A summary of key points of mold slider design

Undercut processing (slider)

1. Action principle and design points of oblique pin block

It uses mold opening action of molding to make inclined pin and slider move relative to each other, so that slider moves along mold opening direction and horizontal direction to separate undercuts. As shown below:

Above picture: β=α+ 2°~3° (to prevent interference in mold clamping and reduce friction when mold is opened) α≤25° (α is tilt angle of oblique pin)
L = 1.5D (L is mating length)
S = T + 2~3mm (S is horizontal movement distance of slider; T is finished product undercut)
S = (L1xsina-δ)/cosα (δ is gap between inclined tip and slider, generally 0.5MM)
L1 is vertical distance of brace tip in slider

2. Oblique pin locking methods and usage occasions

Simplified drawing	Illustrate
	Suitable for use when mold plate is thin and upper fixed plate is not separated from female mold plate. Mating surface is long and stable.
	Suitable for use when mold plate is thick and mold space is large, and mating surface L≥1.5D (D is diameter of diagonal support pin), can be used for both two-plate molds and three-plate molds. It has good stability.
	It is suitable for use when mold plate is thick, can be used for both two-plate mold and three-plate mold. Mating surface L≥1.5D (D is diameter of diagonal support pin), has poor stability and is difficult to process.
	Suitable for use when mold plate is thin, upper fixed plate and female formwork can be separated, with a longer mating surface and better stability.

3. Principle of block pulling action and design points

It uses mold opening action of molding machine to make pulling block and slider have a relative movement trend. Toggle surface B toggles slider to make slider move in mold opening direction and horizontal direction to make it out of barb. As shown below:

Above picture: β=α≦25°(α is inclination angle of pulling block)
H1≧1.5W (H1 is mating length)
S = T + 2~3mm (S is horizontal movement distance of slider; T is finished product undercut)
S = H *sinα-δ/cosα(Δ is gap between inclined pin and slider, generally 0.5MM; H is vertical distance of pulling block in slider)
C is moving surface, so it is generally not necessary to install stop block in the form of dial block. (There can be no gaps)

4. Locking and positioning method of slider

Because product generates a lot of pressure during injection of molding machine, in order to prevent slider and movable core from being displaced under pressure, which will affect size and appearance of finished product (such as running burrs), slider should be locked and positioned. Usually called this mechanism stop block or shovel base.
Common locking methods are as follows:

Simplified drawing	Illustrate	Simplified drawing	Illustrate
	Slider adopts an inlaid locking method. Standard parts can usually be found in standard parts list. Structure has good strength. It is suitable for occasions with large locking force.		Embedded locking method is used, suitable for wider sliders
	Slider adopts an integral locking method, which has good structural rigidity but is difficult to process. Small demoulding distance is suitable for small molds.		Embedded locking method is used, suitable for wider sliders
	Use of pull and stop has poor stability, is generally used when slider space is small.		It adopts embedded locking method, which has good rigidity and is generally suitable for occasions with large space.

5. Positioning method of slider

Slider must move a certain distance during mold opening. Therefore, if slider can be returned safely, a positioning device must be installed on slider, positioning device must be flexible and reliable to ensure that slider does not move in its original position. However, positioning devices may not be used under special circumstances, such as side-running sliders. But for safety reasons, a positioning device must still be installed. Common positioning devices are as follows:

	Use spring screws for positioning. Spring strength is 1.5-2 times weight of slider, is often used for upward and side core pulling.
	Spring steel balls are used for positioning. Generally, when slider is small, it is used for lateral core pulling.
	Use spring screws and baffles for positioning. Spring strength is 1.5~2 times weight of slider. It is suitable for upward and side core pulling.
	Use spring baffle for positioning. Strength of spring is 1.5~2 times weight of slider. It is suitable for large sliders, upward and side core pulling.

6. Connection method of slider

Connection method of top of slider is determined by finished product. Different finished products may have different connection methods to slider. Specific connection method is roughly as follows:

Simplified drawing	Illustrate	Simplified drawing	Illustrate
	Slider adopts an integral structure, which is generally suitable for occasions with larger cores and better strength.		It is fixed with screws and is generally suitable for situations where core is round and the core is small.
	Screw fixation method is generally suitable for situations where core has a square structure and core is not large.		Use pressure plate to fix, suitable for fixing multiple cores

7. Guide sliding form of slider

Sliding block must move smoothly and stably during guide sliding to ensure that sliding block does not jam or jump during mold production, otherwise it will affect finished product and mold life. (Hyperlink of pressure plate specification) Commonly used guide slide form is shown in figure below.

