Inert atmospheric control is the process of removing air from an enclosed space by replacing it with an inert gas. In SLS 3D printing, the inert gas is typically nitrogen. SLS polymers tend to oxidize when held at elevated temperatures for extended periods of time. Limiting oxidation improves the material properties of printed parts and allows you to print with a lower refresh rate.

For example, printing with Nylon 11 in nitrogen allows you to use a 30% refresh rate to print parts with increased ductility compared to parts printed in air at a 50% refresh rate.

The Fuse 1+ 30W is equipped with a sealed chamber held at a partial positive pressure to ensure a low oxygen concentration when printing in an inert atmosphere. The Fuse 1+ 30W includes plumbing, sensors, and controls to enable a plug-and-play inert atmospheric control process. The Fuse 1+ 30W does not contain nitrogen generation capabilities, so an external nitrogen source is needed if inert atmospheric control is desired.

Nitrogen may be sourced in several forms including compressed gas cylinders, liquid nitrogen dewars, or nitrogen generators.

Nitrogen supplies that meet the following requirements are suitable for use with the Fuse 1+ 30W:

• Concentration: 99.5% or greater
• Flow: 0.5 SCFM or greater
• Pressure range: 36–125 psi
• Gas temperature at machine inlet: 18 °C or greater

For more information about sourcing supplies, read the support article Formlabs-approved distributors for supplies (SLS). The table below summarizes the trade-offs between options:

Nitrogen generators

Nitrogen generators convert a compressed air source into a flow of high-purity nitrogen gas, with most of the oxygen removed. The resulting flow of nitrogen can serve as a nitrogen source for the Fuse 1+ 30W. A primary benefit of using nitrogen generators is that they do not require replacing or refilling bottled nitrogen sources.

Air compressors may have a high startup power draw and should be powered by a separate circuit from the printer to prevent print interruption.

Formlabs recommends using a dedicated air compressor or one with sufficient capacity to prevent pressure drops if used by other devices during printing. Compressed air fed into a nitrogen generator must be filtered to remove moisture, oil, and particulate matter.

For recommended nitrogen generators and associated fittings, please see the Formlabs-approved distributors for supplies support article. The listed fittings are compatible with the recommended HSS-7 or HSS-3 model nitrogen generator from Holtec Gas Systems. The fittings include:

1. Quick disconnect hose coupling for air (1x): Quick disconnect couplings allow for ease of setup. Note that smaller compressors typically use ¼” coupling size, but higher-capacity compressors may use larger couplings. Check your compressor to ensure compatible pipe size and coupling size.
2. Quick disconnect hose socket for air (2x): Quick disconnect sockets allow the air hoses to interface easily with the air compressor and printer. The hose sockets are connected to the threaded ends of two separate air hoses.
3. EPDM air hose (2x; 3x if used with an external compressed air filter): Compressed air hoses connect the air compressor to the nitrogen generator and the nitrogen generator to the printer’s nitrogen inlet. Three air hoses are necessary if you are using an external compressed air filter.
4. Compressed air filter (1x, if applicable): Compressed air fed into a nitrogen generator must be filtered to remove moisture, oil, and particulate matter. If your air compressor is pre-equipped with a filter, you do not need an additional external filter. The filter must be in line prior to the nitrogen generator.
5. Thread sealant tape: Use thread sealant tape to ensure an airtight connection on any threaded connections.
6. Nitrogen generator: Formlabs has tested the HSS-7 nitrogen generator from Holtec Gas Systems. Any nitrogen generator that can supply the required nitrogen input requirements may also be used. If using other nitrogen generators, ensure that the couplings are compatible with your hoses and adapters as applicable.

The diagram below depicts how the components above are assembled to successfully provide nitrogen to the Fuse 1+ 30W, starting with an air compressor (not shown). Note that the items in the dashed box are not required if your air compressor is pre-equipped with a filter.

The picture below shows the location of the nitrogen inlet on the Fuse 1+ 30W. Note that the included quick disconnect hose coupling is installed.

Nitrogen bottles, dewars, and tanks

Nitrogen may also be supplied to the Fuse 1+ 30W from nitrogen containers such as compressed gas cylinders, liquid nitrogen dewars, or micro-bulk or bulk containers. The best option depends on printing volume, budget, and facilities. For a recommendation on your best option for nitrogen, use the Formlabs Gas Calculator developed by Airgas.

Nitrogen cylinders may serve as a low cost way to begin printing with an inert gas atmosphere without the need to invest in a compressor and nitrogen generator. Bulk supplies may also serve as a cost-effective option for high-volume printing in production environments.

When using compressed gas sources of nitrogen, install a regulator at the outlet of the compressed gas source in order to lower the nitrogen pressure to the input range of the Fuse 1+ 30W.

When using liquid nitrogen sources, install an evaporator at the outlet of the liquid nitrogen source in order to convert it to a gas which can be used as an input to the Fuse 1+ 30W.

Der Fuse 1+ 30W verfügt über die Möglichkeit, Stickstoff als Inertgasatmosphäre in der Druckkammer zu verwenden. Die inerte Stickstoffatmosphäre verhindert die Oxidation des Kunststoffpulvers.

Der Fuse 1+ 30W verfügt über zwei atmosphärische Kontrollmodi:

• Luftmodus: Die Atmosphäre des Druckgehäuses besteht aus atmosphärischer Luft.
• Stickstoffmodus: Das Druckgehäuse wird mit einer Stickstoffgaszufuhr gespült.

So bereiten Sie den Fuse 1+ 30W für den Druck mit einer Inertgasatmosphäre vor:

1. Schließen Sie die Stickstoffzufuhr an die Stickstoffschnittstelle auf der Rückseite des Druckers an.
2. Bestätigen Sie, dass der Druck der Stickstoffzufuhr zum Fuse 1+ 30W zwischen 248 und 862 kPa liegt und die Durchflussrate mindestens 14 L/min beträgt.
3. Falls Sie eine Stickstoffversorgung über Gasflaschen oder Flüssigstickstoff verwenden, stellen Sie sicher, dass für den Druckvorgang genügend Stickstoff vorhanden ist. Beim Drucken unter Inertgasatmosphäre benötigt der Drucker ca. 14 L Stickstoffgas pro Minute.
4. Tippen Sie auf das Druckersymbol in der linken Seitenleiste, um den Bildschirm Druckerstatus aufzurufen. Schalten Sie das Stickstoffsystem auf ON.
5. Vergewissern Sie sich, dass der Touchscreen N₂ Mode (N2-Modus) anzeigt und dass sowohl der Inlet Pressure (Einlassdruck) als auch der Valve Pressure (Ventildruck) im Bereich liegen.

So stellen Sie den Ventildruck ein:

1. Tippen Sie auf das Druckersymbol in der linken Seitenleiste, um den Druckerstatusbildschirm aufzurufen.
2. Tippen Sie unter Nitrogen System (Stickstoffsystem) auf Valve Pressure (Ventildruck). Das Fenster Nitrogen Setup (Stickstoffeinrichtung) wird geöffnet.

6. Wenn der Stickstoffdruck ausreichend eingestellt ist, tippen Sie auf Fertig.
7. Schließen Sie die IR-Sensorklappe.

If a nitrogen source malfunctions or is set up improperly and nitrogen displaces the existing oxygen in the room containing the printer, a significant hazardous situation may be created. A safety assessment should be performed by your company’s safety officer in order to ensure that your nitrogen system is set up and operated in a safe manner.