DIRECT METAL 3D PRINTING FOR JEWELLERY
A REVOLUTIONARY TECHNOLOGY
WHAT IS DIRECT METAL 3D PRINTING?
Starting from the 3D file in .stl format, optimised for printing.
PRECIOUS POWDER LOADING
After the precious powder comes out of the cartridge the wiper spreads a layer of precious powder on the platform.
PRECIOUS POWDER LASER MELTING
According to the 3D model, the actual melting phase is carried out by the laser.
PLATFORM LOWERING DOWN
The operation keeps repeating as the platform simultaneously lowers down.
REMOVAL OF RESIDUAL PRECIOUS POWDER
Once the process is complete, the residual precious powder must be removed.
The obtained item is a semi-finished piece, ready to be polished according to the designer's project.
HOW DOES PROGOL3D® WORK?
Simply upload your file in .stl format on the dedicated area of the website to obtain the quotation.
Our technical dept. evaluate the printability of the piece and set the printing parameters.
PRECIOUS POWDER PRODUCTION
The alloy (after fineness testing) is atomized to produce precious metal or Titanium powder.
DIRECT METAL 3D PRINTING
The laser printer melts the precious powder according to the desired design.
The obtained piece is detached from the platform and the supports are removed.
PACKAGING AND SHIPMENT
The semi-finished jewel is packed and sent to its destination.
HOW DO 3D JEWELS "GROW"?
The objects directly made in melted precious powder by a laser beam stand and "grow" on standard measure platforms. To ensure that the jewelry pieces develop appropriately, so-called "supports" are used. They consist of actual precious metal scaffolds that meet multiple needs:
1) make sure the jewel is well attached to its platform.
Then to separate the jewel from the platform, the supports are cut off and removed.
2) make sure that every single point of the jewel surface (inside and outside) is supported.
3) dissipate the excess heat developed during the laser fusion. Supports are a theme that is strictly connected to SLM since it’s inherent to the technique.
However, supports are only required for surfaces with a tilt angle of less than 45° with respect to the platform.
For this reason, some designs are particularly suitable for 3D printing (i.e. pieces whose angles are greater than 45°, and therefore not particularly affected by the need for supports) while others are less suitable (i.e. pieces which would need to be so heavily affected by supports to the point of distorting the design and the jewel quality).
The operator's experience, when setting the files for printing, will help to choose the structurally necessary solutions to affect the design of the piece in the least invasive way.
Compared to investment casting, extra metal supports are spread across a wider area, but the surface of the piece is, on average, much less affected than by the conventional spruing system of traditional investment casting.
METALS: MECHANICAL AND PHYSICAL PROPERTIES
SIX METALS, DIFFERENT SOLUTION
Most of the 6 materials proposed by PROGOL3D® are compliant to the colour standard ISO 8654 as well as compliant to any restriction reported on REACH regulation. Our materials are totally nickel free. The white Gold Palladium based, 13% Pd, gives a "Grade 2" white according WGC yellow index scheme. The red Gold coded 5N+ gives a colour's tone a bit more reddish than standard 5N.
3D printed jewels' mechanical properties, if compared to casting, show a slightly higher hardness, in the range of no more than 5%, higher tensile strength and a lower elongation. This means that printed alloys are free of defects as well as their grain structures are much finer than in casting.
Casting grain size could be up to 40 times bigger (from 100µm up to 2000µm) than 3D printed one (generally below 50µm). In metallurgy this is a value! When a goldsmith works a 3D printed material doing grinding, assembling and polishing always feels only positive behaviours.
Many wonder what the maximum dimension (and volume) of a direct 3D printed jewel is.
PROGOL3D printers feature different areas of printability depending on the chosen metal.
SLM50 (yellow, red, white gold and platinum) 70 mm x 70 mm x 80 mm
SLM100 (titanium) 125 mm x 125 mm x 200 mm
Within these measures, the whole area can contain the designs and shapes to be printed in metal.
Necklaces and bracelets can be positioned within the printing area so to guarantee the creation of the piece as a whole.
A standard for metal printers resolution is not available yet. However, following the best practices on polymers' printers, the table below shows the XY and Z resolution expressed in DPI (dots per inch).
