Sanding your molding with a flap wheel head after the molder will help decrease surface markings and aid in creating a better product. In working with molders it is critical to keep spindle tooling clean, sharp, and well balanced. With this combination and making sure to not over drive feed speeds a decent profile can be produced on most molders.
The next step is proper sanding of the material after the shapes have been created. I have found only two methods that will work well for sanding profiled material. One is using a shaped wheel that matches the profile of your product. These shaped wheels are similar in nature to a grinding wheel. These shaped wheels can remove a fair amount of material and will help with removing tooling marks but will not finish sand your surface nor help with color balance. You will also need a head to match each profile you want to create.
The second way to sand the profile is with a flap wheel. Flap wheel heads are designed to be flexible in order to conform themselves to the shape being sanded. This has the unique benefit of very small changes in machine or head settings to accommodate different profiles. When sanding molding with a flap wheel head you must understand that only a small amount of material is going to be removed.
Sanding in this way will do no harm to your profile but only a limited amount of tooling marks will be removed. If you start with good tooling and produce a good clean molding cut then flap wheel sanding will finish sand your product to the point of being ready to apply stain or primer.
The flap head will remove the small fibers that pop up when sanded in any other way or when any type of chemical or water is applied to the surface of the material. These fibers if not removed will raise up and set in a dried position causing a rough primer or stain and seal coat.
If not removed the raised fibers will require additional sanding time between coats to achieve a smooth top coat. Utilizing a flap wheel head will remove these fibers resulting in much less sanding time between coats. You will also benefit from the fact that flap wheel heads will insure a uniform pore opening in the material. Uniform pore openings result in uniform color balance throughout the work surface.
Building your own flap wheel head as an attachment on the out feed end of the molder could be your solution. With today’s availability of inexpensive motors and controllers you should give this idea some consideration. In most cases a little fabrication work to mount a motor or two with heads on the out feed end of your molder is not difficult to do. You will want to make sure the heads can be adjusted up and down and also the ability to tilt the head can be very useful. Up and down adjustment is a must to accommodate different thicknesses of material. The ability to tilt your heads will help when running a profile that is considerably thicker along one edge than the other. Just keep in mind the need for more heads as feed rates increase. It will take approximately two heads for up to 20 feet per minute feed rates.
Using four heads will get you up to approximately 60-70 feet per minute feed rates and still give good quality sanding. You will also want to make sure the heads are counter rotating. Counter rotation insures that one direction of spin will lift the fibers while the other direction of rotation successfully removes the lifted fibers. Giving you a better finish that required less sanding between coats and used less sealer coat to get there.