March/April 2020

www.smartmachinesandfactories.com March/April 2020 | 27 | | SOLUTIONS | and large blocks of plastics can be expensive, it results in high scrap rates, swarf removal can cause production concerns, CNC machining time is expensive, production runs for any volume will require expensive robust jigs and fixtures, and the end use product can be compromised by the fact that plastic does not conduct away any of the heat produced during the machining cycle. With vacuum casting issues arise with applications that incorporate intricate details and / or that require hollowing out. Repeatability is the key issue for hollow parts that need to be cast out, while maintaining tolerances on fine features and thin walls is also extremely difficult. The SLS 3D printing process exhibits none of the drawbacks associated with these methods, and as an additive process involves littlein the way of waste during production. Of particular interest, however, is that SLSis not constrained in the same way as traditional production technologies when it comes to geometric complexity, and can cost-effectively produce intricate and detailed parts without extending lead times. When parts become extremely complex, injection moulding, vacuum casting and machining require that individual elements of the finished part are made separately, which demands extra tools and considerable expenditure on finishing and assembly. With SLS 3D printing, the process is much more flexible, and parts can be made in one, reducing the need for assembly, or multiple components can be built within the same build volume on demand, which still requires some assembly but brings significant unit cost savings by negating the requirement for multiple tools. SLS 3D Printing The SLS 3D printing process is a technology solution that has been around for almost three decades, but its use in industrial applications has changed radically over this period. It is rightly categorised as a disruptive technology, but perhaps uniquely it has disrupted industry twice! When it first emerged, 3D printing was more typically referred to as rapid prototyping, and it was at the early design stage of the product development process that it disrupted. The ability to have a 3D prototype in hand a few hours after a 3D CAD design was completed meant that various departments that would usually have been engaged sequentially during product development could now work together. In short, your tooling manager could sit early in the design to market process and tell you immediately whether your amazing design could be manufactured, instead of waiting for it to be passed over the wall. The talk was of concurrent engineering, and time-to-market times tumbled, facilitated by rapid prototyping technologies. Today, the full spectrum of 3D printing processes is used this way and have penetrated deeply into many industry sectors. However, the hype cycle that 3D printing encountered through the middle of the last decade damaged its image as a serious industrial technology leaving it with a legacy of looking like a solution in search of a problem. Today, this image must be dispelled by anyone involved in low volume manufacturing, as now 3D printing, particularly the SLS process, is disrupting industry in its second iteration, as a bona fide production technology. If they do not realistically assess the possibility of using SLS as an alternative production technology, manufacturers are genuinely missing an opportunity to make parts and components quickly, cost-effectively and accurately. And you don’t have to invest in the capital equipment in- house to make this move, as there are agencies that exist that have invested in numerous 3D printing machines so that you can subcontract your manufacturing to real experts in the technology. In this way, you also eliminate the necessity to learn a whole new set of manufacturing protocols. Let the agency take the strain! The SLS 3D printing sweet spot The key is making the ability to assess the viability of 3D printing for production of plastic parts as simple as possible. It needs to be appreciated from the start, that additive manufacturing is by no means suited to every application. To assess where the best fit is, you need to factor in all the benefits and the constraints. First and foremost, consider how big the proposed part is. Pricing is effectively based on size, and as a rule of thumb, the larger the part, the less viable 3D printing is for production. Small components like jigs, fixtures, housings and fittings, however, are perfectly suited to the process. Next you need to assess the complexity of the proposed design. As we have seen, additive manufacturing is agnostic to part complexity, where traditional production technologies are not. Again, as a general rule, the more complex the part, the higher the associated tooling or machining costs, and therefore the more viable additive manufacturing becomes. Finally, what sort of run volume do you have in mind? If you are looking for hundreds of thousands or millions, then injection moulding is your only option. If, however, you want hundreds or multiple thousands of small parts, then you are in the sweet spot for SLS 3D printing as a production process. Summary Understandably today you may be confused, and in some instances disillusioned, about the role that 3D printing can really take on when looking at production scenarios. There is a lot of work to be done to illustrate that 3D printing is really now established as a viable and robust production technology when used for the correct applications and the sweet spot volumes where alternative processes struggle due to cost, timeliness, and versatility in terms of part complexity.