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IndustryArena Forum > MetalWorking > Moldmaking > Looking for help to decide CNC or 3D printing.
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  1. #1
    Join Date
    Feb 2017

    Looking for help to decide CNC or 3D printing.

    Hello all,
    I am trying to start a business with a frined in plastic miniatures on 28mm scale. This kind of miniatures http://www.1-72depot.com/wp-content/...99417427_o.jpg

    I am in the procces of building a simple cylinder/piston plastic injection machine and we have started developing the models in Blender.

    Now we are stuck with deciding which way to go regarding the mold making, we have thought about SLA 3D printers and CNC machines but we cannot find anything that will provide enough detail, and we don't know if it is a case of we are underestimating the capital needed or there isn't something at hobbyst/desktop level.

    We wouldn't have a problem on purchasing a 5000€ machine in Europe if there is one that can deliver this kind of quality.


    As an example this head might be 5mm tall so we need an accuracy or resolution in the microns scale. So whatever surface we do is completely smooth and doesn't look like this. https://cdn.instructables.com/FVY/X0...RR7.MEDIUM.jpg

    Another problem we have found with CNC machines is that the plastic injection machine has to have an angle, so effectively those surfaces will look like stairs, so the better the resolution the straighter it looks rather than stairs like.

    Any help or recomendations would be appreciated.

  2. #2

    Re: Looking for help to decide CNC or 3D printing.

    The stairstep is a function of stepover and endmill shape. It is possible to achieve almost a mirror surface on any shape using a CNC machine with proper G-code and tooling.

  3. #3
    Join Date
    Feb 2017

    Re: Looking for help to decide CNC or 3D printing.

    Cool, if that is something that can be taken care of perfect.

    What machines are available in the 3000 to 5000€ in Europe? If you know any.

    Most of the good ones I have seen are in the US and import taxes will be almost 30% of the cost.....

  4. #4

    Re: Looking for help to decide CNC or 3D printing.

    I don't know what machines are available in the EU. Given the resolution and accuracy you want, finding a machine in your price range might be difficult. That is not normally something you find in the hobby class machines. A used commercial machine might be your best option. If you can find one that is in mechanically good condition with bad controls, upgrading the controls is not that difficult expensive. I'm not sure if a stepper driven machine will give the resolution that you want, maybe if the motors are geared down it would work.

    Maybe something like this?

  5. #5
    Join Date
    Feb 2017

    Re: Looking for help to decide CNC or 3D printing.

    The problem I see, and it might just be me from outside the industry is that there is no middle ground CNCs.

    You have desktop grade and instantly you jump at industrial 3 phase ones that are literally as tall as a human and cost 30000€

  6. #6
    Community Moderator ger21's Avatar
    Join Date
    Mar 2003

    Re: Looking for help to decide CNC or 3D printing.

    $30000 is the middle ground.

    If you're trying to make something like the figures in your first link, then you're probably going to find that there are a lot of areas that the tool won't be able to reach, without a 5 axis machine.
    Also, you're going to need to use really small tools, and could possibly be looking at run times of 20 hours or more, if you want a really good finish.
    There's going to be a fairly steep learning curve here.

    UCCNC 2017 Screenset

    Mach3 2010 Screenset

    JointCAM - CNC Dovetails & Box Joints

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  7. #7
    Join Date
    Feb 2017

    Re: Looking for help to decide CNC or 3D printing.

    The miniature I put is an example, ideally all our models will be able to be machined in such a way that there are no negative angles that the CNC machine has to take care.

    In the following image I explain what I mean, the shape on the left can be done with a 3 axis machine, that will do the angles by stepping, the question is can a machine with a 3 micron step create a mirror surface while working on angled surfaces, or will it inevitable be visible and you will see the mold like this https://cdn.instructables.com/FVY/X0...RR7.MEDIUM.jpg

    The shape on the right is something that you will need a 5 axis machine, but that is not effective cause the piece that is injected won't be removable from the mold, so we would never do thing like those. It will be always positive angles.

    As for the time I am not worried, it is more a case of if I can do a mirror finish with those machines, even if doing the mold takes a week because I go at the slowest speed posible and take the smallest step possible.

  8. #8
    Junior Member
    Join Date
    Jan 2019
    I want to ask question about 3D printing .
    Can 3D printing be used in mechanical engineering ?

  9. #9
    Join Date
    May 2019
    Quote Originally Posted by sonali31 View Post
    I want to ask question about 3D printing .
    Can 3D printing be used in mechanical engineering?
    Yes, you can use in mechanical engineering also in creating 3D models printing.
    Also, I am planning to use it cover pages of dissertation writing.

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