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Thread: Thor

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  1. #21
    Join Date
    Jul 2014
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    215

    Re: Thor

    Quote Originally Posted by Chazaxl View Post
    Thanks. Appreciate the effort.

    In terms of the fibreglass epoxy, does this need to wrap around the entire surface area? I need the top to allow me to mount the rails once I have used the DWH putty, so do I also cover this top part or is doing the 5 out of 6 side useful enough?
    Yes, pretty much needs to be on all sides to be the most effective. The top gantry beam could probably benefit a great deal by using that method. You should be able to mount the rails right on the fiberglass surface if it is flat. You can also drill through it into the concrete if needed. I'm not sure how you intended to mount the rails. Were you planning on embedding steel pieces in the concrete to mount the rails on. You can drill and sand the fiberglass outer layer just like anything else. It should be easier to sand than concrete. If you mount the rails first in the DWH putty you could run the fiberglass right up to the rails afterward just leaving enough for clearance, but it is not as strong as having a continuous covering.

    As far as rebar sizes. I always thought the thickest you can afford is better. But I am not so sure of that. Usually, there is a rebar budget and it is placed in the areas of stress where it will do the most good. You can have too much rebar but I think with your design more would be better than not much because those beams although very thick by steel standards are not very thick by cement standards. I'm just guessing but I think it would be better to have four half inch pieces of rebar in those side beams than 1 piece of 1 inch. And half inch rebar is easier to bend around curves.

    Have you given any thought to how you are going to cast the pieces and assembly them together? Or were you planning to make one monolithic casting?

    Paul

  2. #22
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Ive made some parts for the mill as well as start on the moulds. The moulds arent nearly ready yet, Ill take some pics when they are.

    Started with the layout of the electrics yesterday as I now have space since completing another retrofit on a very nice small Concept machine.

    Ill mount onto a stainless plate most likely, this was just on MDF to get a feel for the size and get the basic X axis movement sorted.









    A quick video, nothing is really calibrated but the motor seems happy to spin to 4000 rpm. Its a Panasonic 1.5KW motor and A4 drive powering it.

    https://www.youtube.com/watch?v=Az4RkyfsDTE

  3. #23
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    A number of hours later, some marking, measuring, drilling, fitting, wiring and we have the bulk of the electronics mounted.






  4. #24
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Electrics now mostly done. Running 2 of the 3 axis in the video below. I'm missing a plug needed for the 3rd drive but all tested and runs. I still need to wire up:-

    Spindle (when I decide what Ill use)
    Limits
    E Stop etc

    Some pics below showing the 'mass' of wiring and what it looks like near completed. Still need to remove the white protective cover from the plate.

    https://www.youtube.com/watch?v=RLCvlyi4Z_E







  5. #25
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Starting to finish off the mold for the first casting as well as one of the bearing holders for my Y leadscrew.

    The part was flipped over as its 50mm deep, my probe doesnt have the best accuracy so there is a 0.2mm or so step, doesnt affect the part however.






  6. #26
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Managed to pour the mould today.

    Some lessons learnt.

    1. Make the mould stronger.
    2. You use mix than you expect .... dont ask me where it all goes.
    3. It's tedious .... just stick with it.

    Here is the mix (0.2 water / cement) mix without superplastisizer.

    https://www.youtube.com/watch?v=2IeEhFW44F8

    Add some magic juice and it changes completely. Just to make it clear, the mix below has no more water, just 1.25l of plastisizer.

    https://www.youtube.com/watch?v=4KfWcawy7b4


    Just checked the pour now, still very liquid. One of the boxes moved but as it wasnt set yet I was able to fix it. Hoping that it will harden overnight.


  7. #27
    Join Date
    Feb 2009
    Posts
    2143

    Re: Thor

    So no wire, mesh, rebar, fiber at all in that pour? I think you are going to be disappointed... What is the solids recipe you used?
    CAD, CAM, Scanning, Modelling, Machining and more. http://www.mcpii.com/3dservices.html

  8. #28
    Join Date
    May 2013
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    70

    Re: Thor

    Quote Originally Posted by mcphill View Post
    So no wire, mesh, rebar, fiber at all in that pour? I think you are going to be disappointed... What is the solids recipe you used?
    Nope. I know its a bit contraversial. Suppose time will tell.

