International Vacuum Diecasting Engineer
Chartered Engineer, (CEng)(UK registered)
Member of The Institute of Engineering & Technology (MIET)
Gating and venting development for minimising porosity and die fill flow defects.
Provision of technical support to designers, buyers, producers and finishers of diecastings.
Used in UK since 1990, and now internationally.
My vacuum technique really does stop gas problem porosity.
Its simplicity, reliability and effectiveness result in success. ¦:-)
VACUUM TECHNIQUE DEVELOPMENT HISTORY
In November 1990, faced with an extremely difficult porosity problem in zinc alloy high pressure diecastings for IBM, I designed and developed a very effective, economical low-cost, reliable and successful new vacuum technique. When commissioned in January 1991, it immediately saved the Company's most lucrative and prestigious order and reduced production costs.
Initially, the technique was used on two 400 ton hot chamber diecasting machines at Dyson Diecastings Ltd.
Rejections for gas porosity and surface imperfections were immediately reduced from well above 40% to below 2%, and then with vent development and improved die sealing to below 1% (total after all secondary processes).
Complaints and batch rejections from the customer ceased, and the product became very profitable.
The need to get vacuum in the die as rapidly as possible led me to develop a new venting technique, which I called ZZVs (from zig zag vents). It was so effective and simple to apply, that the foundry manager had it cut into almost all standard (non-vacuum) dies.
Within eight months, the vacuum system was extended into the aluminium foundry; initially, for newly acquired order for technically challenging heat-sinks with deep thin fins.
The vacuum technique was progressively applied to new and existing dies to increase process yield, productivity and profits.
The technique is now used in at other plants in UK, China, Canada, Colombia, USA, Iran and Egypt.
COMMENTS & SECONDARY BENEFITS
Having for decades before using vacuum, optimised diecasting injection parameters, feed and vent geometries on thousands of dies to minimise porosities, the more I applied vacuum, the more I became convinced that when applied with due attention to die sealing, exhausting vents and ducting port sizes, vacuum provides the most powerful means for eliminating gas porosity in high pressure die castings.
Sometimes, using vacuum enables shot speeds and metal pressures to be reduced from the days when very high speeds and pressures were used for squeezing gas bubbles to smallest possible size.
The method creates relatively high vacuum in the die, and enables the number and size of overflows to be reduced; so reducing melting energy costs and carbon (CO2) emissions.
It has been proven that vacuum has enabled thin die casting to be made with even thinner walls and still have excellent quality.
This high vacuum diecasting method can even render remedial processes like impregnation unnecessary.
In 2004, the technique was named ZVAC®; an acronym derived from the radical geometry of its deep Zigzag
THE TECHNIQUE BECAME THE PROTOTYPE FOR ‘SUPER VACUUM DIE CASTING’
Initially, use of the vacuum technique was revealed only to customers, but after extensive use over six years, during the period that the Alumasc Group owned the Company, the valuable benefits of Dyson's ‘own-developed’ vacuum technique were proudly anounced in the group brochure and websites. (Note: In 2016, Broadways Stamplings Ltd. became proud new owners of Dyson Diecastings Ltd., following restructuring of the Alumasc Group.).
View Dyson's original web page of their brochure from October 1998 <click>
View a scanned image of Dyson's page in Alumasc's 1996 brochure <click>
PUBLICATION OF THE PROCESS PRINCIPLES
In 1998, I published the fundamental principles and examples of my vacuum technique on the Internet, to promote my technical services.
In 2001, the vacuum technique was installed in a Taiwanese owned large zinc diecasting facility in Shanghai, to improve quality of chrome plated zamak die-castings.
Following that success, in 2003, a technical paper was published by the China Foundry Association. link
In 2009, a translation to Japanese was made by Makoto Kitamura of Temco Inc, Japan. link
Links goes to: independent.academia.edu
APPLICATIONS OF ZVAC
The range of products benefiting from ZVAC is diverse:
since 2001, ZVAC® has been adopted by die-casting companies large and small around the world, for magnesium, aluminium and zinc alloy diecast parts:
automotive parts such as large V8 engine cradles, transmission transfer cases, console fascias, carburettors and oil pumps
electronics parts such as heat exchangers, heat sinks, enclosures, computer parts and hi-fi units
products for office and domestic environments, such as: gold and chromium plated parts for lighting, bathroom fittings, kitchen appliances and door furniture
In general, the greatest productivity and financial benefits of using vacuum for die casting are enjoyed when making parts that require expensive secondary finishing processes, such as: polishing, plating, powder painting, machining, impregnating, PVD coating with TiN, ZrN or CrN, or have demanding service structural requirements for strength and/or pressure tightness.