My job as a technician for Dixon Abrasives is to make sanding make sense. This is not as simple a task as most people would think. Every part of the sanding process must work together to accomplish a few simple tasks. The sanded wood must have the right surface texture, it must be able to accept the desired finish, and it must look pleasing to the eye of the customer. Each step of the process must compliment and improve the process before it, but each step of the process has impact on the later processes. The wide belt machine is the first step in the process for most companies so it is always one of the first things I want to see as a tech. This article covers most of what I look at in an initial visit to a shop.
Let’s start with what we are trying to accomplish with a wide belt machine.
- The coarser belts should tear open and flatten the surface. The goal is to create tiny mountain ranges of scratches that cover the entire surface evenly.
- The depth of these scratches should be very consistent, making them easier to remove by subsequent operations.
- The belts creating this scratch should be sharp and cut cool because compression of the grain structure is very bad for color consistency, and that starts at this step.
- Over taxing the first belt will start to smash the wood closed at the very first contact surface. Loss of color and consistency is the result.
A nice hard drum with a coarse belt is just right for creating a flat, open surface ready to take stain properly. The scratches might be too rough at this point, but the surface is right. The first belt in contact with the product sanded has as much to do with the final color and openness of the surface as the last, and all the subsequent sanding as well.
The sanding heads after the first head will break down the little mountain ranges of scratch pattern, without ever reaching below the bottom of the original valleys. The subsequent contact surfaces are often softer drums to give a slightly bigger foot print with a more shallow scratch, or platens to give huge surface area with much less grain penetration into the wood. The removal of previous scratch pattern is exceptionally easy for a sanding belt. Nearly 50% of the thickness removed, to get rid of a scratch pattern by a sanding belt, is empty space between the little mountains of wood. The belts are not removing solid wood. When this is realized it is easier to understand why skipping a belt grit between heads is often okay, and even preferred in some situations.
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