Graeme Smith, BE(mech), 3D Product Designer
Many people are confused by where and when to use Additive Manufacture (AM) and Selective Laser Melting (SLM). Firstly, we need to define the difference between subtractive manufacture and additive manufacture?
It simply comes down to where you spend your time and money. If you spend your time and money removing material to create the part you want, that is subtractive manufacture. If you spend your time and money adding material to create the part from nothing, that is additive manufacture.
Turning/Milling/grinding etc. are subtractive manufacture. Starting with a billet of material, you spend money making swarf. To save cost you often leave as much material on the part as possible resulting in a non-optimised part.
Casting/Molding etc. are additive manufacturing techniques as the material is placed onto the part, however, these techniques require a large tooling component, hence cost, and a lack of flexibility to change. Also, the parts must be relatively simple to make the tooling feasible.
Selective Laser Melting, (3D printing of metals) is purely additive manufacture and requires no tooling. Each change in design is easily handled in the programming. Highly complex and hollow parts are easily achievable allowing optimised design.
At RAM3D, the parts we see on a daily basis generally fit into one of the following 3 categories…
Usually a part more suited to a casting/moulding type process but is still being developed. RAM3D can make your parts in metal to a fully functional state prior to any investment in tooling for production. The part will cost more than a cast part but there are no tooling costs and the part can be altered easily between revisions.
If you are open to redesign, then SLM is a viable production method and is cost competitive for parts that have been optimised for the process.
On many occasions, we have had clients come to us with a one-off prototype that is often a solid piece destined for casting or similar. The RAM3D designers can offer a design service or advise the customer how to alter the part’s design to make the part stronger, lighter, and therefore cost competitive using dedicated design for production, using additive manufacture.
2. Part direct replacement
This is often a tricky area where a customer just wants to try/test the technology by making a part that is currently made by another process. We can do this but the result will often be more expensive, since the part is not designed for the process.
The best way forward in these situations is to give the RAM3D designers the existing part design, tell us what the part is used for and include geometric constraints, loading and material. We will suggest improvements to remove mass from the part without compromising strength. This will improve the part by reducing weight and will greatly decrease the cost; making it competitive with the current method of manufacture.
3. Part design optimised for SLM and part functionality
Often used where you have a part that is limited in its use by the manufacturing method. Usually the part cannot be created conventionally without a large compromise in design, (for example where you may have to make it in multiple parts due to manufacturing limitations, however, it would be better if it were made in one piece).
Design for additive manufacture requires a very different outlook compared with design for subtractive manufacture. When using subtractive manufacture, often excess material is left on the part as it may be costly to remove resulting in an overdesigned part. Also, the method of material removal will often determine the part’s shape. (i.e., pocketing a machined part). That method of material removal can also compromise the part’s usability, strength, and function.
Using an approach focussing on design for additive manufacture means that the part will only have material where it needs it and all applied loads are transferred in the most efficient way possible. The result will be a highly optimised part in both functionality and cost.
RAM3D currently print in the following materials: Inconel 718, Stainless Steel 15-5ph, Titanium 64.
Call us to discuss you projects on 07 557 0344 or email us at email@example.com