All over the world, Maxon is known for its high-precision drives. But only a few people know that the company has its own injection moulding department for ceramics and metal. Here, not only ceramic spindles are produced but also special parts for the watch and music industries.
Ceramics are an excellent material for reinforcing gears. For this reason, the drive specialist Maxon founded its own powder injection moulding department 20 years ago. In the meantime, ceramic parts are also produced there, which provide a better music experience.
The department's greatest pride and joy gets its own room. Andreas Philipp, head of the powder injection moulding department at Maxon, heads straight for the newly raised walls, opens the door and points to the only machine housed in the room - a laser machine for hard machining ceramic components. The latest acquisition is capable of cutting ceramics to an accuracy of 2 micrometres, Philipp explains. Machining spring elements with a wall thickness of 17 micrometres and taking precise measurements at the same time. This should make the department fit for the future, and customers will be supplied with precision parts even faster.
Ceramics for longer life
Few people are aware that Maxon has its own injection moulding department for ceramics and metal. After all, the company is mainly known for its micromotors, which are used on Mars but also power countless applications on Earth - from surgical robots to laboratory machines to tattoo machines.
In addition to precision drives, Maxon also develops and produces controllers, encoders and, above all, gearheads. And these need to be reinforced for certain applications. More precisely: individual components such as gear wheels, axles or planet carriers. Ceramics are particularly suitable for this "upgrade"; after all, the material is more resistant to chemicals, high temperatures and wear than steel. Ceramic axles in gearboxes extend the service life considerably. Especially when the drive is used in start-stop operation. For this reason, Maxon started manufacturing the ceramic parts itself about twenty years ago. Today, 45 people work in the injection moulding department, including developers, application engineers, quality experts and production staff.
From the motor to the spindle
The powder injection moulding specialists are part of the maxon production plant in Sexau in southern Germany, which specialises in gearheads. Accordingly, about half of all the parts that leave the department are used in maxon drives. The ceramic spindles for linear drives are particularly sought after because they are smooth-running and wear-resistant. "We are the only company that can offer the customer motor, gearhead and ceramic spindle from a single source," says product manager Walter Kuhn.
The development and production of precise ceramic components is complex and not entirely cheap. The processes are complex and diamond tools or - as already mentioned - laser machines are needed for hard machining. Therefore, ceramics are usually only chosen because of very specific requirements that cannot be met with conventional materials. Or as Andreas Philipp puts it, "Ceramics are used when all other materials have failed."
Two days in the kiln
At the beginning of the production process is the granulate, also called feedstock. This contains a certain amount of binder so that the material can be pressed into moulds at all. After the parts have left the injection moulding machine, they can already be easily processed, but they do not yet have much in common with finished ceramic components. These so-called green parts are brittle, easily breakable and much larger than the final product. To give them the outstanding properties of ceramics, the binder is first removed from them in a chemical process. Then they go into the oven for two days for sintering, where the components shrink by up to 30 per cent at a maximum of 1500 degrees Celsius.
This volume loss is difficult to calculate, especially when tolerances in the micrometre range are the goal. For this reason, many components go to post-processing after the furnace, where the required tolerances are achieved by grinding. For some components, on the other hand, a simple polishing process is all that is needed and they are then ready for delivery.
Fast machining of prototypes
The special properties of ceramics ensure that maxon not only manufactures components for gearheads. The products manufactured include the smallest nozzles for industrial automation, pawls for the watch industry but also housings for headphones. The latter have been produced in the maxon factory for years and, according to the manufacturer, have a positive effect on sound quality. In addition, unlike metal housings, they are scratch-resistant and retain their beautiful shine for a long time.
The basic principle in powder injection moulding has remained the same over the years. Nevertheless, certain changes are noticeable. According to Andreas Philipp, the processing of green parts will probably decrease in the future. Instead, there is an increasing trend towards injecting simple basic shapes and then machining them with high-tech machines until they have the perfect shape. "This gives customers a prototype much faster," says Andreas Philipp. Small series can also be delivered more quickly. What doesn't change is the fascination for powder injection moulding, which is palpable throughout the department. "Every order is different, nothing is standard. Ceramics is a massively challenging material and that's what makes it so exciting."