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  1. #41
    Is anyone able to give me a rough order of magnitude for the sort of price I will be paying for having the custom aluminium parts (gantry side etc) machined? I really don't have too much of an idea right now!



  2. #42
    Just my 2p worth... I'd say you have a lot of designing still to do. My guess is that you will replace some of that extrusion with plate and you'll probably add more (machined) plate into the design. Any guess at a machining cost at this stage would be unrealistic I think. You might also like to consider whether your design will require machining on both sides of any plate as that will increase the cost due to the set up time needed to machine one side, flip the plate and align it accurately for machining on the other side. If you have a look at my design I've specifically made it so that it can all be machined from one side with the exception of some counterbores that I'll do myself. Lets put it this way, I spent a lot more on parts than I did / will on machining costs.

  3. #43
    Thanks for the help, I will try and keep all parts machined one side only.

    Slowly but surely I'm starting to make some progress...

    Click image for larger version. 

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  4. #44
    My thread moved?!

  5. #45
    Small update...

    Click image for larger version. 

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    Now I've mounted the FF blocks on the outside of the plates I don't think I'll get an off-the-shelf motor mount which will fit over them? So I might need to use pulleys?

  6. #46
    Pulleys are the way forward, they give you flexibility in the final machine and generally make the design simpler. It's slightly more expensive to use pulleys rather than a direct connection and there are more moving parts which means more points of failure but I think that's a small price to pay.

    One thing I would say about your design is start pricing it up. I'm guessing those corner connection blocks are the 90x90 ones - they are quite expensive if you need a load of them and they don't result in a machine that is all that stiff (they are great for display stands, not so great for machines). Once you start getting into the nitty gritty of placing components and pricing up I think you'll begin to consider using aluminium plate and box section more.

    Looking good though.

  7. #47
    You are very right. I have been keeping an eye on the cost and realising that it soon adds up. The reasons why I am not leaning towards a steel box section frame; the first is I don't have a MIG welder! The second is that even if I could justify purchasing one then I cannot see how people manage to weld everything so that it is all square and flat? In my mind that would be quite a hard thing to achieve?

  8. #48
    I was meaning aluminium box section, you can get some really large sizes if you shop around. It's more expensive than a frame made from steel box sections but it's easy to work with and the supplier will cut it to length normally (I used aluminium warehouse iirc).

    My first CNC design included a steel frame and I actually rushed out and bought a halfway decent MIG welder. I never actually built the frame in the end though, doh! Anyway, you don't need a fancy MIG to weld the steel frame together - a cheap and nasty stick welder from ebay will do the job, there's one up for 26 at the moment. The trouble with MIG is unless you go for one with some grunt it won't handle the 4mm thick box you'd want to build the frame from. As for keeping it square and level if you look around you'd be amazed what can be done with epoxy resin. Basically you weld up the frame as square as you can (lots of small welds + clamps) and then pour very thin epoxy over where you'll mount the x-axis rails. The epoxy will self level and should leave you with two sides that are in exactly the same plane. Check out this thread as Neil will be doing another epoxy pour any time soon (actually the technique in the first pour was fine he just fluffed the mixture).

  9. #49
    Dave don't be fooled into thinking profile is flat or level because it often isn't and to make this worse your design makes it so your pretty much guaranteed you'll have issues with the rails binding.? . . .Your relying completely on the quality of cut on those uprights to keep the rails aligned and 90deg to the base. The 90Deg brackets are not accurate enough or strong enough to hold everything square. The fact your using 45x90 orientated in it's narrow section when the Y axis forces will be trying to rock the profile doesn't help and this is compounded by the fact the 90deg brackets don't hold it in that direction either.

    Sorry to say this but while you think the frame is strong it's actually weaker than you think because it's not braced or held the directions that matter and your under sizing the profile. To make profile work for this design you'll need 90x90 for all the base and much more bracing in correct locations using plates not those poxy 90deg brackets.

    For this reason Steel is much cheaper, stronger and more accurate if used with the epoxy method.

  10. #50
    Hmm maybe it's time for yet another re-think then...

    I don't want to go OTT with the design but obviously it needs to be useful. What are you opinions on the gantry design as it stands so far? Are there any other alternatives to a steel box section base?

    Thanks for all the help,


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