Process Design of Trimming Blow Molding Mould

The rationality of the process design for trimming dies directly affects the quality of stamped parts and die service life. A well-designed process can shorten commissioning time, improve the first-pass yield of parts, and greatly boost the efficiency of automated production.

1. Extreme Operation Design for Trimming and Piercing

Stamped parts come in various shapes. The profile at trimming/piercing lines usually forms a certain angle with the die base. When the angle exceeds a specified value, a cam mechanism shall be adopted for trimming and piercing to guarantee die life and part quality.Design criteria: Obtuse angles are preferred; acute angles shall not exceed 20°. If the acute angle exceeds 20° in actual production, the shearing surface shall be designed as a flat surface, and a secondary trimming process will be required in the subsequent working procedure.

2. Clearance Design for Trimming and Piercing

Blanking clearance is the fundamental guarantee for high-quality stamped parts. Clearance values vary according to material types and sheet thicknesses. Blanking clearance shall be increased accordingly with the rise of material hardness and sheet thickness.In addition, reasonable stamping frequency and regular die maintenance are also essential for producing qualified parts.Practical experience shows that the optimal blanking effect is achieved when 1/3 of the cross-section is sheared and 2/3 is fractured. This clearance effectively eliminates burrs, prolongs the service life of cutting edges and reduces maintenance intervals.

3. Separation & Cutting Process

This process separates scrap materials first before final cutting. It is mainly applied to large outer panel parts such as front/rear door outer panels, roof outer panels and hood outer panels.Its core advantage is reducing scrap debris generated during trimming and preventing debris from scratching workpieces in subsequent processes.Common technical requirements: The scrap cutter shall be 3~5 mm lower than the trimming line and closely fitted to the trimming surface; alternatively, a height difference of approximately 3 mm shall be set at the joints of trimming cutter blocks.The separation process shall be determined by comprehensively considering die structure and overall dimensions, with reference to the process parameters of stamping presses.

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