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IndustryArena Forum > MetalWorking Machines > CNC "do-it-yourself" > Headstock Design, Materials and Construction.
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  1. #41
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    Re: Headstock Design, Materials and Construction.

    Hi Craig - Yes the modal in basic Fusion is a pay as you go thing I just found out. If you publish a step or fusion file here I'll run it in Simsolid. The closed shape will have few low vibes. Things with open edges have lots of vibes. Triangular panels have very high freq responses vs square or rectangular panels. Peter

  2. #42
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    Re: Headstock Design, Materials and Construction.

    Hi Peteeng,
    when I first started using Fusion you could solve static analyses either locally on your own PC for free or pay to have it solved on the Cloud. I thought 'you dirty, thieving b********'ds
    until I worked out even a moderate analysis that would take half an hour on my PC would cost about 5 credits, or about $1.00. I calmed down a bit and realized it was not as rip-off as
    I thought. At that time I was doing the basic calculations for my C frame mill. Some of the more complex analyses I did on the cloud, I think I spent about $15.00.

    Just recently I have started using Simulation again and I don't seem to have the option, or at least I can't find the option to solve locally, but in the dozens of analyses I've run over the
    last couple of days my credit balance has remained the same, I can only guess it must be solving locally. I'm at home now and the Internet service is patchy out here, about 30k from the city,
    so its an exercise in frustration trying to use Fusion out here. I'll try a modal analysis tomorrow. Even if it does have to be paid for it would be interesting to know how much it costs.

    Craig

  3. #43
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    Re: Headstock Design, Materials and Construction.

    Hi ardenum,

    you could get two direct drive torque motors for that amount and not worry about any wear, ever.
    I guess you are right, worm drives will wear and probably faster than any other solution and that direct drive torque motor, excepting bearings I suppose, do not wear at all.
    The truth is that because I can't afford direct drive torque motors you are 100% correct, I'd never wear them out because I don't/can't have any.

    What I've actually got is two robust worm drives in perfect order. Even if they lasted only 1000 hours, I still get 1000 hours use out of them verses zero hours if I waited
    for direct drive torque motors to ' droppeth as the gentle rain from heaven Upon the place beneath.', as Shakespear put it.

    Craig

  4. #44
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    Jan 2023
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    436

    Re: Headstock Design, Materials and Construction.

    if you were looking in shops in the west, you're right, I doubt that $5 grand would even get you one over here.

    here's an example

    https://servomotor.en.alibaba.com/pr...ary_table.html

    or if you're worried about poor english manual for tuning you could build your own with these, would be more expensive than the above.

    https://www.ctbservo.com/product-cat...-vector-motor/

    drives are $500 for whatever kW you want, the motors start at $500.

  5. #45
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    Re: Headstock Design, Materials and Construction.

    Hi ardenum,
    the best I've seen on Ebay are about $750USD second hand for a motor and matching drive, but they have about 40Nm max torque and about 10Nm continuous rated torque.
    A 40Nm max NSK weighs 16kg......Thats a lot of money for a modest torque....but is still about the closest that I've seen to the solution I adopted.

    https://www.ebay.com/itm/32512126731...Bk9SR8i68YmHYg

    The second link could be useful but would require the user to engineer the bearings etc. One of the things that appealed about the servo reducers is that the bearings, seals and housing
    is included in a one time purchase, that requires no more engineering input from me.

    If we compare apples with apples the Atlanta Drives servos reducers cost (new old stock) $200USD and the servos to drive them cost $438USD. I have yet to find a better solution for a fourth of fifth axis.
    My fourth axis, which will ultimately be the trunnion table has about 46.8Nm cont and the fifth axis has 15.5Nm cont. In both cases the overload is threefold or 138Nm and 48Nm respectively.

    I'd need a M-YS5120FN001 weighing 52 kg just for the trunnion table and a M-YS4080FN001 weighing another 29kg for the fifth axis. I keep looking but they don't come up for under $3000USD.

    Craig

  6. #46
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    Re: Headstock Design, Materials and Construction.

    Hi,
    I have just tried a modal analysis on Headstock7 model, that is 12mm thick steel walls and 20mm thick flange and nose.
    Still trying to work out what all the results mean. For instance there are a number of modes, mode 1 thru mode 6 that are 0Hz and really show
    very little. Mode 7 at 471Hz shows a much more gratifying pic, a sort of twisting oscillation.Mode 8 at 967Hz is a more 'fore and aft' type oscillation.
    Both oscillations show gratifyingly small amplitudes, so I think need not concern me unduly.

    The analysis cost three Cloud Credits. It would appear that Cloud Credits are now a thing of the past and there are some kind of tokens that you buy. I have yet to get
    a straight answer on what a token is worth.

    Craig

    PS I have tumbled to what the different modes mean. Modes 1 thru 3 represent translation in the three primary axes, and modes 4 thru 6 represent rotation about the three
    primary axes. Further I would guess that at 0Hz means a straight out and sustained deflection based on the load, rather than some oscillatory deflection.

