Philips Oneblade 360 - Design For Manufacturing Explained
- Zaid McAllister
- Jan 2
- 5 min read
Updated: 6 days ago
Index:
Design for Manufacturing Explained is back. This year, I'll be posting one high-quality blog post every month with a focus on design & manufacturing techniques.
This post looks at the Philips OneBlade 360 blade. A small hybrid razor-shaver designed for both wet and dry use that gives a close shave without the constant blade changes of a cartridge razor or the bulky package of a rotary shaver.
Mechanisms & their function
1a. Scotch Yoke
Many systems are driven by either an AC or DC motor, which outputs a rotational motion. In a shaver, the blades move back and forth in an oscillating motion.
To achieve this, a Scotch-yoke–style mechanism in the blade assembly converts the motor’s rotary output into the oscillation required for cutting hair.
Why not convert the rotary motion within the handle instead?
Water ingress - It is much easier to seal a rotating shaft against moisture than an oscillating one, and the blade itself does not house electronics
Noise/vibration - If the conversion happened at the blade, a longer, heavier shaft would need to oscillate, increasing inertial forces and vibration
Wear - The conversion relies on sliding contact, creating a wear point that is better handled in a disposable component than in the permanent handle.
1b. Modified Parallel Linkage
To maintain contact with the skin and avoid injury, the shaver head pivots relative to the handle.
The OneBlade achieves this using a modified parallel linkage rather than a traditional one. Unlike a true parallel linkage, the upper link is shorter than the lower link. This geometry allows the blade angle to change based on how much force is applied.
With a conventional single-pivot design, the blade rotates about a fixed instantaneous centre of rotation (ICR), resulting in a simple motion path. The modified parallel linkage instead creates a moving ICR that shifts to beneath the blade as pressure is applied.
This creates a more adaptive motion. The blade tracks the skin more closely while presenting a less aggressive leading edge, improving comfort while maintaining contact.
The pivot arms are connected to the blade end via two moulded pins per arm (D), while each arm connects to the handle through a single ball and socket joint (C).
This arrangement allows the blade to pitch independently of the crank. When the blade rolls, the crank follows that motion, maintaining planar alignment.
Design For Manufacturing Highlights
2a. Sheet Metal V-Spring
i. Design for assembly
Instead of using a traditional coil spring, blade pressure and return are achieved with a folded leaf-style spring. This type of spring achieves the required force while fitting into the constrained geometry of the blade assembly.
One area of DFMA (design for manufacturing & assembly) that I find particularly interesting is the integration of sheet metal and plastic components.
The V-spring incorporates dimples (E) that are formed by pressing the flat sheet prior to folding. The dimples snap into corresponding recesses moulded into the injection-moulded frame.
Once assembled, the spring is fully constrained without the use of adhesives or fasteners. This is an ideal outcome from a cost & assembly perspective.
ii. Material
The spring is formed from 0.25 mm thick steel sheet. A simple magnet test, combined with observed corrosion behaviour was used to guesstimate the material selection.
Plain carbon steel would require a protective coating in a wet environment and would exhibit significantly stronger magnetism than observed, making it unlikely.
Martensitic stainless steels, such as 410 or 420, also tend to show stronger magnetic attraction and offer only moderate corrosion resistance.
Fully austenitic grades such as 316 or 316L provide excellent corrosion resistance but are typically only very weakly magnetic.
Austenitic stainless spring steels such as 301, 302, or 304 offer good corrosion resistance and can become mildly magnetic when cold-worked during stamping and forming.
This aligns well with both the observed magnetism and lack of corrosion, making these the most likely candidates.
iii. Forming
The part is expected to be produced from a continuous steel strip rather than from a plate, which is typical for high-volume stamped components.
The flat profile, including holes and slots, would be created first while the material remains flat, ensuring accurate alignment before any forming occurs.
Bending would then be introduced progressively as the part moves through a die, with bends added in stages to minimise distortion and maintain consistent geometry.
The slots likely serve both manufacturing and functional purposes. They help the strip track and form more reliably through the die while locally reducing stiffness to concentrate bending where it is needed.
2b. Injection Moulded Crank Frame
i. Tooling
When designing plastic parts, mould cost is strongly influenced by how easily the tool can open and release the part. Features that trap the part in the mould increase complexity and cost.
In some designs, that extra complexity is a deliberate trade-off. More advanced features can replace secondary operations, eliminate fasteners, or enable assemblies that would not otherwise be possible.
The crank frame is an example of this trade-off in practice. Its geometry and the location of the split lines indicate the use of a tool with multiple core elements, rather than a simple two-plate core and cavity mould, producing a complex geometry that serves multiple functions.
To illustrate how this would be moulded, I modelled a simplified version of the part and tooling in CAD. The overall tooling complexity seems to be driven less by the undercuts themselves and more by the challenge of ejecting thin, delicate features without causing damage.
At production volumes of this scale, the component would almost certainly be moulded in a multi-cavity tool producing several parts per cycle. In that context, sliding elements within the tool would be used to replicate the function of a segmented mould.
ii. Material
A surprising amount can be learned about a plastic material by burning it and observing its behaviour. Characteristics such as how it melts, how it burns or self extinguishes, the smell produced, and the nature of the smoke can all be used to make an educated guess of the material.
One of the first things apparent when burning this part was the presence of a significant amount of glass fibre introduced during moulding.
Glass fibre-filled plastics are frequently chosen for load-bearing components where increased stiffness and dimensional stability are required.
The added fibres reduce creep under load and limit warping during cooling, but also introduce trade-offs, including brittleness, higher tool wear, and more anisotropic mechanical properties driven by fibre orientation during mould filling.
While my sense of smell is far from a calibrated instrument, the odour was strongly reminiscent of burnt nylon. Nylon is often combined with glass fibres during moulding to achieve the desired part properties.
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