How Should You Approve a Trial Sample Before Bulk Production of a Metal Conveyor Belt?

What readings should a trial sample come with?

Not a photo and the words "as per drawing". A number for every dimension that decides fit, taken the same way on your original and on the sample.

Ask for a caliper reading of every fit dimension, on your original and on the sample, with the same tool. For a Melbourne bakery I read pitch 27.41 mm on the original and 27.40 mm on the new sample.

Original vs sample, read the same way

The bakery had no drawing, only a worn section of its old spiral cooling belt. Reading both belts with the same caliper turned "I think it will fit" into numbers the buyer could check. The photo shows the instrument and the reading; nothing is retyped.

For a spiral belt, the fit dimensions are usually pitch, rod diameter, link thickness, link height and link opening, plus the edge detail. For a self-stacking belt add side plate height and thickness. For a chain-edge belt add chain pitch and sprocket data.

Should a worn original be copied exactly?

No. An old belt is a good sample but not a perfect master. Some dimensions change in service and must be corrected, not copied.

Measure the worn original, identify which readings are wear, and correct them to new on the drawing. On a waffle cooling spiral the link read 2.42 mm after years of wear; the trial run and the bulk belt read 2.71 mm.

What was kept and what was corrected

If I had copied 2.42 mm, the new belt would have started life already worn. The trial run showed the corrected link before bulk, and the same reading was taken again on the bulk belt before packing.

Why join the trial section to your original belt?

Because a join shows pitch and link fit directly. No drawing, no photo of a single link, shows it as clearly.

Link the trial section into a piece of your original belt. If pitch, links and edge line up across the join, the fit is shown, not promised. I did this on a spiral belt for Malaysia and on a self-stacking belt for Brazil.

What a joined comparison shows

In Malaysia the customer approved the trial run from photos of exactly this join, plus the readings. In Brazil the join was the first step; the next one happened on the customer's own freezer.

Which function test should the sample pass?

It depends on the belt. A dimension check is always done; a function test is agreed when the belt's job needs one.

Agree the test before the sample is made: a full-circle turn test for spiral belts, a stacking test for self-stacking belts, a sprocket running check for chain-driven or sprocket-driven belts. Where possible, run a short length on your own machine.

Which test fits which belt

The strongest test is your own line. The Brazilian meat plant ran about 50 m on its freezer before ordering the main length. That run answered the one question no drawing can: does it stack and run on this machine?

What happens after you approve the sample?

Bulk production follows the approved sample and the drawing revision on the record. The record is kept for your next order.

After approval, bulk follows the approved sample and drawing revision, and is checked against the same dimensions before shipment. The record stays on file, so a repeat order starts from it. In Brazil, a 50 m trial led to 350 m and then a repeat 350 m.

The approval record

If a detail changes after approval, I re-confirm it with you in writing before production continues. Price, quantity and delivery are confirmed in writing in your quotation.