wide belt sander
The wide belt sander is the important sanding machine in the woodworking industry. By definition, the wide belt sander is the sanding machines that use an abrasives belt 12 or more in width. It has a straight-through feeding device for work piece, the abrasives belt guidance systems utilizer either a contact roll, sanding platen or both. The rapid of feed speed may vary and adjustable, the sander are available for single or double side sanding as one or more sanding heads per side. The machine is more used to sand wood out from machine to make calibration surface and make the same thickness for the wood panel and plywood.
In general the resin over resin bond aluminum oxide open coat cloth belt is recommended for wide belt sanding of raw wood. Some time resin over glue aluminum oxide sandpaper belts work well when used under lesser work load in the finer abrasives grade. For most operation the resin bond paper belts are superior to either silicon carbides or garnet for hardwood sanding. Usually the sandpaper grade from 60 through 150 is used.
It won’t give you the sanding result, as excellent as the stroke sander since it just sand the surface in 1 stroke sanding operation, but it will give you speed and fairly good enough sanding quality. It works best to prepare the wood panel or plywood as the side panel, back panel or even the top panel before goes to the finishing or assembling line. Sometime it is also used to sand the flat component in the unfinished wood preparation. It is also mostly used in the finishing line for flat panel, associated with the roller coating machine for the water based coating or u.v. coating.
Most common problems associated with the wide belt sander are: belt creasing, tracking failure, rotation marks and streaking.
This is usually the result of the unequal contraction and expansion in different areas of the belt caused by the differences in the moisture content. It is more frequent encountered in the paperbacks belts than in the cloth back belts. Prior to being placed on the machine, the new belts should be hung on spindles at least 4 inches in diameter with no shorter than the width diameter of the belt in near the sander where air can pass over the entire surface.
During the periods of shut down, the used belts should be handled in the same manner. If this convenient, the tension should be removed from the belt and the vent pipe shut off to prevent unequal pickup of water. It is also advisable to turn the belt by hand while it is on the machine to permit areas which have been in contact roll or idler roll to equalize before starting a belt that has been idle for time on the machine.
- Tracking failure
Unless belt happens to have an appreciable in length from one side to other, this problem usually stem from malfunction of he the machine tracking mechanism or insufficient belt tension. Abrasive belt have very high tensile strength and there is little danger of breaking a belt by applying too much tension. Segment belts should be run with just enough tension to track tem and prevent slipping.
- Rotation marks
There are defined as lateral marks which extend completely across the panel. They may be caused by out of balance contact rolls, faulty belt splices or erratic speed in the feed bed or rolls. It can readily determined arithmetically whether the marking stems from the splice or contact roll, since a high area in the contact roll or the splice has define frequently of contact with the stock surface.
Uneven speed indicates the mechanical fault. On some machines, an increase in sanding pressure will eliminate mild mark produced by the contact roll or spices.
Streaks are longitudinal marks in the sanded work pieces and they normally are caused by unequal cutting action in the abrasives belt. They may be detected as shiny streaks or undetectable to the touch, or in the more extreme cases, the ridges which are easily felt.
The streaks is the first indicator that the belt beyond its useful life. Premature streaking result from loading or dulled areas in the coating can be caused by hard foreign mater or loose mineral. Loading can be caused by the inadequate dust collection or failure of mechanism which provides for diagonal movement of the coated abrasives across the work piece by the belt oscillator or by orbiting sanding platens.