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Stencil Template Design

The main formworks of continuous die include punch fixing plate, pressing plate, concave formworks, etc. According to the accuracy of stamping products, production quantity, processing equipment and method of die, and maintenance mode of die, there are three forms as follows: (1) block type, (2) yoke type, (3) insert type.

1. Block Type

Integral formwork is also known as integral construction, and its processing shape must be closed. The whole template is mainly used for simple structure or low precision mold, and its processing mode is mainly cutting (without heat treatment). The template adopting heat treatment must be processed by wire cutting, discharge machining and grinding. When the size of the template is long (continuous mold), two or more pieces of one body will be used together.

2. Yoke

The design considerations of yoke formwork are as follows:

For the fitting of yoke plate structure and block parts, the intermediate or light fitting method shall be adopted. If the strong pressure fitting is adopted, the yoke plate will change.

The yoke plate must be rigid enough to bear the side pressure and surface pressure of the block parts. In addition, in order to make the groove part of yoke plate closely combined with the block part, the corner of the groove part shall be processed into a gap. If the corner of the groove part of yoke plate cannot be processed into a gap, the block part shall be processed into a gap.

The internal shape of the block parts shall be considered at the same time, and the datum plane must be defined. In order to avoid deformation during stamping, attention should also be paid to the shape of each block part.

When yoke plate is assembled into many pieces of block parts, the pitch changes due to the accumulated processing error of each block part. The solution is that the middle block parts are designed to be adjustable.

For the die structure of block parts adopting side-by-side combination, the block parts will bear the side pressure during punching process, which will cause the gap between the block parts or cause the tilt of the block parts. This phenomenon is an important reason for poor stamping size, chip blocking and so on, so we must have adequate countermeasures.

There are five fixation methods for the massive parts in the yoke plate according to their size and shape: A. fix them with locking screws, B. fix them with keys, C. fix them with "a" keys, D. fix them with shoulders, and E. fix the above pressure parts (such as guide plate) tightly.

3. Insert Type

The circular or square concave part is processed in the formwork, and the massive parts are inlaid into the formwork. This kind of formwork is called inlay structure, which has less accumulated machining tolerance, high rigidity, and good accuracy and reproducibility when disassembling and assembling. Because of the advantages of easy machining, accuracy of machining, and less engineering in the final adjustment, the insert template structure has become the mainstream of precision stamping die, but its disadvantage is the need for high precision hole processing machine.

When the continuous stamping die is constructed with this template, in order to make the template have high rigidity requirements, the empty station is designed. The precautions for the construction of inlaid formwork are as follows:

Processing of embedded holes: vertical milling machine (or jig milling machine), comprehensive machining machine, jig boring machine, jig grinder, wire cutting and discharge machining machine, etc. are used for processing of embedded holes of formwork. In order to improve the machining accuracy of the wire cut EDM, the secondary or more wire cut machining is used.

Fixing method of inserts: the decisive factors of fixing method of inserts include the accuracy of machining, the ease of assembly and decomposition, the possibility of adjustment, etc. There are four fixing methods for the insert: A. screw fixation, B. shoulder fixation, C. toe block fixation, D. upper part of the insert is pressed by plate. The fixing method of the insert of the concave formwork also adopts the press fit. At this time, the relaxation result caused by the processing thermal expansion should be avoided. When the circular die sleeve insert is used to process the irregular hole, the rotation prevention method should be designed.

Consideration of assembly and disassembly of embedded parts: the machining accuracy of embedded parts and their holes is required to be high for assembly. In order to obtain that even if there is a slight dimensional error, the adjustment can be made when assembling, the countermeasures should be considered in advance. The specific considerations for the processing of inserts are as follows: A. there is a press in guide part; B. the press in state and correct position of the inserts are adjusted by the spacer; C. the bottom surface of the inserts is provided with a press out hole; D. when the screws are locked, the screws of the same size should be used to facilitate the locking And loosening, e. in order to prevent the error of assembly direction, anti dead chamfer processing shall be designed.

Post time: Aug-19-2021