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  1. #1
    Hi My names Danny i have some work background in using 2d cad cam ( lectra) top spin cutters for cutting fabric and some skills in solidworks. I have been interested in home building boats and have designed and built my own craft designing it in SW using sheet metal functions to create flattened patterns, i am currently making a 17 ft Thames skiff from plans purchased from Selway fisher. i am looking for a DIY solution for drawing 1:1 scaled lines directly onto 8x4 sheets of plywood .
    Being a novice to cnc building i have a very simple an probably unrealistic idea of what is required:
    i would like to build a vertical mounted (to save on space) x y plotter that's cheap and easy to build so i can jigsaw out patterns .
    Is this possible ?
    What should i buy?
    Can i make this happen on a shoestring?

  2. #2
    that sounds like a lot of work just to get markings for you to follow with a jigsaw..... it "MIGHT" be only a little bit more heart ache and pain to build a lightweight router to do the cutting for you that will at the very least be as acuraite as following lines with a saw... (a cnc router is really only a plotter with a bit of backbone)

    if your only ever going to cut woods with a max thickness of say 2" it needent be a heavy monster of a machine and mounting it verticaly should still be an option.

    plenty of people build usable cnc machines with less experience than it sounds like you have.... with a lots patience and the guys on this forum you should be able to get there

    ps: we were or are all novices at building cnc's so dont be thinking your going to get a roasting for asking daft questions

    Can i make this happen on a shoestring?
    that really depends an what "you" mean by "shoesting"
    http://www.ebay.co.uk/itm/CNC-Kit-3-...item2a14d75139

    180 driver steppers and power supply.... it wont be fast but it should get you there

    http://www.ebay.co.uk/itm/3-linear-r...item3a53ea7f05

    this is a tipical kit from linearmotionbearings2008 on ebay.... there are other options but lots of us have splashed a little exta cash and bought from this guy (you need to do some research to find a price for the sizes that you are after) however, considering that you where happy to follow lines with a jigsaw you may be able to find a much cheaper option for screws and rails that would match your jigsaw skills for acuracy :)

    now you need to have a look at frame options.... aluminium extrusion, easy to use and a bit pricy.... steel box section needs welding

    do you have access to a lath and welder ?

    do a bit of research and get some drawings up so we can pull them apart and you should soon start getting a feel for how much blood sweat time and cash its going to take
    Last edited by blackburn mark; 28-10-2011 at 12:03 PM.

  3. #3
    Quote Originally Posted by blackburn mark View Post
    if your only ever going to cut woods with a max thickness of say 2" it needent be a heavy monster
    Unless you try cutting it in one pass

    If you're only using it for plotting them a timing belt drive (instead of ballscrew) would be fine since the force on the pen is very small compared to cutting. With the stepper kit that Mark just linked to and belt drive it could still be fairly fast as the distance moved per revolution for a belt drive is high ... so the motors don't need to move at a high rpm to get a good feedrate. You just sacrifice resolution which isn't a big issue for a plotter.
    I wouldn't advise those motor or that driver for an actual router though - you'll only get fed up with how slow it is and want to upgrade.

    I was going to mount my machine on the ceiling originally (so at a funny angle) as that would take up less space and the swarf will just fall away and clear more easily.

    Quote Originally Posted by blackburn mark View Post
    now you need to have a look at frame options.... aluminium extrusion, easy to use and a bit pricey.... steel box section needs welding
    Doesn't have to be welded, but that's the easiest option. A frame made from wood should be fine for a plotter. Can get away with one of the cheaper bearing options.
    Last edited by Jonathan; 28-10-2011 at 12:53 PM.

  4. #4
    What about thinking outside the box ?
    Print your drawings onto film then project them onto the 8 x 4 sheet then go over them with a felt tip, even if you do a series of dots you can later link these.

    You will have to play about with the focal length but a simple test would be to project a 300 mm square and measure it.
    John S -

  5. #5
    Quote Originally Posted by John S View Post
    What about thinking outside the box ?
    Print your drawings onto film then project them onto the 8 x 4 sheet then go over them with a felt tip, even if you do a series of dots you can later link these.
    Surely the lens will distort the image? In theory you could compensate for that on the printout ...

