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Sanders
A wide belt sander is a sanding machine that sands down either raw lumber, once it has gone through different operations such as a jointer or planer, and has already been brought down to the approximate thickness that the operator requires; or, it will be used in the panel industry to sand down the final component parts, or sheets of veneered plywood.
Sanders are very popular machines; they are required in all forms of finishing. You have to have some sort of sanding to finish a product, which can either be by a wide belt sander, or Miscellaneous Sanders, or you could have a whole crew of people manually hand sanding. Most wide belt sanders have a conveyor belt that passes through the machine. The part is put on this conveyor belt as it feeds through the various sander heads and comes out on the other side. The head configuration of sanders would vary depending on the operation. A wide belt sander would normally have quite a long belt (to be discussed later). The width of the machine will be determined by the width of the belt; therefore, when we talk about a 36" machine, the width of the belt would be 36" wide; or a 54" machine would have a 54" wide belt and so on. The length of the belt would be determined either by the manufacturer of the machine or what is required; the longer the belt, the better the belt life because it will have more surface area to do continuous sanding. These belts that are now, say, 36" wide could be eight to ten feet long and are joined together to form a constant loop. The belt fits around a drum on the top of the machine and then is looped around a drum or shoe (pad) on the bottom, depending on the head configuration. On a top sander, the sand paper is above the feed belt; on a bottom sander it would just be upside down with the sanding belts on the bottom and a feed mechanism from the top. In most cases sanders will comprise one drum and one shoe or pad, but this is completely determined by the needs of the individual. It is possible to have a six head top and six head bottom machine with various head configurations.
The drum would normally calibrate, that is, bring the part down to the final required size, or do the rough sanding using a lower grit paper (the lower the grit the rougher the sanding paper); the second belt would be a fine grit paper to do the final finishing operation and the final smoothing of the part. The shoe or pad generally vibrates a little while the panel passes through and will do the final sanding, sometimes called polishing. A traditional machine for a solid wood application, such as component parts for doors would normally be two drums very close to each other to do small parts as well as long ones. The two drums would have different grits of paper, rough on the first and fine on the second head.
The horsepower will also vary, depending on the operation, somewhere between 10 and 50 HP would be the norm. In the manufacture of particle board, the sanders that are traditionally used would have three heads on the top and three heads on the bottom thereby allowing sanding on both sides of the particle board, that has just come out of the press, at the same time. Kimwood a manufacturer of this type of machine make a machine with a 125 HP top and a 125 HP bottom first head, and the other four heads being 100 HP each, giving a total of 700 HP. This is not the norm.
As discussed above, a top sander and a bottom sander could be placed in line behind each other, to sand both sides of a part in a single pass. Some sanders used in the veneering industry might also have what is commonly called a cross belt sander attached to the rest of the machine. This means the belt will go across the grain of the material instead of going up and down with the grain as the other belts previously described. This belt is very narrow, normally being approximately 6" wide, and travels across the panel as the panel feeds through the machine. The reason for this is that once the final shoe (sanding head) with the finest grit paper has sanded the part, fine hairs can still be left on the veneer. The cross belt head will make the fine strands (hairs) stand up. If the cross belt head is the first head, as previously discussed, it will make the hairs stand up and the next heads will remove these hairs. The cross belt can be either the first or last head and in some cases both.
Some sanders today are C.N.C. controlled, that is to automatically set the thickness for various parts or to allow numerous parts of different thickness to be sanded side by side at the same time. These machines have computer controlled sectional pads normally at 32mm from each other that operate by a scanner pre-determining the size of the part that is going through the machine. This, in turn, determines which pads have to come down to actually come in contact with the part. The C.N.C. control is also used for parts that have fancy edgework, the computer will determine the shape and activate the pads that are needed and will also determine how much pressure to put on the panel near the edgework.
Note the difference between an abrasive planer and a wide belt sander; they almost look identical but the heads in an abrasive planer are normally made of steel drums as opposed to a sander where the drums are rubber and in various forms of hardness. Abrasive planers normally have much higher horsepower and will also have a hydraulic feed mat to feed the rough material through the machine; they take a lot of abuse. Sanding is a finishing operation while abrasive planing is a starting operation.
MANUFACTURERS OF THESE MACHINES INCLUDE:
Activa, AEM, Boere, Burlington, Cantek, Castelli, Cemco, Extrema, General, Holytek, Powermatic, Ramco, Sandingmaster, SCM, SCMI, Sicar, Stemac, Steton, Timersaver, Verboom, Butfering, Casolin, Cemco, Costa, DMC, Egurko, Heesemann, Powermatic, SCB, Sicar, Steinemann, Tagliabue, Timesaver, Viet, Zintex.
Copyright © MLS MACHINERY INC. 2008 All rights reserved.
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