Design experience points for injection mold slider and lifter

Time:2020-03-16 08:49:06 / Popularity: / Source:

Due to special requirements of product, stripping direction of a certain part is inconsistent with mold opening direction of injection machine, side splitting and core pulling are required to smoothly eject product. There are two types of side splitting and core pulling mechanism: slider and lifter.

First, slider

1. Slider calculation (example below):
In order to ensure smooth demould of product, distance of movement of slider must be sufficient. Generally, minimum distance that product can be demolded plus 2~3mm is taken as minimum stroke:
2. Structure of back mould is in the form of press block + oblique pin + slingshot as shown in the figure (sometimes when slider width exceeds 100, and it is not convenient to use this structure, T block structure can be considered). However, when slider is in the direction of up and down, it is limited by position of return needle and size of mold, it can be made from original steel rather than briquetting.
3. Relationship between bottom, top surface of slider and that of mold, see as blow:
4. Regardless of whether there is sealant on the side of slider, slope should be inclined on both sides. General value is 3~5° on one side, but angle is 45° when two sliders are perpendicular to each other. If product has sliders for four sides, designer should consider extending one of sliders to ensure accurate positioning.
5. Ratio of height of slider to thickness is at most 1. Otherwise, movement of slider will be affected by turning moment, resulting in motion failure. Generally, L≧1.5H is required.
6. Angle of oblique pin of slider is generally 15 ° ~ 25 °, maximum can not exceed 25 °, angle of oblique pin is 2 ° smaller than slider, generally try not to use a small oblique pin to ensure smooth movement of slider.
7. Oblique pin hole is 1/64" larger than single side of oblique pin, about 0.4. When oblique pin passes through slider, it needs to leave enough space on template.
8. Position of oblique pin in slider: oblique pin is placed in middle position of slider as much as possible. Specific size requirements are as follows:
oblique pin 
9. Matching surface of wedge and slider is required to exceed 2/3 of height of slider, and screws used for wedge should be as large as possible. Following figure shows wedge of two different structures, try to avoid structure of Figure b.
oblique pin 
10. Length of slingshot in slider should be determined to ensure that space is sufficient to prevent from failing.
Set stroke of slider to M, total length of slingshot is L, and set spring compression to 40%. After slider is completely exited, slingshot is still preloaded by 10%.
(40%-10%) L=M
Slingshot space is 0.6L
11. However, when L is too small, in order to prevent slingshot from failing, it is often necessary to increase length of slingshot.
When slider completely wraps side of product, in order to prevent component from being scratched during movement of slider, a side top device is required on slider, and its structural form is as shown in the figure: in the design, appropriate structure should be selected according to whether mold space is sufficient. It is recommended to use structure of Figure a.
12. In order to make movement of slider smooth, there should be no sharp corners that hinder movement Generally, corners of R3~R5 should be inverted.
13. When installing slingshot under slider, size requirements are as shown in the figure. To prevent screw from being caught by slingshot, refer to table when selecting slingshot and screw.
14. Large sliders should be cooled separately, and wear blocks should be placed on sliders or wedges. At this time, sliders or wedges are avoided by 0.5, as shown.
15. When limit slot is to be set on slider of front die, structure is as shown in the figure, h is determined according to slider stroke (attaching limit block size). Limit block is fastened with at least M3/8" screws.
Sometimes, when front mould slider is too small, T block guide is not used, and limit block guide and positioning are directly used.
16. In front mould slider, T block and T slot are avoid by 0.3~0.5 on one side, and only one side is mating surface. As picture shows:
17. Calculation of length of front mould slider slingshot.
Set slider stroke M, total length of slingshot L, 40% compression, 10% preload after slider is completely exited, slider angle α, total height of slider H, then:
(40%-10%) Lsina=M
At the same time it should be checked: 0.3Lcosa < 1/2H, otherwise angle should be increased, but maximum should not exceed 25 °, sometimes to prevent failure, often to increase size L.
18. Front mould slider must have slider pull.
19. Front mould slider is changed to T block to be in slider, and T slot is set on wedge.
20. Front mould slider generally requires wear block to be set, as shown in the figure. At this time, mating surface of front mold and slider avoid 0.5 mm.
21. Front mould slider must not exceed 1/2 of total length of slider as shown in the figure.
22. Front mold inward slider, product is required to set front mold inward slider, as shown in the figure. At this time, in order to avoid problem of excessive A-plate avoidance, T-block is often placed in slider, and T-slot is set on slider.
23. When “V” type oil groove is opened in slider, direction of slider should be inclined. “O” shaped oil groove should be perfectly coherent, oil groove depth is 0.5-1.00mm, and oil groove is not open to prevent oil leakage. .
24. Parts with mutual movement on slider are quenched. For example, limit blocks, beading, and so on.

Second, lifter

Use of a lifter is often a very effective method when there is an undercut on inner surface of side wall or inner surface of top end of products. Working principle is as follows: while product is being ejected, it is restricted by bevel and simultaneously moved laterally to demould product.
1. Angle of lifter is generally 5°. Size depends on stroke and ejection space. Sometimes C plate is raised to ensure ejection.
2. Minimum thickness of slider is 8.00. In most cases, it can be appropriately increased to 10~15mm. At the same time, slider should be equipped with wear blocks to ensure accurate positioning.
3. When product arc is required to set lifter, processing method is shown in the figure:
4. Lifter is fixed by T seat and screw, and minimum screw is M3/16".
5. When size of lifter and height of ejector are limited by surrounding bone position, boss, or distance between two lifters, solution is to set limit ejector and communicate with design department to change product.
6. Limit ejector mechanism, basic form of limit ejector mechanism is shown in the figure, generally two. H is set according to limit ejector height.

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