What is the standard of precision injection mold tolerances

First, the concept of mold tolerance

Mold tolerance refers to the allowable size deviation range of each part of the mold in the manufacturing and assembly process. For precision injection molds, the control of mold tolerances is particularly important, because any small dimensional deviation can lead to product size out of whack, surface defects or functional failure.

Second, precision injection mold tolerance standards

1. 
   1. Dimensional accuracy level
   According to the national standard GB/T 1804-2000 "Tolerance and fit", dimensional tolerances can be divided into four levels: precision (IT5-IT7), high precision (IT8-IT11), medium precision (IT12-IT14) and rough (IT15-IT18). For precision injection molds, an accuracy grade of IT6 or higher is usually required.

2. Cavity and core fit tolerance
Parallelism and verticality tolerance: it is generally required to be within 0.01mm to ensure the exact match between the cavity and the core, and to avoid defects such as sidewall and flash edge of the product.
Clearance tolerance: For moving parts such as sliders, guide posts, guide sleeves, etc., the clearance is usually controlled between 0.005mm and 0.02mm to ensure smooth movement and prevent loosening and wear.

3. Machining surface roughness
Cavity surface roughness: In order to obtain good product surface quality, cavity surface roughness is generally required to reach Ra 0.2μm or less.
Parting surface: the roughness of the parting surface should be within Ra 0.8μm to ensure good mold closure and prevent material leakage.

4. Tolerance accumulation control
In the process of mold design and manufacturing, it is necessary to consider the cumulative effect of tolerance, adopt the method of optimization design and precision machining, and control the cumulative tolerance within the allowable range.