not.
    I'm looking at an X axis which will be 1500mm to 1800mm long. These measurements are not set in stone.

    I have a small benchtop mill (TM20LV) with max travel 500mm. I don't think I'd be able to accurately mill a tube flat in a multi-step setup.

    Are there any Newcastle members with a large mill / planer / grinder that could help me out?
    I'd be happy to pay, or preferably, trade machine time.

    Cheers,
    Nick

  2. #2
    Ueee's Avatar
    Ueee is offline Blacksmith, Cabinetmaker, Machinist, Messmaker
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    Hi Nick,
    I think we all leave with longer "to buy" lists!

    1500 is an awfully big machine, far bigger than anything i know of on the forum, Except maybe a planer.

    What sort of accuracy are you looking for with the new machine build? I might suggest either going to a round rail and turning it, but even then the machine size may be an issue. The other option may be to use smaller lengths, machine them and join them. Some stoning/lapping of the joins should be enough to ensure reasonably straight travel, again it depends on what you want to do.

    Ew
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  3. #3
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    Ew,

    Yep, it is a big machine. Other options I'm thinking about include painstaking shimming.

    I'll be using bearings like:
    ProfileRails.jpg
    They are by far and away the stiffest type available. I've used round bearings in my current machine and they are just not adequate.

    Well, the manufacturers normally talk in tens of microns for mounting surface parallelism etc (e.g. 20 microns), but I'm not expecting to achieve that. RHS vary by quite a bit though.

  4. #4
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    Quote Originally Posted by Ueee View Post
    Hi Nick,
    I think we all leave with longer "to buy" lists!

    1500 is an awfully big machine, far bigger than anything i know of on the forum, Except maybe a planer.

    What sort of accuracy are you looking for with the new machine build? I might suggest either going to a round rail and turning it, but even then the machine size may be an issue. The other option may be to use smaller lengths, machine them and join them. Some stoning/lapping of the joins should be enough to ensure reasonably straight travel, again it depends on what you want to do.

    Ew
    Yeah. First thing you really need to state is what level of flatness/straightness you must have over the distance. Without that who knows how it can be machined.

    Second thing is load carrying ability - what forces are you going to apply? Mass and power equals deflection, how much deflection needs to be resisted?

    RHS *is* going to move when machined unless it's a light cut on a heavy wall section. So that's another thing to consider.

    Linear ways bedded on RHS would probably be better but not cheap.

    I can do 1200 long but wrong state and I'm not doing work for money anyway. If you were local we could work something out on a time basis as I always need the weeds etc hacked back, but as it is, you need someone more local.

    There was a person who made a couple posts here who had a 6' planer (or maybe it was on PM). He was up Armidale way I think. That would be the machine for the job.

    PDW

  5. #5
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    Ueee is offline Blacksmith, Cabinetmaker, Machinist, Messmaker
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    Are you going to buy the rails and bearings as shown in the image?

    If thats the case i would mount them on something solid (I beam maybe) and either shim or use adjustment screws to level the tracks with a precision level. That way it will be as good as your patience is. It may not stay that way for long though depending on just how solid the rest of the machine is.

    Ew
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  6. #6
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    Quote Originally Posted by pippin88 View Post
    Ew,

    Yep, it is a big machine. Other options I'm thinking about include painstaking shimming.

    I'll be using bearings like:
    ProfileRails.jpg
    They are by far and away the stiffest type available. I've used round bearings in my current machine and they are just not adequate.

    Well, the manufacturers normally talk in tens of microns for mounting surface parallelism etc (e.g. 20 microns), but I'm not expecting to achieve that. RHS vary by quite a bit though.
    I hate to say it but shimming or epoxy putty is likely to be your best bet. I'd probably drill all the holes in the RHS then use epoxy putty to bed down those linear rails. That's assuming the rails have bottom tapped holes, otherwise tap the RHS if thick enough or weld nuts to the bottom.

    But FIRST you really must design and build a rigid and well triangulated base frame to support the rails and work. Then you need it on a solid floor so it can't twist. Machined RHS has to have all the welding for brackets done first before any machining.

