The Peter Wakeman Memorial Technical Presentation
As in previous years the Branch AGM preceded the technical presentation. As part of the business of the AGM Mark Holliday, Prof MICME, was voted in as the Branch President for 2019/2020. Senior Vice President for 2019/20 is David Hall, Prof MICME, and Junior Vice President is Pawel Maclewicz, Prof MICME.
Concluding the AGM Darren Pritchard Prof MICME, the current Branch President, introduced Andrew Tagg of John Winter as the speaker for the Peter Wakeman Memorial presentation and his subject the Geopol W binder system.
Andrew explained how for the past 15 years John Winter had been working in partnership with a company from the Czech Republic in the development of Geopol W. It is a warm air cured inorganic binder system for aluminium which has a greatly reduced environmental impact compared with cold box systems. It does, however, compete favourably with cold box in terms of core costs, production rates and core strength. The resultant cores are resistant to moisture. One of the tests is placing core test pieces in both water and a high humidity atmosphere and measuring the strength after 24 hours. Geopol W cores will retain significant mechanical strength whereas both cold box and other warm air cured samples have zero strength.
The system is based on a liquid resin with an addition rate between 1.5% and 1.8%. A powder accelerant is added between 0.7% and 0.9%. The optimum temperature of both the corebox and warm air is 150°C. Lower box or air temperatures will adversely affect production rates.
The low binder content ensures a flowable sand that achieves good mould density with a high binding strengths which results in an excellent casting finish. The process is particularly suited to thin section aluminium castings because the very low residual moisture, typically around 0.2%, ensures defect free product with superior surface finish.
Benefits of the system include the improved working conditions for the coremaker, caster and operators at knockout. There are no VOC’s and no need for chemical scrubbing. The waste sand can be reclaimed by a combination of thermal and mechanical methods. The process can be used with a range of sand types and will tolerate poor quality silica sands. The bench life is good, better than cold box, but if held in a hot environment then bench life suffers as could be expected of a process dependent upon drying out the sand with hot air.
In terms of tooling costs cold box machines are readily converted to the process but obviously resin coreboxes have to be replaced with metal. Shell process equipment is easiest to modify as coreboxes are already metal, and with up to four times the output rates then conversion costs are more easily justified.
Environmental pressures will continue to grow as is already being seen in areas of Europe with tighter regulations on formaldehyde emissions. New products with less environmental impact are essential for the future and it was therefore pleasing to hear that John Winter are working towards having a similar system coming to market, possibly later this year, for the iron founders.
Following a lively Q&A session Eddie Lindsay, Prof MICME gave a vote of thanks for an excellent presentation with good practical and technical content. Members and guests then enjoyed a very good buffet sponsored by John Winter Ltd.