Are Aluminium Moulds Right For You?

The use of aluminium moulds in injection molding is an emerging trend because of its ability to reduce cycle time by as much as 50% when compared to P20 tool steel.

Aluminium molds are finding application in automotive, consumer electronics and industrial markets.

There are several benefits to using aluminum molds in injection molding but there are also a number of challenges that need to be taken into consideration before deciding if it is right for you.

The Benefits

For injection molders:

  • Faster cycle times – up to 50% compared with P20 steel
  • Increased productivity which reduces the number of molds and molding machines required
  • Less wear and tear on machines because the moulds are lighter than steel
  • Lighter mould means reduced energy consumption by the machine making it cheaper to run
  • Can use glass filled materials

For injection mold makers:

  • Easier to machine than P20 and H13 tool steel so delivery lead times are shorter
  • Less wear and tear on machinery
  • Reduced machine energy consumption making them cheaper to run
  • Easier to handle and transport

The Challenges

For injection molders:

  • Changing mindset. There are some practical differences required with aluminium moulds compared with tool steel moulds. Daily mould maintenance is required to protect the shut off edges so flash doesn’t develop on the part. Also, lower injection pressures and clamp tonnages are required.
  • Unpredictable wear on molding surfaces especially when processing parameters are set too high (such as high injection pressure) which puts extra stress on the aluminium mould.
  • Limited production quantity (up to 1 million shots)

For injection mold makers:

  • Part design. Aluminium molds will not suit all part designs. Tall parts that require a lot of cavity machining time in the mould will give the greatest time cost savings when compared to tool steel.
  • Mold design. How to design and build a mold so that it lasts for the required life production run? Some mould makers use steel inserts in the shut off area for greater reliability.
  • Mould polishing. Polishing aluminium is different to polishing tool steel. Care must be taken when buffing not to generate too much heat or the moulding surface will be damaged and will show on the molded part.

Grades of Aluminium

There are a number of commercially available aluminium alloys made for injection molding. They include Alumec, Bohler 7075, Hokotol, Alumold 500 and QC-10.

Some aluminum molds have made more than 1,000,000 automotive parts when properly maintained.

Aluminium can be hard anodized, hard chromium plated or nickel plated for increased hardness, wear resistance and corrosion resistance.

Aluminium can also be welded. Good for repair jobs.

Aluminium Moulds In The Mining Industry

Each year, the mining industry requires millions of screening panels made from polyurethane plastic. There are hundreds of different panel designs so the injection moulding process requires frequent mould changes.  To make the changes as easy as possible only core and cavity of the mould are changed and these parts are made from aluminium so one operator can change to a different panel design in less than 30 minutes without the use of lifting equipment.                                                                                                               

The main problem with using aluminium cores and cavities is that they are often damaged during change overs which results in flash on the plastic panels. This flash needs to be removed on every panel produced which is a secondary operation and reduces productivity.

Additional Comments

Aluminium moulds are not for every molder. They will benefit those who have life time production quantities of less than 1 million parts and are committed to solving the challenges they present.

Its not as simple as saying you would like to make all of your future moulds from aluminium. R&D must be done and your mould maker must support you.

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Plastic Today Magazine August 29th 2012 Article “ Aluminum vs. steel tooling: Which material is right, and how to design and maintain?” by Clare Goldsberry

Injection World Magazine June 2012 Article “Aluminium tooling proves its value in auto part production”