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  1. It may be a little premature to start a build log - but I think it makes more sense to be asking questions regarding my design/build in a single thread rather than scattering questions across the forum.

    I built an MDF CNC router a few years back using a design modified from the original buildyourcnc.com plans. We moved house a couple of years ago - the machine has sat unloved in (warped) pieces in the garage since.

    I was planning on building a modified FLA-100 using aluminium profile - but i've already been talked out of that approach (see this thread).
    I'm now instead designing a machine from scratch using 50 x 50 x 3 steel box bolted together. I'm aiming for a cutting area of 1200mm x 600mm. The machine will mainly cut MDF & wood - but plastics & aluminium are also a distinct possibility.

    I have all the electronics from the previous build which include:
    3x Nema 23 motors
    all control boards, breakout board, 24v power supply (to be upgraded in the future) & dedicated PC at the ready.
    Spindle will just be a trend router for now - another part to upgrade later.

    I now plan on using supported rails from Chai/ebay.
    Leadscrews are, as yet undecided.

    I'd like to use 2 X-axis leadscrews - but the financial side of things may keep this as a single leadscrew for the initial build...then move to 2 as an upgrade later.

    I've started drawing up a design which is far from complete. The board on the curtting surface is sized at 1200mm x 600mm for use as a guide only. In practise the lower shelf surface & full table would be covered with MDF. There's no diagonal bracing anywhere either..that can be added in later.

    At the moment i'd like some feedback on the general approach & layout. I have a few minor concerns at the moment one being am I over engineering it?

    I've also started wondering about bolting the frame together - there's a lot of holes to drill/tap & bolts to buy which will be time consuming & more expense....which leads to me to wonder whether its worth buying a cheap arc welding starter package (60-75) & weld the frame instead?

    Be gentle with me ;-)
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  2. #2
    Quote Originally Posted by CraftyGeek View Post
    I've also started wondering about bolting the frame together - there's a lot of holes to drill/tap & bolts to buy which will be time consuming & more expense....which leads to me to wonder whether its worth buying a cheap arc welding starter package (60-75) & weld the frame instead?
    Bit busy at minute to reply properly to machine but I will later.!! . . . .This is just a BIG Yes to welder, it's not has difficult has you may think. Buy good rods and keep them dry, warm them in oven before using makes striking up much easier which is were most first time welders struggle.

    You won't or don't want to be doing long continuous runs of weld just short runs and spread around to keep heat from distorting metal. Less than 1hrs practice on some scrap and you'll have it sussed good enough to do what you want.!!
    Last edited by JAZZCNC; 06-08-2013 at 02:33 PM.

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  4. i thought you might say that...is a cheap Arc welder up to the job in hand though? Anything I need to be aware of? (sorry I have absolutely zero knowledge of welding)

    I'll need to rework the machine assembly to allow for welding rather than bolt together...it'll be cleaner layout.

  5. #4
    yeah, get a cheap machine, it will be fine

    beauty of arc welding, is its EASY especially if your welding 2mm+ mild steel. even easier with new steel

    get 6013 rods. say about 3.2mm (which again are good allrounders)

  6. Thanks kingcreaky - i've spotted a Ferm 100A unit on ebay that comes with basic accessories that looks like it should be enough to get me started.
    Regarding the rods - what does the 6013 bit mean?

    I've done a quick reworking on the design so far for welded assembly - it currently has a bottom on the gantry for a single leadscrew, not sure if this is staying yet or not (probably not).
    As mentioned before, i'm interested in comments about the approach as a whole - not anything too specific yet as i've still got quite a bit to do on it.
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  7. #6
    a 6013 is just a type of welding rod. Reading into it before posting this it appears 6013 seems about the most common type used but here is the speal if your interested

    Different Types of AC Welding Rods | eHow

    no doubt this clever lot on here will tell you these are the wrong ones... but they are the ones ive always used. Work perfectly fine all weather for me

    regarding your design...

    Good start... ive seen a lot worse.. but in my opinion...

    *id have a center leg on each side rather than use the bed horizontal as brace (you could use that aswell)
    *more bed frame crossmembers
    *forget the single ballscrew arrangement for the X, use two one on either side
    *triangulate the corners wherever possible
    *If you think its over-engineered at any point... its not.. you watch it dance round the workshop like its made out of carboard when its cutting. You wont regret stregth in design

    read ALL the other build logs...

