Measuring gas flows in the building space of 3D printers

Process data

Measuring task: Recording flow velocity in building spaces of 3D printers

Measuring point: Oncoming flow with different gases with different gas composition and density

Measuring range: Mostly 1 – 3 m/s and lower

Process pressure: Atmospheric

Process environment: Measurements in development in clean machines / 3D printers

Application

Measuring flow velocities in building spaces of 3D printers to determine regularity of flow. At a manufacturer of industrial gases, metal powder 3D printers from various manufacturers are being used to determine inflow conditions and regularity of the horizontal gas flow across the construction panel. This is important to transport the resulting gases and spray that result when melting different metal powders. An even flow and sufficient flow velocity is essential. These measurements can also be used in machines with other applications that come from Rapid Prototyping such as Stereolithographie (SLA), selective laser melting (SLM), selective laser sintering (SLS) etc.

Flow condition in the 3D printer housing

3D printers have become quite popular. Different materials like metal powder, plastic powder or other work pieces that are built in layers with a laser or other construction parts are being built. There are continuous enhancements like regularity of flow distribution on and around the printing plate and the use of other gases.

Why the tests?

Tests help with further developments of other new materials, improve material properties, optimise gas consumption, develop other gases and optimise process by-products.

What do different gases do?

Different things influence material properties by melting the material in combination with the gas. The lighter the gas becomes the more important are process by-products such as splashes and smoke and the question whether the gas transports these undesired by-products sufficiently away. Another important factor is making sure the laser source is clean because even one grain of dust on the protection glass can cause melting and therefore destroy it. Therefore an even flow across the entire building board is desired.

Practical implementation

For some tests a vane wheel sensor ZS25 was built into an existing frame and the corresponding handheld unit put into the building space; to reduce the risk of contamination it was covered in a transparent packaging. The printer version „Glove Box“ as a hermetically shielded space with access through gloves, the vane wheel could be moved within the frame across the length of the building plate and record the velocity profile. With other customers or manufacturers, like operators of 3D printers with metal and plastic powders vane wheel sensors were built into the mobile frames. That way the interior does not have to be rinsed with the gas that’s being tested before each measurement as the sensor can be moved without opening. Recording measuring range is few millimeters up to about 30 mm above the printing plate. Vane wheels ZS25 and ZS30 cover this area pretty well. The version with aluminium or titanium vane wheels can start measuring at 0.2 m/s. Specific starting values of the different gases can be compensated with the density correction in the handheld unit. For flow analysis above the printing plate vane wheels with flow direction sensing are suitable to detect changes in the direction of flow.