When to use Metal 3D Printing?

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…

1. Prototype
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.

Example of the lug showing internal lattice structure which has been added by RAM3D’s designer

Example of a connection lug of one of Bastion Cycles custom made parts for Carbon-Fibre bicycle.

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 info@ram3d.co.nz

The process of printing 3D parts

Written by Phil Owen & Rew Noland

It is a often misconstrued that a 3D printed part magically appears straight out of the printer and is “good to go”.  Firstly 3D printed parts come out of the machine attached to a build plate via support which has been carefully placed to optimise the build. Material is also placed in openings and overhangs to help support the build process.  If the part has been designed specifically for 3D printing, it often requires less support, is easier to clean up and process.

We then cut the part off the build plate and carefully remove the support from the part. When the base part is fully exposed, we can move on to finishing the part. Where support has been placed there will be raised dimples or grids, so we file, die grind and/or linish these areas to achieve a smooth finish.

When the part is smoothed back and we are happy with it, we move on to media blasting. We have a few different media we use to try maintain a consistent finish over the whole part. The material of the part can also determine which media we use. Our standard final finish is done with glass beads and is often sufficient for a majority of parts.

Some customers require a higher level of finish so we can also rumble parts.  This is an additional service and incurs an extra cost.  This process is good for reducing minute irregularities, de-burring and produces a clean, smooth surface.

Hand polishing is another option to take it the next level of finish and this is suitable for the likes of implants and decorative items.

We are looking at options for better finishes with new tooling and machines, so watch this space for more updates!




Graeme Smith, BE(mech), SLM Product Designer

Over the coming issues I am going to look at part design for the SLM additive manufacturing process and how designers can optimise parts to provide the best part at the best price.

Part 1. Understanding the cost of additive manufacture

As a design engineer I like nothing better than designing a part that functions perfectly and looks good for a reasonable cost. But designers are being pressured to create cheaper and cheaper parts. This is often achieved by compromising on function and forgetting about looks. We have all done it…a piece of RHS welded to a plate with a couple of holes drilled in it. Result…cheap, does the job but heavy and really ugly. Imagine if sleek, light and perfect for purpose was also cheap? Additive manufacturing could be your answer.

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