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Thread: Generic parametrised cnc machine design

  1. #1
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    Default Generic parametrised cnc machine design

    Hi,

    I thought I should post some progress on my new machine design/build to get some feedback before I move to the next phase.

    My design is for a fully parametrised generic linear actuator that can be adjusted and assembled to make cartesian or parallel robot kinematic motion platforms.

    It uses cheap DIN standard ball screws in every size and shape I could commonly find. Standard fully supported rail in sizes 10 to 35. Nema standard motor sizes from 8 to 42.

    A design assumption is that stock parts are being used in order to minimise the costs involved in ordering custom lengths and sizes. So you would enter the parts you want to use in the design, the materials you want to construct it from and expected loads, including cutting forces and masses. The design should optimise itself to maximise travel and rigidity while minimising resonance given the desired material and external forces.

    It is designed to be made from engineered timber and for parts to be through cut with 2D cnc processes. This is because my first machine, a cnc router, can sag by as much as 1.5mm in the middle. Tool diameters for corners are adjustable, as are offsets between cross lap joints. Thickness of every material sheet is adjustable.

    However because all parts are intended to be through cut and the corner radius is adjustable the design could be made out of steel using a plasma cutter or other processes.

    Design includes space for bellows to protect rails and screws and space for internal routing of cabling.

    Generic parametrised cnc machine design-capture-jpg
    Parameters adjusted to make a dual ball screw portal style table axis.
    Generic parametrised cnc machine design-capture2-jpg
    Parameters adjusted to make a long axis given a surplus NSK ballscrew I have around.

    This is my progress thus far. I still need to add mounting hardware for connecting actuators to each other, the tool, limit switches and to the stand/enclosure. I need to fix up my code for placing fasteners and fix a few bugs with pattern placement for lap joint cutouts on the carriage, but these can be fixed manually for now.

    It's for a uni project and I need to get moving on the next phase, so I can write my thesis as I'm a month behind schedule.

    The next phase is to set up the software to automatically adjust the parameters to optimise for rigidity and minimise mass/inertia of moving parts using modal/stress analysis. This means the number of supports and part part thickness. As well as the size of motors based on calculations required torque to drive the calculated inertial resistance.

    Similar Threads:
    Attached Thumbnails Attached Thumbnails Generic parametrised cnc machine design-capture-jpg   Generic parametrised cnc machine design-capture2-jpg  
    Last edited by Agebot; 06-15-2018 at 03:44 AM.


  2. #2
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    Default Re: Generic parametrised cnc machine design

    This is what I've done on this project.

    The idea was to develop an automated design for CNC machined CNC machine actuator, made from wood-composite panels.

    Generic parametrised cnc machine design-ui-jpg

    These actuators are intended to be a basic 'block' in a modular CNC machine construction kit.

    Generic parametrised cnc machine design-reprapstyle-jpgGeneric parametrised cnc machine design-prusa-style-jpg


    The design adapts automatically to suit specified motors, ball screws and linear guides. Thicknesses of individual panels and parameters driving the amount of internal reinforcing in the torsion box structure are all user adjustable.

    Generic parametrised cnc machine design-assembly-joints-jpgGeneric parametrised cnc machine design-resizing-jpgGeneric parametrised cnc machine design-sizes-jpg

    For anyone attempting a design automation project of similar complexity using inventor, I'd recommend avoiding iLogic and just using the API. I've taken the design for this project as far as I can without needing to refactor all the automation code and possibly move to an open source CAD suite, which will let me program with C++ or Python instead of VB.NET.

    I made an example actuator using the design to test if all the systems worked as intended. I found my method of using finite element analysis to optimise the structural parameters just didn't work as well as I'd hoped. It takes too long and I have doubts as to the meaningfulness of the results.


    Other than that, the idea of using design automation to simplify the development of custom parts for CNC machined CNC machines worked well. Future work needs to look design automation for other modular components, like connecting structures, frameworks and tool holders.

    However, this project really got me interested in the idea of developing an algorithm for automatically converting 3D models into structurally function interlocking assemblies made from CNC machined panels. Something that lets you place a 3D object down, apply forces to it, specify panel thicknesses and then automatically generate optimised rigid structures.

    Attached Thumbnails Attached Thumbnails Generic parametrised cnc machine design-reprapstyle-jpg   Generic parametrised cnc machine design-prusa-style-jpg   Generic parametrised cnc machine design-ui-jpg   Generic parametrised cnc machine design-assembly-joints-jpg  

    Generic parametrised cnc machine design-resizing-jpg   Generic parametrised cnc machine design-sizes-jpg  


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    Default Re: Generic parametrised cnc machine design

    Are these parts available at my local LEGO store?

    Don



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    Default Re: Generic parametrised cnc machine design

    The prototype block was a little... bricky.
    Generic parametrised cnc machine design-cncblock-jpg

    Attached Thumbnails Attached Thumbnails Generic parametrised cnc machine design-cncblock-jpg  


  5. #5

    Default Re: Generic parametrised cnc machine design

    Cool concept...is there a real benefit regarding strength and rigidity?



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    Default Re: Generic parametrised cnc machine design

    Compared to my existing machine yes. However, there are obvious drawbacks to rigidity with a modular design, depending on the quality of the coupling connections between modules.



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    Default Re: Generic parametrised cnc machine design

    Cool project! I wish you the best of luck with this. In woul love to see what your program spits out or a 2 foot and 4 foot beam.



  8. #8

    Default Re: Generic parametrised cnc machine design

    For sure! But it doesn't seem to be all that different from a torsion box except that it has interlocking tabs. I can see where I could have benefited from using interlocking tabs on my design as it would have helped in aligning and squaring the various parts. Probably would be just as strong.

    Quote Originally Posted by wizard View Post
    Cool project! I wish you the best of luck with this. In woul love to see what your program spits out or a 2 foot and 4 foot beam.




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