This morning We had a customer who was trying to figure out how many heaters and what kind he needed to heat his mold to a certain degree in a certain amount of time. The only piece of information that we had was the size of the mold. He is using a mold that is 375mm x 50mm x 75mm. He needed it to be heated to 238 degrees Celsius. We determined that it would take 1500 watts to heat a mold of that size in 5 minutes, 750 watts for 10 minutes, and 500 watts to heat the mold to temperature in 15 minuets. The customer was looking to be able to heat to temperature in fifteen minuets or less. When our engineers did the math however it was determined that the mold would require a cartridge heater 3/8 x 5 and that size heater can only handle a max of 400 watts under warranty. Having two heaters of this size we should be able to heat the customers mold to temperature safely in 8-10 minuets. Our customer measured to make sure that the 3/8 x 5 would work and still leave room for his part cavity with no problems. The only thing that we can not take into account is the heat loss from the surrounding ambient air or if another mass is connected to the mold. When ever I am working on a project where we are designing heaters and it is not something standard I always at this point have a drawing made to make sure that I am communicating correctly between both the engineer and the customer so we all know what is being made and there are no surprises. We had solved the problem for our customer with one thing left to deal with, he needed to be up and running by the middle of next week. We are able to make these heaters is 2-3 days and ups red them to him by Tuesday of next week. I would call that a success!