    I hope that you've got a precision machinists level and a decent sized and accurate straight edge if you're trying for anything close to 20 microns.

    Sounds like a fun toy when finished....

    PDW

  7. #7
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    If the bearing rails are true, how about setting them onto a bed of epoxy then bolting through that?
    Few details to work out of course....

  8. #8
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    Quote Originally Posted by Ueee View Post
    Are you going to buy the rails and bearings as shown in the image?

    If thats the case i would mount them on something solid (I beam maybe) and either shim or use adjustment screws to level the tracks with a precision level. That way it will be as good as your patience is. It may not stay that way for long though depending on just how solid the rest of the machine is.

    Ew
    Hot rolled parallel flange channel might not be a bad choice. You get a deep section and a flat flange to attach the rails to. Bolt all the transverse bracing pieces to avoid weld induced distortion. I'd probably go for 150mm to 200mm channel.

    In theory you could machine one face and bolt 2 or 3 sections together. Big horizontal mill like yours with a decent face cutter in the horizontal spindle, slide the channel along, I think 1500 to 1800 length is very do-able for a cleanup cut. 2 to 3 moves.

    PDW

  9. #9
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    Thanks for the input guys.

    Firstly - I would not be expecting to achieve 20microns. 10 times that would be acceptable over the length I'm looking at.
    This will be a router for wood and plastic. The work surface will be a spoil board that is routed flat by the machine itself, so a fair bit of tolerance is allowable. But too much and the rails will bind and wear.
    Many of these machines have been built with similar linear bearings without machining mounting surfaces.

    I suppose part of the goal of this machine is to 'build it right' rather than half arsed and not satisfactory like some of my previous / current projects.
    My current router uses round bearings - they allow rotation and introduce quite a bit of slop.

    Plan is for all bolted construction, no welding, so as to avoid warping and allow shimming.

    Epoxy - is certainly a possibility and has been done by others in same situation.
    • Dealing with mounting holes can be difficult. Drilling after disturbs the surface and is difficult. Drilling before requires plugging holes, with posts sticking up through epoxy which results in a meniscus around each
    • Meniscus at the edge - not a big deal if make the surface wide enough that the rail will sit on the flat portion
    • Stiffness - mounting to epoxy is not as stiff as metal to metal.
    • Cost - epoxy is not cheap in the US where I've read about this being done, and with the australia rip off added it gets expensive. Need proper slow setting epoxy.


    Square tube is much stiffer than an I beam or C section.

    Using a machine that doesn't have the full travel in one movement is *possible* with careful setup, but very difficult I think.
    I would envisage clamping the tube on mill table. Taking a skim cut (full travel) to flatten. Then move the tube along part of the travel, indicate it in, clamp etc.
    Problems being with no flat reference when I move it along there will be variance in height and rotation / yaw that would require very careful shimming etc to get it right.

    No one has a 1500mm blanchard grinder in there shed?

    A roughly similar design to what I am thinking of is: New Machine Build Steel frame Ganrty router build
    I'm looking at using ~100mm square RHS for the frame, with ~200mm square tube for the gantry beam.

  10. #10
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    Default

    Why not use 100mm universal column?
    Gold, the colour of choice for the discerning person.

  11. #11
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    There are plenty of commercial gantry style routers around, what sort of specifications do they have for straighness of the axes? table flatness? Knowing what sort of precision is required will go a long way to determining the sort of frame construction to be built.

    You can do a lot of work with a good machinist level, and wires with wire sag tables will give you more than enough accuracy as far as straight lines go.

    Ray

  12. #12
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    See if you can make contact with Jayson, ( maybe send him a PM ) I recall he had a nifty solution to this problem of grinding the rails on his 8'x4' router table..

