Polymer concrete is widely used in machines today. And the producers of any high quality machine puts a large amount of experience and calculations into controlling the temperature in the machine. This is done by distributing masses, cutouts, webs etc. at the right places. Also by using local temperature control and insulation materials. But controlling the room temperatures is also done. The machine constructors cannot take into account temperature differences in the machine's environment.
This I believe is one way to keep the dimensional changes in a selfmade machine within reasonable limits. Keep it in a room with a stable temperature. It's all the more important when you mix building elements of steel, aluminum and other that have great differences in thermal expansion. Ball guides on aluminum profiles may stay within the relaxed demands of hobby use in room temperatures. But in your garage, on a cold winter day, you could make banana shaped parts.