Precision mould is a mould that requires high machining accuracy, but there is no unified standard for its specific definition. It refers to products with high requirements, strict product size requirements, good product consistency, high surface finish requirements, complex and durable structure. The tolerance can reach +-0.001.
Compared with ordinary injection moulds, precision injection moulds have significant differences in processing equipment and methods. For example, ordinary injection moulds use wire cutting as the processing method, while precision injection moulds may need to use slow wire walking.
1. Complex surface:
For some products such as car covers, aircraft parts, toys, household appliances, their shapes are composed of multiple curved surfaces, and some curved surfaces must be processed using mathematical calculation methods.
2. High machining accuracy requirements:
A mould generally consists of a concave mould, a convex mould, and a mould frame, and some may be composed of multiple assembly modules. The combination of upper and lower moulds, insert blocks and cavities, and module assembly all require high machining accuracy. The dimensional accuracy of precision moulds often reaches the μm level.
3. Multiple machining processes:
The production of moulds generally requires the use of milling, boring, drilling, reaming, tapping and other processes.
4. Repetitive production:
The use of moulds has a lifespan. When the lifespan of a mould is exceeded, a new mould must be replaced, so mould production often has repetitiveness.
5. Small batch production:
The production of precision moulds is not mass production, and in many cases, only one is produced.
6. Copying processing:
Sometimes there are no drawings or data in mould production, and it is necessary to carry out copying processing based on physical objects. This requires high copying accuracy and no deformation.
7. Superior mould material and high hardness:
The main materials of moulds are mostly made of high-quality alloy steel. Especially for high-lifespan moulds, LCrl2, CrWMn and other Laisite steels are commonly used. Such steels have strict requirements from forging, processing to heat treatment. Therefore, the formulation of processing technology is even more important, and thermal deformation is also a problem that needs to be treated seriously in processing.
Many key dimensions of precision moulds cannot have slopes. However, when making moulds, tolerance bands are usually utilized with small slopes, such as gear mounting columns, etc. When establishing a digital model, attention must be paid to adjusting tolerance. Generally, the 3D model provided by customers is useless because many of its dimensions are extreme dimensions. If the mould is designed according to this, it is basically scrap.
The manufacturing process of ordinary moulds may not have so many specific requirements, and can be processed according to the normal mould design and processing process.