Arburg was showcasing its new approach to RP technology. Designers can now process hard/soft combinations, as well as own materials and colours, to form individual pieces or small batches. The RP system, given the name “freeformer” by Arburg, has yet to achieve the speeds set by the classic RP lines. However, a glance at the basic design reveals that in the not too distant future we can confidently expect a highly flexible as well as a very fast system.
Arburg presents its high gloss, monolithic freeformer with much fanfare at the K-Fair. We are unable to recall quite so much hype attending an Arburg presentation at a major exhibition.
The Arburg freeformer (photo: Arburg)
An entire branch of industry is involved in the construction of prototypes. This is especially the case in evaluating developments in plastic componentry, when the developer turns to Rapid Prototyping (RP) or “additive manufacturing” as it is also known. Here, laser sintering or modelling with the aid of a plastic wire are tried and tested technologies aimed at generating initial parts without a mould on the basis of the CAD data set. There are, however, three serious stumbling blocks encountered by all forms of rapid prototyping:
1. The prototype component can be restricted only to the limited range of materials/colours offered by the manufacturer of the RP lines.
2. Multi-component technology is feasible only to a very limited extent or not at all.
3. Because of the fine layer structure it generally takes several hours to produce a component.
Arburg is anticipating a huge market demand for the production of individual pieces and batches and for this reason the company has been focusing intensively on the topic. The result is the freeformer, presented for the first time at the K fair, which attracted a considerable amount of attention.
Essentially, what we are looking at here is a small screw-operated system that is able to dispense individual plastic drops one after the other by means of a fixed piezo-controlled nozzle. Under the nozzle there is a three-axis table (a five-axis table is also available as an option) which positions the component during the process so that the drop is always applied in the correct place.
In Arburg plastic freeforming, standard granulate is first melted. The functional part is then produced layer-by-layer from plastic droplets via a clocked nozzle and a movable component carrier. (photo: Arburg)
The great thing about this is that standard granulate is fed into the screw-based mechanism so that the user can work with his own materials and colours. This is particularly important if he wishes to create hard/soft components. Up to now it has not been possible to produce hard/soft combinations using the usual RP processes. With its new system Arburg has done away with the disadvantage of limited materials. The only limiting factor is that filler materials, be they fibres or talcum, will not go through the small nozzle.
An appropriately equipped freeformer can be used to process two materials or colours in combination. This means, for example, that movable hard/soft combinations can be produced on an additive basis. (photo: Arburg)
As regards speeds, the freeformer has yet to demonstrate that it has actually progressed by comparison with the other RP processes, however, it does have the capability to do this. By using a second injection moulding unit it is possible to process two different materials in parallel or to produce two components simultaneously.
Currently, the processing speed is being restricted by the traversing tables. After each movement they first have to come to rest so that the injector can position the droplet exactly. This currently happens at the rate of 100 times a second. The piezo control is, however, capable of discharging more than 2,000 droplets per minute. Therefore, in the future, the speed at which the product is built up will be automatically increased through the use of vibration-free tables. It is also possible to help the freeformer gain speed by varying the size of the droplet. This means that it is possible to work with larger drops inside the component so as to get the mass through and with small drops on the edge in order to achieve a high degree of surface accuracy.
However, these possibilities meant that Arburg was not able to use existing software tools for RP lines. Arburg has developed its own software which processes CAD data so that the freeformer can work with it in an optimum manner.
In addition, Arburg has also given some thought to where the equipment might be deployed. The freeformer is of narrow construction, so that it can also fit through normal-sized doors to get into the design workshops, it is quiet in operation and with no dust emissions.
www.arburg.com
