Tolerances in plastic what can you expect

Tolerances in plastics: what can you expect?

When working with plastic products, such as sheets, rods and tubes, it is essential to keep track of the tolerances. But what do tolerances in plastics really mean, and what can you expect? We will take a look at the standards DIN 16941 and DIN 16942, which regulate the tolerances for extruded and cast plastic products.

Extruded and cast plastic products

Extruded plastic products, which are manufactured through a process where molten plastic material is pressed through a mold, generally have better tolerances than cast plastic products. This is because the extrusion process provides a more controlled process, where the material can be shaped with great precision. Cast plastic products, which are manufactured through a process where molten plastic material is cast into a mold, can have larger tolerances due to the more variable process.

For example, according to DIN 16941, extruded PE-HD sheets have a tolerance of +/- 1.5 mm for the thickness, while cast PE-HD sheets have a tolerance of +/- 3 mm. It is crucial to find out what type of plastic product you need and what tolerances can be achieved.

Tolerances during processing

When you process a plastic product, such as cutting or drilling into it, the tolerances can change. This is because the processing can cause variations in the material's shape and size. But how large can you expect the tolerances to be during processing? It depends on several factors, such as the material's hardness and the processing method.

For example, if you cut a PE-UHMW sheet with a thickness of 10 mm, you can expect a tolerance of +/- 0.5 mm for the cut edge, if you use a cutting machine with high precision. But if you drill into the same sheet, the tolerance can increase to +/- 1 mm, due to the material's elasticity and the drill's vibrations.

Another important factor to consider is the material's Shore hardness. For example, a PE-UHMW sheet with a Shore hardness of 65 Shore D can have a better tolerance during processing than a PA6G sheet with a Shore hardness of 80 Shore D, due to PE-UHMW's lower elasticity.

Thermal expansion and moisture absorption

When plastic products are exposed to temperature changes or moisture, they can expand or contract. This can lead to changes in the material's shape and size, and affect the tolerances. For example, a PA6G sheet can expand by up to 2 % when exposed to a temperature change of 100 degrees Celsius.

But how can you take into account thermal expansion and moisture absorption when designing a plastic product? One possible solution is to use a material properties database, which provides information on the thermal and moisture properties of different plastics. In this way, you can predict how the material will behave under different conditions, and design the product to minimize the effects of thermal expansion and moisture absorption.

What can you do to minimize the effects of thermal expansion and moisture absorption in your plastic products? Should you consider using a material that has low thermal expansion and moisture absorption, such as PE-UHMW? Or should you design the product to take these effects into account, by using for example expansion gaps or moisture-proof constructions?

Practical tips for designers

When designing a plastic product, it is essential to consider the tolerances and material properties. Here are some practical tips to help you:

• Use a material properties database to predict the material's behavior under different conditions.
• Consider using a material that has low thermal expansion and moisture absorption.
• Design the product to minimize the effects of thermal expansion and moisture absorption.
• Use expansion gaps or moisture-proof constructions to take these effects into account.

Do you want to know more about how you can optimize your plastic products to achieve better tolerances and performance? Contact us to get more information and advice from our experts at PlastShop. You can also visit our website at https://www.plastshop.com for more information on our products and services, which meet the standards of ISO, DIN, FDA, EU 10/2011, and UL 94.