Welcome to Our Community

Some features disabled for guests. Register Today.

Model choice, precision and dimensions

Discussion in 'CNC Mills/Routers' started by Benjamin Vg, Apr 28, 2019.

  1. Benjamin Vg

    Builder

    Joined:
    Jan 13, 2016
    Messages:
    73
    Likes Received:
    0
    Hello,

    I am completelly new in the world of the CNC, I observe this forum since 2-3 year but I never used a CNC myself.
    I would like to buy one but I don't know the differences (advantages/disadvantages) in the models.
    I also found this model WorkBee CNC Kit – A Complete CNC Machine Setup who could be interesting because I live in Belgium and they ship it to Belgium.

    Ideally, I would like to be able to work on a full MDF panel with a size of 244 x 122 mm.
    Is it possible to tweak the the presented model by just changing the rails or do I also need to change other parts for it? Is it reasonnable or is it just too big and it will have an impact on the precision?

    About the precision, I have found this post Improving accuracy and precision the speak about a precision of 0,078 mm is it the kind of precision that I could expect?

    Thanks a lot!

    Regards,

    Benjamin
     
  2. Colin Mccourt

    Colin Mccourt Journeyman
    Builder

    Joined:
    Jan 23, 2019
    Messages:
    353
    Likes Received:
    164
    Hi Benjamin,
    By a full sheet of MDF do you mean 2440 x 1220mm or is what you've written correct?
    Regards
    C
     
  3. Alex Chambers

    Alex Chambers Master
    Moderator Builder

    Joined:
    Nov 1, 2018
    Messages:
    1,047
    Likes Received:
    518
    The maximum using Openbuilds components is 1500mm. You would need to use belt drive at that length, reducing your accuracy to +/- 0.2mm. Also you would have issues with the aluminium extrusions used flexing and sagging. Several people on the forum have found ways round this - using larger diameter leadscrews, strengthening frame members, but you won't find a kit of parts that will do what you want - it will have to be a custom build.
    Spend some time looking through the builds section of the forum to find examples of people doing something similar.
    Alex.:)
     
  4. Alex Chambers

    Alex Chambers Master
    Moderator Builder

    Joined:
    Nov 1, 2018
    Messages:
    1,047
    Likes Received:
    518
    PS - on the workbee you lose 240mm on the Y axis and 200mm on the X axis from the overall dimensions. If you went with an ☓ axis of 1500 you could machine the width of a whole sheet and there are ways to use software ("tiling") to deal with the full length. With an axis of 1500 mm on the workbee as supplied you would be restricted to belt drive which would limit your accuracy to around +/- 0.2mm.
    Alex.
     
  5. Benjamin Vg

    Builder

    Joined:
    Jan 13, 2016
    Messages:
    73
    Likes Received:
    0
    Yes you are right, I mean mean 2440 x 1220mm sorry.
    I guess that 0.2mm should be still acceptable for wood working what is the accuracy I could expect if I didn't need to use a belt drive?
    Will I spend a lot of money if I start with a standard kit and then evole to a larger dimension later? I mean will I need to change a lot of stuffs?
    Also what are the main differences between the different kits (I didn't find a newbie post about it)
    Thank for your info I really appreciate it!
     
  6. Colin Mccourt

    Colin Mccourt Journeyman
    Builder

    Joined:
    Jan 23, 2019
    Messages:
    353
    Likes Received:
    164
    Sorry if this goes against the grain of this forum by outsourcing other agents for CNC parts but because your workpiece is so large I found this vid that may be of some relevance.

    Regards
    C
     
  7. Alex Chambers

    Alex Chambers Master
    Moderator Builder

    Joined:
    Nov 1, 2018
    Messages:
    1,047
    Likes Received:
    518
    Unless you want to import a kit from the US then you are looking at the Workbee in Europe. (The Openbuilds designs are open source so there are other suppliers - you pay your money and take the risk - from Openbuilds and Oozenest you know you will get support). Screw drive should give an accuracy of around +/- 0.1 mm, depending on how well the rest of the machine is built and adjusted. With standard leadscrews supplied with the kit you are limited to an axis length of 1000mm. +/- 0.2mm is more than accurate enough for woodwork - that's the thickness of a glue layer (and also the amount wood can change in size within an hour or two of being cut).
    If you really need a machine that can cut a full sheet look in the builds section to see how other people have done it.
    Alex.
     
    Mark Carew likes this.
  8. Benjamin Vg

    Builder

    Joined:
    Jan 13, 2016
    Messages:
    73
    Likes Received:
    0
    Yes of course I will appreciate some support the issue is the shipping in europe and the additional taxes...

    About the video, I really appreciate the design of this machine it looks great and the dimensions are just enough for a MDF sheet. They also provide all the instructions but not the measures: Instructions - Standard CNC Machine Kit Assembly Instructions
    Unfortunately!, I cannot spend 4200$ for a cnc for the moment. I will need to find a cheaper solution my maximum would be 2000$
     
  9. Rob Taylor

    Rob Taylor Journeyman
    Builder

    Joined:
    Dec 15, 2013
    Messages:
    474
    Likes Received:
    196
    The obvious solution to get out under $2k is simply to roll your own. Kits are expensive because you're paying for the value-add of having everything pre-cut, pre-counted, designed, tested, warrantied and supported.

    However, most of these extrusion kits are incredibly simple. There's nothing stopping you from replicating the designs on your own, or improving on them, or whatever- that's the beauty of open-source, after all. I'm yet to design any machine that can't be built- even with linear rails and ballscrews- for around $2k. The only way to significantly bump it up past that point is by adding more complex systems and components like ATC spindles.

    If you've been poking around here for a couple of years already, you should have a pretty good idea of what goes into a machine and why (pre-requisites for successfully building and running any machine, kit or otherwise, really).
     
    GrayUK and Mark Carew like this.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice