Up until now, all of our posts have been about 3D printing with polymer materials or Fused Deposition Modelling. This makes sense since our site is generally directed to 3D printing for the home user.
I thought for this post that I’d review what’s available at the other end of the spectrum – 3D printing metal materials.
In this 3D printer evaluation, I take a closer look at Desktop Metal’s Studio System (TM) for fabricating parts out of metal alloy powder. While this system may be out of reach for the conventional home user, it might just be the ticket for the small business owner.
The Studio System (TM) is designed for lower volume prototype builds and is comprised of 3 modular components, printer, debinder and furnace, that work together to create objects using Desktop Metal’s Bound Metal Deposition (TM) process. The modular design allows each component to be moved and located to accommodate each user’s unique work area.
The process starts with proprietary cloud-based Fabricate (TM) software to define the component fabrication plan, generate printing supports and process control parameters based on component model geometry and material characteristics.
The fabrication plan is sent to the printer where the ‘green’ component is built up one layer at a time by extruding bound metal rods.
After printing, the green component is submerged in a bath of proprietary liquid to dissolve the binder material.
The resulting porous component is then placed in the furnace where any remaining binder material is burned off and the metal particles are sintered together creating an essentially fully densified component.
The Bound Metal Deposition Printing Process
The printing process utilizes rods of metal alloy powder bound together with polymer and wax binders. Just like Fused Deposition Modelling, which utilizes polymer filament, the Studio System (TM) printer heats the metal alloy rods and extrudes the molten material onto the build plate in 0.4 mm diameter strands to form the component in a layer-wise fashion.
As expected from a 3D printing system at this level, the printer includes live print job monitoring, automatic build platform leveling and extruder calibration.
Two extruders, one for depositing the metal alloy build material and one for the ceramic support structure interface material, are mounted via a quick release mechanism for straightforward change out.
Another quality feature is the use of encoded ball screws for precisely translating and positioning the extruders during the printing operation providing smooth operation and fine print features. Similar types of linear actuators are used in semiconductor manufacturing equipment.
The metal alloy print media is contained within easy to handle cartridges that can be swapped out one the fly.
The “hot-swappable” cartridges drastically shorten material change overs to a matter of minutes. To put this into perspective, changing materials in other metal 3d printing modalities, such as selective laser sintering, can take weeks and poses safety risks from airborne powder particulates.
The printer occupies a fairly compact volume with dimensions of 33.7 x 20.9 x 37.4 inches and has a pre-sintered build volume of 11.4 x 7.4 x 7.7 inches allowing for max post-sintered part dimensions of 9.6 x 6.3 x 6.4 inches.
Prior to printing, the Fabricate (TM) software automatically resizes the part to account for post-sintering shrinkage, aligns the part for optimum build orientation, adds required support structures and searches for other components in the build queue that could be added to the print job.
Support structures are separated from the component by a non-sinterable ceramic interface layer allowing for machine-free part separation.
Other printer specifications:
- Max build rate 16 cm3/hr
- Min layer height 50 μm
- 7″ touch screen user interface
- Build plate heated up to 70 °C (158 °F)
• Vacuum-enabled print bed
- Build chamber heated up to 50 °C (122 °F)
- Weight 97 kg (214 lbs)
The Debind Process
The component printed via the Bound Metal Deposition (TM) process is a ‘green’ part consisting of metal powder bound with polymer and wax.
The polymer binder, referred to as the primary binder, has a relatively high molecular weight which enables high print quality and strength of the printed component. The wax, or secondary binder, helps maintain the shape of the printed component throughout the debind and sintering process.
In the debind process, the green component is submerged in 4.6 gallon stainless steel tank within the debind module. A proprietary solvent dissolves the primary binder leaving a component with an open-pore channel structure bound by the secondary binder which is insoluble in the solvent.
To make the Studio System (TM) “office friendly”, thermoplastic saccharides can be used as the primary binder and an aqueous solution containing enzymes as catalysts for debinding can be used as the solvent. Using such a binder and solvent will create a waste stream of monosaccharides that are safe to handle and dispose of.
