Over the past few years selling flat table CNC machines, I’ve noticed some of the same spoilboard questions being asked by almost everyone who buys a new machine, so I have put together this FAQ to answer the most common questions.
What material do you recommend?
The correct material is low density fibreboard (LDF). A spoilboard needs to be solid enough that it doesn’t compress drastically with material on the table and vacuum on, and needs to be porous enough to allow good vacuum airflow. Ultra low density fibreboard is too soft, and typical medium density fibreboard (MDF) is too dense to allow proper air flow. A client of mine did some head-to-head material testing, and found that a density of 34 to 40 pounds per cubic foot worked the best for them.
***UPDATE: Our thinking on this has changed. While LDF is typically the correct material for holding down larger parts like kitchen cabinets, the porosity of the board can cause problems with liquid ring vacuum pumps in certain situations. A less porous material like MDF may be more suitable for certain applications. Contact us for more information.
Okay, where can I buy LDF?
Start with the company that supplies your plywood, particle board or MDF core products. If they don’t carry the right LDF, they should be able to point you in the right direction. Ensure you ask for a fibreboard with the density listed above.
***Update: We currently stock 5×12 spoilboards in two different densities. Contact us to place an order.
Should I flatten both sides of the spoilboard before I use it?
Yes, you should flatten both sides for a few reasons. The first is that the thickness LDF will vary from one corner to another, and this will mess with your finished product. The second is that while the core of an LDF board is quite porous, the faces of the panel are not porous at all. If you do not remove both faces of the panel, air will not flow through properly, and your parts will not be held down properly.
How do I flatten my new spoilboard?
Every CNC machine we deliver includes a “surfacing” program for flattening the spoilboard, and we always add in a face milling cutter with the tooling package. After adjusting a work offset in the controller to set the new thickness of the board, you load and run the surfacing program – using the face milling cutter – and you will have a nice fresh surface.
Do I need to do anything to the edges?
Yes, the core of the panel is very porous, and this means that the cut edges of the panel will flow air very freely. If you use a spoilboard without sealing all four edges, you will bleed most of the airflow out the edges, and you will have very little vacuum at the top of the spoilboard where you really need it. There are a variety of ways to seal the edges of a spoilboard, ranging from simply applying edgebanding to all four edges, painting the edges (two solid coats please), coating the edges with wood glue, or even taping the edges.
Do I need to bolt the spoilboard down?
This is somewhat personal preference, and depends on how you want to work. We typically recommend bolting the spoilboard down, but some people prefer to slide the spoilboards on-and-off the machine after each cut cycle. Some of the reasons to bolt spoilboards down include: Less chance of getting dust and debris under the spoilboard and into the vacuum pump; Eliminates bowing and warping of the spoilboard due to moisture and/or stresses in the panel; Allows you to slide your product on and off the spoilboard without the spoilboard moving. In short, unless you have a good reason otherwise, you should bolt it down.
How often will I need a new spoilboard?
This is impossible to answer, because it depends on the amount of cutting you do, the depth you cut through your finished material into the spoilboard, how small the parts are that you’re cutting, how picky you are about having a smooth spoilboard, and other factors. We recommend buying some spare spoilboards so you’re not stuck if the one you’re using gets damaged or machined down to minimum thickness.
Can I cut a 2×3 piece on a 4×8 table.
If you place that small piece on a full spoilboard, you will lose a large amount of vacuum pressure because of the open area of spoilboard. With a wide range of sizes to cut, or you’re only going to cut small pieces occasionally, it’s easy to cover the open areas with scrap material. When you need to cut smaller – and fixed – sizes regularly, you could paint or apply glue to the open areas, or we can custom vacuum zone your machine at the factory (call for more information). In a pinch, a layer of duct tape on the open areas will also work well.
I have more questions.
If you have any spoilboard related questions, or would like more information about the CNC machining centers we offer, please contact us for more information.