    1/3 Sharp Sand, 2-8mm Basalt Stone and 52.5R High Grade Cement with added super plastisizer.

  9. #29
    Join Date
    Jul 2014
    Posts
    215

    Re: Thor

    Quote Originally Posted by Chazaxl View Post
    Nope. I know its a bit contraversial. Suppose time will tell.

    1/3 Sharp Sand, 2-8mm Basalt Stone and 52.5R High Grade Cement with added super plastisizer.
    You can always put in loose glass fibers instead of rebar. I think it would work very well for this application and is relatively inexpensive. They are often added to super plasticized concrete to improve the concrete's performance.

    You might consider doing that on the upper gantry since it will need to support more of it's own weight over a span than the base does. you could also lay the base on a 5-6mm high density rubber pad which would kind of help it self level as long as the bottom is pretty flat with no large distortions.



    Paul

  10. #30
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Some progress. Have removed some of the wood to see. Nice clean finish, no air bubbles (as expected with the plastisizer). Struggling to get the wood out, even with a mold release agent, its too tight to come out.

    I need some advice on sizing some metal. I want to build a frame below the concrete to hold the mass and allow some castor wheels to be mounted. Estimated weight will be 2000kg when done. Can anyone suggest what size mild steel tube I can use?

    Thanks


















  11. #31
    Join Date
    Jun 2004
    Posts
    6618

    Re: Thor

    I think the toughest part of the releasing is caused by your mold material choice. OSB would not release well even if you had steep draft angle built in.
    A better choice would be melamine. Almost as cheap and would release cleanly with little effort and leave a smooth surface.

    As for the base, if you have Fusion 360, it can help with the base design. This is one area where it really does not hurt to over build. You don't really want something that will do the job, but with borderline specs.
    Consider longevity of the base too. It will spend it's life supporting that weight. Not just when the lights are on.
    Lee

  12. #32
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quote Originally Posted by LeeWay View Post
    I think the toughest part of the releasing is caused by your mold material choice. OSB would not release well even if you had steep draft angle built in.
    A better choice would be melamine. Almost as cheap and would release cleanly with little effort and leave a smooth surface.

    As for the base, if you have Fusion 360, it can help with the base design. This is one area where it really does not hurt to over build. You don't really want something that will do the job, but with borderline specs.
    Consider longevity of the base too. It will spend it's life supporting that weight. Not just when the lights are on.
    Thanks. Lesson learnt and I have another 5 sheets of it left. Wonder if I could glue some form of cheap 'layer' over it to help?

    I do use Fusion 360. What's best, try and do a share of sorts?

  13. #33
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    May 2013
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    70

    Re: Thor

    Oh, the sides have come off easily, Its the smaller pieces and those that are 'sunk' in that I struggle with.

  14. #34
    Join Date
    Jun 2004
    Posts
    6618

    Re: Thor

    I haven't gotten into sharing on Fusion yet, but I think it can do FEA analysis if you want to stress test a design.
    You can cover it with 1/8" masonite.
    It is fairly cheap and smooth as well. Just tack them on the surface of the MDF with hot glue and you would be able to reuse them for something else.
    One thing about what you decide to use. You will always be looking at that texture.
    On some buildings that have finished concrete walls, they purposely use something with an appealing texture that will remove cleanly.

    I have been using an exterior siding product for inside.
    It looks like old barnwood and has deep grove textures and knots in the boards. Nice stuff, but it would not release well. Not sure if the relief of that pattern would look as natural either.
    Lee

  15. #35
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quote Originally Posted by LeeWay View Post
    I haven't gotten into sharing on Fusion yet, but I think it can do FEA analysis if you want to stress test a design.
    You can cover it with 1/8" masonite.
    It is fairly cheap and smooth as well. Just tack them on the surface of the MDF with hot glue and you would be able to reuse them for something else.
    One thing about what you decide to use. You will always be looking at that texture.
    On some buildings that have finished concrete walls, they purposely use something with an appealing texture that will remove cleanly.

