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  1. #1
    AndyUK's Avatar
    Lives in Southampton, United Kingdom. Last Activity: 3 Weeks Ago Has been a member for 1-2 years. Has a total post count of 6.
    Hi All,

    First things first - Thankyou everyone. This forum is an amazing resource. I've spent the past year lurking and researching, and thought it was about time to get a build log started. Now, if you don't mind, lets begin the self-indulgence!

    What do I want out of this?
    The biggest draw for me is learning the skills in building and improving the thing. I want your opinions and suggestions. Secondly, I want an awesome tool that can help with my DIY projects going forwards - I would like to be able to work primarily in wood (I'm thinking small furniture building, engraving etc), but want to do small things in aluminium too (like parts for models, handy things for the house or whatever). One of the more exciting applications I have in mind for the future is helping my wife with her glass work - either by scoring / cutting / engraving glass, or creating moulds for the kiln.

    Tools
    So, I intend to expand my garage substantially... but, I have the basics like a chop-saw, bench drill, etc. My designs are conscious of the fact I have (occasional) access to a Bridgeport milling machine and a reasonable size lathe. The largest 'tool' in the garage is me (in every sense)... I'm a Physicist by trade so can handle electronics and equations - I have greater trouble with the structural design aspects and the physical creation, so those are what I want to learn the most about - I've never welded or tapped a hole before, so they're going to be fun to learn.

    The Design So Far
    I've thusfar chosen a gantry-based design, about 1.2m by 1.0m which gives me a working area of approximately 1.0m by 0.8m. I think this will be large enough for any project I can throw at it, but small enough to fit in the garage and still have a degree of stiffness! I've particularly liked the common design on this forum, and have used Joe Harris' thread and video logs in particular for ideas and inspiration (cheers!). I've also chosen a L-shape gantry, currently proposed to be created from a rectangular and box section steel extrusion, and a C style carriage to wrap around it, after looking at the gantry design study threads and following through the mathematics (largely helped by the cutting forces calculation spreadsheets on this forum). I was thinking of having a dual X-motor setup, which I know is the slightly less-favoured setup around here, but I don't like the idea of large timing belts - they just weird me out. I do plan to use small belts on all the drives though to give myself some gearing and alignment flexibility. I'd expect to go for one of the large Chinese water-cooled spindles with a VFD. I was anticipating welding the square sections for the gantry, and then using the milling machine to give me good parallel even faces - same goes for the large square tubes that the gantry moves along, but they won't be welded. Not sure if the gantry side plates and the z drive plates should be made from 20mm aluminium or steel yet, so would appreciate comments on that aspect - I think the weight is still feasible with steel, and as I can machine it...? I'm also not very good at knowing where it would be good to add adjustment features, and what form they should take.

    Heres a few pictures of my plans so far.... Forgive my Solidworks skills... they're not the greatest!
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    I'd like your help with...
    Everything!
    Specifically at the moment, I'm at the stage of wanting to get the build started. I plan to construct the base frame and the adjustable height bed first, which means learning to weld. Before I dive in head first - I'd like your opinions on the overall design and in particular my base and bed design. Is there anything I've completely overlooked? The base is made from 80x80x4mm and the bed is made from 60x60x4mm square mild steel tubing, with the plates and angles you see made from 3mm mild steel. I planned to construct the base in four welded parts which will then bolt together - the two end squares, and the two central sections.

    Here are a couple of detail shots:
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    Thanks All, and Happy Christmas!
    Last edited by AndyUK; 23-12-2017 at 08:17 PM.

  2. #2
    Andy Welcome to the forum and a merry Xmas.

    You have certainly done some good research with the design. I use dual motors and home them independently with no problem.
    The usual advise on here is to advise not to order any electronics (or kits of electronic)s as thing often change in the design. I don't think you will need the dual screws to be full length as you can move the nut mounting a bit further back on the gantry side and save about 200 mm of screw length.

    I would also consider for the gantry HD ally profile say 90 x 45 two pieces one horizontal and the other on top vertical the slots in them are correct for BK12 bearing mount etc. so make it very simple.

    Anyway just two sleeps for Xmas
    Last edited by Clive S; 23-12-2017 at 08:51 PM.
    ..Clive
    The more you know, The better you know, How little you know

  3. #3
    Looks awesome!

    I see a few improvements in your design that I will use if I start again with a new machine ;)

    One thing I cant see clearly is the spacing of the bearings on the gantry sides compared to the spindle?
    Its generally recommended to have the cutter inside of the bearings if you look from the side..
    And it might be thats the case here.. but cant see clearly ;)

    Skickat från min SM-G955F via Tapatalk

  4. #4
    AndyUK's Avatar
    Lives in Southampton, United Kingdom. Last Activity: 3 Weeks Ago Has been a member for 1-2 years. Has a total post count of 6.
    Quote Originally Posted by Clive S View Post
    Andy Welcome to the forum and a merry Xmas.