Basically, the values mean that on XY plane our metals printers can print details not smaller than 0.15-0.20mm while on Z axis they are able to reproduce details down to 0.02mm. In casting this is not always possible especially for high melting range alloys such as Platinum and Titanium. However, even for Gold alloys it is difficult to cast, meaning formfill, thin elements below 0.25-0.30mm.
CASTING: HOLLOW OBJECTS AND TAILORED WEIGHT
HOLLOW OBJECTS / CASTING
In casting it is not possible to get a monolithic hollow jewel. In this example, the ring needs to be cast in 2 parts and then assembled to have a hollow core. This is a mandatory procedure to get an acceptable weight. This also means that after assembling, a visible and unwanted soldering line will be visible, whether due to colour issues or polishing subsidence.
MONOLITHIC HOLLOW OBJECTS / DIRECT 3D PRINTING
The 3D printed ring shown in the picture is monolithic and free of any soldering line problems. This advantage can be applied both to the example given and also to any other kind of jewellery that needs to be split in several sections to be then assembled through soldering procedures.
SAME APPARENT VOLUME, WEIGHT DECREASE UP TO 80%
Designers can now work with a greater level of freedom. They no longer need to pay attention to the relationship between weight and volume. Direct metal 3D printing introduces the possibility to decide which will be the final weight of the jewel in advance, without affecting the desired apparent volume. This is an opportunity for perfect market positioning as well as it allows the jewels to be more comfortable to wear, i.e. earrings.
CONSTANT WEIGHT / DIFFERENT SIZES
One of the main advantages of direct metal 3D printing is the possibility to change the apparent volume, i.e. as the ring's size changes, the ring's volume remains constant. This means that each ring size will have the same weight and the same precious metal cost. It is well known that high end jewellery rings, for example, are sold at the same price, regardless of their size.
CASTING: DENSITY BENCHMARK
VERY HIGH DENSITY
Directly metal 3D printed jewels show no visible porosity if compared with casting, as shown in the metallographic pictures. As well the above table gives the typical density limits, shown as residual porosity, of both techniques: casting can achieve in the best conditions a maximum density of 99,9% of the bulk density while direct metal 3D printing can achieve a solid 99,99% one.
CASTING: ROUGHNESS BENCHMARK
The chart above shows the total roughness of the jewels, so called Rt, comparing traditional casting, direct casting and direct metal 3D printing. In the case of casting the highest roughness is not distributed as in 3D printing. It's often connected to localized holes due to some casting defects as shrinkage porosity. This will however force the goldsmith to remove all the metal surrounding the hole to get a flat and bright porosity-free surface. However the average roughness of 3D printed jewels is comparable to the one coming from direct casting. As shown on the roughness profile, all the surface peaks need to be removed to get the full dense surface without imperfections and porosity. The advantage in 3D printing, in case of similar roughness value, is that the amount of metal that needs to be removed is much smaller. This in case of non local laser repairment performed on casting parts. The table reports the average grinding and polishing loss to be considered when comparing direct metal 3D printing and traditional or direct casting.
CASTING: THICKNESS AND SURFACE BENCHMARK
THICKNESS / SURFACE
Molten metals, during casting process, have the ability to fulfil thin parts proportionally to their surface extension. In casting, greater surface area and thickness are needed to achieve complete parts . In direct metal 3D printing this relationship no longer stands. Whether the part's surface is large or small, the printable thickness is always the same. In absolute terms, 3D printers are able to build parts with a thickness at least 50% thinner than casting.
CASTING: GREEN TECHNOLOGY
GREEN TECHNOLOGY - CARBON FOOTPRINT AIMING AT A MORE SUSTAINABLE PROCESS!
The graph shows a lower quantity of equivalent CO2 produced by 3D printing process to have 1kg of jewels. The benchmark should be considered with casting yields' values below 50%. This because very often in jewellery the equipment are used below their real production capacity. A burn-out furnace, the equipment with higher equivalent CO2 produced, is hardly ever filled with casting flasks. In case of metal 3D printing there is no connection between the quantity and process yield.