During my visits with manufacturers who work with nested based CNC machines I am often confronted with questions regarding hold-down vacuum performance. Surprisingly, there is very little information available to these manufacturers apart from the specs of the vacuum pumps. Manufacturers have told me when they have problems holding down parts to their table they often refer to the machine distributor who sold them the system. On occasion, they are told that the pump is not strong enough and that they must purchase a bigger pump. In some cases, after purchasing a bigger pump, the problem persists and they are told that the vacuum is not the problem, they must be doing something
In order to hold down a piece of wood to a table using vacuum, more than just the performance of the vacuum pump has to be taken into consideration. The air that will be drawn by the pump must first travel through a spoilboard; then through a plenum in the table; then through different valves and plumbing fittings and finally through a pipe or tube to the pump itself. Let’s take a look at each of these elements separately.