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Determining Powder Coating Thickness and Tolerance

November 8, 2016

Professionally applied powder finishes use electrostatic technology and uniformly heated ovens to armour parts. In order to form that protective barrier, the equipment needs to be configured so that adequate surface coverage is assured, for under-coverage problems will starve the curing stage of free-flowing resin. Likewise, over-coverage headaches carry their own set of issues.

Why Does Coating Thickness Matter?

Logically, thin powder coating membranes are weaker than dense finishes. They melt and flow in their special ovens, but an optimized high-quality finish is unlikely to form. Surface defects crop up, sharp edges remain unprotected, and decorative accents are corrupted. Conversely, too much powder impairs uniformity and wastes expensive materials. Too much powder is entering the process, so the part cures unevenly. On top of this unrefined finish, imagine the resin filling threads or coupling edges until the part no longer connects to its neighbouring components. Tolerance guidelines prevent such amateurish blunders.

Determining Powder Coating Tolerances

Fortunately, there are techniques and tools that allow application technicians to evaluate the thickness of the coating. Some of these techniques even work before the curing stage. The selected method does require data on the applied substrate and the material used in the coated object, but these measurement variables should be easy to determine. For example, a powder substrate that covers a ferrous-heavy material suggests a non-destructive magnetic induction gauge. Conversely, ultrasonic transducers work on non-magnetic materials.

Thickness as a Quality Control Issue

Overly generous finishes are uneconomical, but they also pose a threat to the basic functions of the part if it's designed to function as one element within a number of precisely assembled components. Similarly, an emaciated coating is not likely to melt and create an impervious shell. There's just not enough substrate and pigment in the resin to physically make this possible. These nondestructive gauges measure thickness before the part enters the oven, which then enables the process to reverse or pause until the electrostatically induced resin satisfies established coating protocols, as determined by the resin manufacturer's own material guidelines.

A number of process variables determine the thickness of the powder coating process. They include the type of gun and its electrostatic power supply. Obviously, the scale of the operation impacts the process, so powder baths and powder guns also affect dimensional consistency. Otherwise, it's up to a diligent process technician to take charge of thickness tolerances by incorporating an in-house quality control mandate, something that approaches the ISO9001 guidelines.

GP Industries Pty Ltd

Head Office

1 Regal Court,
Vermont South VIC 3133

Phone: (03) 9802 1355

Fax: (03) 9802 6027

Email: gp_ind@bigpond.com

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20 Burgess Road,
Bayswater North VIC 3153

Phone: (03) 9761 7676

Fax: (03) 9761 7671

Email: gpfactory@bigpond.com

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