Whatever the 3D print technique is, some kind of post-processing will be needed to make the part complete. Whether it be removing supports, using ultraviolet light to make a part strong, removing excess powder, or making a part smoother. I would like to review the optimal methods that MJF and SLS printing use to complete the Additive Manufacturing process. The methods (especially those automated) can increase productivity, create higher cost-efficiency, improve component performance, and faster implementation.  

After the unpacking process, the first step in post-processing is CLEANING, removing the excess powder in MJF/SLS printing. 

Media blasting systems need significant airflow to work properly to remove the unsintered loose powder, which can be accomplished with a sandblaster. 

There is an extensive list of sandblasters that are on the market and these machines can be classified into four categories:

• Benchtop media blasters
• Floor top media blasters
• Tumbling blast cabinets
• SLS/MJF-specific depowdering blast cabinets

Benchtop blasters are recommended for users on a budget, typically with small to medium-sized print volumes and pricing up to around $1,000.  

Floor top blasters are generally over $1,000 and offer a larger working space and are considered industrial quality.

You can have the best 3D printed parts in the world, but if you do not have a good cleaning/post-processing workflow, your parts are likely not going to look their best or be as functional as possible. This is especially true with powder-based 3D printing technologies. 

The most common cleaning process for powder-based 3D printing is bead blasting.  In the past, this was done manually bent over a bead blaster; you would have a bead blaster hooked up to an air compressor and clean each part one at a time.  This process not only takes time, but you could damage and/or discolor the parts by putting the spray nozzle too close to the part.  See example A for discoloration, called burn marks. If any of you have ever bead blasted by hand you know what a pain in the back, neck, and eye strain it can be, not to mention a major time suck especially if you have many parts to clean. 

Now with the DyeMansion Powershot C automatic cleaning system what would take me hours has been reduced down to 10 minutes a load.  The other advantage with the DyeMansion Powershot C is I get consistently clean-looking parts.  See example B.  The cleaned parts are ready for finishing or shipping depending on your or your client's needs.  Again, remember the advantage of additive manufacturing is cost-effectiveness and turnaround time.  

In the video below, you can see I am unpacking parts from the HP Multi Jet Fusion.  I am just cleaning the loose powder off the parts as the HP recycles the unused material back into the system for reuse.  The parts are then loaded into the DyeMansion Powershot C and cleaned. 

After using the DyeMansion cleaning system, I would never want to go back to the cleaning process manually again.

Please feel free to give me a call at 800.873.7238 x2735 or send me an email at gene.call@mastergraphics.com with any questions or if you want to discuss post-processing.

Having been in the 3D print industry since 2012, I have sold various types of 3D print processes including SLA, SLS, FDM, Polyjet, and CJP.  Post processing is one of the key topics clients need to understand.

When I have the initial conversation about HP’s MJF technology, one of the first questions I get from experience engineers who have worked with 3D printing is often about the post curing and processing of parts that is needed.

As a background, let’s go through some of the common 3D technologies and the post processing required.  Then I will go through the HP Multi Jet Fusion process and its unique post processing requirements.

Beginning with SLA:   Most engineers are familiar with SLA since it started 3D printed and are aware the SLA process uses a laser to cure photo curable polymers in a vat.  After the build is complete, the parts are then cleaned using alcohol to remove remaining liquid material that was not hardened.  Support structures are needed for printing and often at this point they are removed either by breaking them off or using tools to remove.  The parts are then post cured in a UV oven for a period of time to ensure the part is fully hardened now that the excess material has been cleaned off.  Finally,  the parts can then be hand sanded, painted, or plated or provide the final finish.

SLS:  The SLS process uses a laser and a powder bed system.  The laser traces the part into a bed of powder.  The printer lays down one thin layer at a time, traces the parts as needed for the layer wit the laser, and continues this process until the build is finished.  The support material for the SLS process is the powder itself which eliminates the need of removing any support material.  Since the process uses heat to actually melt the material, the parts need to cool over a period of time.  After the cool down process, parts can be removed and any remaining powder is cleaned using a bead blast system.  The SLS parts can then be sanded and/or infiltrated to improve density and then painted if needed.

FDM: FDM is a tracing technology using various types of extruded materials from a spool.  Often you have one spool of part material and one spool of support material.  After the FDM printer has finished you must remove the support material used in the build process.  This can be done by hand or using pliers depending on the how small or dense the support structure needs to be.  Hand sanding often is done now to remove any of the remaining support attachment points or to ensure a smooth surface.  In many cases, the parts are washed with a caustic material to smooth the layer lines that are apparent due to the process steps.

Polyjet:  In my opinion, Polyjet is by far the messiest 3D print technology when it comes to post processing. This a printing process that uses an industrial print head to jet material versus extrude like FDM and has some advantages such as speed and surface finish.  However, once the part is printed you must place the part into a part washing system to remove the support material versus breaking off like FDM.  The support material is literally a blob that must be washed out.  It has many challenges such as the melt material is caustic and if not careful fine detail on the parts can be washed away during this process.

CJP:  Color jet printing is a process that uses a liquid binder jetted into a bed powder bed.  The powder is actually gypsum.  Since you are jetting a liquid you can actually add color to the parts as you print them.   The parts, full color even, are printed in a “green” state and must be moved from the printer very carefully since they are not fully solidified.  You must clean the excess powder off and very carefull infiltrate the part with super glue to make the parts firm.  Even though solidified, these parts are fragile. 

Having worked with all of these technologies before HP introduced the Multijet fusion technology I was very curious to see how this HP process stacked up.  Most people don’t spend enough time understanding post processing before they implement technology.  I knew this had to be an area HP addressed to improves usability. 

MJF:  First of all I must note, MJF parts are not chemically bonded, they are actually fused parts melted with a combination of agents and heat.  HP jets fusing agents into a powder bed system much in layer process like SLS, but then instead of a laser used to melt the powder a heating lamp applies the needed heat.  The proprietary fusing agent actually intensifies the heat from the lamps to actually melt the material and melts up to that3 layers deep to create parts are almost 100% as strong in the Z axis as in the X and Y axis.  Another result of using fusing agents is a very dense part.  No infiltrating need to make the parts dense.

Post processing for the MJF parts is a quick bead blast in a cabinet using common glass beads. This is the real advancement from HP – the post process improvement.  Once completed the parts can be dyed, painted, and plated if needed. There is no post cure needed, no infiltrating to make the parts dense or support structure removal since the powder is the support structure.