Choosing the right bed thickness



  • I'm currently building a rather large CoreXY with a build volume of 500x500x500.
    The bed will be slightly larger at 520x520 and will be supported at 3 points.
    The 3 points will be the front left and right corners and at the back in the middle.
    It will be mounted on 3 balls with slots in the material to allow for expansion while heating.
    I will also be getting pockets milled in the underside so I can fit magnets throughout the bed as I have not quite decided on what surface I am going to be printing on.

    What i'm undecided about is what thickness to make it out of.
    I'm thinking about 10mm but could easily go for 12mm.
    What I don't want to happen is for it to sag in the middle when heated.
    So does anyone have any thoughts on this?



  • I have a RailCore IIZLT
    My bed is approx 320x320 in mic6 Aluminium and I heat this to 100 degress C and it does not sag.
    In metric it is about 6.4mm thick, and then I have a 4mm glass plate on top.
    Supported with 2 mounts on the left, front and back, and one on the right, middle.

    The mag bed version by 713 has the magnets in the top surface and a thermistor in the underside.
    See this link, it may help with your decision. https://713maker.com/railcore/railcore-ii-300zl/railcore-ii-300zl-magnetic-heated-bed
    Also heating a 10mm thick plate will take a while. I have a Keenovo heated mat, 240V and takes about 3 mins to reach 70 degrees.

    HTH
    Paul



  • @jay_s_uk It isn't going to sag under it's own weight. My maths isn't good enough to do the calculations these days but I plugged the numbers into an online calculator for deflection assuming a point load equal to mass applied to the centre and came up with a deflection of 0.02mm for a 10mm thick plate. In reality the mass is evenly spread and not a point load so the deflection will be much much less - maybe one tenth of that or even less so less than 0.002mm. If you heat the plate to around 600 deg C, the aluminium will lose about half it's strength so the deflection might be double but a), it's still negligible and b) I doubt you'll be heating it to anything like that ☺



  • The thicker it is, the longer it will take to heat up. This calculator will tell you how long it will take to heat the bed based on dimensions and power applied. The numbers it produces seem to correlate well with reality.



  • Thanks for all your answers.
    I feel a lot more comfortable going with 10mm.

    In terms of warm up time, it should take me 3 minutes to get to PLA temperature and 6 minutes to get to ABS temperature.
    I'll be using a 2000w heater.


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