Autoclave capacity increased by over 33%
Summary
In a 16-week project, the capacity of an autoclave facility for curing composite aerospace parts was increased by 33%, which enabled a capital expenditure of over £1.2m to be avoided.
Background
The client had a significant rate increase in one of their key projects and needed to increase capacity to meet this demand. Some areas were in a position to cope but others would limit capacity. The aim of this project was to increase the capacity of the autoclave facilities, which were the process bottleneck for carbon fibre parts, by at least 10% . The alternative route to achieving this was the commissioning of a new autoclave, at a capital investment of over £1.2m and lead time in excess of one year.
Project
The first challenge was to understand exactly what the current performance was. The existing measures suggested the process was around 80–85% efficient, but it was important to understand what the performance was versus the ideal world (zero downtime, optimum cycle time and a fully loaded autoclave). This may have seemed idealistic and certainly met with challenge from the team, but once everyone understood that it was to ensure that all of the problems and opportunities were exposed, they agreed. The actual efficiency was more like 35% which meant there were some exciting opportunities.
Curing time
Many of the cycles on this autoclave were running beyond their design cycle due to the way the machines were set up to control temperature. Because a variety of tools were planned in each load and the differences between the tools meant that some heated quickly, some slowly, the cycle was often ‘held’ waiting for the slow ones to catch up. By understanding which temperature differences were critical, which parts of the autoclave were hottest and by using improved airflow within the autoclave, a 38% reduction in this ‘holding time’ was achieved. No changes to the specifications were required and all parts were successfully trialled before employing any of the changes.
Unfilled volume
Although different cure cycles did limit how many parts could be put into each load, there were a number of groups of parts which shared the same cycle, meaning that in these cases the load size was limited by space in the Autoclave. By designing a suite of tools with detachable trolleys, ensuring safe & stable stacking of tools, as well as increasing the thermocouple and vacuum connections inside, larger loads could be fitted into the autoclave, reducing the number of cures required each week.
Changeovers
Changeovers were also identified as a significant opportunity, and procedures were developed with the operators to minimise the time taken for each changeover. This was achieved through early preparation of the autoclave loads, and more rigorous pre-processing checks to further reduce potential lost time and errors. Visibility was given to all of the problems that contributed to lost capacity on the autoclaves, with a new measurement system; and the reports generated by it were used to continue to drive improvement. Operators continued to monitor and drive down each source of lost capacity on a daily basis.
Results
Sixteen weeks after the start of the project, capacity of the bottleneck autoclave facility had been increased by 33%, well above the Project target of 10%. In addition, the tools and methodologies were in place for the in-house team to achieve an additional 50%.
This increase was sufficient to avoid a capital expenditure of over £1.2m that would have been required for a new autoclave to meet medium term increases in demand.
The longer-term project of upgrading the remainder of the tooling was driven by the client after the completion of the project, and has continued to deliver increased autoclave capacity.
Click here to go to the Newton Aerospace section.
For more information on our work, please contact us.