Simplified drawing	Illustrate	Simplified drawing	Illustrate
	It is difficult to process in one piece and is generally used in situations where mold is small.		It adopts form of pressure plate and central guide rail, is generally used in situations where slider is long and mold temperature is high.
	Rectangular pressure plate is simple to process, has good strength, and is widely used. Specifications of pressure plate can be found in standard parts list.		It adopts “T” shaped groove and is installed inside slider. It is generally used in occasions with small space, such as slider inside running.
	“7” shaped pressure plate is used, which is simple to process and has good strength. Generally, pin holes are added for positioning.		Adopts embedded T-shaped groove, which has good stability and is difficult to process.

8. Calculation of tilt slider parameters

Since undercut surface of finished product is in an oblique direction, movement direction of slider must be consistent with oblique surface of finished product, otherwise finished product will be strained.

(1). Relationship between core pulling direction of slider and closing angle of parting surface is sliding moving die of slider. As shown below:

α°= d°-b°d°+ b°≦25°
c°=α°+(2°-3°)
H = H1-S *sine°
S = H1 * tgd°/ cosb°
L4 = H1 / cosd°

(2). Relationship between angle of slider body and closing angle of parting surface is slider body to fixed mold. As shown below:

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9. Female mold tunnel slider

1. Application features
a. Product is undercut molding on the side of female mold
b. Appearance of product allows traces c. Slider forming area is not large

2. Schematic diagram of female tunnel block is as follows: (hyperlink 2183 animation)
Clamping state

First mold opening

Second mold opening and ejection state

Third. Design considerations

a. Thickness of upper fixed plate H2≥1.5D (D is diameter of large tie rod; calculation of diameter of large tie rod is calculation of large tie rod of super link three-plate mold; H2 thickness of upper fixed plate)
b. Depth of dial block inserted into upper fixed plate H≧2 / 3H2
c. Make a taper on right side of sprue bushing and close mold. And it must be installed on upper fixed plate to prevent nozzle on molding machine from separating sprue bushing, which will cause drawing phenomenon and inconvenience to retract, affect next injection.
d. Shift block must escape material in female mold plate.
e. Wear plate should be 0.5mm higher than female mold plate to protect female mold plate. And support shift block prevents shift block from deforming under force.
f. Limit stroke of small tie rod is S≦2 / 3H1 to facilitate mold clamping. (H1 is height of slider)
g. Front end of shift lever is best equipped with a fixed block, which is easy to adjust and easy to process, forming a three-point support to increase strength of shifting block.
h. To make assembly of wear block smooth, point E is required to be on the right of point D. As shown below:
i. When assembling slider seat and shift block, pay special attention to relationship between size B and B1, which should be B> B1, but for smooth assembly, mold plate part behind slider seat can also be dug out.

Fourth. Calculation formula and precautions for double “T” slots:

As shown in picture above
S3 = H *tgγ(H is descending height of slider, that is, stroke of small lever; γ is angle of block);
S2 =δ2 *cosγ(Δ2 is gap between shifting block and sliding block, generally 0.5mm);
S = S3-S2 = H *tgγ-δ2 *cosγ=(H *sinγ-δ2)/cosγ(S is horizontal movement distance of slider);
S4 = δ1 /cosα(Δ1 is gap between sliding block; is inclination angle of sliding block);

In above picture, (see right picture) β=α+ 2°~3° (mold opening and interference friction are available), slide insert can be smoothly embedded in male mold core, requiring S1>S or opening male mold plate.
H≥1.5D (H is mating length of diagonal brace pin; D is diameter of diagonal brace pin) Double T-slot mechanism example

10. Female mold explosive slider

(1). Explosive slider applicable occasions
Generally, it is formed on the side of female mold and adheres to molding area of slider, especially slider is used when female mold side is deep. (Picture below is a typical example of explosive slider:)
(2). Schematic diagram of fried slider is as follows:

(4). Design requirements and precautions of explosive slider are shown in right picture:
a. Bottom wear plate should be inclined to reduce wear between slider and male mold plate, generally 1.5˚~3˚, and assembly position must be at 3/4 of center of gravity of slider.
b. S1> S (S is horizontal movement distance of slider)
c. Wear plate at the top of slider should be 0.5mnm higher than top of slider
e. Angle between stopper and grab hook γ> inclination angle of wear plate f.β=α (β is angle of “T” groove; α is angle of limit rod).
g. Length of T block should be as long as possible, 10mm higher than female mold plate.
h. Head of slider should be fitted with a clamping screw, mold should be assembled properly, and trial mold should be removed.
I. Screw of lock T-block should be perpendicular to T-block j. Head spring requires weight of slider.
k. Front of sliding block is set to knife plane l. Limit grooves on both sides of slider.
m. Top of slider must be a datum plane, which is suitable for mold assembly and processing datum, generally above 8mm.
n. Explosive sliders must be made of shoulders (positioning wings) to facilitate mold clamping and have a benchmark.

