The thermoform tooling process can be quite complex and involves a number of technical steps that require precision parts and handling. It is critically important to choose the best materials for the job, as mistakes and sub-optimal performance can cost a company time, money, and resources.
One of the decisions that manufacturers must make is what material mold to use. Cheap materials, such as wood or wood composite, while they might be okay for a small, in-house project that’s meant to quickly test equipment, a more permanent solution is needed for most thermoforming needs. On the other hand, more expensive materials, such as steel injection molding, take more time to make and provide for less flexibility in the fabrication process.
Aluminum mold plates offer the best combination of cost savings and adaptability thanks to its ability to offer close tolerances, tight specifications, and sharp detail, as well as the relative ease of using it to produce parts of various sizes and shapes.
What Is An Aluminum Mold Plate?
Part of the thermoform tooling process, molds are rigid frames that form liquid or plastic materials into a variety of shapes. Any number of molds and mold techniques can be found in the industry, including blow molding, injection molding, compression molding, and extrusion molding.
Aluminum continues to grow in popularity as a choice for thermoforming molds, in no small part because aluminum injection molds can be reliably used to produce more than one million parts over their lifetime. Additionally, the design and production of aluminum molds are cheaper than using steel, and it allows for more flexibility in the production process.
A wide variety of aluminum alloys are available on the market today. When deciding which alloy to use, factors to consider include the material’s dimensional stability, part geometry, mold operating temperature, and welding effects.
For example, when choosing an aluminum alloy, you must know whether or not a mold will be exposed to higher temperatures. The following are some approximate figures for how various alloys respond to high temperatures:
A 7xxx series alloy has a yield strength of 51,000-71,000 psi at 75°F, and its strength is reduced by approximately 63 percent at 300°F, and reduced by around 82 percent at 400°F. For a 6061 alloy, the yield strength is 40,000 psi at 75°F, with a 22 percent reduction at 300°F, and a 62 percent reduction at 400°F.
For 2xxx series cast mold plate, the yield strength is only 20,000 psi at 75°F, but with only a 22 percent reduction at 300°F and a 45 percent reduction at 400°F. The 2xxx series is more resistant to thermal fatigue because it does not undergo the same heat treatment as some of the other mold alloy series. The fact is that cast mold plate materials derive their properties from the alloy composition rather than from the heat treatment. The same properties apply to the 5xxx series cast plate material, a popular choice for prototype molds.
Different series of alloys react differently to being heated. The 2xxx and 5xxx series cast mold plate maintain their original properties upon cooling to room temperature. However, after being exposed to extremely hot temperatures, alloys that have been heat-treated do not return to their original strength. For example, the 7xxx series alloys may lose 50 percent or more of their strength after being exposed to temperatures greater than 400°F.
Some thermoforming aluminum molds require welding. New techniques and materials have been developed to minimize the effect of heat on the mold caused by welding. Because applying the welding heat to a material that has been heat-treated can cause a loss of strength, as illustrated above, welding filler wire has been developed to work with specialized 7xxx series mold alloys. The filler wire offers improved color matching and reduced porosity in the welded area. There have even been advances in welding techniques for the 7xxx series aluminum. Using a DC pulse welding technique reduces the heat on the welded area, meaning there is less strength reduction.
For cast mold plate alloys in the 2xxx and 5xxx series, there are also welding techniques that employ specialized filler wires, shielding gas, and DC pulse procedures. These alloy series do not encounter the same problems when it comes to over heating, because their properties come from the base alloy composition, meaning they offer increased resistance to thermal fatigue.
Industries That Use Aluminum Mold Plates
Because of its affordability and flexibility, aluminum mold plate is commonly used for thermoform tooling across a range of industries, such as automotive, medical, aerospace, electronics, and consumer goods. Everyday products that can be made from thermoforming include plastic trays, food containers, medical devices, vehicle doors and panels, refrigerator linings, and machine housings, bezels, and enclosures.
Summary
This is what makes aluminum mold plates such a good choice. With so many different alloy molds to chose from, it’s easy to find just the right material to meet whatever demands your application requires. Aluminum mold plate, with its variable attributes and adaptability, helps save time and money for manufacturers across nearly every industry.
Sources:
http://www.moldmakingtechnology.com/articles/applying-the-right-alloy
