Components of a Mold

There are many benefits to working with standard components. For starters, the leadtime on a project can be reduced. The time that would have been spent squaring up blocks, machining, heat treating and grinding all of the slide components can be used to focus on the molding area—cores, cavities, slide faces, etc. Programming time for the slide components is eliminated, and once the mold designer is tuned in to the idea of using standard slides, design time should also be reduced.

What about cost? It is debatable. Depending on how long you determine it takes to manufacture all of the components of a slide assembly and what you use for a shop rate, the price of standard slides could be considered a bargain or overpriced. You will need an accurate assessment of the time it takes to design and build a slide assembly.

Source: Calculating the Benefits of Standard Slides

Many problems can be solved by simply providing enough preload force on the core to prevent movement. Nonetheless, blocks and pins only provide a backstop to a core and often provide little to no active support to prevent movement. These methods rely on steel’s mass or volume to minimize flex and movement to yield a “good enough” result. In this way, there is always some reaction to the forces of injection from the perfect positional geometry, rather than a proactive preloading of metal into position.

Source: How to Solve Core Pull Flash and Part Issues

Using self-lubricating mold components has significant benefits, but only if the molder truly understands what these components are: essentially a conventional component with lubricant added in the form of graphite plugs. Graphite is a solid lubricant, so, for those molders who are used to working with liquid lubricants such as grease or oil, a solid lubricant may seem a little strange, and so might the graphite itself.

Graphite has a near-zero coefficient of thermal expansion, which means that it doesn’t expand and contract with temperature changes like ordinary substances do. It’s not a metal, but it conducts electricity like one. It also doesn’t melt. Instead, it remains a solid at temperatures ranging to 10,000°F and then becomes a gas. It’s not very strong, but it can be formed into composites with incredible strength.

Features and Functions
The main function of a self-lubricating mold component is to guide and control movement. Such a mold is typically made of aluminum bronze, an excellent bearing material, with embedded graphite plugs. The mating part of the mold (the one being guided) is usually made of hardened steel. As the two parts move relative to each other, the very slippery one-atom-thick sheets of graphite peel off and become distributed over the wear surface. With each cycle, a bit more graphite is distributed, so the process continuously replenishes. Graphite doesn’t evaporate and is relatively inert, so the lubrication it imparts is essentially permanent.

Although self-lubrication adds about 20 percent to the cost of a conventional component (one that must periodically be greased), there are several benefits for this extra cost:

• Maintainability. The need for periodic greasing is eliminated, which means, over the life of the tool, the savings in preventive maintenance (PM) is likely to be several times the upfront cost for self-lubrication.

• Reliability. Lubrication is always present, eliminating the risk of failure or shortened life due to skipped PM. Also, the absence of liquid lubricants means there is nothing to attract grit and other contaminants to wear surfaces.

• Simpler designs. With self-lubricated components, there is no need to make provisions for periodic lubrication, which removes a design constraint, potentially reducing costs and/or improving functionality.

• Clean operation. No liquid lubricants to drip or spatter on parts means a very clean operation with less scrap and rework.

Source: Understanding Self-Lubricating Components