Use of plastic powder in additive manufacturing

In addition to filament, synthetic resin and foil, there is another starting form for 3D printing material, the powder.

Powder as a starting material was first used by Carl Deckard in the development of SLS printing technology.

Over the years, this form of material has spread under various printing technologies. Powder printing is particularly widespread in industry.

The big advantage of the powder compared to filament and synthetic resin is its versatility. This not only applies to the materials that can be used, but also to the type of processing.

As with SLS printing technology, powder is fused using a high-power laser beam. It is also possible to crosslink the powder grains with one another using UV light or infrared lamps and a special binder.

Depending on the printing process, plastics, metals, ceramics, plaster or sand can be processed in this way.

In this post, we will look specifically at the plastics in powder form.

The colors of the different types of powder are different. Depending on the manufacturer and the printing process, the powder is usually white or gray.

The white powder is mostly used when a possible coloring comes into play, for example with the 3D printer JF580 from HP.

There is now also printing powder that is completely dyed blue, which is interesting for the production of components in the food industry.

The powder grain sizes for plastics are between 0.08mm – 0.11mm.

The powder is supplied in plastic cartridges or tin cans.

HP’s Multi Jet Fusion Technology (MJF) is used to show how the powder is processed.

In additive manufacturing using plastic powder, the powder is usually distributed evenly in the pressure chamber layer by layer. The so-called powder bed is created.

This powder bed is heated below the melting point throughout the print.

With MJF, a thermally conductive liquid wets the powder granules provided according to the CAD model. After this process, an infrared lamp moves over the entire printing area and only hardens the wetted powder grains.

This process is repeated until the modeled component is completely printed.

When the pressure chamber has cooled down, the component can be removed from the powder cake.

No support structures are required for powder printing processes, since the support function is taken over by the powder bed, i.e. the loose or uncured powder.

Other printing technologies that also work with powder material use other processes for the fusion. If you would like to learn more about this, you will find more detailed explanations under the individual printing processes.

The plastic powders are particularly well received in industry, since similar material can be processed, which is often also used in conventional production (such as injection molding).

In the meantime, these plastic powders, including the associated printing processes, have been developed to such an extent that they can be used for economical series production.

The following small list shows a range of plastic powders that can be processed with various printing processes.

• Polyamide (PA) with various additives
• PA 11
• PA 12
• PA 12 GB (with glass bead content)
• PA 12 with aluminum content
• PA 12 carbon fiber reinforced
• PA 2210 FR (PA 12 flame retardant)
• PACA (polyamide carbon)
• PP (polypropylene)
• PEKK (polyetherketoneketone)
• PS (polystyrene)
• TPA (Thermoplastic Polyether Polyamide)
• TPU (Thermoplastic Polyurethane)

Powder can be processed using the following printing methods:

• laser SLS – Selective Laser Sintering
• infrared light and binder – MJF – Multi Jet Fusion
• Binders only – BJ – Binder Jetting, 3DP – 3d Printing, CJP – Color Jet Printing

Powder printing is used in a wide variety of industrial sectors. We are no longer just talking about prototypes. Series up to 10000 pieces can now be realized economically.

Industries that do not want to or cannot produce and sell mass-produced goods benefit from this.

In addition to mechanical and plant engineering, more and more plastic powder is being printed, especially in the medical sector. The manufacture of individual orthoses has meanwhile become an important sales market.

The rapid development in the field of materials research will inspire some industries for 3D printing in the future.

Due to their price and the necessary accessories (blasting cabinet, powder preparation, etc.), 3D powder printers are mainly suitable for industry.

The additive powder printing process works without support structures. The loose powder in the so-called powder bed serves as support here.

All components that are manufactured using powder printing must be freed from the loose powder particles. This is done by blasting with glass beads in a blasting cabin provided for this purpose.

Depending on the blasting material and the amount of pressure with which the glass beads hit the component, the “rough” surface can be smoothed at the same time.

In the case of filigree model structures in particular, a sure instinct is required here.

The finishes differ depending on the printing process used.

Osurface treatment:

• vapor smoothing
• Epoxy resin coating
• polishing
• inking
• paint
• to coat (galvanize) metal
• rays

Some of the big 3D printer brands rely on closed systems. These 3D printers can only be used with the proprietary powder materials to be worked.

Since these have been developed for the special printing process, it is also advisable to use them.

The provision of so-called test material, as is usual with filament or synthetic resin printers, will not be the case here.

Compared to other printing materials, the powder is in the higher price segment. Since we only work with plastics that are used in the industrial sector, the material costs are correspondingly high.

Plastic powders, which generally have special properties or can be assigned to engineering plastics, are traded between 75€-300€ per kg.

PA approx. 75€ – 200€ per kg

TPU approx. 150€ – 300€ per kg

I haven’t been able to find any freely accessible prices for high-performance plastics such as PEEK.

Year after year, the topic of recycling plays an increasingly important role in additive manufacturing. The large printer manufacturers are also working on developing materials and printing systems in such a way that unused powder can be reused.

In the early days of powder printing, the loose powder often had to be disposed of. The heat that was generated in the construction space to prevent stresses in the component changed the structure of the loose powder in such a way that it was then no longer usable.

All that “lost” powder was a big expense.

Here the industry had to find solutions to make 3D powder printing more marketable.

Today the unused powder is mixed with fresh powder. The refresh rate is 70:30 or 80:20, depending on the printing system. So a large part of the “old powder” is mixed with “new powder” and printed with it.

In most printing processes, the mixing takes place in separate machines. The JF 580 from HP is one of the few 3D printers that “recycles”, i.e. refreshes the old powder in the machine itself.

Specialist service providers who specialize in the disposal and recycling of plastics melt the powder residues together. The powder blocks are then further processed into granules and thus fed back into the raw material cycle.

In addition to the blasting cabin, an industrial vacuum cleaner is required to clean the 3D printer, depending on the printing system.

This must meet certain fire protection regulations and standards so that the suction of the powder particles does not cause flying sparks or fires.

These prices for these industrial vacuum cleaners start at around €2000. This should be taken into account when planning costs for powder printing.