    I have been using an exterior siding product for inside.
    It looks like old barnwood and has deep grove textures and knots in the boards. Nice stuff, but it would not release well. Not sure if the relief of that pattern would look as natural either.
    Thanks. Ive been playing with the FEA stuff but not sure if I am doing it right.

    PM me your email address you use for Fusion, Ill see if I can share my model with you.

    Thanks

  16. #36
    Join Date
    Jul 2014
    Posts
    215

    Re: Thor

    [QUOTE=Chazaxl;1903878]Some progress. Have removed some of the wood to see. Nice clean finish, no air bubbles (as expected with the plastisizer). Struggling to get the wood out, even with a mold release agent, its too tight to come out.

    I need some advice on sizing some metal. I want to build a frame below the concrete to hold the mass and allow some castor wheels to be mounted. Estimated weight will be 2000kg when done. Can anyone suggest what size mild steel tube I can use?

    Thanks

    What's the largest size steel that you can work with? 50 x 50 mm square would be about the smallest I would use. 50 x 100 mm would be ideal with the long side oriented up and down. At least 3mm thick or more. Weld up a flat torsion box with mitered corners and several cross pieces that correspond to the walls of the base plus a couple of extra cross braces, and then weld a flat piece of steel at least 2-3mm thick on the bottom of the torsion box. It will be in tension if any part of the torsion box sags under the weight. Then fit your heavy castors in place at the corners. Make sure to grind and lap the top of the steel support structure flat so it doesn't introduce any stresses in the base.

    You might also want to put some kind of thin resilient material of uniform thickness between the steel support and the cement base so that any imperfections in flatness of the base or structure can have less effect of throwing the base out of it's natural position.

    You might also want to fill the open chambers in the base with a sticky expanding foam. It will strengthen the whole base and add more dampening without adding much weight.

  17. #37
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    [QUOTE=Hezz;1904072]
    Quote Originally Posted by Chazaxl View Post
    Some progress. Have removed some of the wood to see. Nice clean finish, no air bubbles (as expected with the plastisizer). Struggling to get the wood out, even with a mold release agent, its too tight to come out.

    I need some advice on sizing some metal. I want to build a frame below the concrete to hold the mass and allow some castor wheels to be mounted. Estimated weight will be 2000kg when done. Can anyone suggest what size mild steel tube I can use?

    Thanks

    What's the largest size steel that you can work with? 50 x 50 mm square would be about the smallest I would use. 50 x 100 mm would be ideal with the long side oriented up and down. At least 3mm thick or more. Weld up a flat torsion box with mitered corners and several cross pieces that correspond to the walls of the base plus a couple of extra cross braces, and then weld a flat piece of steel at least 2-3mm thick on the bottom of the torsion box. It will be in tension if any part of the torsion box sags under the weight. Then fit your heavy castors in place at the corners. Make sure to grind and lap the top of the steel support structure flat so it doesn't introduce any stresses in the base.

    You might also want to put some kind of thin resilient material of uniform thickness between the steel support and the cement base so that any imperfections in flatness of the base or structure can have less effect of throwing the base out of it's natural position.

    You might also want to fill the open chambers in the base with a sticky expanding foam. It will strengthen the whole base and add more dampening without adding much weight.
    Thanks. Appreciated.

  18. #38
    Join Date
    Apr 2009
    Posts
    5516

    Re: Thor

    The best stuff by far to use for forms is PSF (Phenolic Surface Film) plywood. Very smooth, hard, and stiff; and the glues used to bond the plies are water resistant. I would also treat the exposed edges with finish or wax or both.

  19. #39
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Just need to drill some holes into the bearing holder, quick test fit. Have bought some reference surfaces (surface plate for the table) and also a fairly large box (engineering type, flat within 5 thou) that Ill use to cast the DWH against. I was going to try something cheaper but its risky and this will be better.






  20. #40
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quick update, been slow as I have been ill.

    Getting ready to place the putty for levelling.




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