534,924 active members*
2,853 visitors online*
Register for free
Login

Thread: Thor

Page 1 of 5 123
Results 1 to 20 of 83
  1. #1
    Registered
    Join Date
    May 2013
    Posts
    70

    Cool Thor

    So not sure if this should be in the EG section or not, will place it here and see if mods move it. The construction of this will be done with concrete using 52.5R grade, sand, stone (basalt) and superplastifier to assist the mix / flow. Estimated weight of the machine will be around 2 ton when done.

    Some initial reading material of how the design came to this can be found here - BUILD LOG: Thor, or should that be Zeus?

    Since then, the design has changed many times, pics below. For reference, I have put some of the pics of the rails and ballscrews for size reference. Spindle options are still being considered. Currently its drawn with a 4KW Chinese spindle. No ATC. This may change. The other design goal was to run this from 220V @ 32A single phase max. Motors will be 1.5KW for Y, 750W Panasonic Servo for Z and X.

    Thoughts / comments / concerns welcome.










  2. #2
    Gold Member
    Join Date
    Jun 2004
    Posts
    6618

    Re: Thor

    Looks pretty cool.
    Very nice looking parts. The design looks great.
    My first question is how will you mount those rails?
    Lee

  3. #3
    Registered
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quote Originally Posted by LeeWay View Post
    Looks pretty cool.
    Very nice looking parts. The design looks great.
    My first question is how will you mount those rails?
    Good question :-)

    Ill be making a flat surface using DHW putty (DIAMANT DWH: potting epoxy & casting compound for machine construction) and then once that has set, Ill be drilling into the concrete, thru the putty and epoxy nuts in the concrete. The 'flat' will be created by lowering a surface plate onto the area or some form of reference surface to be made out of steel.

  4. #4
    Gold Member
    Join Date
    Apr 2009
    Posts
    5516

    Re: Thor

    Holy linear rail and ballscrews! Is that stainless tape over the top of the rail, or are those rails rear-mount?

  5. #5
    Registered
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quote Originally Posted by louieatienza View Post
    Holy linear rail and ballscrews! Is that stainless tape over the top of the rail, or are those rails rear-mount?
    Stainless cover. Top mounted.

  6. #6
    Registered
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    So this weekend I turned some spacers on my newly acquired (old) Boxford A lathe. Ive also spent a bit of time with the initial layout for the control panel.


  7. #7
    *Registered User*
    Join Date
    Jul 2014
    Posts
    203

    Re: Thor

    Really nice design Chazaxl and nice renderings. It looks like a pretty good size machine with those rails and ball screws.

    I think the structural design of your machine is very good. The only problem as I see it is the material to select. With the kind of heavy rails and ball screws you have it has the potential too be a very heavy duty machine. The structure you have would lend itself to steel or aluminum construction in my opinion but that would make it extremely expensive and perhaps too heavy for a DIY machine.

    I'm not sure the concrete approach will give you the rigidity you desire for this heavy duty machine unless you fill all of those spaces with concrete. EG would be a better material for this but would still need an approach similar to concrete. The problem with concrete is that it's only stong in compression and needs extremely large cross sections to compensate. The same essentially holds for EG except it has better dampening. The structure would seem to lend itself best to steel reinforced EG. But the problem with steel reinforcement in both concrete and EG is that a little bit of rust on the reinforcement causes a breakdown in the bond between the reinforcement material and the EG. This starts to happen in only a few years. One approach is to use stainless steel as reinforcement members but this makes the cost go up a great deal. With stainless the system can last about 100 years before it starts to go bad.

    A good approach might be to built the structure from EG as you have designed it and then fill all of the holes in the frame with cheaper concrete. Or better yet. Cast the void shapes in concrete first and then put them in the mold cavity so that the epoxy will bond to them in the mold.

    Just some thoughts. I'm sure it will work with plain plastisized concrete or EG but it might not measure up to it's full potential.

    Another approach might be to make the structure with a skin of epoxy fiberglass about a half inch to one inch thick and then fill the core with glass fiber reinforced EG. The thick fiber reinforced skin would make it almost as strong as steel and the fiber reinforced EG core would add both high dampening and some added strength in all directions due to the random placement of the glass fibers.

