Causes of air restriction and ways you can correct these issues
Manufacturers sometimes have trouble holding down their parts to the cutting table. Typically, if you were to go to your machine distributor they would suggest getting a stronger vacuum pump to hold down your parts, but this is not always necessary. In some cases, manufacturers will purchase a more powerful pump only to have the problem persist. Other things besides the strength of the vacuum pump have to be taken into consideration as well. The air drawn in by the pump must first travel through a spoilboard, a plenum in the table, and various piping before finally making it to the pump itself. All of these components can affect the suction of the vacuum and whether or not a part is held down effectively.
Spoilboard is usually made of either medium-density fibreboard (MDF) or light-density fibreboard (LDF). MDF and LDF are permeable materials made from wood fibres and particles that allow air to pass through their surface. Although some people believe MDF is better because it is more durable, LDF is a better choice as a spoilboard because it is lighter, which allows for better suction from your vacuum. Ideally, a proper spoilboard should allow a high quantity of air to pass through it and only decrease suction pressure very little. Although, good air flow does not always correlate perfectly to good hold-down ability. You should be looking for a balance between air flow and pressure to maximize your hold-down ability. To effectively achieve this balance, you should try to ensure that your table is sealed because air will always take the path of least resistance. For example, if you are only cutting on one half of your table, consider covering the other half with spoilboard to ensure air is drawn evenly across the table and your parts are held down effectively.
The plenum of the table aims to distribute air evenly from the piping to the surface of the table. It is sometimes the case that this plenum table is not deep enough. When this is the case, buying a more powerful vacuum pump will do very little to solve hold-down problems because air flow is already limited by the depth of the plenum table. Some manufacturers will integrate a table surface that can machine deeper plenums to alleviate this issue.
Piping under the table
Piping could be another source of your hold-down problem. Sometimes the valves that connect the piping are smaller than the piping itself, which restricts air flow. The length of the pipe can also affect air flow. The longer the pipe and the more turns it makes, the harder it is for the air to get to its destination. It is generally a good idea to keep the piping as short and direct as possible to alleviate this issue.
It is probably a good idea to investigate some of these potential issues before making the decision to upgrade your vacuum pump. Buying a more powerful pump will not only cost you money unnecessarily, but may not even solve your issue. By understanding the source of your air restriction, you can determine exactly what is causing the hold-down ability of your pump to suffer.