Myths have invariably been around: the entire world is flat and the sun revolves around the planet earth- for example. The realm of manufacturing is not any different with its own false beliefs. Today we have the myth that aluminum tooling is “junk tooling or prototypes only”. This can be a stereotype that has grown from earlier grades of Medical PCV sheet which were gummy, tough to cut and improperly employed in a manufacturing environment.
The introduction of aircraft grade 7075 aluminum brought forth a durable and quality product. In 1998 the SPE and Douglas Bryce wrote “Plastic Injection Molding: Mold Design and Construction Fundamentals” that discussed the quality of 7075 as well as the capability to produce numerous parts. However, many manufacturers failed to follow his recommendations. Instead, many chose the wrong aluminum alloy and did not follow good tooling practices. Unfortunately, the damage to aluminum’s reputation had already been done.
Cost factors are forcing manufacturers and major OEMs to consider an additional look at aluminum. Back in 1991 IBM did a five-year study on aluminum tooling with many credible findings. Currently, Honda’s ongoing aluminum tooling study can be a success along with other companies are taking a renewed interest in the charge savings that aluminum offers. Unfortunately, old beliefs are difficult to conquer.
Aluminum can be used production volumes: The mistaken belief that only steel alloys including H-13, S-7, stainless steel or P20 steel should be useful for production molds can be quite a costly one. An aluminum mold can provide volumes between 100,000 approximately 1,000,000 components. This is due to current aluminum grades that are heat treated as part of their creation process resulting in a 6 – 18RC hardness. Surface coating treatments can harden aluminum around 56 – 62RC based upon this process. When these hardness levels are compared to P20’s 28 – 32RC and 420 stainless steel’s 34 – 38RC (pre-heat treated), this estimate of 1,000,000 seems conservative.
All resin types works extremely well on aluminum: Aluminum’s excellent thermal conductivity allows resins to circulate more evenly than steel. Certain resins like clear acrylics and polycarbonates frequently have processing issues on account of cold and warm spots inside a mold. Aluminum’s even heat dispersion reduces these areas resolving bubble along with other aesthetic issues. Other high-temperature resins can run successfully in aluminum with cartridge heaters that happen to be normally combined with steel molds. Difficult-to-fill resins having a high viscosity rate also make use of even heating mainly because it reduces sheer stress upon the fabric by balancing the flow of material using a hot runner system. Glass-filled as well as other abrasive resins could be run with success given that special care is taken to either hard coat or steel insert critical areas. Glass-filled resins may actually run more proficiently with aluminum due to the consistent thermal conductivity that assists from the flow of resin. PVC is frequently incorrectly believed to be abrasive, during times of fact it is corrosive. For this reason steel alloys are chosen over P20. Both stainless-steel and aluminum are corrosion-resistant by nature. Aluminum forms a .000001 (microinch) self-healing layer as being a reaction to oxygen called aluminum oxide. The chromium in stainless-steel reacts the same way to oxygen forming a layer called chromium oxide. A few of the newer grades of aluminum have chromium added for greater corrosion resistance. There are surface hardening processes that really work well with PVC that will increase component output.
The saying “production” is subjective, as Tropical type blister aluminum can achieve high volumes: So how exactly does “100,000 – one thousand,000 production-quality plastic parts” sound? Not quite short-run or low-volume. For many projects this is ample for the whole project until the next design change or upgrade. Obviously higher production quantities can be achieved depending on the resin and design. Aluminum tooling can also be perfect for keeping marketplace share when bridge tooling is required. An additional benefit is that if the tool life is exceeded, aluminum is forgiving and easy to maintain or enhance to obtain those last few plastic parts up until the hardened steel production tool is prepared.
Unlimited surface finishes: Almost any surface finish or texture that may be used on a steel mold does apply with an aluminum mold. Including Class A diamond finishes (SPI A-1), that are essential for chrome plating. Certain grades of aluminum will be more suitable for this, which might also need a hard coating process to enhance this finish. Bead blasting or any aesthetic texture finish may also be achieved with success.
Faster process cycles: As outlined above, the thermal conductivity is really a benefit that eliminates many processing issues. Fast and also heating and cooling brings about less shrink and warpage issues from uneven heat dispersion. Less scrap is really a financial savings, but cycle times will also be reduced by 30 percent generally, bringing down overall piece price. As a way to run aluminum, a molder need to have good tooling practices and maintenance routines to prolong the tool life and fully realize every one of the cost and time savings. Including watching parting lines and shutoffs for wear to get rid of parts sticking and excessive wear. A sticking part can damage aluminum tools worse than steel. However, when the tool was built correctly and maintained to industry standards, it is really not a common occurrence.
Design modification: Commonly, many projects in the planning and design verification stages experience some type of design modification. Aluminum could not be easier to modify or groom for maximum efficiency when in the build or when the tool is running parts, modifications for the initial design or even to troubleshoot production issues are essential. Welding aluminum has become very successful recently, allowing consideration for cosmetic changes as well.
No design restraints: Complex design geometries that need under cuts, which require mechanical slides, lifters or hand loads can be done the same as in a steel mold. Careful project planning, a robust understanding of mold design, as well as experience with machining aluminum means there is no reason to never expect aluminum to keep up dexjpky71 dimensions. Steel inserts could be used to further maintain critical areas for higher volume projects. This can all be accomplished in a shorter time than traditional tooling because aluminum can be cut faster than other alloys.
Lower overall cost: Pricing is the 800 lb gorilla everyone wants to talk about. While PVC fluorescent slice costs more per pound than P20 and also other steel alloys, aluminum is lighter in weight so the cost per pound usually is less in total cost. Aluminum is easier and faster to reduce than steel; and, polishes faster, which reduces build time by weeks with substantial cost benefits. Even hard coating aluminum does not increase the final price of the tool significantly. Improved thermal conductivity decreases process issues, with less scrap and faster cycle times, which cuts down on the overall per piece price. Then consider less machine wear and less electrical costs because of improved efficiencies. Moreover, when the tool is no longer needed, aluminum is readily recycled.
In today’s economy and business climate every company that wants to stay lean and competitive in the industry should think about the cost savings from aluminum tooling. Although there were many improvements from the grades of aluminum alloys, proper design, tooling and molding practices should be considered to truly reap the benefits of this alloy. In 35 numerous years of aluminum tooling, the final five have been the highest due to attention that aluminum has finally been given. Like the majority of successful innovations that happen to be born from the desire to survive, aluminum tooling is not only the bridge to your faster product launch or the cost savings needed for the planned budget; it is a successful replacement for steel tooling with huge benefits that may still advance and influence the future of the plastics industry.