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  1. #21
    Join Date
    Jan 2023
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    436

    Re: Haas mini-mill FEA

    you can download cad models of haas frames from their website, they made most if not all of their machines cad available to download, just run FEM on those.

  2. #22
    Join Date
    Jan 2016
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    100

    Re: Haas mini-mill FEA

    Quote Originally Posted by ardenum2 View Post
    you can download cad models of haas frames from their website, they made most if not all of their machines cad available to download, just run FEM on those.
    Unfortunately the models aren't really detailed enough to get an accurate answer. They're meant more for space reservations then to show the detailed internal structure. For instance on the minimill, the base is just a solid block.

  3. #23
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    Jan 2023
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    436

    Re: Haas mini-mill FEA

    Quote Originally Posted by jaguar36 View Post
    Unfortunately the models aren't really detailed enough to get an accurate answer. They're meant more for space reservations then to show the detailed internal structure. For instance on the minimill, the base is just a solid block.
    try different models, I checked a dozen of the big ones and they have detailed frames, I haven't tried any c frames, tried the gantry and horizontal moving columns

  4. #24
    Join Date
    Mar 2021
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    41

    Re: Haas mini-mill FEA

    Quote Originally Posted by jaguar36 View Post
    Right, that's why its odd that they [Langmiur] are advertising their stiffness.
    Not that strange for that company. I bought one of their arcflat tables that was no where near the claimed spec. In the end they didnt want to bring the table to spec so they just returned my money and let me keep the table.

  5. #25
    Join Date
    Nov 2013
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    4282

    Re: Haas mini-mill FEA

    Hi,
    shoot for the best/highest rigidity you can afford. My machine turned out about 20N/um, but I actually wanted more, I'd hoped to get 50N/um.
    There are some improvements I can make that would get me closer.....but even if I got 50Num I'd then be shooting for 100N/um.

    Craig

  6. #26
    Join Date
    Mar 2021
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    41

    Re: Haas mini-mill FEA

    Outside of modelling/formulation is there a practical way of measuring stiffness? IIRC I saw a youtube video of a guy who put a dial indicator on the spindle and then a tether with a scale on it. He pulled the tether to a certain resistance and measured the dial indicator deflection. He did this to compare two different vertical bench mills.

    It was kinda shocking how much twist was in both the columns.

  7. #27
    Join Date
    Nov 2013
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    4282

    Re: Haas mini-mill FEA

    Hi,
    that's roughly what I did. I put one end of a fish scale on the nose of my spindle and hooked the other end of the scale to the vice somewhat offset, and jogged until
    the scale read 10kg and measured the deflection of the spindle mount relative to the table with a dial gauge. Crude but it works, repeat measurements
    were within about 20% of each other. I had my ball park figure.

    Craig

  8. #28
    Join Date
    Jan 2016
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    100

    Re: Haas mini-mill FEA

    Quote Originally Posted by joeavaerage View Post
    Hi,
    that's roughly what I did. I put one end of a fish scale on the nose of my spindle and hooked the other end of the scale to the vice somewhat offset, and jogged until
    the scale read 10kg and measured the deflection of the spindle mount relative to the table with a dial gauge. Crude but it works, repeat measurements
    were within about 20% of each other. I had my ball park figure.

    Craig
    Yep, that's how I've done it too. +/- 20% is perfectly fine for this kind of work.

  9. #29
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    Jun 2023
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    136

    Re: Haas mini-mill FEA

    Hello everyone

    The FEA you discussed, I'd love to learn and apply it in depth.
    But mineral castings are composite materials, a mixture of stones, bonded with epoxy resin. How to analyze this composite mate.

    Even more difficult to analyze is that FEA,For example, the interior of the steel plate welding is filled with epoxy resin.

  10. #30
    Join Date
    Jul 2018
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    6254

    Re: Haas mini-mill FEA

    Hello Mr-MaW - using modern FE to analyse machines is straightforward. The issue with FE is that you need accurate youngs modulus of the material to do an accurate analysis. Do0 you do tensile testing of your materials? flexural testing? compression testing? If so what sort of modulus do you get from them? Peter

    Re- mineral cast materials. At the strain levels applied in machine parts mineral cast materials are effectively isotropic. They have good vibration damping as they are viscoelastic, so absorb energy by changing internal movement into heat via friction. Same as cast iron. The starting point is a good understanding of the materials stiffness. If you don't know the exact stiffness you can use an approximate stiffness to compare different designs with as the stiffness is then apples to apples.

  11. #31
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    Jan 2016
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    100

    Re: Haas mini-mill FEA

    Quote Originally Posted by peteeng View Post
    Hello Mr-MaW - using modern FE to analyse machines is straightforward. The issue with FE is that you need accurate youngs modulus of the material to do an accurate analysis. Do0 you do tensile testing of your materials? flexural testing? compression testing? If so what sort of modulus do you get from them? Peter

    Re- mineral cast materials. At the strain levels applied in machine parts mineral cast materials are effectively isotropic. They have good vibration damping as they are viscoelastic, so absorb energy by changing internal movement into heat via friction. Same as cast iron. The starting point is a good understanding of the materials stiffness. If you don't know the exact stiffness you can use an approximate stiffness to compare different designs with as the stiffness is then apples to apples.
    You can reasonably estimate the youngs modulus of a composite based on the E of it's constitute materials and the volume fraction of each. Depends on the particle shape, for instance for cube shaped particles the formula is:

    E/Em = Em+(Ed-Em)V^2/3/(Em+(Ed-Em)Vd^2/3(1-Vd^1/3))

    That's from Jones (Eq 3.81). There are some different methodologies and formula's depending on the matrix and the reinforcement. They vary in accuracy, but are all going to be close enough for this type of work.