    Ray

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    Quote Originally Posted by pippin88 View Post
    Epoxy - is certainly a possibility and has been done by others in same situation.
    • Dealing with mounting holes can be difficult. Drilling after disturbs the surface and is difficult. Drilling before requires plugging holes, with posts sticking up through epoxy which results in a meniscus around each
    • Meniscus at the edge - not a big deal if make the surface wide enough that the rail will sit on the flat portion
    • Stiffness - mounting to epoxy is not as stiff as metal to metal.
    • Cost - epoxy is not cheap in the US where I've read about this being done, and with the australia rip off added it gets expensive. Need proper slow setting epoxy.
    There are plenty of epoxies available. Devcon liquid steel comes to mind but no idea on price. I use quite a bit of epoxy for woodwork, I buy it from the boat shops. There's a nice non-slumping type used for fillets etc.

    All depends on the applied load.

    Quote Originally Posted by pippin88 View Post
    Square tube is much stiffer than an I beam or C section.
    Yes, for the same flange width. However a 150mm parallel flange channel is going to be a lot stiffer than 100 x 100 x 3 RHS. You want depth for stiffness more than width so using square section is a mistake anyway.

    Quote Originally Posted by pippin88 View Post
    Using a machine that doesn't have the full travel in one movement is *possible* with careful setup, but very difficult I think.
    I would envisage clamping the tube on mill table. Taking a skim cut (full travel) to flatten. Then move the tube along part of the travel, indicate it in, clamp etc.
    Problems being with no flat reference when I move it along there will be variance in height and rotation / yaw that would require very careful shimming etc to get it right.
    This depends entirely on your mill; a horizontal mill is excellent for this sort of work. The mill that Evan has, no real problem. My old Victoria U2 can do 700mm length of cut so 3 moves as follows:

    Bolt alignment guide to table. Couple of angle plates for example.

    Cut.

    Shift 2/3 and use DTI on machined section to keep parallelism.

    Cut.

    Shift etc.

    Scrape off ridge where interrupted cuts start & stop.

    It'll come out well within your stated tolerance *provided* the material doesn't stress-relieve which IMO is another good reason for using parallel flange channel. It's hot rolled and has a lot less locked in stresses than RHS.

    Quote Originally Posted by pippin88 View Post
    No one has a 1500mm blanchard grinder in there shed?

    A roughly similar design to what I am thinking of is: New Machine Build Steel frame Ganrty router build
    I'm looking at using ~100mm square RHS for the frame, with ~200mm square tube for the gantry beam.
    As I've said I think using square RHS is a big mistake. If you want stiffness, 150 x 75 RHS is going to give it to you a lot more than 100 x 100 is. Somewhere there's a deflection table for this stuff but I can't remember where - that's what you want to know, not what someone else on the net has done.

    What you have to realise is, this is a hobby for you and businesses aren't going to be interested as you are obviously not prepared to pay. Yes, we do know of at least one place that can do it. Marco comes to mind. In Melbourne. The starting price is likely to be around $2500 with no guarantees because of the nature of the material.

    Find someone with a 1500 to 1800 long precision straight edge (good luck there, too, I know where there are 2 of them. One in Melbourne and one in Hobart). Or use the taut wire and sag tables to do the same. Spot your RHS or channel after getting rid of any mill scale etc. Use a die grinder to knock down the high spots then shim or bed in epoxy. You probably only need a series of planar spots every 100mm or so, the rest could be slightly lower. That will teach you a lot as well as being faster, probably, than finding someone who will do the machining for you in return for the equivalent of a slab of beer etc.

    PDW

  14. #14
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    Quote Originally Posted by RayG View Post
    See if you can make contact with Jayson, ( maybe send him a PM ) I recall he had a nifty solution to this problem of grinding the rails on his 8'x4' router table..

    Ray
    Ray jaysons router is 4ft x 12ft
    Nick look up mechmate for details its capable of very acurate work its simple and got a good track record no need to reinvent the wheel

    cheers
    Harty

  15. #15
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    Quote Originally Posted by harty69 View Post
    Ray jaysons router is 4ft x 12ft
    I just remembered it was very impressive!

    Ray

    PS MechMate CNC Router - Build your own with our detailed plans

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