Thread: FEA Software

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  1. #1
    This thread is a follow on to the discussion in http://www.mycncuk.com/forums/genera...-bearings.html



    I've answered previous posts on sideways mounted open bearings by pointing out that they will open up a bit with load in that direction. This time however I decided to carry out some stress analysis on a simplified part. The results were quite interesting.

    For a 16mm open bearing:

    1N load was applied vertically to inner bearing whilst restraining the outer face (the area you would clamp your gantry to).
    Displacement is 1.85e-5 mm, therefore 1.85e-5 mm/N.
    So for a 30kg gantry spread over 4 bearings thats 73 N per bearing, which is about 0.00136 mm or 1.36 microns.

    Initially that seemed pretty small so either there was an error in the calcs or I was worrying over nothing - but then realised that I should really model the supported rail and include that since I think it would be quite significant. Will have to wait for another night . . .

    Here are the pretty pictures for the open bearing under 1N vertical load. Stress on the left in N/m2 and deflection on the right in mm.

    Attachment 6986Attachment 6987
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    Last edited by irving2008; 25-09-2012 at 10:10 PM.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  2. #2
    Thanks for that routercnc!

    BTW, can you do modal analysis of parts?

  3. Hi RouterCNC, what package are you using for that?

  4. #4
    Hi Tenson, Irving2008

    The software is called Catia V5 made by Dassault. It is a very powerful piece of software designed for high end use, and very expensive. FEA is just one small part of the software.

    I'm sure there are cheaper packages out there which will do the FEA part of the job - on simple parts at least.

    It will also do modal analysis although I've not used it for that.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  5. Been looking for a freeware FEA package. Been playing with LISA but the 300 node limit of the free package is... limiting ! And I'm too tight fisted to spend $80 on the full one until I'm sure I can use it properly!

  6. #6
    Hi Irving2008,

    I don't want to hijack Tenson's thread so if you want to ask around the forum then maybe with your access permissions post #8 onwards (that would be yours and mine then!) could be edited out into a new thread, asking about experiences of FEA software?

    I did a search of this site for 'FEA' and there were a few mentions of it but not a specific discussion or list of more affordable software. Maybe only a few people become interested enough to go that far. I know Jonathan has used some software which looks a bit like something from the SolidWorks family, but could be wrong - the end results displays are often similar between packages.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  7. Ok so far I've looked at/tried...

    AxisM11 Lt

    Z88Aurora v2

    Lisa FET

    Analysis for Windows 2.04

    GeoTec

    All have their limitations or complexities - usually the free version is limited to a few 100 nodes. Z88 is the most flexible having no limit to the model/structure size but its harder to work out how to use.... Lisa works well, but for the 300 node limit, but I've not figured out how to model what I want in it yet... my understanding of the way to get my real world model into the tool is limited...

    what I'm trying to do is model a concrete slab with reinforcement. I've not found a tutorial on this online yet. I'm guessing I can model it as a set of stacked beams/fibres?
    Last edited by irving2008; 26-09-2012 at 11:35 PM.

  8. #8
    Quote Originally Posted by irving2008 View Post
    ... what I'm trying to do is model a concrete slab with reinforcement....
    Does that explain the slower than normal progress on your workshop build Irving ;-)

    Lol

  9. Quote Originally Posted by WandrinAndy View Post
    Does that explain the slower than normal progress on your workshop build Irving ;-)

    Lol
    No, progress halted by the fact the hole is doing a poor impression of a swimming pool filled with porridge :(


    But before I order the reinforcing mesh I want to check out that A142 mesh is sufficient and whether I should put 1 layer mid beam or 2, top and bottom, or fold the top one down the sides and back under the footings

    The reason being thast the clay soil I am 'floating' the raft into can experience 'heave' of up to 150mm potentially so there's quite a bit of stress on the raft if thats all at one end...
    Click image for larger version. 

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    Last edited by irving2008; 26-09-2012 at 11:48 PM.

  10. #10
    I'm not sure about what free FEA software for stress analysis you can obtain, but for magnetics I use FEMM however it does also do heat flow. I remember you were calculating the heat loss from the building earlier, perhaps it could help with that?

    At the very least you'll get some pretty pictures...
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

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