There aren't universally applied tolerance standards in plastic molding. However, there are general guidelines and industry practices that manufacturers follow to achieve parts with the desired level of dimensional accuracy. Here's a breakdown of the key factors to consider:

• Part Complexity: Simpler parts with less intricate features can typically be molded with tighter tolerances compared to complex parts with many variations in thickness or tight corners. More complex parts inherently require more wiggle room during manufacturing.

• Material Selection: Different plastic materials have varying shrinkage rates, which can affect the final dimensions of the molded part. Resins like Polypropylene tend to shrink more than ABS, so tolerances for parts made from these materials would need to be adjusted accordingly.

• Molding Process: The specific molding technique used (injection molding, compression molding, etc.) can influence achievable tolerances. Injection molding generally offers tighter tolerances than other methods.

• Application Requirements: The functionality of the final part plays a crucial role. Parts with critical dimensions that need to fit precisely with other components will require stricter tolerances compared to purely aesthetic parts.

Here's a general range of tolerances typically encountered in plastic molding:

• High Precision (tolerances of +/- 0.025 mm or 0.001 inch): This level of precision is uncommon and typically reserved for critical medical parts or components requiring exceptionally tight fits.
• Medium Tolerance (tolerances of +/- 0.1 mm or 0.004 inch): This is a common range for many industrial parts and functional components where precise dimensions are important but not critical.
• Normal Tolerance (tolerances of +/- 0.25 mm or 0.01 inch): This range is suitable for non-critical parts where dimensional accuracy is less crucial, such as housings or consumer goods.

Additional factors affecting tolerances:

• Mold Design and Manufacturing: A well-designed and precisely machined mold is essential for achieving tight tolerances.
• Process Control: Consistent monitoring and adjustments during the molding process can help minimize variations and ensure parts meet the specified tolerances.

It's important to communicate your tolerance requirements clearly to your plastic molding manufacturer. They can then advise on achievable tolerances based on your part design, material selection, and budget. They might also suggest design modifications to improve manufacturability and achieve your desired tolerances.