  7. #47
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    Re: Headstock Design, Materials and Construction.

    Hi Craig - a 0htz freq usually means a "free body" motion. ie the body is globally moving as it is not restrained or lightly restrained (you maybe holding a corner?). So you have to restrain it differently more like reality. Is the model restrained? amplitude is non meaningful, its for visualization only. Well done. So if you have something exciting the part at 471htz or a harmonic of this say 2x471=942htz then this is the way it will vibrate. These are relatively high freqs and I don't think they will actually behave like that. I'll try to find a general discussion on machine vibs. Peter

    I can see from the images that the bolt lines are not restrained. So you need to restrain that edge or make a small feature along that bolt line to use as a restraint. Plus I think you will need a bolt or two top and bottom... model the bolt holes and place a washer at the back. A std washer is about the correct contact area from the bolt preload. Then you can use the washer surface as a load point or restraint feature.

  8. #48
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    Re: Headstock Design, Materials and Construction.

    Hi,
    Ok found some more out about the tokens. They are called Flex Tokens. They can be used to pay for a daily use of a particular Autodesk product, if you don't have a subscription,
    but can also be used to pay for a per result service such as Modal analysis.

    When I first started using Fusion Simulation I could direct Fusion to solve on my PC at no cost. It does not appear that is an option anymore. The basic Static analysis is now solved on the Cloud
    but if you have a Fusion subscription it does not cost anything. More advanced simulations do cost. I have attached a pic showing the two classes of analysis. The modal analysis cost three Flex Tokens.
    for example.

    Heres the kicker, Flex Tokens cost $300USD per 100Tokens, so $3.00USD per token, meaning my Modal analysis cost $9.00USD. Pays to know that before you go racking up
    a bunch of analysis costs!

    Craig

  9. #49
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    Re: Headstock Design, Materials and Construction.

    Hi peteeng,
    I adopted the same technique that you pictured that the model be constrained over a 40mm x 50mm pad at each corner, essentially directly above the cars.
    That the sides wobble in and out is not surprising because they are un restrained however I'm mystified why the model appears to be 'floating around in space'.
    The model is 'Fixed' at the four pads.

    Craig

  10. #50
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    Re: Headstock Design, Materials and Construction.

    Hi,
    so when I changed from Static analysis to Modal analysis I assumed the load and constraints would remain unchanged. That is not what actually happens.
    I now have recalculated the Modes with the same restraint, ie the four pads, one at each corner. Now the modal analysis starts making more sense.
    There are three groups of modes, Modes 1 thru 3 at around 1300Hz, another group of Modes 4 thru 6 at around 1700Hz and Modes 7 & 8 at around 2400Hz.
    I would appear that the frequencies are harmonically linked, and that makes perfect sense.

    As fun as this is...I need to slow down. I've spent 6 of my 100 Cloud Credits that I have remaining. For a long time I haven't spent a one....now I am, and I can tell,
    my arse is starting to pucker!! Still, six Cloud Credits still gets me out of going to Church....and that might be considered a bargain.

    Craig

  11. #51
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    Re: Headstock Design, Materials and Construction.

    Hi Craig - Publish the step or fusion file and I'll do it for $1usd per run nah just joking happy to run the modal for free.... Peter

    Oh I do accept vegemite tokens

    Vegemite releases limited edition $2 coins in collaboration with Woolworths and the Royal Australian Mint to celebrate its centenary | Sky News Australia

  12. #52
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    Re: Headstock Design, Materials and Construction.

    Hi,
    Vegemite, pure rubbish, you'd actually eat that stuff?. Poor sick puppy. What you need is Marmite, food of the gods!

    Craig

  13. #53
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    Re: Headstock Design, Materials and Construction.

    Hi peteeng,
    thanks of the offer re Modal analysis. At the moment I rather feel that Modal analysis is premature. I have still to work out constructional details and materials
    before I start worrying about vibrations. It is quite probable that the flat faced pyramidal shapes I've been investigating will have significant vibrational modes,
    but its still some ways down the track.

    I have done a Static analysis of yet another model of fabricated steel. In this case the wall thickness is down to 10mm, the nose and base remain 20mm, but there is a flange
    both vertically and horizontally. While I have restrained still on the four pads in each corner I anticipate if I had a ring of bolts all the way around the result would only improve,
    but as it stands the model shows a deflection of only 0.26um for a stiffness of 385N/um. This handily exceeds my target stiffness, so is there any need to get worked up about improving
    on what is already more than adequate?

    The bottom line is that a fabricated steel headstock could easily achieve a good result, and is likely to prove cost competitive as well. That steel is a viable option is no surprise.
    I would now like to experiment with some other options. For instance you posted a model of a fabricated steel beam that showed very good stiffness. I'm inclined to experiment with
    that style of construction, even if only for comparisons sake to the hollow pyramid design.

    I will repeat the same model with increased wall thickness but with cast iron. I am going to presume that with suitable adjustments to wall and flange thicknesses I can get the same
    level of performance as steel. This then would be a good candidate to price accurately for the purpose of price comparison.