    My machine

    http://www.mycncuk.com/forums/router...ation-cnc.html

    is similar to your design

  8. #7
    Quote Originally Posted by CraftyGeek View Post
    Thanks kingcreaky - i've spotted a Ferm 100A unit on ebay that comes with basic accessories that looks like it should be enough to get me started.
    No Don't buy 100A welder you need more Amp's spare for duty cycle. Biggest problem with cheap Arc welders is low Duty cycle or better put the time you can weld before the it trips out from over heating is short.!!
    Now your not going to be running long welds or in a rush so it wouldn't probably be a major problem but for 10-20 more you could get 140-160A and have decent duty cycle with less stress on welder.

    Like Matt says 6013 rods but more important is ONLY buy decent quality IE: branded name BOC, MUREX etc none of this rubbish you see at Aldi or car boot sale etc and keep very dry.

    Regards 6013 it's the AWS standard (American Welding society). Rods usually have prefix like E-6013 and it breaks down like this.!!
    E= Suitable for MMA welding and flux coated
    60= Minimum tensile strength in KSI(Kilo-pounds(force) square inch) IE 60Ksi = 60,000psi pounds(force) per square inch.
    1= Suitability for welding positions . . . IE: 1= All positions 2= flat & horizontal positions
    3= Flux coating type and suitable Current types IE: 3= High titania potassium (Rutile) AC or DC+ current.

    See here for a good Arc tutorial and loads of info.
    Arc Welding Tutorial

    I'll look at frame and come back to ya.!!. . . . Get ya hard hat on ready. . .Lol

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  10. #8
    Ok I'm back with my wrecking ball . . Get ready.!!. .

    So I see you've been paying attention with using the high sides and gantry sat on rails design which is great for twin screw machines but in this case it's actually hurting your design badly.?

    Because your wanting to use single screw (with option to upgrade) this means having gantry cross brace but with those high sides it means having long gantry sides which are acting has levers. They will flex, twist and stress the bearings, they will also resonate like crazy, this all transfers back to the work or like Matt hinted at make the bloody thing dance around the room if bad.!!. . . Not good design for this way of doing it.!

    Really because of your budget restrictions then your going to have accept a bit of compromise on design.? In this case it's flexibility regards cutting height and materials you'll be able to cut. The high sides with gantry on rail design works very well if you want strong rigidity and flexibility of lifting the bed but it just don't work for use with single screw.

    So your going to need a way to keep Gantry sides short has possible but yet high enough to give clearance you'll need for cutting what you want to cut.? . . . . It's simple enough you can't have high clearance and high strength,it's always a compromise with this way of doing it.
    So best thing is first decide the lowest clearance you can work with a build frame that allows gantry to be kept short and strong.!

    There's several ways to build frame to allow this and I'm not going to try telling them all I'm just going to show the sort of thing I'd build for this Budget and upgrade has you can afford way of doing things. (It's just something I knocked up to show principle not finished design)

    This gantry/frame design will be very strong and use's roughly 2.5 x 7.5mtr lengths of 80x40x3. It can easily be converted to twin ballscrews.
    It's shown has desktop machine to keep cost's down but making it free standing would be simple enough just cost more.

    Hope this helps and carry on it's perfectly do-able to build strong machine even on budget.

    Oh one more thing or Tip with modelling.? . . Get accurate dimensions or better still Cad models for the things you plan to use, like ballscrews, motors etc has it's easy to think I'll use this or that like this and then it doesn't fit or interferers with something else.
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  11. Thanks Jazz.
    I have made a few changes since I posted that last image...the main one being the removal of the single leadscrew option. I've decided that I want to do a decent job of this, which means it'll take me longer to get it running - but the end result will be worth it...so dual leadscrews from the start - hopefully driven from a single motor.

    I'm still very much tinkering with the overall dimensions - I have shrunk the z depth & reduced the overall height a bit as well.
    I hope to have a bit more time to spend on it tomorrow to make some more changes, then i'll come back for another slap on the back of the head :-)

    On the gantry you posted above - I assume that the spindle mounts between the *ahem* open legs?
    Question...does the distance fore/aft that the spindle is mounted (relating to the x rail bearings) have any effect other than allowing the cutter to reach different areas of the table?

  12. I can recommend the Clarke Easi arc welders from machine mart... Mine has been great so far. Also just got an evolution rage 2 cut off saw for slicing up all the steel - again it's awesome but chucks little bits of swarf everywhere! Good luck with it - you're in good hands with Jazz he tells it how it is!!

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