Analysis of main points of mold sliding mechanism, you can easily demould if you understand it

Time:2020-03-19 08:52:20 / Popularity: / Source:

Common types of sliding mechanism

Mechanisms with lateral parting and core pulling are collectively referred to as sliding mechanism. There are many types of sliding mechanism and various classification methods. According to use characteristics of various types of slider structure, common sliding mechanism can be summarized into following categories:
Front mold sliding mechanism
Rear die sliding mechanism
Inner sliding mechanism
Harvard mechanism
Lifter, swing bar mechanism
Hydraulic (pneumatic) sliding mechanism
Design requirements of mold sliding mechanism

Each component of sliding mechanism should have reasonable processing technology, especially forming part. General requirements:

a. Try to avoid slider line. If it is unavoidable, position of slider line should be located at an inconspicuous position of parts, and length of slider line should be as short as possible. At the same time, a combined structure should be used as far as possible, so that slider line position and cavity can be processed together. As shown in Figure 7.2.1a, 7.2.1b.
b. In order to facilitate processing, molding part and sliding part should be combined as much as possible. As shown in Figure 7.2.2.
mold sliding mechanism 

Components of sliding mechanism and their assembly parts shall ensure sufficient strength and rigidity.

Sliding mechanism is generally designed based on experience, simplified calculations can also be performed. In order to ensure sufficient strength and stiffness, general situation is:
A. Structure size is the largest. When space position can be satisfied, slider component adopts maximum structural size
B. Optimize design structure. For example:
1) Position end of long slider pin to avoid bending slier pin, as shown in Figure 7.2.3
sliding mechanism 
2) Increasing section size of lifter, reducing slope of guide slide of lifter, and avoiding bending of lifter rod. As shown in Figure 7.2.4, if structural space "D" of parts allow, increase section size "a" and "b" of lifter, especially size "b". At the same time, on the premise of satisfying side core pull, angle "A" is reduced to avoid bending of rod portion of lifter under action of lateral force.
lifter rod 
3) Change structure of shovel to increase strength of mold at assembly site. As shown in Figures 7.2.5a, 7.2.5b, 7.2.6a and 7.2.6b.
slider structure 
4) Increase locking and increase strength of shovel.

Movement of sliding mechanism should be reasonable

In order for sliding mechanism to work normally, it should be ensured that during process of opening and closing mold, sliding mechanism does not interfere with other structural components, movement sequence is reasonable and reliable. Following points should generally be considered:
A. When using front mold slider, mold opening sequence should be guaranteed. As shown in Figure 7.2.7, when opening mold, it should be typed from A-A first, then B-B.
sliding mechanism 
B. When using a hydraulic (pneumatic) sliding mechanism, type and reset sequence of slider must be well controlled, otherwise it will be damaged. In Figure 7.2.8, sliding mechanism can be parted only after locking block 2 leaves slider position. Before mold is closed, sliding mechanism must be reset first. After mold is closed, lock block 2 is used to lock sliding mechanism. In Figure 7.2.9, because slider pin passes through front mold, slider pin must be pulled out before mold is opened, sliding mechanism can be reset after mold is closed, and slider is locked by cylinder pressure.
hydraulic sliding mechanism 
C. sliding mechanism prevents interference with ejection mechanism when mold is closed.
When projection of sliding mechanism and ejection mechanism in mold opening direction coincide, a reset-first mechanism should be considered to allow ejection mechanism to be reset first.
D. When slanting guideposts of slider or slant slide driving is longer, length of guideposts should be increased.
guideposts length L> D + 15mm as shown in Figure 7.2.10
Purpose of lengthening guideposts is to ensure that front and rear molds are fully guided by guideposts and guide sleeve before inclined guideposts or inclined slide plate is introduced into driving position of sliding mechanism, so as to avoid sliding mechanism from being damaged during mold clamping process.

Ensuring sufficient travel distance to facilitate stripping of plastic parts.

Slider stroke is generally taken from lateral hole position or depth of concave and convex plus 0.5 ~ 2.0mm. Slider and swing bar should be smaller, other types should be larger. However, when plastic parts such as coil bobbin are formed by a split mold, stroke should be greater than depth of undercut, as shown in Figure 7.2.11, stroke S is calculated by following formula.
Slide guide 

Slide guide should be stable and reliable, at the same time, it should have sufficient service life.

Sliding mechanism generally adopts T-shaped guide chute for slide guide. Figure 7.2.12 shows several common structural forms.
Slide guide 
When sliding mechanism completes side parting and core pulling, length of sliding block remaining in guide chute is not less than 2/3 of total length. When size of mold plate cannot meet minimum mating length, an extended guide chute can be used, as shown in Figure 7.2.13.
sliding mechanism 
Slide guide surface (that is moving contact surface and force receiving surface) should have sufficient hardness and lubrication. Generally speaking, slider components need to be heat-treated, their hardness should reach above HRC40, hardness of guide sliding part should reach HRC52 ~ 56, and guide sliding part should be processed with oil groove.
In sliding mechanism of slanting top swinging rod type, guide sliding surface is a hole wall that cooperates with slanting top swinging rod. In order to reduce wear of sliding surface, actual mating surface should not be too long. At the same time, in order to increase hardness of sliding surface, high-hardness inserts should be used locally. As shown in Figure 7.2.14.

Slider positioning should be reliable

After sliding mechanism terminates parting or core pulling action, slider should stay at position where movement has just been terminated to ensure a successful reset when mold is closed. To this end, a reliable positioning device must be provided, but sliding mechanism such as lifter and swing rod need not be provided. Following are several commonly used structural forms, as shown in Figures 7.2.15a, 7.2.15b, 7.2.15c, 7.2.15d.
Figure 7.2.15a) It is generally used, but due to limitation of built-in spring, slider spacing is small.
Figure 7.2.15b) It is suitable for sliding block located above, on the side and slider with a larger distance after mold is installed. When sliding block is above, spring force should be more than 1.5 times weight of sliding block.
Figure 7.2.15c) It is suitable for mold installation, sliding block is located on the side.
Figure 7.2.15d) It is suitable for mold installation, sliding block is located below, and slider is used to stay on block.
sliding mechanism 

Opening of slider needs to be guaranteed by a mechanical mechanism, avoiding use of a spring alone.

Figure 7.2.16a uses a spring to provide opening power alone, and structure is unreasonable. Figure 7.2.16b is mainly provided by pull block "3". Driving force of slider is guaranteed and structure is reasonable.
sliding mechanism 
sliding mechanism 

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