  14. #54
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    Re: Headstock Design, Materials and Construction.

    Hi,
    a model along the lines that Pete first posted, in effect a fabricated steel beam with 20mm base and nose with 12mm sides and web. Very creditable 0.31um
    deflection for 320N/um. This would be a relatively easy welding task, that I'd probably do myself.

    With a few tweaks I think this style of construction could match the hollow pyramid type.

    Craig

  15. #55
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    Re: Headstock Design, Materials and Construction.

    Hi,
    i'm trying to set up some custom materials in Fusion, it's not as easy as I thought.

    The basic idea is that you copy and existing material and then edit its properties and give the new material a unique name.
    I started with steel, which may not be the best choice. Editing the Youngs modulus to 50GPa is easy, but there are many other properties for which I'm unfamiliar
    and my likewise need to be edited to reflect a real world material. Density, is no trouble, and I doubt thermal properties are of importance for this part (headstock), but
    what about strengths and Poissons ratio?. I imagine they would have an effect on the analysis of a model.

    I'm thinking that I want a material E50 to represent grout, maybe an E35 to represent epoxy granite. Any suggestions on the parameters I need to set to make these
    hypothetical materials match reality? Maybe also there is an existing Fusion Library material that is a better 'donor'?

    Craig
    Attached Thumbnails Attached Thumbnails CustomMaterial.jpg  

  16. #56
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    Re: Headstock Design, Materials and Construction.

    Hi Craig - The way Fusion manages materials is atrocious. I have sent them a nasty note about it. They are big on appearance but what a nightmare setting up real materials.... Peter

    The main thing with isotopic analysis is getting the shear modulus right. So check the value in Fusion for the G. See equation attached. For common metals Poisson's Ratio is 0.3 for cast EG its about 0.2 but your results won't change much if you used 0.3.

    So for E70 material the shear modulus is around 27GPa. For Grout with u=0.2 E45 G=19GPa.

    Shear modulus - Wikipedia

    Poisson's Ratio (engineeringtoolbox.com)
    Attached Thumbnails Attached Thumbnails shear modulus.jpg  

  17. #57
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    Re: Headstock Design, Materials and Construction.

    Hi peteeng,
    this is the first time I've tried to set up some custom material and is as you say far from easy. Beautiful renderings, colors and such but when you want to model a real world
    material....if its not in their list...... your right up against it!

    I think I'm close however. As I say, the procedure is to use an existing library entry as a template and edit as required. While I know what Youngs Modulus I want for this new material
    its the other properties that I'm not so sure of. I suspect strength and Poisson ratio will have an effect on the Static Analysis.

    Craig

  18. #58
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    Re: Headstock Design, Materials and Construction.

    Hi All - For a static isotropic analysis the material needs to know its young's modulus E, its shear modulus G and its poissons ratio u. Usually the material spec allows you to select "isotropic" and the system will calculate the G for you if you put in the u. So in Fusion as each value is entered individually you have to check that the numbers are valid (see prior equation). Plus it uses scientific notation for its values which means it's hard to immediately identify if its wrong. The americas really don't cope with metric stuff sometimes. In Fusion you can check "properties" in 3 places and get snippets if info. Should be a lot easier and cleaner then this... But they may get it fixed over time.... Peter

    The strength figures do not change the results (deflection and stress) but it does make plotting what areas have failed easier.... Materials don't fail in machine parts as they are super stiff parts vs their strength and loading. But it is useful to look at where the high stresses are so you maybe able to smooth that out a bit. But if your optimising a part the stress increases locally as the part becomes more optimal. In this case you look at the deflection. The deflection should stay the same or decrease as the part is developed. If the part is "lightweighted" as they say or weight optimised less material is used to carry the same load so the stress goes up.

    once you set up a material move it into your Favorites, they have a hundreds of materials in their library to sort through.

  19. #59
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    Re: Headstock Design, Materials and Construction.

    Hi peteeng,
    I have found some published figures about the Poisson Ratio of concrete, and am guessing grout would be similar.

    I have found no setting (yet) that would make a material anisotropic, so I think its safe to assume that if I choose an isotropic material as a template then any resulting
    derived material would also be isotropic.

    As you say each parameter may be entered individually, thus if I specify a certain Poisson Ratio I could also put in a shear stress that contravenes that. I need to do a little digging
    so I can calculate one from the other. I think I may even have some books from University days that cover it.! Does you suppose after thirty years a book will still open?

    Craig

  20. #60
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    Re: Headstock Design, Materials and Construction.

    Hi Craig - Again here is the eqn that relates the isotropic elastic properties. From what I've read u=0.2 to 0.25 for concrete so if you used a u=0.25 for everything it would be OK for basic machine part design. Shear modulus is important for short beams and some parts like gantries and webs. If the book is not rusty I expect it to squeak a little when it opens to let the silverfish out. WD40 is not recommended for books. Books are good for varying our activity vs having a massive click finger and Google eyes... Peter

    concrete https://eurocodeapplied.com/design/e...ign-properties

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