Unlimited possibilities: Sintering as a smart production solution
In the mass production of metallic components for plant and machinery construction, consumer durables, the sanitary industry and the automotive sector, the sintering process offers significant advantages over other forming techniques. The benefits include precision, reproducibility and enormous savings potential, e.g. because finishing processes are no longer required. The following case study describes the creation of a complex sintered mass-production component for the furniture industry from the moment of the client enquiry all the way to the finished product.
Simon Sintertechnik and the client – Brief backgrounds
The sintering division of Karl Simon GmbH & Co. KG, based in Aichhalden in the Black Forest, received a client enquiry about manufacturing a functional component for a new kind of hinge for headrest adjustment for high-quality domestic furniture. The client is a traditional, mid-market supplier of mass-produced furniture adjuster modules for kitchen, bathroom and office furnishings.
Simon Sintertechnik is part of the Simon Group of Companies, a subsidiary of Indus Holding AG. The division is certified to ISO 9001 and TS 16949. Using over 60 machines of the most varied kind, it produces more than 140m parts per annum. The division specialises, in particular, in the automotive sector, plant and machinery construction and the sanitary and furniture industries. Simon Sintertechnik has decades of experience in all of these areas.
The development stage
The initial development drawings were assessed internally at Simon as part of a feasibility study. In direct dialogue with the client's R&D department, a design suitable for sintering was worked out for the item.
The drawings were then fine-tuned until all external bevels, radii and crossovers were designed in such a way that the compacting tool could be viably made and the tolerances required of the item and the necessary functions could also be achieved.
In parallel with this, decisions were taken on the material to be used. This is where one of the outstanding benefits of the sintering technique came into play, as the choice of material can be matched completely freely to the specific requirements of the item concerned. In the case of the component described here a high degree of rigidity needed to be achieved. We therefore defined a steel powder with varied proportions of carbon, copper, nickel and chromium. Cost and production-related factors were naturally also taken into account, e.g. that given the item's shape it would be possible to produce a reliable process of compacting the chosen sintering material inside the tool and then removing it.
The tool design
Simon's tool design work then began with creating a compacting tool for the component. The task was to mount a compacting tool onto a fully hydraulic powder press with nine regulated axles. We also determined how the parts would be handled. The challenge was to transport the green compacts from the compacting room without damaging them in order to then position them in such a way in special sintering containers that all of the parts can be fed through the continuous-feed internal plant without getting damaged.
Taking into account its own process data, our in-house tool-making shop converted the 3D CAD data resulting from the development stage into a file, from which the respective erosion electrodes were then made.
Manufacturing the necessary tool components required nearly all of the tool-making department's material-working options: turning, milling, grinding, sink erosion, wire erosion and hardening, plus final extreme polishing of all touching surfaces to keep tool friction as low as possible in order to facilitate friction and make it easier to take the components out.
The production process; compacting and sintering the samples / pilot batch
After all of the tool elements had been made, the powder press was rigged up. A press programme was produced for the entire press process, i.e. from filling the mould with the powder material, via moving the tool elements together and compacting the powder, all the way to taking the pressed component out. The green compacts get removed by an automated claw and transported on a conveyor belt to the press.
In the subsequent sintering process the particles, which up to then are just loosely compacted together, become firmly bonded.
The parts are given their required rigidity at a final temperature of c. 1,150C° and with a process gas mix of nitrogen and hydrogen. The parts initially go here through a dewaxing stage, in which the press additives are forced out, and a subsequent sintering stage, in which the individually compacted granules assume a solid bond.
Finally, the parts were case-hardened in order to achieve the specific torques required.
After the first batch of sintered components fulfilled the client specification in every attribute, the prototype test report was written up.
At present, c. 300,000 parts are being produced a year, with good prospects for increasing volumes in the future.
Summary
Between receiving the enquiry, fine-tuning the item, the design work, the production trial run and producing the prototype no more than a few weeks elapsed.
Analyses done by the client indicated that machine-cutting production of the component would not have been economically sustainable. Amongst other factors, the reproducibility of the sizes gave sintering a clear advantage.
The client's R&D managers were very impressed by the comprehensive technical advice and constructive ideas contributed by Simon, as well as by the speed, with which it was possible to successfully complete the product development. A workshop being held at the client's premises is teaching staff in development, design and purchasing more about the benefits and possibilities of sintering, as it can be assumed that several existing products – which have until now been laboriously made by machine-cutting – can be substituted more cost-efficiently by means of moulding.