    You have certainly done some good research with the design. I use dual motors and home them independently with no problem.
    The usual advise on here is to advise not to order any electronics (or kits of electronic)s as thing often change in the design. I don't think you will need the dual screws to be full length as you can move the nut mounting a bit further back on the gantry side and save about 200 mm of screw length.

    I would also consider for the gantry HD ally profile say 90 x 45 two pieces one horizontal and the other on top vertical the slots in them are correct for BK12 bearing mount etc. so make it very simple.

    Anyway just two sleeps for Xmas
    Hi Clive,

    Thanks for the comments, much appreciated! I'm glad to know dual motor setups will work and I'll have someone to bug when I come across some niggles ;)

    I'll try adjusting those motor mounts to see if I can shorten the screw - from memory, I think I put them there to have the motors embedded into the end of the frame (may not work, but its nice to dream - I'm thinking of adding cooling into there...) and I sort of thought having the nut mounted half-way between the linear bearings made sense - I don't suppose you happen to have any advice on placement?

    Definitely will head your warning on the electronics - at the very least technology will have advanced somewhat before I'm ready to get them going! ;) I'll also try and run the numbers on the Ally profile.

    Best Wishes, and a Happy New Year!




    Quote Originally Posted by Nr1madman View Post
    Looks awesome!

    I see a few improvements in your design that I will use if I start again with a new machine ;)

    One thing I cant see clearly is the spacing of the bearings on the gantry sides compared to the spindle?
    Its generally recommended to have the cutter inside of the bearings if you look from the side..
    And it might be thats the case here.. but cant see clearly ;)

    Skickat från min SM-G955F via Tapatalk
    Thanks Nr1madman! I don't think theres anything too original in here, I've just pulled in ideas from a couple of people around here - its essentially intellectual theft! ;)

    The spindle vs. gantry spacing is an interesting point; at the moment the spindle is just outside the bearing (see picture below), which I gather isn't ideal. Originally this was so I could get right up to the edge of the waste board - should I make the bearing footprint larger to encompass the spindle or is the current setup okay? If so - do you have any suggestions as to how far within the footprint the spindle needs to go?

    Click image for larger version. 

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    Thanks!
    Andy

  5. #5
    The way to get ahead is to steal the best ideas and improve on them. So well done ;)

    The way you have the bearings probably will work just fine because of the square rails you have chosen to work with. They should take the load.
    Just so you know its unnecessary leverage and will intruduce forces that you could avoid.
    If you were using other types of rails like unsupported rods it would be a much bigger issue :)

    I know I spotted something else that I wanted to comment on but right now Im drawing a blank.. must be the snaps yesterday :D

    Skickat från min SM-G955F via Tapatalk

  6. #6
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 4 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,150. Received thanks 208 times, giving thanks to others 5 times.
    You could take the top rails slightly beyond the end of the machine to allow travel of the spindle past the edge of the base board and still keep it within the bearing span. I pinched that idea from somewhere else (sorry - "research") and it works well.

  7. #7
    Design is basically sound. Setting motors inside the section has probably occurred to most people at some point. If worked hard they may reach 80 degrees or more so you may want vent holes in the section.

    I can't see how the gantry cross beam connects to the platforms it sits on apart from the small angle bracket. You will need more than that. You can bolt down through lower inner edge of the gantry into the platform on the rectangle and possibly the square if you can get a tool inside. Or if you can weld then cap off the end of the section and drill and tap to fix the side plates. Popular way to do it for steel.

    Alum profile was mentioned and this is another way to do it as you can easily tap the ends.

    I would go steel as it is stiffer but both can work.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  8. #8
    AndyUK's Avatar
    Lives in Southampton, United Kingdom. Last Activity: 3 Weeks Ago Has been a member for 1-2 years. Has a total post count of 6.
    Quote Originally Posted by Nr1madman View Post
    The way to get ahead is to steal the best ideas and improve on them. So well done ;)

    The way you have the bearings probably will work just fine because of the square rails you have chosen to work with. They should take the load.
    Just so you know its unnecessary leverage and will intruduce forces that you could avoid.
    If you were using other types of rails like unsupported rods it would be a much bigger issue :)

    I know I spotted something else that I wanted to comment on but right now Im drawing a blank.. must be the snaps yesterday :D

    Skickat från min SM-G955F via Tapatalk
    Thanks Nr1madman, I guess its an easy thing to fix if I'm not happy - just need to remake the end plates to the gantry to extend the bearing location. Let me know as soon as you remember the other issue - personally I'm on 'Bad Santa' ale this evening which is going down a treat...!


