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  1. #1
    Hi all

    I'd be interested in any comments about my ex-work scrap router design, I've not got a lot of cash to spend and am trying to use parts sourced cheaply through work, so the build is based around the parts I can get, I want to cut parts to length at work then assemble them at home in my workshop, keeping it a simple bolt together assembly. I frequently use a local laser cutting company at work and they don't mind cutting small batches of parts for me for cash so I've used quite a few 6mm ally laser cut parts in the design.

    So far I've managed to get a pre machined 16mm ballscrew with a thread length of 1360mm and 12 Hepco dual V bearings, so I'm leaning towards a similar system used on Joes hybrid machine using steel angle for the V bearings to run on, all the aluminium is standard section with some commercial vehicle ally bearers (15 for a 2.5m length) for mounting the bearing runners on. I have a 16mm ballscrew for the Z axis, I was planning on buying cheap trapezoidal for the X axis hoping to upgrade later on.

    I've pretty much finished the design and want to make a start on the build but I've got a bit of a dilema, I'm thinking that only having one drive on the Y axis might make the X axis carridge 'walk' up and down, and I'm thinking about using my 1360mm ballscrew for the X axis instead of the Y (gaining 200 or 300mm of travel on that axis) and using two trapezoidal rods and two steppers for the Y axis, the rods would run in the channels (see image 3) and I would remove the cross beam from underneath.

    This would be my second router, I've built a Rockliffe fixed gantry prior to this and got hooked

    Cheers

    Vic
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  2. #2
    I forgot to mention cutting area is currently about 720 x 1230 x 150

  3. #3
    Hi Vic.
    Nice work, Looks very well thought out. I like the idea of using ali channel instead of the profile bars. There was a thread looking at an open source mid range Ali router machine and it looks like this could be it.....

    not sure on your axis terminology but i take it by y axis you mean the longest axis? if so then you could use belts or wire to control the racking and stil use one ballscrew. If you increase the distance between the bearings then that will also reduce the racking but require longer rails or reduced travel.

    My main concern is why use c channel for the rail supports if the ballscrew is in the middle? it would be much stronger to use rectanglar box section, I would at least provide support at the ends and mid point.

  4. #4
    hi vic
    looks like a very sturdy design, how long did it take you to draw up your plans?
    could i ask was it solid works you used? as i am learning autocad at night school but would be struggling to draw that kind of design.:confused:
    what are you planning on cutting with it wood or alloy? i am no expert but i think your idea of two ball screws each side would be the best for alloy etc.
    could you use one stepper and two toothed belts out to each side, just a thought!
    hope you get started with the real thing soon.and keep use posted
    Tom

  5. #5
    Quote Originally Posted by Ross77 View Post
    Hi Vic.
    Nice work, Looks very well thought out. I like the idea of using ali channel instead of the profile bars. There was a thread looking at an open source mid range Ali router machine and it looks like this could be it.....

    not sure on your axis terminology but i take it by y axis you mean the longest axis? if so then you could use belts or wire to control the racking and stil use one ballscrew. If you increase the distance between the bearings then that will also reduce the racking but require longer rails or reduced travel.

    My main concern is why use c channel for the rail supports if the ballscrew is in the middle? it would be much stronger to use rectanglar box section, I would at least provide support at the ends and mid point.


    Hi
    I get confused with the axis terminology, but I did mean that the Y is longest.

    I havent got the model to hand at the moment (at work) but I think the bearings are about 270mm centres I'd like to keep it around 4ft cutting area and don't really want to make them wider if I can get away with it.

    I'm not certain what you mean about controlling the racking with belts or wire ? do you have any links to something that has used something like that ?

    The design started off using box section, I am aware that I might get some flex with channel, I have some ideas about strengthening it if I need to, the problem with box section is bolting the steel angle to it, you cant get to the nuts to tighten them up, I thought about using large self tappers but I think they might vibrate loose so I went for channel, it's a pretty strong channnel as it's meant for supporting the floors of trucks but your right, it will twist more than box.

    Vic

  6. #6
    Quote Originally Posted by dickieto View Post
    hi vic
    looks like a very sturdy design, how long did it take you to draw up your plans?
    could i ask was it solid works you used? as i am learning autocad at night school but would be struggling to draw that kind of design.:confused:
    what are you planning on cutting with it wood or alloy? i am no expert but i think your idea of two ball screws each side would be the best for alloy etc.
    could you use one stepper and two toothed belts out to each side, just a thought!
    hope you get started with the real thing soon.and keep use posted
    Tom

    Hi Tom

    I use Autodesk Inventor 2010, very similar to Solidworks, making the model doesnt take that long it's thinking about the design thats time consuming and constantly changing stuff, it's difficult to know when to stop

    I still use ACAD but usually only to look at customer/supplier drawings that have been done in that format, I've been using Inventor professionally for about 4 1/2 years and really like it.

    I want to cut wood with the router, model aircraft parts and general wood working bits and pieces, occasional light ally would be nice but I don't think I'd be doing much of that and don't think that this machine would be rigid enough.

    I also think that the twin ballscrew or some sort of drive on both sides would be better but built this around my single ballscrew, hoping I can pick up some ideas about how to improve things before I start

  7. #7
    Hi Vic
    Cant find any pics at the mo. there here some where......The belts are basically mounted each side and conected will a bar, the same setup as if you where going to use belts for the main drive. The belts work indipendently of the ballscrew and just control the racking. If the ball screw is in the middle and your aiming for 800mm O/A width then it might be worth trying with out it (only 400mm each side)

    If youve got ACAD Inventor why dont you you run a FEA test for stesses, Im trying to get my hands on that program so I can do the same. Ive got Vannilla cad at the momment.

  8. Quote Originally Posted by Vic66 View Post
    ... the problem with box section is bolting the steel angle to it, you cant get to the nuts to tighten them up...
    Think back to those old cars with box section chassis, how did they get round the problem? SImply drill/bore out a hole in the box opposite the nut so a long socket or socket+extension can be passed through the hole withthe nut held in the socket with a dab of grease.. If the rear of the box isnt accessible then cut a slot in the wall of the box sufficient to get a spanner and nut through. Third option is to create captive nuts by drilling/tapping out a piece of steel that is a sliding fit in the box section (only really works for narrow section). A fourth option, if the wall of the box section is thick enough, is to tap it directly. And a fifth option is to cut a rectanglular slot where the hole should be, slide in a tapped piece slightly narrower but longer than the hole and weld in place.

  9. #9
    Using box section why not bolt right through your only problem then will be collapsing the box with to much tightening!

    Peter

  10. Quote Originally Posted by ptjw7uk View Post
    Using box section why not bolt right through your only problem then will be collapsing the box with to much tightening!

    Peter
    if you do that you never get the bolts to stay tight. There is a solution to this.. drill through the bolt size then get some tubing whose ID is the bolt size and open up the reverse side hole to the tubing OD. the length of the tube needs to be the inside dimension of the box plus one wall thickness. Then you can bolt through with a washer under the bolt head, the tubing is strong in compression compared to the box section and prevents it crumpling.

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