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Stock removal on a widebelt sander is determined as much by the abrasive belt as by the machine. Each abrasive belt is designed to remove a certain amount of stock and if that amount is surpassed, the life of the belt is affected and workpiece burning or other heat issues may occur.
As a rule, use the lower grit belts for heavy stock removal (36-80 grit belts can remove approximately 1/8 to 1/32 inch respectively) and medium grit belts for lighter stock removal (100-120 grit belts can remove approximately 1/32 to 1/64” respectively). Belts in grits from 150 on up should only be used for finishing and are not considered cutting belts.
Other factors affecting stock removal are: abrasive belt speed, type of sanding head, feed speed and horsepower.
Holddown shoes in a widebelt sander are similar to chip-breaker shoes in a planer. Their uses include controlling the part as it passes through the machine, prevention of dubbed or sniped lead and trailing edges and to allow for shorter parts to be run. They are used on short parts, narrow parts and parts under ¼" thick, veneered panels, or any time the user needs to hold close tolerances.
It is used for optimum control when sanding veneered panels or sealer/lacquer. The platen or shoe is made up of individual segments that receive sanding pressure individually, either pneumatically or electronically. The segments are controlled by a CNC controller and a sensing unit, both of which are programmed to activate only as needed. This allows the user to conform to the irregularities of the panel and sand without fear of sanding through the sealer or veneer.
The number of required sanding heads should be based on production needs and final finish requirements. If production will not allow for multiple passes, a multi-head machine may give the required finish in one pass. If a 3 headed sander is run with a grit sequence of 100-150-180, approximately 1/32" can be removed in one pass.
Know how much stock is needed to remove and what is the final grit finish. Work backwards to determine how many heads are needed, remembering not to skip more than one grit size in a sequence.
Drums are normally used for stock removal and a platen is used for finishing although a drum is occasionally used for finish sanding. If more than 0.0003 to 0.0004" needs to be removed, use a drum. The difference between the two is also seen in the finish. Drums produce shorter scratch patterns that are deeper per grit. Platens produce longer scratches that are not as deep. Determining stock removal requirements and desired finish are the first steps in deciding which will fit the user's specific needs.
The first coating applied to a product after finish sanding or staining is a sealer (lacquer). Its purpose is to fill in or seal the wood pores and protect the wood. Applying sealer will usually result in the grain of the wood rising, producing a fuzzy or rough surface. Sealer sanding is used to create a flat, smooth, properly textured surface so that the top coat will adhere properly. Sealer may be sanded by hand, widebelts, brush sanders or orbital sanders.
Crossbelt sanding is used primarily in veneer tape removal applications. The sander is designed to run across the grain of the wood. This aggressive sanding removed the tape with one head instead of two heads that would need to be used with other widebelt methods. Cross belt sanding may also be used on long panels in which the grain runs in the narrow direction, such as desk tops and front panels. When processing these, the cross belt is located on the out feed of the machine and the scratch pattern produced by the belt runs with the grain.
Wet machines eliminate the risk of fire and increase belt life. Normally the finish is finer and requires fewer steps to achieve. The working environment around the sander is normally cleaner as are the actual sander parts as the water keeps dust, oil and grit washed away. Never use a wet machine in a wood application, but it is a viable and attractive option for metals.
Many sizes are available from many manufacturers. Normally wide belts would be at least over 12" in width (small wide belt sanders normally start at 15" width) with lengths as small as 43 up to or past 142". Check with a local widebelt manufacturer/distributor or search online for the right size for your workpieces.
Shortest part length is determined by the distance between the infeed holddown rolls and the out-feed holddown rolls. Although, these distances vary machine to machine, it is possible to do the following:
- Build a fixture to group small parts in a way to meet the minimum part length
- Leave the part tabbed together in sheets after punching or stamping the parts.
- Use a vacuum bed conveyor.
- Use a magnetic bed conveyor on ferrous parts.
Coolants, when mixed with water in the correct proportion, protect the machine and the workpiece from rust and corrosion.
Generally, less than .001" and usually less than .0005", depending on the material being sanded and grit selected.
We do not normally make specific wide belt sander recommendations. Wide belts for the most part are similar in construction and function. However, through the years we have found that the better known manufacturers tend to have less troublesome products and better service if and when a problem does arise. Some of the most common machines we see in the field are Timesaver, Butfering, Costa, SandingMaster, Ramco, SCMI, Weber and Woodmaster. Discuss your needs and what type of service after the sale is available with your distributor or manufacturer’s rep to make the choice that is right for you.