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Fuel Cell

Candidate on the electrical race

Fuel cell postulates as one of the future technologies for the future cars, but for us, manufacturers, being ready for the type of machining it will require...can be essential for the survival of the manufacturing companies.

New driving systems

Drive systems that can be operated with products from renewable energies are becoming more and more important as an alternative to the internal combustion engines (IC) which are currently suffering by international laws and available resources. In addition to the battery technology that is currently in the focus of attention, the Fuel Cell technology represents another possibility for the drive technology of electrically powered vehicles. Due to the special advantages such as the sufficient starting products hydrogen and oxygen, the low-emission end products, a higher efficiency than IC engines and the possibility of fast refuelling the Fuel Cell is a serious option for vehicle drives.

What implies this technology? New breakthroughs come with new challenges and the producers are wondering what production resources do they need to feed the demand of the market. 
New car models keep being launched to the market such as the Mercedes GLC F-Cell, coexist with more experienced cars such as the Toyota Mirai.
New driving systems

The basics!

First, let's go to the basics. What is a Fuel Cell car? These type of cars use an electrical motor connected to a battery. The electricity needed to run the car is coming from the battery which is charged by the Fuel Cell.

In a hydrogen Fuel Cell, the electricity is generated when molecules of hydrogen and oxygen reacts together, driving to a result of water (H2O), electrical and thermal energy.
Bipolar plates guides the reaction gases constant and evenly distributed in a specific structure over the complete active face of the catalyst layer. A single cell just generate 0.7 V (approx.). So, a stack of 250 to 1000 bipolar plates are necessary for powering one car.

There are several types of Fuel Cell. The Proton Exchange Membrane Fuel Cell (PEMFC) is mostly used for car mobility. The different types of Fuel Cell can be also established for many other applications like power supply, combined heat and power plant as well as aerospace and submarine applications. Not only hydrogen is used, methanol and methane can be used in some types of Fuel Cell.
The basics!

Production necessities

Regardless of the Fuel Cell, the bipolar plate thickness goes down to 50 µm. Currently each manufacturer is making their own design (no standard/dominant design yet).

Due to the high number of plates and the application where it is used, these plates have to fulfill high requirements in parallelism, flatness, contour accuracy and surface quality. And of course, low volume production costs are necessary for those high amount of plates.

There are several ways to achieve these type of production:
  • Progressive stamping
  • Hydroforming
  • High-Velocity forming
All of them will be as good as the tool used for them. And here is where Makino comes in place.
Production necessities

Forming die requirements

The tool used have really high accuracy requirements, especially on a long time processing part.
Here is one example of typical forming die requirements (varies slightly with real one):
  • Tolerances:
    • Contour accuracy in +/- 5 µm
    • Flatness in 10 µm
    • Parallelism in 10 µm
    • Roughness Ra less than 0.2 µm 
  • Materials:
    • approx. 60 HRC
  • Machining Times: 
    • approx. 150 - 200 hours
  • Smallest Tool diameter:
    •  0.3 - 0.4 mm
Forming die requirements

Why Makino? iQ500!

The active cooling of the iQ500 allows us to have an excellent thermal stability in the z-axis over long machining times (>150 hours). 

The machine is prepared to achieve even tighter contour accuracies so shapes and radii of the dies, even when getting smaller, won't be a problem. 

Thanks to the linear motors and high precision path control, the iQ delivers the fastest feedrate while keeping accuracy even in small movements. 

Large amount of tools is necessary. All of these tools have to be measured precisely, so that there is no difference in z-direction between them.
This can only be achieved by a precise tool seating on the spindle and a precise measurement (in our case given by the Precision Tool Image Measurement Device – PTIM). 

The tool wear can be kept to a low level due to the smooth spindle running and excellent axis control. 
Surface quality as well is better than on other machines (even with standard tools). 

Finally and as important as the machine, our Application Engineers have experience in milling the plates and can support the end-user in technology and the development of cutting strategy.
Want to know more?
Why Makino? iQ500!