3D printing minimises heat transfer in co-extrusion nozzle

One of the many engineering challenges that we help our customers overcome is managing the thermal properties of precision components that are either extremely small or designed to be used in restricted spaces.

A recent project called for a precision engineered co-extrusion nozzle designed to extrude two materials with dissimilar consistencies and thermal properties simultaneously. The nozzle had extremely thin internal walls and needed to incorporate an internal cavity, which acted as a thermal barrier between the two materials as they were extruded. 

Previously, the part had been manufactured using traditional subtractive engineering techniques. The nozzle had been CNC machined in two parts from S162D maraging steel, with one section then requiring further work using electro-discharge machining (EDM), before the two parts were vacuum brazed and heat treated. This was a relatively slow process, requiring a considerable degree of programming time to ensure that the required tolerances were met; for example, the external dimension of the outer part had to be machined to within 0.03mm to ensure that the braze formed a dependable bond.

Metal additive manufacturing reduces production time
Our approach was to manufacture the co-extrusion nozzles using metal additive manufacturing (AM). 

Once we had translated the designs to our 3D CAD system and created a suitable model, we were then able simultaneously to produce multiple parts (up to 64) on our advanced AM machine. These were grown layer by layer using maraging steel (MS1) powder on a standard base. Once complete, each part was quickly removed from the base using a wire EDM machine, before being ultrasonically cleaned to remove any residual powder, bead blasted and then heat treated. Each part was then precision-finished on a lathe prior to an internal and external polish.

Using metal additive manufacturing for this project had a number of advantages: it allowed multiple parts to be produced at the same time, minimised the total number of process stages, reduced the total production time and cut both unit cost and the amount of scrap material generated.