It's difficult to answer with limited information. A couple of more questions then some broad suggestions.
Is the oven open (conveyor passes through at a steady rate) or closed (conveyor moves the parts in, door is closed, conveyor moves the parts out)?
If closed, is it vacuum, atmosphere, or overpressure?
It's unlikely you'll find an actuator that will just run at 250-300 C. But if that is the maximum temperature in the oven (heating by convection if in atmosphere, by radiation if relatively high vacuum), one could engineer a solution that uses an off-the-shelf actuator as a starting point. It would involve some combination of radiation shielding, thermal isolation, and active cooling (forced air, water).
As Mike Halloran noted, moving the actuator outside of the oven is a nice solution if possible. If the atmosphere inside the oven is controlled (some level of pressure or vacuum and/or precise mixture), there are a number of options to transmit linear or rotary motion between the two sides of the seal:
- Glyd ring or similar low friction sliding seal (linear or rotaty motion; reciprocating or continuous; least expensive by far)
- Ferrofluidic seal (linear or rotary motion; reciprocating or continuous; much more expensive than glyd rings)
- Metal bellows (reciprocating linear; cost depends on stroke; most robust from a sealing perspective)
Motion involving high temperatures, vacuum, and or high purity is a challenging but fun problem to solve. I've encountered it more than once in semiconductor manufacturing equipment, flame reactors, and furnaces.
Rob CampbellImagitec: Imagination - Expertise - Execution