Thermal Expansion

[mikie]

Hey,

Is anyone building their machines with thermal or any expansion in mind.

If so, what precaustions/systems have you employed to cater for this.

Andy - you do not need to respond.

/Michael

[jeffs555]

I am building mine all from steel, so differential expansion won't be a problem. If you are building an alumuinum frame with steel rails and screws, you might see some problems on a larger machine in an unheated shop. The thermal expansion rate for aluminum is 24 parts per million for each degree C, and for steel it is 13 ppm. For a 48" long axis, aluminum would expand about .0012 inches per degree C, and steel would be about .0006 inches per degree C. With a 48" axis, in an unheated shop over a 20 deg C temperature range that would be an expansion difference between aluminum and steel of .012 inches, which sounds significant to me.

[mxtras]

The best bet is to keep the equipment in a climate controlled environment if this is a concern. Most high precision or larger machines that I am familiar with are in controlled environments for this reason.

More importantly - where are your measuring tools and standards kept? These grow and shrink, too! If your hot part was cut on a warm machine and measured with cold tools - there's no telling where your dimensions really are!

Scott