    Paul

  8. #8
    Registered
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quote Originally Posted by Hezz View Post
    Really nice design Chazaxl and nice renderings. It looks like a pretty good size machine with those rails and ball screws.

    I think the structural design of your machine is very good. The only problem as I see it is the material to select. With the kind of heavy rails and ball screws you have it has the potential too be a very heavy duty machine. The structure you have would lend itself to steel or aluminum construction in my opinion but that would make it extremely expensive and perhaps too heavy for a DIY machine.

    I'm not sure the concrete approach will give you the rigidity you desire for this heavy duty machine unless you fill all of those spaces with concrete. EG would be a better material for this but would still need an approach similar to concrete. The problem with concrete is that it's only stong in compression and needs extremely large cross sections to compensate. The same essentially holds for EG except it has better dampening. The structure would seem to lend itself best to steel reinforced EG. But the problem with steel reinforcement in both concrete and EG is that a little bit of rust on the reinforcement causes a breakdown in the bond between the reinforcement material and the EG. This starts to happen in only a few years. One approach is to use stainless steel as reinforcement members but this makes the cost go up a great deal. With stainless the system can last about 100 years before it starts to go bad.

    A good approach might be to built the structure from EG as you have designed it and then fill all of the holes in the frame with cheaper concrete. Or better yet. Cast the void shapes in concrete first and then put them in the mold cavity so that the epoxy will bond to them in the mold.

    Just some thoughts. I'm sure it will work with plain plastisized concrete or EG but it might not measure up to it's full potential.

    Another approach might be to make the structure with a skin of epoxy fiberglass about a half inch to one inch thick and then fill the core with glass fiber reinforced EG. The thick fiber reinforced skin would make it almost as strong as steel and the fiber reinforced EG core would add both high dampening and some added strength in all directions due to the random placement of the glass fibers.

    Paul
    Many thanks for your response.

    My mechanical design skills and knowledge is limited. Most of what I have come up with is based at looking at other machines as well as getting advice from the person that has supplied me with the rails etc. By no means is this a perfect design.

    I am interested in how it can be improved however. I have bought the plastisizer but none of the concrete materials yet. So open to suggestions.

    In terms of weight. My understanding is that there cannot be too much weight. Weight helps with rigidity. Now, there must be a point at which its just 'too heavy' for practical reasons. Is the comment regarding weight related to the ideal of using Concrete?

    I looked at EG. I could not find a suitable mixture that would work. Perhaps there are too many variables. Costs compared to Concrete? My current costs indicate around £750 ish I think to make this from Concrete. The DWH putty etc additional.

    In terms of the 'holes'. My understanding is that a hollow object is stronger than a solid. If you look at many machine designs, they have ribbing or they have a 'pattern' of hollowness. I am not sure how the logic works to now fill these in with something. Can you please explain this, perhaps some reference pics of other machines?

    In terms of making any of this from steel. It was considered. Ive seen many examples where people try this and are still welding / grinding (months) later. Suppose the cost of the material goes up quickly then too. In all the cases I have looked at here, they then add concrete (or similar) after to give weight / ridigity. Certainly pouring concrete into a steel structure is arguably easier than making molds. I think (please confirm) that anything made from steel needs to be stress relieved? I dont fully know what it means but this isnt something I can do in my garage.

    Please dont take any of my responses as being defensive. I'm keen to learn and before I spend any more of my hard earned pounds .....

    Many thanks.

  9. #9
    Registered
    Join Date
    Jan 2008
    Posts
    1175

    Re: Thor

    A hollow object is not stronger than a solid. A larger section is stiffer than a smaller one.

    If we have limited material, we can maximise stiffness by increasing the size of the section.

    structural steel & oil field suppliers,channels, sections, angles, sheets, bars & gratings, beams, flange beams, columns, is of interest.

    Have a look at some of the smaller tubes and compare to the larger tubes. In particular pay attention to the kg/m and the moment of inertia

    For example, 100x100x10mm tube weighs 27.4kg/m, with a moment of inertia of 462cm4. 150x150x6mm weighs 26.8kg, with a moment of inertia of 1174cm4. That's 2.5 times stiffer for the same amount of material.

