Direct digital manufacturing - also known as rapid manufacturing - promises advantages that are impossible with conventional manufacturing techniques. Tim Heller explains.
Direct digital manufacturing (DDM) introduces new concepts such as freedom of design and freedom to redesign. It allows ultra-low volume manufacturing that can be taken to the extreme-bespoke, custom products. But many are still resisting it.
Much of the industry chooses to staunchly remain with the status quo. Before taking this easy way out, it's worth considering what is important when selecting the best manufacturing process. Recognise that what is important will change with each component in every product: DDM is good for some products but certainly not for all. The same is true for injection moulding, die casting and thermoforming. The key to manufacturing effectively and productively is to select a process that meets the important criteria for the task at hand.
For those companies and individuals who still remain unconvinced, I offer three reasons to disregard DDM:
- Speed: For DDM, the cycle time to make a part is measured in hours, not minutes. By this measure, DDM is very slow compared to injection molding, blow moulding or die casting. As a result, DDM is simply not fast enough for high-volume production of parts with an unchanging design. DDM, which excels when production volumes are small or the design is subject to frequent changes. For this reason, DDM's speed should be measured relative to other low-volume production methods instead of long-running, high-volume processes.
- Strength: This also a relative term. Is a plastic DDM part as strong as some of the high-end thermoplastics, carbon fibre composites or ferrous metal castings? Of course not. But the vast majority of manufactured goods do not require this level of strength, so it is an arbitrary statement to say that DDM does not manufacture parts that are strong enough.
Another consideration is how strength is measured and in what terms. If evaluated as strength-to-weight ratio, for example, DDM is superior to other manufacturing processes. It has the ability to produce hollow walls with internal structures to reduce weight and material consumption while delivering the desired part strength.
The technology allows the operator to change the way the part is produced in order to adjust the strength by feature, layer or axis.
- Finish: As a layer-based, additive process, DDM will yield visible evidence of material deposition, and in some cases, visible 'tool paths'. Without secondary processing, the surface finish of a DDM part will not be smooth. However, consider that most part finishes are not smooth and glass-like. In fact, a texture is preferred for many applications. And when the component is not visible and smoothness does not impact performance, surface finish will not be among the key criteria for process selection.
These three factors may be barriers for some products, but by no means are they justifications to ignore what DDM has to offer. It is important not to disregard DDM based on a few preconceptions that are not global facts.
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Tim Heller is Managing Director, Stratasys Europe, Frankfurt, Germany. <a href="http://www.stratsys.com"target=_blank>www.stratsys.com</a>
