Product name: Lower Finish Panel
Compound: PC / ABS
Shrinkage: 1.006
Number of cavities: 1
Mold life: 500,000 times
Product dimensions: 96.31x245.72x134.15
There are multiple column positions and hole positions on the product, so axial direction of column positions and hole positions is used as direction of demoulding. As shown in figure above, purple surface is injection surface on fixed mold side of product, and blue surface is injection surface on movable mold side. Analyze structure of product on mold according to direction of demoulding. It can be seen that two sliders need to be made on both sides of product, and shape of product on one side is as shown (shape on both sides is same)

 

 

There is a circle of bone positions under round hole, which is at two angles to direction of demoulding, as shown in figure. Blue surface is rear mold surface, purple surface is undercut surface, and there are two square holes on both sides. Therefore, a special core pulling mechanism needs to be designed to form gate position here.

 

 

 

 

Name of this core pulling mechanism can be called one-to-four delay core-pulling slider.

 

 

 

 

 

 

Two holes on both sides of bone position of product circle are formed by two movable rows.

 

Small sliding block forms a sliding fit with outer movable sleeve and 7-shaped ear position on side, small sliding block can slide with sleeve along direction of 7-shaped guide groove.

 

 

 

Lower end of small slider is J-shaped, matching with rectangular hole on center insert, and can slide relatively.

 

Therefore, there is relative movement between two small rows and movable sleeve, small rows and central insert, central insert and movable sleeve. Their power and movement sequence control are derived from large row underneath, which is driven by oil cylinder.

Movable sleeve slides down, small slider slides off, and center insert does not move. Lower end of purple movable sleeve and large slider are connected by a sloped T-shaped groove, upper part of step is a sliding fit of straight body surface and rear mold, rear end of large slider is screwed to oil cylinder.

 

 

After mold is opened, cylinder is pumped backwards, pulling large slider back together, and movable sleeve falls back along direction of core pulling under action of inclined T shaped groove. Large slider and central insert have a plane contact, which is used to control delayed core pulling. Within a distance from beginning of oil cylinder driving large slider back, due to effect of flat position, center insert is stationary relative to mold and product, movable sleeve slides between mold and center insert.

 

Two small sliders on the head are matched with sleeve through a 7 shaped groove. Direction of 7 shaped groove is at a certain angle relative to direction of movement of sleeve. Lower end of small slider is J-shaped and cross section is rectangular, both sliders slidingly cooperate with center insert. When sliding sleeve is pulled down, small slider is pulled out of core under action of 7 shaped groove and center insert hole to pull out undercut.

 

Relative position diagram after small slider core pulling:

 

 

Small slider, center insert and movable sleeve move back together to pull out core, and pull out all undercut surfaces. After small slider is pulled away by a safe distance, center insert completes horizontal distance on large slider. At this time, center insert passes through step surface of lower stage and is driven by sleeve to move relative to inclined surface of T-slot of large slide along direction of hole of mold meat sleeve.

 

 

Two small sliders are also moved down together by sleeve and center insert until all moving parts are completely disengaged from product surface and core pulling action is completed. After core pulling is completed, relative positions of small slider, movable sleeve and central insert are as follows:

 

 

 

After core pulling operation is completed, product is ejected by ejector pin.

 

As shown in figure above, A is product undercut distance, and stroke of small slider is C. Due to space limitations, stroke of small slider is approximately equal to product undercut plus 0.5mm, that is C = A + 0.5, B is stroke of movable sleeve during first core pulling, C is stroke of small slider, that is, core pulling distance, and M is angle between 7-shaped groove and moving direction of movable sleeve. Three sides B, C, and L form a right triangle. When determining stroke, directly draw above right triangle, and required lengths can be obtained according to known conditions.

As shown in following figure, B is delay distance of center insert, that is core pulling distance of first core of movable sleeve, D is sliding distance of center insert on the plane of large slider, E is sliding distance of movable sleeve in slope T groove of large slider. Three sides B, E and F form a triangle. We can find values of F and E according to known condition B and angle G.

 

In figure below, H is product undercut, J is core insert stroke, J is greater than or equal to H + 2mm, K is movement distance of large slider, I is distance that movable sleeve and central insert slide together in slope T slot of large slider, N is angle between T slot and direction of movement of large slider. In the figure, I, J, and K together form a triangle. We can find values of K and I according to known condition H and angle N.

 

We must know working stroke of cylinder when choosing type of cylinder. In this case, working stroke of cylinder is total moving distance of large slider: K + F, and then select cylinder according to calculation result plus margin of 10 to 20MM.