    Quote Originally Posted by Neale View Post
    You could take the top rails slightly beyond the end of the machine to allow travel of the spindle past the edge of the base board and still keep it within the bearing span. I pinched that idea from somewhere else (sorry - "research") and it works well.
    Hi Neale,

    Great plan! I guess if I do this or not sort of depends on the gantry rails levelling method I choose. I'd like to avoid epoxy if I can get away with just using the Bridgeport (which has a 4ft bed travel - hence the limitation of these rails to 1.2m) - but I guess that doesn't perfect the height between the two rails, so I may end up with having to epoxy anyway.



    Quote Originally Posted by routercnc View Post
    Design is basically sound. Setting motors inside the section has probably occurred to most people at some point. If worked hard they may reach 80 degrees or more so you may want vent holes in the section.

    I can't see how the gantry cross beam connects to the platforms it sits on apart from the small angle bracket. You will need more than that. You can bolt down through lower inner edge of the gantry into the platform on the rectangle and possibly the square if you can get a tool inside. Or if you can weld then cap off the end of the section and drill and tap to fix the side plates. Popular way to do it for steel.

    Alum profile was mentioned and this is another way to do it as you can easily tap the ends.

    I would go steel as it is stiffer but both can work.
    Thanks - Its really encouraging to have experienced eyes looking over things.

    My plan for the motors was, as you point out, cut some ventilation holes in the rails, and to try and mount a fan inside the rail (assuming the vibration isn't too much) - I'm not massively set on having them there, whilst its aesthetically pleasing I can see that placement causing all sorts of headaches while I'm trying to diagnose things!

    The gantry cross beam is connected with the small angle bracket, and a pair of M6 bolts from the carriage plate up into the square steel sections (see below - this view is from below the gantry with the bearings removed). I must admit, this connection was one of the most puzzling parts of the design for me, and I'm not entirely sure that this will be up to the job. What I haven't added to the model yet, but intended to do in order to firm up this connection was add a square-ish steel plate to the back of the gantry with bolts into the smaller square steel tube, carriage plate, and gantry side plate (see second picture). I like your idea of welding a cap onto the end, thankyou - although I might not block it off completely and just half-cap to thread into - would be nice to retain an exit path for swarf and I've gathered the impression from youtube that welding things like this completely shut was generally a bad idea?

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    Regards the Aluminium profile, I've been running the numbers of 90x45 Heavy Duty profiles against the steel box section. The biggest draw for me simply, as you say, the stiffness of steel - Aluminium's young's modulus is a quarter that of steel. Practically, thats the difference between 0.1mm and 0.05mm max deflection under weight once the profiles are taken into account - I'm not even sure if that'll be noticeable at the accuracy levels this machine will eventually keep - but may as well aim high now while I can!
    Last edited by AndyUK; 25-12-2017 at 08:37 PM.

  9. #9
    Hi Andy,

    I think bolting the gantry beams to the platform will be a bit awkward from underneath and will make it difficult to align everything.
    Better to bolt from the top side - you will also get a better joint because the bolt will pass through the thin gantry section and tap into the thick platform. These can be cap head bolts, but if tool access it tricky then hex head will be better.

    I didn't quite follow your 'square-ish steel plate idea' but if you want to bolt the gantry in place (i.e. without any welding) then better to use a solid block at the top and bolt it to the gantry, and bolt the side plates to that. Will get a nice support from the top of the gantry down to the platforms. The small L corner brackets are not really up to the job.

    Click image for larger version. 

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    I think you said as much but make sure the gantry pieces are connected to each other otherwise you don't get the benefits of the much larger overall shape. Either bolt the inner faces together, using a clearance hole in the rear face of the small square to pass the bolt through, or weld them.

    p.s. aluminium is 1/3 the Young's modulus of steel, not 1/4. So in like-for-like sizes steel is stiffer. But as aluminium is less dense (therefore lighter in a like-for-like size) you can increase the aluminium size or wall thickness and recover the stiffness and be no heavier than the steel version. Aluminium profile is easier to bolt together, so good if you don't have a welder. But then aluminium is expensive. In short, use what you feel comfortable working with - either can work well.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  10. #10
    Aluminium profile is easier to bolt together, so good if you don't have a welder. But then aluminium is expensive. In short, use what you feel comfortable working with - either can work well.
    It might also be worth noting that the 90x45 ali profile can be tapped 12mm with a spiral tap very easily in the end holes which make a build quite simple.
    ..Clive
    The more you know, The better you know, How little you know

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