The debinding module, occupying a space of 29 x 23 x 40 inches, is about the same size as the printer though it weighs over 300 pounds and the flip up lid will need an additional 21 inches of space. The automatic fluid distillation and recycling system enables ready reuse of the solvent and saves cost as there is no need to replenish the solvent between debind cycles. The process has low emissions eliminating the need for external ventilation further reducing costs and increasing flexibility for users with limited space.
Other features include:
- Over-temperature shutoff control
- High vapor pressure shutoff control
- Automated debind plans based on geometry and material
- Job progress tracking
- 7” touchscreen user interface
The Sintering Furnace
After debinding, the ‘brown’ part is placed into the furnace module for sintering and densifying.
With a SiC heating element on each side of the 11.8 x 7.9 x 7.9 inch processing chamber, the component is heated to near the material’s melting temperature to remove any remaining binder material and fuse the metal particles together.
A common problem with laser based metal 3D printing systems is the residual stress imparted to the part during the metal powder sintering process. This problem is avoiding with the Studio System (TM) by managing the heating and cooling cycles via pre-programmed temperature profiles that are tuned to the component build and material.
The furnace is about twice the size of and 4 times heavier than the printer. With external dimensions of 54.3 x 29.7 x 63.7 inches the module is sized to fit through an office door though, at a weight of almost 800 pounds, will require a couple of people to handle. Half inch air exhaust and liquid drain lines will require a bit of plumbing and could limit the placement of the module to specific locations within the users lab.
Other features and specifications:
- Automated temperature profiles based on geometry and material
- RFID-enabled onboard gas monitoring
- Job progress tracking
- System health monitoring
- 7” touchscreen display
- Thermal interlocks, front-mounted E-stop
- Over-temperature protection
- Finger-safe light curtain protection
- Adjustable multi-level graphite trays with ceramic setters
- Removable binder cold trap
Final Processing Steps – Completed Part
After cooling, the sintered component is taken out of the furnace and separated from the supports.
During the printing process, a non-sinterable ceramic layer is built up between the support structures and the actual component. Because the support structures are not fused to the adjacent component layer, part separation can be performed by hand. The Separable Supports (TM) eliminate the need for expensive post processing equipment such as electric discharge machines which are commonly used to remove laser sintered components from their support structures.
3D Printing Materials
The Studio System (TM) uses materials previously developed for Metal Injection Molding processing thus providing access to a large selection of existing, pre-engineered material compositions.
Desktop Metal currently offers six alloy materials and has over 30 material systems under development.
- AISI 4140 – low alloy, mid-carbon steel for high strength and toughness
- 316 L – stainless steel for corrosion resistance at high temps
- Copper – for thermal and electrical conductivity
- Inconel 625 – superalloy for strength and corrosion resistance at high temperatures
- H13 – tool steel for hardness and abrasion resistance at elevated temperatures
A few of the material systems under development:
- Aluminum 2024
- Aluminum 6061
- Cobalt Chrome F75
- Hastelloy® X
- Carbide WC-3Co
Desktop Metal’s main competition is Markforged with their Metal X Atomic Diffusion Additive Manufacturing system.
In fact, Desktop Metal sued Markforged in March 2018 alleging infringement of two patents directed to their Separable Supports (TM) technology. After a 3 week trial, the jury found that Markforged did not infringe Desktop Metal’s patents. The results of the lawsuit shows that these two companies have very similar yet differentiated technologies. Each company is competing on the merits of their respective technology and product offerings without riding the other’s coat tails.
The lawsuit notwithstanding, Desktop Metal leads the patent race by a significant margin with 46 patent applications filed in 2017 alone. Though having a large patent portfolio is no guarantee of market success, it is a measure of a company’s innovative pulse.
If you are a manufacturer wanting to step up your game through 3D printing, I would give the Desktop Metal Studio System (TM) some serious consideration. Coming in at a price on par with a medium to high end 5 axis CNC machine, this printer has an attractive return on investment especially when you factor in the savings from shortened development times and associated material costs.
The full, 3 module system including software upgrades and a 1 year warranty is offered at a price of $120,000.00. Throw in the starter package which includes starter materials, installation and 12 months maintenance and service and you are all in for $150,000.00. A three year financing option is also available.
What will you create?
If you have experience with using or other insights on the Desktop Metal Studio System, please contribute in the comments section below.