I agree with the thin-walled tube approach. Use stainless steel. Stainless conducts 1/3 as much heat as regular steel, and 1/10 as much as aluminum.
There is a table of thermal conductivities at http://www.engineersedge.com/properties_of_metals.htm There are a few materials in that list that are even lower, than stainless, but probably much harder to obtain. A lot will depend on the available space. The heat transfer is proportional to diameter times wall thickness divided by length. So you want as thin-walled as possible without buckling, just large enough diameter to handle the mechanical load, and as long possible in the available space. I would avoid putting holes in it - instead I would go for the thinnest wall I could get that can handle the required forces. Holes would just make it weaker and thus you would have to use thicker material to make up the difference. For attachment to a thin walled tube, press a lathe turned plug into it. That avoids stress concentrations from holes or other machined features, and so you don't have to oversize the tube. You want it to be just strong enough to do the job - extra metal just means more heat transfer. McMaster Carr won't be very useful in Europe, but it does give a feel for what is readily available. They have alloy 304 and 316 stainless tube with a 0.02" (0.508mm) wall in diameters up to 5/8" (15.9mm) and alloy 321 up to 2" (50.8mm). For example, part number 6622K15. Actually, you could do even better with several small tubes. Suppose the stamping tool is a 1" x 2" rectangle. You could use a 1" diameter x 0.020 wall tube, with a cross section of 0.0628 square inches. Or, you could also use four smaller tubes at the corners. McMaster sells part number 6100K221, which is 304 stainless, 1/4" diameter tube with a wall thickness of only 0.005". That reduces the cross sectional area to 0.00397 square inches per tube, 0.0157 square inches total. On Mon, Jun 24, 2013, at 01:40 PM, Viesturs Lācis wrote: > Hello! > > A client is asking me for a small machine that would burn their logo in > wooden parts. They want to do it with a heated element that would be > actuated by pneumatical cylinder. > > My only concern that I have not yet figured out is keeping down as much as > possible the amount of heat transfered to the rod of pneumatic cylinder. > > I would like to ask, if somebody has ever done something similar and could > share some tips about best practices how to attach that heated stencil to > pneumatic cylinder. > > My current thought is to take a piece of thin-walled pipe and machine the > wall in somewhat like a web (drill lots of holes or something similar). > That would reduce the crossection of material and thus the amount of heat > transfered to the rod of cylinder. > > I would like not to reinvent the wheel, so will appreciate any advices. > Thanks in advance! > > -- > Viesturs -- John Kasunich [email protected] ------------------------------------------------------------------------------ This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
