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    Default Few questions about temperature expansion.

    Hi All.

    My first question regards mounting steel profile rails to aluminum t-slots. The tightly mounted rail and the t-slot form basically a bimetallic strip. The difference in coefficients of temperature expansion would create forces and moments that would try to bend the two beams (rail and t-slot). So my question is: How concerned should I be about that effect? Of course it depends on the particular construction but in the end, should one take some measurements to reinforce the t-slots that the rails are mounted on?

    My second question is how resistant epoxy-granite is to uneven temperature expansion, especially regarding metal inserts? Should I be concerned that the steel inserts, the rails are mounted on might become loose, or that the EG might crack under the stress created by the expanding insert?

    My third question is about the motion system: Now, the Fixed-Supported system there we have one axially fixed bearing body supporting the screw form one side and one axially free bearing supporting the other side. this way the screw is allowed to expand and contract as the temperature changes. However there is also the Fixed-Fixed system. How does that system cope with temperature changes? Is it only employed in machines where the frame and screw have the same temperature expansion rate?

    Lastly, How good of an idea it is to fill steel or aluminum profiles with epoxy-granite? What's the probability of it becoming loose (or brake) inside due to temperature expansion?

    Thanks a lot in advance.

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    Default Re: Few questions about temperature expansion.

    Quote Originally Posted by Ivan-Ivanov View Post
    Hi All.

    My first question regards mounting steel profile rails to aluminum t-slots. The tightly mounted rail and the t-slot form basically a bimetallic strip. The difference in coefficients of temperature expansion would create forces and moments that would try to bend the two beams (rail and t-slot). So my question is: How concerned should I be about that effect? Of course it depends on the particular construction but in the end, should one take some measurements to reinforce the t-slots that the rails are mounted on?

    My second question is how resistant epoxy-granite is to uneven temperature expansion, especially regarding metal inserts? Should I be concerned that the steel inserts, the rails are mounted on might become loose, or that the EG might crack under the stress created by the expanding insert?

    My third question is about the motion system: Now, the Fixed-Supported system there we have one axially fixed bearing body supporting the screw form one side and one axially free bearing supporting the other side. this way the screw is allowed to expand and contract as the temperature changes. However there is also the Fixed-Fixed system. How does that system cope with temperature changes? Is it only employed in machines where the frame and screw have the same temperature expansion rate?

    Lastly, How good of an idea it is to fill steel or aluminum profiles with epoxy-granite? What's the probability of it becoming loose (or brake) inside due to temperature expansion?

    Thanks a lot in advance.
    You have some good questions EG I have not worked with, there always is going to be some problems when using different materials with different expansion rates

    For the Ballscrew with the Fixed at both ends, Fixed / Fixed, are almost always under tension, so expansion is not a problem, they usually have around 4lbs to 6lbs tension load on the Ballscrew, this allows you to run higher speed, and have greater Ballscrew stiffness also, this is a simple explanation, it really is much more tec than this

    As for linear rails mounted on Aluminum, if they are 1m or below it does not seem to be a problem, above this length I would expect there to be some problems with the large difference in material expansion

    Mactec54


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    Default Re: Few questions about temperature expansion.

    I think you are over complicating it. Unless you are going to see some major swings in the ambient temperature where your machine is kept I don't think you need to worry about this. The machine itself shouldn't generate heat in these locations either. At least not enough to worry about it.



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    Default Re: Few questions about temperature expansion.

    Quote Originally Posted by plasmamatt View Post
    I think you are over complicating it. Unless you are going to see some major swings in the ambient temperature where your machine is kept I don't think you need to worry about this. The machine itself shouldn't generate heat in these locations either. At least not enough to worry about it.
    Well my concern is that I don't have an adequate temperature conditioning in my workshop. In the winter regularly it drops to -20C and below during the night. I come in during the day, turn up the temperature to +15C. And that repeats every day. That's why I'm concerned. I've lost a set of plexiglass covers I have bolted to my current machine. Now I have the new ones bolted lightly and with rubber paddings to avoid them being broken by the shrinking and expanding t-slots. I even got the coolant in my flood-cooling system frozen XD (It took me 3 days to unfreaze the cooland pump off of the ice block that formed. and the coolant was no good after that). After that occasion I had to drain the coolant from the machine into a barrel, every night and store it in the house.
    So yes maybe I'm over complicating it, but that's because I had some unpleasant experiences...



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    Default Re: Few questions about temperature expansion.

    Fixed or stretched ballscrews are set up by distance. You calculate diameter and length, and add stretch to the screw. On a typical 40" mill let's say, it is usually about .0018" stretch, however this is quite a load, so ballscrew support blocks need to be pretty strong, and alignment is critical.

    Sent from my SM-T813 using Tapatalk



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Few questions about temperature expansion.

Few questions about temperature expansion.