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STONE-GRINDING STEEL BELTS TO CRITICAL TOLERANCES

IP.com Disclosure Number: IPCOM000245268D
Publication Date: 2016-Feb-24
Document File: 2 page(s) / 21K

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The IP.com Prior Art Database

Related People

Hans-Kurt Schromm: AUTHOR [+2]

Abstract

Mr Hans Strandell, Senior Technical Manager at Sandvik Process Systems, explains how the company is able to meet the extremely tight tolerances of belt thickness required for the production of filter membranes using a combination of stone grinding and precisely manufactured conveyor drums.

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STONE-GRINDING STEEL BELTS TO CRITICAL TOLERANCES

Sandvik in-house expertise enables production steel belts for filter membrane casting

Mr Hans Strandell, Senior Technical Manager at Sandvik Process Systems, explains how the company is able to meet the extremely tight tolerances of belt thickness required for the production of filter membranes using a combination of stone grinding and precisely manufactured conveyor drums.

The flat, smooth and hard surface of a stainless steel belt makes it the ideal medium on which to press, cast, laminate or otherwise process a whole range of different product types, from wood based panels, engineered stone and fiber composites to high gloss films, thin films for printed circuit boards, and the specialist films required for LCDs on cameras and notebooks.

In every case, the quality of the steel press or casting belt is reflected, quite literally, in the quality of the end product, and this is determined by a number of factors.

Flatness and straightness are fundamental requirements, of course, and are achieved through a series of specialist leveling and finishing processes.

The next consideration is the surface finish itself. For some applications, a standard cold rolled or ground finish – with a surface roughness of Ra ≤0.4 mm – will be sufficient; others will need lower levels of roughness. For more demanding applications, the belt may need to be polished and grades range from ‘Fine grind’ (FG) and ‘Buff’ (BF) to ‘Polished finishes’ (PF), the latter encompassing grades that increase in quality to super-mirror-polished steel belts with a surface roughness of just Ra ≤0.01 mm.

Other surface finish options include chrome plating, embossing and coating with fluoropolymers (PTFE/FEP).

Achieving critical belt thickness tolerance

Consistency of belt thickness is another key factor and one in which we have the expertise to meet extremely fine tolerances.

The example that follows relates to a steel belt manufactured by Sandvik Process Systems for the production of a type of polymer film, a thin porous membrane used for diagnostics in the pharmaceuticals industry; other applications requiring similarly tight thickness tolerances include the production of advanced foils and paper materials.

In most instances, belt thickness is managed by grinding with a form of belt grinder, a technique that can deliver a thickness tolerance of +- 20 µm on either side, equating to 40 µm in total. The steel belt is endless welded into a conveyor where it is ground. Depending on if the belt can be mounted endless on to the customer’s machine or not, the belt is delivered endless or the weld is opened and the belt is delivered as a coil.

For this particular order however, the customer’s specifications included an exceptionally tight thickness tolerance of less than 10 µm, and this required a different approach.

First of all, in order to eliminate the risk of even the most minor variation in thickness across the...