Technical Design – Screwdriver

Peer Bothner

Technical Design I – 03/2021

Supervised by Prof. Tom Philipps

design industrial product screw screwdriver Schraubendreher schraubenzieher Rapid Prototyping technical voronoi parametric

The designed tool represents a new type of screwdriver, which allows more favourable two handed screwing. To achieve this, its handle consists out of two independent parts, where the front handle-part exerts pressure against the screw, whilst the rear handle-part generates the torque. Through the built-in bitholder, it‘s universally applicable and can be equipped with any standartized bit.

Concept

Regular screwdrivers are not as ergonomic efficient as they could be and are not living up to their true potential which the current state of industrial production allows for. The usually single-handedly applied pressure- and the rotating-motion are not only tiring for the musculature, but can even lead up to a tendinitis.

The conventional design comes from a time, when more complex ideas mechanically could not be implemented and integrated into low cost tools such as screwdrivers. Nowadays, especially 3D-printing allows the implementation of complex technical designs in compact spaces like screwdriver handles, whilst being an affordable option for serial production. Moreover, the enlarged and dividable handle allows for a much more efficient workflow because the user has the ability to use both of his hands simultaneously.

Implementation

The shell of the screwdriver is generated from a Voronoi-cellstructure, originating from nature, for example in the grid structures of honeycombs, insect wings or foliage leafs.

Because of the cellstructure-design the handle gains aesthetic lightness and apart from the material savings and weight reduction benefits, it allows the inner mechanism to get visible and thereby comprehendable for the user. On top of that, the cell-structure offers a high stability and provides an enjoyable haptic and improved grip. Complex structures like those can be rarely seen with common production methods and are barely implementable with subtractive manufacturing processes.

The shaft inside the rear handle-part is based on a rectangular cross-section and is optimally fitted in the grid of the shell, whereby the rotation of the rear handle gets applied on the whole shaft. Furthermore, with the help of a hinge fitted in between the two handle parts, the user has the possibility to fold the rear handle-part to one side to create a lever and multiply the applied torque by that. The spring inside the back of the handle is used to lock the two handle parts in place, both in the linear, and folded stadium. In the front handle part, the shaft goes through two teflon bearings, which on the one hand stabilize it and ensure a low-friction rotation, and on the other hand allow the shaft to be moved independently of the front handle-part. This allows for one hand to exert permanent axial pressure.

Printing Process

The outer shell, as well as the axes of the final screwdriver will be printed using Selective Laser Melting (SLM). Due to the high precision and robustness, as well as temperature resistance, when printing with metal powders, this rapid prototyping process is ideally suited to guarantee the necessary stability of the tool. For economic reasons, the model shown below was made of resin using the stereolithography process (SLA), which also impresses with its enormous accuracy and surface smoothness, but does not come close to the mechanical properties of an metal-printed SLM-printed prototype.

The two bearings and the spring need to be obtained from manufacturers, as it would not be profitable to manufacture them with 3D-printing processes. Even though the production of bearings made of PTFE with the help of known rapid prototyping processes would already be possible, such production does not make economic sense.