The use of Mass Flow Controllers in 3D-Printers

December 20, 2017 Jens Kiene

It is real common nowadays to use 3D printing techniques as process optimization in industrial production evironments. In our Bronkhorst premises in Ruurlo we also use 3D-printers for our own product and process development. 3D-Printers are indispensible within our production environment, it has brought us a new and very accessible and flexible way of manufacturing.

Within a few hours, we can evaluate the design of a component: will it really work in the way we expected it, does it really fit? You can read all about our experiences here in our blog ‘Product & process optimization by use of 3D printers’.

But it also goes the other way around. Not only do we use 3D printers in the production proces of flow meters, but these flow meters and flow controllers are also used inside 3D-printers as well.

In this blog I would like to share an application with you explaining how mass flow meters are used in the 3D printing machines of one of our German customers in the machine building industry.

example 3d dental slm
Example 3D dental SLM

Selective laser melting (SLM)

3D-printing, also known as additive manufacturing, is a technique where products are made by building a product layer by layer. This is the opposite of machining operations such as drilling or milling, where pieces of materials are removed to yield the product.

Selective laser melting (SLM) is a 3D-printing technique where a layer of powder is deposited, after which a part of these powder particles is selectively melted together by means of laser heat.

SLM Solutions Group AG is a machine builder who makes 3D-printing machines that print metal parts out of steel, aluminium or titanium powder using this selective laser melting technique. Their customers are in the fields of aerospace, automotive and medicine & dental. High purity inert gases are necessary around the metal powder bed within the 3D-printer.

Application requirements

It is essential to have a gas atmosphere around the to-be-melted metal powder particles that is oxygen-free, to prevent the metal from oxidation during the laser melting. To that end, an inert shielding gas has to be applied: argon gas for steel and titanium, and nitrogen gas for alumium.

Flow solution with MASS-STREAM mass flow controller

For the end user of SLM's 3D-printing machine, there are two ways to establish a nitrogen atmosphere: either from the in-house nitrogen supply mains - if present - or from a nitrogen generator, which is an accessory to the 3D-printer. In the latter option, Bronkhorst becomes involved.

Pressurised air from a compressed air supply or a compressor is supplied to the nitrogen generator, and its molecular sieve separates the air flow into two flows. Constituents such as oxygen, water vapour and argon are removed, and nitrogen with high purity (grade 5.0) remains.

Downstream of the generator, a mass flow controller (using direct through-flow measurement technique) is installed to control the nitrogen flow to the 3D-printer. This controller works in two operating modes.

Prior to the printing process, the 3D-printer has to be flushed, in order to establish the shielding gas atmosphere. To this end a high nitrogen flow of 60 to 90 liters per minute is necessary. Next, during the printing process itself, a small nitrogen flow of 3 to 10 liters per minute has to be supplied, for refreshing purposes and to compensate for leakage.

Flow scheme
Flow scheme

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