    The hole doesn't make it stiffer, it's having more material in places that oppose the force.
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

  10. #10
    Registered
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quote Originally Posted by pippin88 View Post
    A hollow object is not stronger than a solid. A larger section is stiffer than a smaller one.

    If we have limited material, we can maximise stiffness by increasing the size of the section.

    structural steel & oil field suppliers,channels, sections, angles, sheets, bars & gratings, beams, flange beams, columns, is of interest.

    Have a look at some of the smaller tubes and compare to the larger tubes. In particular pay attention to the kg/m and the moment of inertia
    Thanks. Ill go through this tonight. Are you saying then that a 'bunch' hollows is a lot better than a single one as there is more 'wall'. Difficult to explain ...

  11. #11
    Registered
    Join Date
    Jan 2008
    Posts
    1175

    Re: Thor

    Sorry, I've edited the post. See above for more.

    It takes a little while to get, but the principle is very simple. You need material to oppose forces (cutting forces, gravity).

    Think of a soft drink can. It is very thin walled, but the walls are tall. You can crush it in from the sides with very little force. However (if undented) a person can stand on top of the can and it will support their weight (so long as the force is applied in the direction there is a lot of material).
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

  12. #12
    Registered
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quote Originally Posted by pippin88 View Post
    Sorry, I've edited the post. See above for more.

    It takes a little while to get, but the principle is very simple. You need material to oppose forces (cutting forces, gravity).

    Think of a soft drink can. It is very thin walled, but the walls are tall. You can crush it in from the sides with very little force. However (if undented) a person can stand on top of the can and it will support their weight (so long as the force is applied in the direction there is a lot of material).
    Ok, that makes sense. In my case, with 1180mm rails (45mm wide), what would you change or is that 'vague'? Any pics of what you refer to in the sense of an ideal structure? Pics are useful :-)

  13. #13
    Registered
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quote Originally Posted by pippin88 View Post
    A hollow object is not stronger than a solid. A larger section is stiffer than a smaller one.

    If we have limited material, we can maximise stiffness by increasing the size of the section.

    structural steel & oil field suppliers,channels, sections, angles, sheets, bars & gratings, beams, flange beams, columns, is of interest.

    Have a look at some of the smaller tubes and compare to the larger tubes. In particular pay attention to the kg/m and the moment of inertia

    For example, 100x100x10mm tube weighs 27.4kg/m, with a moment of inertia of 462cm4. 150x150x6mm weighs 26.8kg, with a moment of inertia of 1174cm4. That's 2.5 times stiffer for the same amount of material.

    The hole doesn't make it stiffer, it's having more material in places that oppose the force.
    Thanks, that helps explain it a bit better for my brain.

  14. #14
    Registered
    Join Date
    Feb 2016
    Posts
    381

    Re: Thor

    Great detailed drawings looks like you are a man after my own heart, design around what you have available I love to use up what I have or can get at the right price to make the best I can.

  15. #15
    *Registered User*
    Join Date
    Jul 2014
    Posts
    203

    Re: Thor

    Chazaxl,

    from the renderings it appears that the cutouts in the gantry side support are hollows that go all the way through. If that is the case, the most simple improvement is to place a 3-4 inch thick wall inside the hollows tying all of the beam segments together. Ideally it would probably be in the center but if it was offset flush with the base it would make for a good mounting surface to the base. It will improve the rigidity a lot. Just by doing those two things.

    You might consider building the molds of thick fiberglass epoxy and then filling the center with concrete. Or make all of the cement castings undersized and laying up at least a half an inch of epoxy fiberglass. It will make the structure much more stiff. The concrete will offer very good damping. Ideally you would place a few pieces of stainless steel rebar in the concrete if you have the budget to do it.

    Also, the sides of the base most likely need to be thickened up since they support the connection between the gantry structure and the bed. I would thicken them by at least two or three inches. You might be able to reduce the center web in the base a little bit. Also, to reduce resonances it might be best if they were offset a little. Not perfectly symmetrical.

