A producer of arterial stents used by clinicians to treat cardiovascular disease had oven manufacturer Carbolite create a class 10,000 clean-room oven, customised to solve its heat-treating problem.
Although the stents only require heat treating to a maximum of 400C, the dimensions and temperature uniformity specifications of the oven posed a major technical challenge.
The solution called for a chamber nearly a metre and a half deep to be heated with a stability of better than +/-1C under steady-state conditions coupled with temperature uniformity better than +/-5C.
To ensure good temperature uniformity, the oven is divided into three separately controlled zones.
The main program controller is digitally linked to two slave controllers that automatically track the program set in the main controller.
A digital time temperature program controller manages the temperature of the oven and is capable of storing up to 20 programmes each with up to 16 segments.
A programme segment relay is fitted that can be set to sound an audible alarm at the end of the program.
The oven employs forced air circulation, carefully positioned to give optimum uniformity of the zones.
A specially designed load management system allows the stent manufacturer to quickly and easily load the untreated arterial stents into the chamber through the front door and unload the medical devices through the opposite door within a cleanroom environment.
Carbolite's engineering team designed and built a custom loading system which allows the stents to be loaded onto mandrels that could easily be transported straight from a carrier on a trolley into the oven chamber, ready for the heat-treatment process.
The loading system features an adjustable support frame that holds 30 shafts, up to 10mm in diameter and 1,400mm in length.
