There are several reasons why you may need a widebelt evaluation. Perhaps production or quality issues have caused you to want to assess your operations with an eye toward improving quality and throughput. Perhaps you are considering changing belt suppliers and want to evaluate competing products. Or maybe you want to qualify a belt for a particular task. In this account, the assumed purpose of an evaluation is a comparison of belts currently used to alternatives from another supplier. Procedures may vary from one abrasives supplier to another when performing the evaluation.
The first step after you decide to have a widebelt evaluation is for a supplier to meet with or call the appropriate individual at your plant and review the steps required for conducting a widebelt evaluation. This review helps ensure that there are no delays or misconceptions when the supplier arrives at your factory.
Once a test date is set, you must create three story boards (4-inch by 8-foot medium- or high-density fiberboard test boards, three-quarters of an inch thick). Following their cutting and before running them, store the boards on a flat surface off the floor. This procedure keeps the boards flat and helps prevent them from absorbing moisture.
Also, in advance, your plant's personnel must pre-select cabinetry components to be used in later stain tests. (See performing stain tests below.)
Running the story boards
Running story boards reveals if the widebelt sander is properly calibrated, and the amount removed per head conforms to the machine setting and removal target. The evaluation will determine the amount of material removed by each head. In addition, it will reveal if:
- Each head is removing material evenly across the belt width.
- The table or machine bed is worn in the middle.
- The machine is calibrated to target.
- The sander's digital setting corresponds to the thickness actually produced.
- Each head is parallel to the conveyor bed.
- All heads are parallel to each other.
The story boards should run before a supplier arrives on site. Usually, they are run on a Friday before the evaluation begins on the following Monday, before the machine is calibrated. For running the story boards, the sander should be outfitted with new belts of the type presently used.
The following steps must be followed when running story boards before a widebelt evaluation:
1. Measure each story board at four places along its length to ensure uniform thickness.
2. On the sander, measure from the front of the first head to the outer side of the last head to ensure that the story boards are long enough to be partially sanded by all heads during a partial pass through the machine.
3. Log the machine's digital (target thickness) setting.
4. Before running the story boards, conduct a start-up check by performing the relevant procedures on your daily start-up checklist. (See widebelt sander daily start-up checklist.)
5. With the sander running, set the target thickness.
6. Feed the story boards into the machine simultaneously, one each 4 to 6 inches from the conveyor belt edges and one in the center of the conveyor.
7. When the leading ends of the boards exit the last head, stop the conveyor and shut off each head.
8. Open the machine about 1 inch and remove the story boards.
9. Note which story board was at which location on the belt and measure each board before and after the stop point for each head.
10. Compare each board's thickness following sanding by the last head to the machine setting.
11. If the measurements indicate that the machine is not calibrated correctly, advise the appropriate person so that adjustments can be made before the arrival of the engineer who will conduct the belt evaluation.
Performing stain tests
Before the widebelt evaluation, a stain test is performed on cabinetry components to be run on the test belts. These tests ensure that the finish on components sanded on the test belts matches the finish produced by the belts currently used and also meets the plant's color and adhesion standards.
To perform this test, application engineers from the abrasives manufacturer use belts of the kind currently being used and sand at least one component for each relevant stain color. If the standard finishing process for the components includes wide orbital sanding, that, too, is done before staining. Then the stains are applied, followed by the standard finishing process: sealing, loose fiber removal and clear finishing. These finished parts serve as controls in the evaluation to be performed on alternative belts.
Next, the test belts are installed on the sander and the same sanding and staining process is performed on at least two parts for each stain color. If the stain test shows that the finishes produced using the test belts meet plant standards, then 30 components are sanded on the test belts for a compatibility study.
When evaluating widebelts, application engineers from the abrasives manufacturer typically spend a week in a plant. Central to this process is maintaining a thorough log of belt changes and the regular checking of workpiece thicknesses.
A belt-change log sheet provides spaces for recording each belt change, including the date and time each belt was put on and removed, the reason for the change and the operator's name. The operator must record belt changes because this information provides the basis for the evaluation of new belts and comparisons with the performance of the previously used belts.
At the end of a week of testing and measuring, it will be clear to all involved whether changing to a new abrasive in a particular widebelt application will improve a shop's performance and its productivity.
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