In injection molding, whenever a plastic part has undercuts, the use of a slider is necessary. Otherwise, the plastic part cannot be ejected properly. For this to succeed, the right material with the right properties is needed.
Since many injection molded products have special requirements, auxiliary equipment is needed from time to time to form complex geometries, especially when it comes to releasing the finished product when the mold is opened. This is where a so-called slider is often used as a core-pulling mechanism.
Sliders are always necessary when the plastic part cannot be demolded without moving tool parts. There is a great variety of slide mechanisms. At its basic level, a slider is used to convert the vertical motion of opening or closing the mold into a horizontal one.
What types of slides are used for injection molding?
Usually, Slides are most frequently used to relieve external undercuts. Generally, slides are categorized by their driving mechanisms:
The most common and versatile slide is the «Cam Pin Slide». Pulling the inclined pin out of the inclined hole drives the slider back. A spring holds the slider in the retracted position. When the press is closed, the cam pin returns to bring the waiting slide almost back to the forming position. Eventually, the lock rests against the back of the slide, driving it to its original position and clamping it there during the next shot.
The cam slide is very similar to the above but uses a metal cam instead of a pin. Furthermore, it is limited to strokes of about 0.080 inches. It is best used to relieve very small localized undercuts.
Other processes involve a hydraulic slide, a locking hydraulic slide, or spring-actuated slides.
What are the requirements for Sliders?
There are certain properties that sliders do need to have to function appropriately. These included in particular:
- Excellent sliding properties
- Good wear resistance
- Great heat conductivity
As the name suggests, slides must above all have good sliding properties so that the slide slides smoothly in the mold and does not block the mold. This would lead to costly repair of the mold. Furthermore, certain wear resistance is needed to ensure long service life. And as often slides are too small to make cooling channels, or it is impossible to attach a water connection to the slider, the slider material must take up the complete heat. Therefore, great heat conductivity is also preferable.
What material is best used for Sliders?
Based on these requirements, not every material is suited for this task. Aluminum bronze offers great advantages when it comes to sliders. The material is well-known for its moderate hardness and outstanding conductivity while offering very good sliding properties. Even though their sliding properties excel when in contact with stainless steel, aluminum bronze also works well in the plastic industry.
AMPCO® 18, for example, is a very versatile, high-performance alloy. Its compact grain structure and high physical properties result from phase distribution and hot working during the extrusion phase, making it a superior bearing material defined by good fatigue resistance.
Picture: Slide plate made of AMPCO® 18
AMPCO® M4 is a tough alloy, offering even more hardness while maintaining good sliding properties. AMPCO® M4 has mechanical properties far beyond the range of conventional commercial nickel-aluminum bronzes. The increase in the Al and Fe content in the alloy results in a material in which the hard gamma 2 phase is present. By expert metallurgical control, this hard constituent is uniformly distributed giving the alloy its unique performance qualities and the ability to resist wear.
Therefore, we suggest using our premium aluminum bronzes for sliders: mainly AMPCO® 18 or AMPCO® 21. However, AMPCO® M4, AMPCO® 18.22, and AMPCO® 18.23 can be used too.
Want to learn more about plastic injection molding and why copper-based alloys are the right choice for your plastic tooling operations? Download our free technical paper «A Rookies Guide to injection molding - How copper alloys add direct value to the plastic industry» now.
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