  6. #6
    Surely the lens will distort the image? In theory you could compensate for that on the printout ...
    i did include the idea in my first post but scrubbed it because of this.... iv just had a quick google though and can only find refrence to the "key stone error" which can be dealt with by mouting the projector so it its projection is square (or use the onboard correcter that you find on most machines)
    needs more google time :)

  7. #7
    Or you could simply print the drawing as a tiled PDF and use spray mount to tack them to the wood...depends on how often you're going to be printing like this I guess!
    Neil...

    Build log...here

  8. #8
    Quote Originally Posted by Danny View Post
    Is this possible ?
    What should i buy?
    Can i make this happen on a shoestring?
    Nobody can truely answer this accurately without knowing the length of the shoe string.!! . . .If your thinking 300-400 then forget it it's NOT do-able and don't let anybody tell you it is because there just pissing up your back.!!. . . . but . . . If you set a sensible realistic Minimum budget of around 800 - 1000 drivers etc but NOT PC or software then yes it's easily do-able.

    Like Jonathan says timing belt driven machine will work out the cheapist option to do what you need, but he's wrong(Sorry jonathan) about the resolution not being a problem with belts.! . . I've built a few belt driven machines to do similiar light weight jobs (cutting out Hypalon for RIBS) and without gear reduction the low resolution becomes a problem with tight radius and medium to intricate detail work.
    The problem without reduction when cutting/drawing small Radius,circes etc or intricate detail the feeds needs to be low otherwise the corners get clipped and because of the high effective pitch using direct drive it makes the motors work in a low speed range they don't like. This cause's them to run rough also because of the Low resoulution the action is jerky.
    The amount of reduction will depend on the diameter of pulleys used but from expeinece at least 3/1 is needed to be usable and keep the motors working in nice range they like.

    Must say thou if your going to the trouble/expense of building a machine then it's a absolute no brainer to let the machine cut the plywood rather than draw it.? . . . Belt drive will easily be upto the job of cutting ply wood if a decent design and job is made of the build.

  9. #9
    Hey thanks for all the good feedback, my shoe string is around 500 quid at the moment ,

    The reason for pen plotting is because the type of shapes i am interested in cutting are to be faired on the job (clinker boat planks).

    Being able to draw on an 8x4 accurately has great DIY potential for allot of budding designers, you also have the option of plotting on paper laid onto the sheet, this then allows accurate patterns for cutting out all kinds of materials, im an upholsterer by trade and have sewn up anything from car headlinings to tents, boat hoods bla bla , i work in the furniture industry where allot of money is thrown at big cnc kit often burdened by service contracts and sytem updates, cat and mouse situations with sofware compatibly, Journeymen asking why they cannot just pick a hand tool up and crack on happens too. extraction of cad patterns and lines into the real world is more the issue for me, i can see low a cost cnc plotter going into all kinds of projects and small business solutions allowing the craftsman not be be burdened with the chance of
    measurement mistakes.

    Funny enough i have too considered image projection but came to the same conclusion about scaling and accuracy.

    I have one last idea id like to put forward that may keep the cost down if only i knew how to achieve it , how about a small robot plotter that runs over the surface on a sheet , although you would have to lay you sheet down it would perhaps be compact and portable! so the sheet could be anywhere temporarily , onsite cnc plotting for builders shop fitters now there's an idea!
    Printing out detailed lines onto floors..

    Could i convert an old scanner to move and draw lines perhaps.

    Thanks guys for all the advise, its good to purge the mind of mad ideas!

  10. #10
    Quote Originally Posted by JAZZCNC View Post
    Minimum budget of around 800 - 1000 drivers etc but NOT PC or software then yes it's easily do-able.
    This is only 2D or 2.5D so the free version of Cambam should be fine. I used it a lot.

    Quote Originally Posted by JAZZCNC View Post
    but he's wrong(Sorry jonathan) about the resolution not being a problem with belts.! ... the low resolution becomes a problem with tight radius and medium to intricate detail work
    I meant not a problem with belts for a plotter, but if you've done a plotter and it's wasn't then fair enough. There was a plotter at school we dismantled that was belt driven without further reduction...and the rapid prototyper, laser cutter.
    Hmm, a cheap low power laser to burn the outline into the wood would be a snazzy way to do it! Might be easier than finding a pen that'll work consistently?
    Given these parts seem to be for a 17' boat/canoe (?) I doubt there's going to be many tight radii or engraving! But still there's no point theorising unless we actually know, and it's clearly better to do it as well as you can afford to start with.

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