    For using FEA to analyze a mill, you really don't need super accurate material properties since you're really comparing using it to compare different geometries. As you're not concerned about strength, the stiffer material is going to be better (ignoring vibration damping of course). Even if you're using a non-homogeneous material, it should be fairly obvious how to align your materials and the benefits/drawbacks vs a homogeneous material.

  12. #32
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    Jun 2023
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    136

    Re: Haas mini-mill FEA

    Hello peteeng
    We have our own laboratory and each batch is tested.
    Even more difficult to analyze is that FEA,For example, the interior of the steel plate welding is filled with epoxy resin.
    We are only used for security analysis and comparative reference.
    The actual amount of deformation and analysis results will be much worse. So just a comparative analysis, refer to the analysis results.
    The amount of deformation we require is specific to 0.005mm, so it is difficult to analyze accurately, and it needs to be verified with actual results.

    You can also share your actual case studies.


    https://grabcad.com/library/ma-miner...inear-motors-1

  13. #33
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    Jul 2018
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    6254

    Re: Haas mini-mill FEA

    Hello Mr-MaW - I have been publishing FE results for machine designs for some years in this forum. Analyzing a steel form filled with material is quite straightforward with the correct FE system. I use Simsolid but any FE program that uses solids can be used easily to analyse machine designs. If you have your own lab then tell us what your material stiffness is as this is the basis of nearly all discussions we have on machine design. See Rampf figures attached. If your test results and real world results are different then you have to review the lab results. See below. I have been doing FE digital twin work and structural testing and lab testing for some decades and FE is always accurate if the data is accurate.

    Hi Jag - I have been using rule of mixtures (ROM) for about 30 years. Unfortunately it does not seem to work with mineral cast material that we are discussing. It does work with high fibre volume long fibres such as glass and carbon. For instance if you use a strain transfer efficency of 0.5 for spherical particles then the alox test I have just done should be E=300GPa for alox so 300x volume fraction x efficency = 300x0.6x0.5= 90GPa but the test scored 18GPa. The volume fraction is accurate by test so either the E or the efficiency is incorrect. Even if the E is 150GPa then the eff=0.2.

    Take glass fibre at 70GPa. At volume fractions over 50% the ROM E=0.5x70x1=35Gpa which is easy to get in a UD tensile test sample as the fibre is dominant. But if the solid volume is less then 50% the figures do not stand up to ROM very well. The less fibre the worse the estimate gets. With high pack mineral casts and very little resin, they use a compression test to measure E and this is mechanically constrained somehow vs achieving a true modulus. I think if tensile and flexure tests were done on mineral casting it would be very good information for designers. So I'm cautious with ROM in castings. Testing is the path needed. Peter

    For instance Rampf publish that their epoxy/mineral casting is ~40GPa stiffness. They use rock so assuming its granite and quartz then Erock=70GPa. If they are grading correctly then I'd expect their solid volume to be 65% maybe 70%. so 70x0.65=45.5 (plus epoxy at 3x.35=1.0) which is say 46GPa. That means their transfer strain efficiency is 0.9-1.0 which is unrealistic. So the particles are mechanically pushing against each other in a compression test vs transferring strain thru the matrix. For instance a lego block stack will have high compression stiffness yet in tension will pull apart easily... This makes machine design hard as most parts are in flexure.

  14. #34
    Join Date
    Jun 2023
    Posts
    136

    Re: Haas mini-mill FEA

    Quote Originally Posted by peteeng View Post
    Hello Mr-MaW - I have been publishing FE results for machine designs for some years in this forum. Analyzing a steel form filled with material is quite straightforward with the correct FE system. I use Simsolid but any FE program that uses solids can be used easily to analyse machine designs. If you have your own lab then tell us what your material stiffness is as this is the basis of nearly all discussions we have on machine design. See Rampf figures attached. If your test results and real world results are different then you have to review the lab results. See below. I have been doing FE digital twin work and structural testing and lab testing for some decades and FE is always accurate if the data is accurate.

    For instance a lego block stack will have high compression stiffness yet in tension will pull apart easily... This makes machine design hard as most parts are in flexure.

    I can easily understand what you mean,We have our own laboratory and have done a lot of analysis, but the precision required by the machine tool is very high, especially the structural parts of the beam type, we want to carry out reverse deformation processing, we need to use finite element analysis specific to 0.01mm, it seems difficult to achieve such an accurate analysis.
    I know that the results of the analysis, his trends and directions are understandable and worthy of reference, and guide us to make the right choice. However, the analyzed data, deformation and other data specific to 0.01mm need to be analyzed in combination with the actual physical object. Because I will basically find similar structural parts for reference analysis, analyze the final data results, and verify whether it is mass produced.
    Attached Thumbnails Attached Thumbnails CNC gantry milling machine.jpg   gantry machining center (2).jpg  

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