MechChem Africa November-December 2023

⎪ Innovative engineering ⎪

3D printing is much faster than CNC machining or traditional manufacturing.

3D printing has expanded UMP’s mould manufacturing capability.

that the pump OEM generally supplies a 3D CAD model of the impeller, which is used di rectly to design a CAD model of a matching mould. “We then machine the whole shape out of aluminium using an advanced CNC machine to make the moulds, which are used to cast bolt-on PU impeller liners. “Particularly with the machining of larg escale and complicated impeller moulds, this is a time consuming and generally ex pensive procedure. One has to buy a large chunk aluminium, which has to be carefully cut away to get the form needed. There is a lot of capital investment, depending on size and complexity, so to make this easier and less expensive, we at UMP started to look at different materials and manufacturing processes for making our moulds. From a materials perspective, we found several 3D printer options. For FDM (fused deposition modelling) for example, we can use several thermoplastics with different harnesses as well nylons, carbon fibre- and glass fibre-reinforced materials. These materials all have the thermal capability and strength to be used in the PU moulding process. And the 3D printing process brings flexibility, speed and cost effectiveness on the mould manufacturing side,” says Saahil Bhartu. Making 3D printed moulds from these materials meets all of the temperature and rigidity requirements and moulds are far cheaper and faster to make than machined aluminium moulds, though they are not quite as durable. This makes them ideal for shorter production runs or prototyp ing work. UMP then started using the stereo lithography (SLA) 3D printing process. A notable success using the SLA process was the manufacture of a hydrocyclone helix for the separation of cyanide and gold recovery. This is a critical process to prevent valuable gold being lost at the end of the liberation process. In partnership with a company called Azmet, which designed and pat ented an optimised cyclone impeller helix

to minimise losses, we were charged with manufacturing a scaled down version of the impeller. The impeller was initially designed to be made in stainless steel, but it turned out to be an impossibly difficult and costly exercise to machine the exact curves needed for best separation, so we decided to cast it in polyurethane instead. Once the prototype had proved suc cessful, the full scale helix with a length of 900 mm had to be manufactured in poly urethane. This meant the large mould had to be designed with interconnecting pieces, so the individual parts would fit into the SLA printer and to enable the mould to be released after casting. “But while the mould design was a bit of a complex jigsaw puzzle, the whole process was so much easier. Using PU reduced the costs, made the hydrocy clone lighter and, in terms of performance, the solution is achieving 20% better gold recoveries. It was a groundbreaking project and a huge breakthrough for the direct use of 3D printing for making polyurethane products,” Bhartu tells MechChem Africa. As a result, his 3D printing department is going from strength to strength: “We have recently got into manufacturing non pneumatic wheels using PU, for example, basically a wheel and a tyre all in one, which

can save millions on the cost of the tooling to manufacture to a steel wheel with a pneu matic tyre. We can now design a wheel and a mould and move directly on to 3D printing the mould. The whole wheel and tyre can then be cast using different grades of PU materials, with rigidity for the wheel and axle and pliability for the tyre,” he explains. UMP is has made wheels for a German company, MöllerWerke, which makes un manned cleaning machines. A key design aspect is that the machine has no suspen sion and the 860 kg load is carried on 300 mm wheels with only the tyres provid ing suspension. “It was quite tricky, but we were able to find a nice balance between stiffness and damping of the PU that does the job very nicely,” Bhartu explains, add ing that for the small volumes needed, this could not have been cost effective without 3D-printing. “We at UMP are a fully-fledged design and development company that is able to do much more than just manufacturing. We are now a complete solutions’ provider that can develop, design and deliver solutions for complex modern problems. When it comes to polyurethane, we are a turnkey solutions’ company,” Saahil Bhartu concludes. ump.co.za

UMP is now a full-service engineering, design, development, casting and manufacturing company for an extended range of polyurethane linings, which includes pipe, pump and pump impeller liners.

November-December 2023 • MechChem Africa ¦ 43