Meeting customer requirements and design for manufacture challenges using innovative practices
Among the many challenges of operating in a highly specialist area, such as the manufacture of vacuum and pressure vessels, is ensuring that components operate to their maximum capacity whilst complying fully with rigorous testing and performance requirements – all while making sure that they come in at the right price point.
This was exactly the scenario faced by LTi Metaltech, a specialist in the fabrication and welding of high-end pressure vessel structure, when its client, vacuum-specialist West Technology, tasked it with designing and manufacturing an autoclave pressure vessel capable of withstanding extreme positive and negative pressures. The vessel was to be used by West Technology’s customer, Megger, for the impregnation of electrical windings in one of its high-voltage testing machines.
How Did LTi Address These Issues?
LTi’s design team’s initial task was to review West Technology’s existing designs to identify where, if possible, any improvements could be made to the pressure vessel, both in terms of the cost-efficiency of its manufacture and the performance of such an advanced component.
Firstly, a number of its major parts were designed to be manufactured from large billets of stainless steel, which LTi’s team considered to be both labour-intensive and costly to finish to the required state. Secondly, the vessel’s counterweight was designed to be made out of a single bar of stainless steel with a mass of 115kg – again, an expensive option against the alternatives.
The original designs also posed some geometric challenges, most notably the cone top structure on the lid of the vessel. In its original state, this part of the structure would have been expensive for LTi to manufacture within existing tooling capabilities, necessitating the part to go through more than one round of this manufacturing process, again adding unnecessary labour costs.
To address these issues and thereby enhance the manufacturability of the autoclave vessel, LTi needed to come up with innovative design for manufacture (DFM) changes. It was here that its expertise in computer-aided design (CAD) came into its own.
Using 3D Modelling and CAD Techniques To Implement DFM Changes
Following a detailed review of all aspects of the original design and intended manufacturing processes, LTi’s team of specialists used 3D modelling to identify structural changes that could make the vessel more cost effective to produce. Working to EN 13445 European Pressure Vessel Standards, which sets the minimum quality standards in the design, fabrication and inspection of vessels, LTi made a number of fundamental design alterations.
Drawing on extensive experience of advanced welding techniques, LTi reworked the design of the parts previously configured to be manufactured from the stainless-steel billets to reduce the extent of required welding and machining. The team also altered the autoclave’s counterweight to a tube design consisting of inserted circular blocks cut from what would otherwise have been scrap metal offcuts. This helped to reduce costs considerably and contributed to greater safety of the assembled parts.
The design geometrics of the lid’s cone top structure were also revised to improve and streamline the required tooling processes. By increasing the cone top’s diameter hole by a factor of two, LTi could roll out the shape on a standard machine – saving approximately £1,000 on this part and its manufacturing process alone.
The resultant changes allowed LTi to reduce the total amount of assembly hardware required to fabricate the array of machined parts. Essentially this reduced the number of assembly steps involved, which further reduced the risk of human error and subsequent rework that can slow down the manufacture of a structure and push up costs.
Speaking about the changes, LTi’s technical director, Edgar Rayner, said: “This project with West Technology, with whom we’ve long had a successful working relationship, proves yet again what is possible through innovative design processes. Producing vessels at the highest quality for the lowest overall costs is often a challenging balance to get right, which is why it was important that we worked closely with West Tech through the all-important redesign process.
Throughout the whole process the teams collaborated excellently, and we are hugely proud of the end product and the economies made possible through this.”