So-called “material fatigue” is one of the typical causes of failure, and in this case, it occurred to the UBS robot head holder and caused it to break. “The spare part no longer exists, the manufacturer doesn’t supply it, or a machine may be so old that even its manufacturer no longer exists”, says Pánek, noting that there is usually no documentation for such a part available either. If there is, the next step is not necessary.
The second phase involves measuring the damaged part in full and creating accompanying documentation to use if the same part fails somewhere else in production. During digitisation, the designers are already thinking about what the new part will look like. It does not even need to have the same shape as the original. “We’re looking for a way to improve its longevity. In this particular case, we know that the aluminium part cracked, in what place, and why it happened, and we can solve everything by using modern materials,” Pánek explains.
After completing the documentation, the preparation of a new spare part begins. It is necessary to specify a number of parameters and create a model of the complete part. For example, by defining the material density in its individual places, it is possible to increase the strength where it is needed. The Markforged printer data utility program used in PSZ for this purpose will help with basic strength calculations.
The selection of a specific raw material composition from a range of durable composite material combinations forms an integral part of this process. The basic material is Onyx (or nylon), which can be reinforced with carbon, Kevlar, or glass fibres, even in their high-performance and high-temperature variants. Each of the elements gives the final part certain properties: strength, flexibility and so on. Different materials can be applied to different part areas during printing, which helps to gradually adapt the final product properties.
This is followed by printing the part, which takes hours – from one for very simple parts to dozens for complex ones. “During printing, we monitor the individual layers and try to find places where imperfections could occur. In contrast with the digital input, the result makes certain allowances. For example, the printer never produces as sharp an edge as we design, so it is necessary to check the part carefully after printing”, Pánek notes.
The finished part, which can be composed of several pieces, as in this case, goes back to the line. Before that, designers can try to fit the part directly at the printer. “A part printed in this way achieves the strength of an aluminium alloy, but it has lower weight, and its production is less expensive than with conventional methods, such as a completely machined part”, emphasises Pánek. In addition, with the same strength and because of the newly designed structure, the chances of repeated failure are much lower.