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  1. #31
    I think I will still have to design around the rails, its the way I have been taught and may sound odd but without a reference it becomes difficult to scale the machine,for me anyways.

    Are these chinese CNC parts decent quality or are they to stay away from?

    A reasonable size sounds reasonable haha. I think I will just do that...I can expand once i get my head around everything and have sufficient finances in the future :)

  2. #32
    Quote Originally Posted by JAZZCNC View Post
    No 40mm is too small section and you don't need stainless steel. 60 x 60 x 4mm Mild steel is what you need. If you have a local steel supplier it will be cheaper and if you buy in full lengths which will be aprox 7.5mtrs you'll get if for around 40-50 per length or less. The minimum size would be 50x50x3 and can be bought for around 35 per 7.5mtr length.

    If you cut careful you should get away with 1 length.

    Would you say that 16mm supported bar is sufficient for my build? In terms of strength and abilities to machine aluminium?

  3. #33
    Quote Originally Posted by FlyHighRC View Post
    I think I will still have to design around the rails, its the way I have been taught and may sound odd but without a reference it becomes difficult to scale the machine,for me anyways.

    Are these chinese CNC parts decent quality or are they to stay away from?

    A reasonable size sounds reasonable haha. I think I will just do that...I can expand once i get my head around everything and have sufficient finances in the future :)
    What is the max size you want to machine?

    As a designer you'll know that first you need to identify the requirement before you can come up with a design/solution. Set out what you want the machine for, then you'll know what size you need to design. Then you can draw your rails and email Chai at linearmotionbearings2008 (ebay store, though don't go through eBay as you get better prices) to get a quote for the rails and balls crews all in one go, the more you order the cheaper prices he'll give you.

    What you're saying is a bit like "I've got a 1000kv 24A out runner. ..I'll design my RC plane round that...which although can be done it's better to say I'll design a 1000mm span plane and then after estimating the Wright of it select the motor, ESC etc...

    Sent from my Galaxy S5
    Neil...

    Build log...here

  4. #34
    true, Its just the way I have designed before, And the irony is a good designed plane is always designed around the propellor... Oh, I do have some big motors. 1600W to run on 22V, it is lying around and never came up with a use for it...And I have seen people use brushless motors as spindles... any success?

    The machine I would Ideally have by the end of this is as:

    roughly 800x600mm though that can give or take a bit...though preferably a little bigger than smaller.
    Be able to machine carbon/glass fibers, plastics, woods and be able to do some aluminium work without feeling restricted
    Be simple,cheap and easy to use.


    They are my basic requirements :)

  5. #35
    If you want 800 x 600 cutting area then your overall size will be approx 1200 x 900 which is just about desktop. My machine is going to have a cutting area of 1000 x 500 so I can cut whole sheets of balsa for ribs etc. Have a look through my build (so far) and you'll get an idea of the size of it, it's larger than you think in the flesh. My frame us from 50 x 50 x 4 mm steel and weighs 70 just for the bare frame...

    Sent from my Galaxy S5
    Neil...

    Build log...here

  6. #36
    Putting a plan together for now :) Just to make sure i meet current and possible future targets...making it as future proof as possible...also simple assembly for maintenance and possible upgrades. With ball screws and rails being the parts that judge the machines length what do you think of these? though these are quite a bit larger,would expect the machine tp be in the region of 1600x1200 which is pretty big but i got the room :)
    Last edited by FlyHighRC; 04-06-2014 at 12:02 PM.

  7. #37
    Quote Originally Posted by FlyHighRC View Post
    With ball screws and rails being the parts that judge the machines length what do you think of these? though these are quite a bit larger,would expect the machine tp be in the region of 1600x1200 which is pretty big but i got the room :)
    Your heading into trouble already and doing the classic mistake new builders make by thinking it can't much more difficult to go larger.? Well your wrong it's whole differant ballgame. First and foremost your Budget is blown to bits.!!
    Long and wide machines need larger ballscrews and more of them.! Strength needs to increase to keep ridgidty this adds weight This means larger motors, drives, PSU and more of them.! Longer cable chains more wire runs and the list goes on and the cost goes up fast.
    Then you have the build it's self with rail alignment and getting on same plane which over longer wider distance requires careful prep and some knowledge which for a first time builder to take on is a risk and not something to do if your on a budget.

    My suggestion is take a step back.! Build to your imidate needs not the future as they will 99% change when you actualy start using the CNC machine. You won't upgrade this machine too much from original you will 99% want to build another machine with all your new found needs.
    If you build this machine correctly and use decent quality components and electronics you will most likely recover all your initial outlay and possible more. Cut corners and you'll regret it later and will make selling on harder.

    Regards the rails then Stay away from round type rails all together because even the supported ones are not so great. Chai as started selling profiled linear rails and they are cheap enough to warrent not using round rail and they make world of differance to the machine and it's sell abilty. They make the diffrance between just average DIY and Great DIY/Professional. They will will certainly add more than there value to the selling price and make sell abilty far higher.

  8. #38
    Wal's Avatar
    Lives in Stockport, United Kingdom. Last Activity: 16 Hours Ago Has been a member for 5-6 years. Has a total post count of 318. Received thanks 29 times, giving thanks to others 13 times.
    Hi FlyHigh,

    I've had a quick scan of this thread and haven't seen it mentioned yet - bear in mind that the profile of box-section isn't 100% flat and might cause you a bit of grief mounting the rails...

    Here's an exaggerated view of what I mean:

    Click image for larger version. 

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    Using the epoxy technique is one way to get around this - quite a few on here have employed that particular method - or getting your metal ground flat (a bit pricier...)

    Good luck with the build - keep us posted with updates.

    Wal.

  9. #39
    Do you have a link to these linear rails?

    I dont know much about CNC but i know how to incorprate strength into a design. If there is one thing Im good at its designing...dont get me wrong...i have seen builds on this forum which to me seem fine but people who have been there and done that have pointed out aspcts of designs that didnt show up to me...but all their critisims and expertise has been written down on my Pukkapad to bear in mind when designing my machine, which will be posted so others can tell me what needs improvong and whats ok etc etc.

    Really appreciate the help :)

  10. #40
    A very helpful tip! Thanks haha. I thought that they probably wont be perfect and could probably do with some work..the epoxy idea sounds good, any particular epoxy? Its just that i have some good westsystems stuff but its made for fiberglass which has a lower viscosity, so might not be hard enough for the job...

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