    Paul

  16. #16
    Registered
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quote Originally Posted by Hezz View Post
    Chazaxl,

    from the renderings it appears that the cutouts in the gantry side support are hollows that go all the way through. If that is the case, the most simple improvement is to place a 3-4 inch thick wall inside the hollows tying all of the beam segments together. Ideally it would probably be in the center but if it was offset flush with the base it would make for a good mounting surface to the base. It will improve the rigidity a lot. Just by doing those two things.

    You might consider building the molds of thick fiberglass epoxy and then filling the center with concrete. Or make all of the cement castings undersized and laying up at least a half an inch of epoxy fiberglass. It will make the structure much more stiff. The concrete will offer very good damping. Ideally you would place a few pieces of stainless steel rebar in the concrete if you have the budget to do it.

    Also, the sides of the base most likely need to be thickened up since they support the connection between the gantry structure and the bed. I would thicken them by at least two or three inches. You might be able to reduce the center web in the base a little bit. Also, to reduce resonances it might be best if they were offset a little. Not perfectly symmetrical.

    Paul
    Thanks. Not sure I understand how the fiberglass epoxy adds strength but will take it for what it is. In terms of the wall, (yes its hollow through) can you draw what you mean please?

    In terms of rebar, my understanding is the rebar 'only' works if the structure cracks. It has no 'role' in providing strength, is this incorrect?

    I can narrow the walls, the current plan is show using 4 x 110mm pipes to create the core 'hole' but I can reduce that.

  17. #17
    *Registered User*
    Join Date
    Jul 2014
    Posts
    203

    Re: Thor

    Quote Originally Posted by Chazaxl View Post
    Thanks. Not sure I understand how the fiberglass epoxy adds strength but will take it for what it is. In terms of the wall, (yes its hollow through) can you draw what you mean please?

    In terms of rebar, my understanding is the rebar 'only' works if the structure cracks. It has no 'role' in providing strength, is this incorrect?

    I can narrow the walls, the current plan is show using 4 x 110mm pipes to create the core 'hole' but I can reduce that.
    Yes the rebar helps to hold things together when it cracks but that is not it's main purpose. When the concrete beams flex and vibrate it creates compressive and elongation forces within the beam. Concrete is very strong in compression but very weak in tensile strength (pulling apart forces). So it needs help to balance out it's nature. The pulling apart forces are transferred into the rebar as long as there is good adhesion to the rebar. This is the main purpose of rebar or internal reinforcement. When you apply a material to the outside like epoxy fiberglass it has different properties to the concrete. The fiberglass is very strong in pulling apart forces in the direction of the fibers. And with the cloth built up in layers you can have the fibers going in many directions. So it has very strong pulling apart resistance in many directions.

    When the beam flexes it deforms a little bit, and the fiberglass exterior, if it is bonded to the inner core of material, resists this flexing to a very high degree. So you have an outer skin that is more resistant to tensile forces. This helps keep the core material in place and from cracking and also resists vibrations much better than the internal rebar by itself.

    Do a Google search for stressed skin panels or stressed skin structures. I'll try and whip up a quick 3D model to show you what I'm talking about

  18. #18
    *Registered User*
    Join Date
    Jul 2014
    Posts
    203

    Re: Thor

    OK, here is a picture of one side of your frame design. Not to scale. I'm just trying to show what I was saying in my previous post.

    Another idea. It's possible you could use the hollow bed sections for a coolant reservoir.

  19. #19
    Registered
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    Quote Originally Posted by Hezz View Post
    OK, here is a picture of one side of your frame design. Not to scale. I'm just trying to show what I was saying in my previous post.

    Another idea. It's possible you could use the hollow bed sections for a coolant reservoir.
    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?

  20. #20
    Registered
    Join Date
    May 2013
    Posts
    70

    Re: Thor

    In terms of rebar, is there a recommended size of bar needed or is this very much determined by cost etc? There is probably a point of too little and too much?

Page 1 of 5 123

Similar Threads

  1. Free MJOLNIR THOR HAMMER GIVEAWAY
    By silverfoxx03 in forum Machine Created Art
    Replies: 0
    Last Post: 03-27-2012, 01:44 PM
  2. MAJOR PROBLEMS with Thor 45cc 2 Stk Petrol engine....PLEASE HELP!!!
    By thkoutsidthebox in forum Hobby Discussion
    Replies: 6
    Last Post: 10-18-2011, 11:12 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •