As a mold mechanism, slider has core function of solving undercut problem. It cleverly converts vertical action of mold opening and closing into horizontal action, so as to adapt to change of undercut position in male or female mold. Slider mechanism is formed by combining several basic mechanisms and has a variety of structural forms.

 

In plastic molds, mold opening action is cleverly utilized to promote relative movement trend between diagonal support pin and slider. This trend promotes slider to produce two different modes of movement in mold opening direction and horizontal direction, so that slider can smoothly detach from undercut. This process can refer to scene shown in figure below.

 

During mold opening process of plastic mold, slider needs to move a certain distance until front and rear molds are completely separated. In order to ensure that slider can return to its position safely and accurately, a positioning device must be installed to fix its position. This positioning device needs to be flexible and reliable to ensure that slider can stay firmly in preset position to avoid collision due to misalignment of bevel and hole during mold closing.

 

Poly screw positioning
Its advantages are easy processing and intuitive operation; however, it also has disadvantage of being easily damaged. This positioning method is particularly suitable for small sliders in X direction (horizontal direction) and sliders with long strokes. In addition, it can also assist slider to achieve delayed mold opening, that is, when bevel is not in effect, slider is fixed by blocking effect of ball.

 

Spring and limit screw positioning
Advantages of this positioning method are easy processing and safe positioning. It is often used for sliders in X and Y directions, especially for sliders with short strokes. In design of spring, we need to pay attention to preload of slider spring, that is, after mold is opened and closed, spring still needs to maintain a certain preload. This preload balances gravity of slider through elastic force generated to prevent it from moving back. We can calculate free length of spring by following formula:
L0(free length) = (L stroke + 3~5 preload) / 40%
At the same time, depth of spring hole also needs to be reasonably designed to ensure that spring can work properly. Calculation formula is:
H (spring hole depth) = L0 (free length) - preload - stroke
Through reasonable selection of these design parameters, we can ensure that application of spring and limit screw positioning in slide is safe and effective.

 

Material selection of slide accessories
In design of slide, selected material is crucial to its performance and service life. Common slide accessories include metal, plastic and composite materials. Metal materials such as steel have high strength and wear resistance, which are suitable for slides that need to bear large loads; while plastic materials are widely used in some slides due to their lightness and corrosion resistance. In addition, composite materials combine advantages of metal and plastic, have good strength and corrosion resistance, providing more options for slide design. When making specific choices, it is necessary to comprehensively consider advantages and disadvantages of various materials according to actual needs of slide and working environment to select the most suitable material.

 

Product and mold slider
In slide design, slider is a key component, and its performance directly affects quality of product. Sliders, locking blocks, pressure blocks, diagonal support pins, and wear blocks will experience long-term wear during operation. In order to extend service life of these parts, they must be surface nitrided or heat treated to reduce wear rate. This not only helps to improve quality of product, but also ensures smooth operation of mold slide.

 

Case 2: Wear problem of slides and wear blocks
In process of slide design, wear of components such as slides and wear blocks is an issue that cannot be ignored. These components will gradually wear due to friction during long-term operation, which will affect quality of product and smooth operation of mold. In order to solve this problem, these components are usually surface nitrided or heat treated to reduce their wear rate, thereby ensuring quality of product and stable operation of mold.

 

Case 3: When product has external thread features, it is usually considered to use slide demolding method for processing. However, not all products with external threads are suitable for this method. Therefore, it is necessary to use demolding angle analysis to determine whether there is an undercut phenomenon in slide demolding direction and to clarify specific value of undercut. If undercut is small, for example, only a few millimeters, it is necessary to further consider whether product tolerance can offset this effect.

 

In order to ensure that product does not stick to front mold, we designed a delayed mold opening function for slide. During mold opening process, front and rear molds have been partially opened, but slide has not yet slid. With the help of clamping force of slide (achieved by buckle), product can be firmly retained in rear mold. Since most of columns of product are located on slide, a water cooling system is specially designed to ensure smooth sliding of slide.

 

Case 4: In mold design, in order to prevent product from sticking to front mold, we introduced a delayed mold opening function for slide. This design ensures that at the beginning of mold opening, front and rear molds are partially opened, and slide has not started to slide. Product is firmly fixed in rear mold through clamping force of slide, that is, effect of buckle. In particular, for situation where most of product columns are located on slide, we carefully designed a water cooling system to ensure smooth movement of slide.

 

Case 5: In mold design, in order to ensure smooth sliding of slide, we designed an efficient water cooling system especially for situation where product column is mainly located on slide. This system not only helps smooth movement of slide, but also effectively extends service life of mold.

 

In mold design, movement of ejector pin is crucial. We need to ensure that ejector pin does not eject when drilling between two workpieces to avoid possible misalignment and clamping problems. To solve this problem, we usually add a runner ejector sleeve or runner insert to outside of ejector pin. In addition, design of push plate also needs to consider space between it and product to ensure that product can be separated smoothly during ejection. Specifically, push plate will first empty ejector for a distance, then contact product for ejection. Sprue ejector is different. It is ejected synchronously with sprue material. Once ejector plate moves, sprue will be immediately pushed upward, and product will move later, thereby realizing automatic separation of sprue and product. When installing ejector pin, you need to pay attention to tightening of screws on upper surface. Therefore, before tightening screws, you need to ensure that ejector pin head has been positioned to prevent it from rotating with screw.