Production Furnace Throughput Defined

It is very common in several industries to discuss the output of a continuous furnace in terms of pounds/hour. This is an interesting number and easy to understand, however, it is misused most of the time. The origins of this output rating came from lower-temperature furnaces, specifically traditional mesh belts. If you were to speak with the belt manufacturers themselves, they would say you cannot exceed more than 10 pounds/foot2on the belt. Most people routinely run at 20 pounds/foot2 and experience a shorter belt life. Pounds/hour is not an accurate number because you do not know if the part is solid or shaped like a doughnut. Depending on these form factor considerations, you would not get as many parts or as many pounds/foot2, so using this as a measure of output can be very misleading.

Higher-temperature pusher or walking-beam furnaces are not load limited. Pusher furnaces can push in excess of 500 pounds/foot2 and walking beams approximately 400 pounds/foot2. The problem still remains that the shape of the part dictates the load you will get in a boat or on a plate. A more meaningful output number for high-temperature sintering is boats/hour. The furnace does not care if you put lots of small parts or a very large, heavy part into it. By design, higher-temperature furnaces have sufficient power for almost any application. Many of these units are designed for refractory metals with tremendous densities. If you have enough power for these very dense materials, you need not be concerned about more traditional materials.

So a better measure of throughput might be related to how many parts can be processed on a single boat which is a function of the size of the part, not the weight. Manufacturers need to consider placement of parts in a single boat to determine how many will be reliably processed as one boat goes full cycle.  And how many boats you can get through a production furnace is really a function of the soak times in your process as well as the physical capability of the furnace.