Segmented platen sanding machines are commonly used for sanding veneers or lacquers because the segments offer more customized control. They are hidden behind a thin stainless steel plate covered in dense felt, providing a relatively flat surface beneath the fired segments for better contact. The felt is covered with a layer of graphite cloth to reduce friction and ensure a quality job. In this blog, we review the various types of segmented platens and how to achieve best results with raw veneer and lacquered surfaces.
The platen heads on segmented platen machines are mainly used to sand raw wood or treat surfaces between coats on finish. Depending on the settings on the computer, they can pop up and down and even add or remove segments on the sides to affect the size of the sanding footprint. Others just adjust the pressure of the segments corresponding to the edges of the parts. These types of heads are used in most segmented platen machines.
Super-finish platens work the same way as regular platen heads, but they are equipped with a Chevron belt between the platen and the sanding belt. This type of belt has angled pieces of felt that break up the scratch pattern for a less obvious final result. These types of platen heads can be more difficult to set up because they can blur the sanding footprint, but with practice, you can determine the right configuration.
How Segmented Platen Machines Work
Nowadays, you can find more and more wide belt sanders offered on the market with segmented platens. This type of platen allows the sanding operation to operate at higher tolerances, which reduces sand-through.
By understanding how segmented platen machines work, what their best applications are, and what controls are available, you can choose the best sanding machine for your needs.
Machine Function Explained
Individual sensors on the platen allow segmented platen sanding machines to detect contours of a part. When in operation, pneumatic or electromechanical pressure can be used to fire down the platens while a sensor bar on the front of the machine reads the parts coming in via rollers or infrared. Pads push abrasive belts to the material surface because segmented pads have an even pressure throughout their stroke. The result is a uniform sanded surface.
Segmented platen sanding machines excel at sanding parts with a wide variation in thickness, like chair seats. By following the contour of the chair seat, segmented platens fill in the areas that need sanding.
Set Up for Raw Veneer
Veneers in modern woodworking operations have become thinner and thinner. As well as taking extra care in layup procedures to prevent telegraphing and adhesive bleed-through, you also need to be more careful when sanding veneered panels since excessive pressure can cause sand-through.
When working with raw veneer, it’s important to set up the segments so that when they fire, they apply ideal pressure over the entire surface. All pressure should be even across the entire footprint.
To set up your segmented platen machine for working with raw veneer, take the following steps:
Apply a pencil mark the entire surface of the veneer and set the height of the machine according to its thickness.
Use only one head at a time, running the abrasive belt at 12 to 18 meters per second.
Set the footprint so that it leaves a pencil mark border all the way around the part being worked on.
With some machines, a smaller number means less sanding while with others, it designated a shorter number of distance passes before action occurs. Be sure to use the appropriate setting on your machine and, if necessary, subtract segments or take pressure off of the outside segments. Then do the following:
Reduce the overall pressure so that the part will not be sanded during the first pass. Run the part and verify.
Slowly raise the pressure until you see the pencil marks smeared in the middle and intact along the outside edges. This is how you determine how much pressure you have on the part.
After you know exactly what the footprint of your program is and how much pressure you have on the part, you can start working the footprint out until you spread the pencil mark across all four sides. It does not have to be completely removed. With just a little smearing, you have nearly perfect pressure over the entire surface.
With your footprint determined, you can increase the pressure until you can just remove fresh pencil marks over the entire part. There is nothing wrong with leaving a little bit behind, as long as it isn't in the same place every time.
Experiment with different parts. If you have set up your setup correctly, you can easily confirm that the veneer edge is the same thickness all around. If it isn’t, run other parts through until you hit on the correct setting.
Set Up for Between Coats
It is important to set up a segmented platen correctly for successful sealer sanding. Use the same methods described in the previous section, although you’ll use less pressure and the belt MPS will be slower- around five to nine meters per second.
Make sure that you don’t set the adjustable-height platens so low that they hit the part without firing down. (A segmented platen should have a minimum clearance of 1mm from the unfired head to the part.) Run the part through and make sure none of the platen heads touch without being turned on or fired.
Allow enough space between parts on all sides so the platen can retract before the next part goes under it. Make sure you turn off the vacuum when running frames so the abrasive belt does not get sucked into drawer boxes or pockets.
These tips for setting up and running a segmented platen machine can help you get a better understanding of how their heads work. You may have to tweak them slightly to achieve the result you are looking for, but once you master the right technique, your output will be of the quality you’re looking for.
Premium Quality Abrasive Belts For Your Wide Belt Sander
While correct setup for your segmented platen is important, you also need to use the right abrasive for the application. At Fintech Abrasives, we manufacture wide sanding belts of different sizes and grits and can even custom manufacture belts for niche projects. Our abrasive technicians can help you choose the right belt for your needs. To speak with an abrasive technician or place an order, you can contact us any time by filling out a contact form or calling (888) 223-8768.