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19.Proposal No.3 to achieve 'factor 4' in molding factories

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19.Proposal No.3 to achieve 'factor 4' in molding factories

The President's Green Column

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19.Proposal No.3 to achieve 'factor 4' in molding factories

- New mold technologies for high cycling -

In my previous entry, I mentioned proposals to minimize the wastage and troubles with cooling water in the molding factories
In this entry, I would like to explain proposals to increase productivity with new molding technologies.

Proposals to improve Productivity

The following can be considered to improve productivity.

  • 1.Shortening of molding cycle
  • 2.Reduce occurrence of defectives
  • 3.Reducing the tendency of changes and shortening the time of changing

From the above, I would write about the cooling of mold that contributes to the shortening of molding cycle.

Issues with regards to cooling of molds

In order to cool the melted resins in the mold, it is necessary to create pipes for cooling water to pass through. Due to technical constraints, only straight water pipes can be created.

However, it is almost impossible to cool 3D molded products with straight water piping at a fast rate. The molding cycle is being decided by the time taken to cool the most difficult to cool part. Hence, it is the ideal to cool all parts of the molded product at a uniformed short time.

Matsui would like to propose the following 2 techniques to achieve this.

3D Cooling Water Pipes as a result of Laser Sintering and Milling Technology

First, I would like to propose the Laser Sintering and Milling Technology. Through this, 3-dimensional cooling pipes can produced to shorten time required for cooling.

Metal powder are laid in a diameter of 20μand thickness of 50μ. They are then laser sintered, melting and uniting only parts that are required. This is repeated at high speed in an upward manner. At such, a 3-dimensional and high flexible design of mold can be constructed. In conclusion, molds can be made as a single structure, have 3-dimensional cooling pipe and porous structure to prevent cavity gas regardless of the complexity in design.

The below shows molded examples of shortened molding cycle by 3D water pipes.The cooling time is shortened from 25 to 10 seconds.

Illustration 2 shows a sprue bush that has a slit form cooling water channel internally. This is also made with the Laser Sintering and Milling Technology. Sprue runners are generally thicker than molded products and requires a longer cooling time. In such cases, required cooling time can be greatly reduced by the sprue bush with cooling channel.

図2.水管付スプルーブッシュ

Matsui works hand-in-hand with OPM Laboratory, who is experienced in the Laser Sintering and Milling Technology. The milling machine is also brought into Matsui and we take responsibility from the proposing to the actual manufacturing. The above is an actual example from OPM Laboratory.

In addition, the porous structure prevents cavity gas fro accumulating in the mold.

Technology of Speedy Cooling by Latent Heat

The 2nd proposal to cool melted resins more efficiently is the Technology of Speedy Cooling by Latent Heat.

Illustration 3 shows an example of this technology. An evacuated chamber is created according to the shape of mold, in which water in the chamber is being decompressed to boil at 30℃~40℃. Heat exchanger that cooling water passes through is then places about the mold.

When melted resin is being injected into the mold, the part of the mold near the melted resin would raise in temperature, leading to the molding of water in the mold. Hot steam rises and is cooled by the heat exchanger, returning back to the bottom as water.

The repetition of the process above quickly transfers heat of melted resins to the water, which is vaporized and cooled by cooling water. The mold itself becomes a heat pipe, not only does it cools quickly but also uniformly.

Illustration 3: Technology of Speedy Cooling by Latent Heat

図3. 潜熱を利用した金型高速冷却技術

For the examples in picture 3 (below), molding cycle has been reduced by 35% from 11.8→7.0 seconds and 3.8→2.5 seconds respectively.

写真3. 潜熱を利用した金型高速冷却技術による成形品事例

Matsui works closely with the patent holder of this technology, Ritemp. Upon providing the drawing of mold without the cooling pipes, Matsui would design the mold incorporating this cooling technology.

Other proposals to enhance productivity

In order to increase productivity, on top of shortening the cooling time of molds, it is also highly advisable to work on shortening the time consumed to change material and molds, and the reduction of defectives due to gas.
I would like to conclude this column in my next entry.

20 Nov 2009 Hironobu Matsui

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