Ceramics have been made for thousands of years. So why print them? The answer has little to do with enthusiasm for technology and a great deal to do with machine hours. In this article we work through a specific part to show what printing with compounds means – and where the money is actually saved.
The process in one paragraph
As with any FFF printer, we build up layer by layer: the machine traces the wall lines, fills them in and lays the next layer on top. The difference lies in the material. We do not feed in filament but raw pellets, which are melted and dispensed in the pellet extruder.
The worked example: a watch case
Take a watch case in technical ceramic – a part with a lot of empty space inside it. Conventionally you need a blank for it, say a 50 × 50 mm block with 15 mm walls. In aluminium oxide that alone costs around 40 euros.
Then the real work begins. Technical ceramic is a hard, brittle material. You clamp or cement the block in place, and every pocket, every recess has to be ground out – carefully, with a shallow depth of cut, on a low-vibration machine. An ultrasonic-assisted grinding machine such as a DMG Ultrasonic costs several hundred thousand euros, sometimes more. Add expensive tooling. And every machine hour counts.
In printing the arithmetic looks different: we produce the green part near net shape, with perhaps half a millimetre of stock. The material then costs more like 10 euros – and above all most of the expensive machine time disappears. The printing machine itself is in a completely different price bracket from the grinding machine.
The part in the video, incidentally, took about three minutes to print. It is not a perfect part – but it shows the kind of timescale involved.
What “technical ceramics” means here
This is not about plates and cups. We process aluminium oxide, zirconium oxide and soft ferrites – the cores you see clamped around cables in electrical engineering, for instance. Steels and stainless steels can be printed and sintered on the same principle. The difference lies only in printing and sintering behaviour, not in the process.
From green part to full ceramic
The ceramic is not printed neat but bound in a polymer matrix – a skeleton carrying the ceramic powder. That allows the material to be printed almost like an ordinary plastic. Two steps then follow:
- Debinding: waxes and plasticisers are washed or burned out, chemically or thermally.
- Sintering: under controlled heat the particles bond into a full ceramic reaching 98 to 99 per cent of the density of a conventionally pressed part.
The part shrinks in a controlled way in the process – hence the size difference between the printed and the sintered part, clearly visible in the video.
Near net shape means threads, chamfers and pockets come printed
Everything you would otherwise have to remove is formed directly. We print the core hole for a thread with it; you only cut the thread, instead of first grinding the hole. With cylindrical parts that have a large internal pocket the difference is even starker: conventionally you grind the entire pocket out of round stock.
Depending on requirements the printed state may even be enough – for sintering aids or furnace fixtures, for example.
The advantage many people overlook
The green part is soft. You can break it – but you can also machine it. If you do not need ultra precision, clamp the green part on an ordinary milling machine, finish it with the shrinkage allowance and only sinter afterwards. That is considerably faster and considerably cheaper than painstakingly grinding a finished ceramic.
With large diameters this is the decisive lever: print a blank and mill it in the green state rather than working on finished full ceramic at the end.
Honestly
It is not the case that you press start and everything runs smoothly. Behind it lies a long chain of parameters that has to be respected for a usable part to come out. That is exactly where we come in: leaving a skilled worker to hunt for parameters for months saves nothing in the end – skilled staff are the most expensive item in a business.
We therefore work with fixed material partners, know how the materials behave and deliver the machine set up for your material. Ideally you really do just press start. And the machine? It is not ugly, but it is not beautiful either – it is built for a purpose. Sturdy, working, made for production.
Chapters in the video
The video is in German; the chapter titles below link straight to the relevant passage.
- 0:00 · Intro – printing with compounds
- 0:33 · How pellet printing works (layer by layer)
- 1:21 · Why print ceramics? The advantage shown on a case
- 2:05 · The conventional route: grinding & expensive machines
- 3:41 · The 3D printing alternative: a near-net-shape green part
- 4:30 · What “technical ceramics” means (Al₂O₃, zirconia, soft ferrites)
- 5:19 · Compounds explained: ceramic in a polymer matrix
- 5:53 · Debinding & sintering – to 98–99 % full ceramic
- 6:54 · Applications: threads, furnace technology, aerospace
- 7:57 · Speed: this part printed in about 3 minutes
- 8:38 · Stainless steel & steel too – one principle
- 9:24 · We set the printer up + sintering partners
- 10:37 · Machining the green part cheaply (milling before sintering)
- 12:03 · Conclusion & sign-off