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April 1, 1997

7 Min Read
Design and Material Development for an Ice Skate Blade

The rapid growth in material and processing technology makes it essentialfor plastics manufacturers, mouldmakers, and designers to keep in closetouch. In the development of plastics components, the properties of thematerial and its processing behaviour should be taken into account rightat the draft

Figure 1. A dynamic biomorphicdesign and
specially selected material combination together
produce the lightest and fastest skate blade yet.

design stage. In this example, material and technological studies offrogdesign, a design agency in Altensteig, Germany, and of WST, a manufacturerof sports articles in Villingen-Schwenningen, Germany, led to the selectionof a suitable plastic and to a creative design for an ice skate blade (Figure1).

Extreme Demands: Material

The blade of an ice hockey skate produces frictional heat through pressureand movement, causing the ice to melt and a film of water to form betweenthe blade surface and the ice. It is only this film of water that makesskating on ice possible. The better the process of water film formation,the faster the ice hockey player can go. Therefore, the aim is for theblade to reach a high temperature quickly and for the
temperature to remain constant, if possible.

The good thermal conductivity of metals, shared by the solid steel bladesused in conventional systems, has the effect of rapidly dissipating thefrictional heat generated. The requirements of the material selected fordevelopment of the new skate blade were specified to combat this effect.

The quest for a suitable plastic began with a definition of the waythe system would function and thus ran parallel to design and engineeringdevelopment (Figure 2).

Figure 2. From the first sketch right through the final
CAD design, the designer allows no compromises.

A

The first draft sketch
serves as a basis for
discussion between the
designers and engineers.










B

The preliminary model,
made from rigid foam,
enables the customer
to visualize the designers'
ideas,three-dimensionally,
for the first time.












C

After design release
by the customer, the
designers, working with the
plastics technical experts,
perfect the design of the
skate system using CAD.











D

The CAD design data make it possible to construct a stereolithographicmodel, which is painted and used to test the entire system structure.

The extreme physical requirements the plastic is exposed to and theconditions imposed by production processes made this search the most time-consumingstage in this entire development project (Figure 3).

Figure 3. The detail modificationsof the
individual component groups are influenced
by different plastics and additives and
directly implemented in the CAD design.

Particular problems were posed by the connection between the blade surfaceof the skate system ? a metal profile ? and the plastic.

When a suitable plastic had been found to withstand the physical stresses,different expansion and shrinkage coefficients of the plastic and metalprofile both in moulding and demoulding caused a defective connection betweenthe plastic and metal. On the other hand, when this connection succeeded,then other properties such as the notched impact strength, inherent rigidity,and chemical resistance of the materials proved inadequate (Figure 4).

After numerous injection moulding trials, testing of prototype moulds,and skating trials, close cooperation between the plastic manufacturer,designer, and mouldmaker led to the selection of a material that met thespecified requirements.

Figure 4. In a test at -41°C,an impact
corresponding to that of a puck traveling at
a speed of 150 km/h destroyed the skate base
made from an unsuitable material.

An injection mouldable, high-impact polyamide with 35 percent glass-fiberreinforcement stood up to the extreme stresses that occur in an ice hockeymatch. This plastic serves as the base material for the entire skate systemand also for the blade itself.

The blade, i.e., the actual runner surface of the system, consists ofa .7-mm-thick, high-strength metal profile. This metal profile, consistingof a spring-hard metal alloy, is laser-welded in a fully automated processto a second metal band provided with apertures, and is then permanentlyjoined to the plastic during the injection moulding process.

The result is a blade which, because of the insulating effect of theplastic, does not dissipate the generated frictional heat so rapidly. Theresulting heat buildup increases the temperature of the blade surface byabout 3°C compared with conventional blades. As a consequence of thisand the highly polished blade surface, the sliding action of the skateblade is improved by 40 percent. This, in turn, increases skating speedas compared with conventional skate blades.

Extreme Demands: Design

The practical implementation of the design for the basic skate andprovision of laterally integrated stabilizers for the skate blade proveda further challenge. The physical demands made on these components werevirtually identical to those made on the blade. However, this time it wasnot necessary to account for expansion and shrinkage coefficients as wasthe case with the plastic/metal composite forming the blade. One designobjective was to reduce the weight of the skate system and yet still meetthe high requirements of competitive sport. The skate blade developed fromthe polyamide/metal composite is 140g lighter than traditional skate bladesand at present the lightest blade system.

This weight minimization was only made possible by the use of plasticsin conjunction with a carefully thought-out design. The reduction in wallthickness required for weight minimization called for a design capableof withstanding the very different force effects. Lightweight structuresfound in nature and the laws of force distribution used in architectureserved as the basis for the design. Thus, it was possible to reduce thewall thickness of the largest part of the basic skate to only 1.5 mm. Theinherent rigidity of the system is retained, even if the player is a heavyweight.The skate blade resists compressive forces of up to 3,000N, such as acton the system when the skate is braked, for example, and also the impactforces exerted by the puck traveling at speeds of up to 150 km/hour, evenat extremely low temperatures down to ?35°C.


Figure 5. The initial mouldingsof the skate
base, stabilizers and blade from prototype
moulds are used for material loading tests
in the laboratory and on the ice.

To find the correct material, numerous injection moulding trials inprototype moulds and tests under practical conditions were required. Thisenabled resolution of problems relating to the flow behaviour of the plastics,such as sink marks in areas of high material accumulation and difficultieswith fit in the individual component groups. By reducing the fiber content,it was possible to adapt notched impact strength at minus temperaturesto the required torsional rigidity of the basic skate.

Adaptable and Interchangeable

Time-consuming blade grinding, required with traditional steel blades,is unnecessary with the skate blade in the plastic/metal system. The servicelife of this blade is three times longer than that of conventional systemsbecause of the special metal alloy and the high surface hardening. Postgrindingof the blades costs more than purchasing a new blade and replacing theold one, which is taken back in the worn condition by the manufacturerand reground.

The skate blade can be changed by the player in a few seconds withouttaking off the skate. The stabilizers at the sides can be removed by undoingspecial screws and the blade changed. It is also possible to use differentblades for varying player requirements. For this purpose, the injectionmould has interchangeable inserts that make it possible to provide differentradial curves on the blade surface in order to meet different player requirements.

The close tolerances between the individual component groups (blade,stabilizers, and base ? Figure 5) favour the force line paths withinthe system. The inherent rigidity achieved is greater than with any otherskate blade. Colour variations in the system are possible by changing thepigment, as is surface decoration with special-effect paints.

Contact Information: frogdesign GmbH Mr. Hartmut Esslinger Grenzweg33 D-72213 Altensteig Germany Phone: (49) 7453-2740 Fax: (49) 7453-27436
frogdesign inc. 1327 Chesapeake Terrace Sunnyvale, CA 94089, USA Phone:(1) 408-734-5800 Fax: (1) 408-734-5801

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