(5). Precautions for extra deep explosive slider:
b. Guide rod should be installed from female mold plate
c. Female mold plate should protrude from male mold plate to prevent female mold plate from lifting out and increase strength of mold
C. Make wear-resistant plates on protruding outer side of female mold plate to prevent wear and easy adjustment
d. Other precautions are same as above

11. Delay slider

1 Outer slider of finished product has a large core pulling force to prevent finished product from pulling deformation

12‧Slanted pin slider

Applicable range of inclined pin slider is generally used when finished product has a slider mechanism, and finished product also has an undercut along direction of slider movement. In this case, inclined pin slider can be used.

Inner slider

Use boss form (as shown below)

In above figure, S1 = S + 1mm or more (S is back hook distance; S1 is sliding distance along slope)
S2 = S1 /cosβ (S2 is relative horizontal distance of slider; β is inclination angle of slider) S2 = S3 = (H1 *sinα-0.5)/cosα (H1 is relative vertical height; α is tilt angle of diagonal brace pin α≦ 25)°
γ＝α＋ 2°~3°
H≥1.5D (D is diameter of diagonal brace pin; H is mating length of diagonal brace pin) detailed size calculation hyperlink calculation of inclined slider

Calculation and strength check of pumping force

1. Calculation of core-pulling force. As plastic shrinks after mold is cooled, it includes mold core and other mechanical parts (such as slanted tips, sliders, inserts, etc.). Therefore, when designing slider, tightness of finished product on the slider should be considered. Force state diagram is as shown on the right, note:
F = F4 *cosα-F3cosα=(F4-F3)*cosα. where F — core pulling force (N); F3 — F2 lateral force (N) F4 — core pulling tension (N );
α-Demoulding slope. Since α is generally larger, cosα=1, which means F = F4-F3 and F2 = F1-cosα
F3 =F2tgα=F1cosα*tgα= F1 *sinαF4 = F2 *μ=μ-F1cosα ie F = F4-F3 =μ*F1cosα-F1sinα= F1 (μcosα-sinα) where F1 —–Packing force of plastic to core (N) F2 —Normal pressure perpendicular to surface of core (N) μ-Friction coefficient of plastic to steel, generally about 0.2 and F1 = CLF. Where
C —-Average perimeter of section where core is wrapped by plastic (CM)
L —Length of core wrapped by plastic (CM)
F0 — Packing force per unit area, generally 7.85~11.77MPA, that is F = 100CLF0 (μcosα-sinα) (N)

2. Diameter of diagonal brace tip diameter check is affected by its own tilt angle, length and required demolding distance. Therefore, in design process, several parameters need to be adjusted with each other to get best rationalization. Slider moves smoothly, and specific calculation formula is as follows:
Note: P — maximum bending force of inclined pin in figure
L —Bending moment
P1 —core pulling tension
H —Distance from center of core hole to point A
α°—Inclination angle of diagonal brace pin
P2 — Mold opening force is obtained from attached drawing:
P = P1 /cosα (KN) M bend = PL (KN) and M bend≦[σ bend] * W (KN) ie PL = [σ bend] * W (KN) where
W-bending section coefficient
[σ bend] — allowable bending stress (13.7KN / CM2 (137MPA) for carbon steel
M-bend-maximum bending moment oblique
That is W = (πd4 / 64) / (D / 2) = πd3 / 32 = 0.1d3 0.1d3 = pL / [σ] bend = PH / ([σ] bend cosα) D = 3√(ph / 0.1 [σ ]Bend cosα (cm)

4. Section size of block

Principle of checking cross-sectional dimensions of pull block is consistent with calculation principle of diagonal brace tip. Just change last step. Formula is as follows:
W = bh2 / b When b = 2 / 3h, W = h3 / 9 h3 / 9 = pL / [σ] bend = PH / ([σ] bend cosα) H =3√9PH/([σ] bend cosα ) (Cm) when b = h, W = H3 / b] H = 3√(6ph / [σ] bend*cosα) (cm) where h — long side of section of block (cm) b– -Short side of block section (cm)