|
ZVAC®
ZVAC is a reliable and economical vacuum die casting technique for making high quality diecastings.
The ZVAC vacuum diecasting technique was first used in 1991, for producing zinc and aluminium die castings; today, it is also being used in foundries around the world.
-
ZVAC can give more effective vacuum in the die at less tool and equipment investment cost than any other method.
-
Big cost savings, substantial improvements of quality, reduction of rejects, increased productivity and satisfied customers, make ZVAC a method well worth trying.
-
ZVAC is a practical method that was developed in a busy, profitable and lean UK subcontract diecasting foundry.
-
ZVAC uses basic engineering principles and innovations, which are very easy to apply, and can be implemented by any well equipped diecasting company.
-
Compared to the established traditional vacuum methods, ZVAC will enable you to mount a vacuum die onto a machine, make the parts and finish the run, without having the hassle and down-time cost of stoppages for clearing blocked vacuum valves or choked corrugated chillvents.
-
ZVAC can be quickly and easily put onto new and old dies
-
When massive venting of the die mold cavity is all that is needed to achieve quality standards, then the ZVAC vents can be used alone, without vacuum. You can even connect them to the feed runners and tangent gates.
-
Dies with ZVAC can run continuously, with only routine die face cleaning.
Curious about how to use ZVAC?
Then ask its originator via contact form below:
TOP
INTRO to ZVAC:
Invented and developed in a leading UK commercial subcontracting foundry in 1990, ZVAC has been in use there since January 1991, and is now being adopted by foundries around the world, for precision engineered die cast products such as:
- Pneumatic, gas and hydraulic valves
- Heatsinks for electronics and motor drive controllers
- Radio communication handset chasses and frames
- Automotive components:
- oil pumps
- transmission transfer cases
- engine cradles
- body shell structural elements
- oil filter mountings and manifolds
- brake components
- Pressure tight components for medical equipment
ZVAC is being used for polished and gold plated die castings. It is alo being used for zinc castparts which are zirconium nitride (ZrN) or titanium nitride (TiN) coated by physical vapour phase deposition (PVD) processes, and for or high temperature powder paint coatings. Typical products which benefit from ZVAC:
- Bathroom fittings
- Door handles and furniture
- Lighting enclosures
- Consumer goods
- Computer components
- Electronic housings and heatsinks
ZVAC is very economical to use, and the small increases in die tool cost is quickly recovered by improved quality, reduction of scrap and higher productivity.
ZVAC has enabled companies to successfully produce die cast parts, for which the customer has specified that vacuum must be used.
Name and Origin of ZVAC:
The name ZVAC was chosen in 2004, during a Canadian project; it can be pronounced zee=vac or zed-vac.
Designed in November 1990 and developed in 1991 by the Technical Manager of Dyson Diecastings Ltd., Chris Hoskyns, ZVAC was first used for producing a zinc alloy die cast product for IBM Computer Company, without any porosity or blisters.
Later, in November 1991, ZVAC was also used for aluminium diecastings on machines from 100 to 700 ton lock.
The ZVAC vacuum method is still used by the company where it was developed, Dyson Diecastings Limited, and they proudly refer to it in their advertising.
During the sale, aquisition and restructuring of the company, the matter of patenting the process was set-aside.
International progress of ZVAC:
- 2001, plant wide application at a fully automated zinc diecasting foundry near Shanghai.
- 2002, at a new aluminium die casting plant in Jiangsu.
- 2003, by another leading English diecaster, in place of Swiss made vacuum valves.
- 2004, in Canada and USA for magnesium die castings weighing up to 10 kg, on diecasting machines with up to 3,200 tonnes force of lock.
- 2005, in Iran, for producing zinc die castings that are 24 carat gold plated or TiN PVD coated.
- 2006, ZVAC at Taiwanese owned aluminium die casting plants in Kunshan, China, for die cast parts that are machined, finished and assembled ready for use, in safety critical products of US and European companies.
- 2007 -2008, ZVAC used for die casting automotive body products on a vacuum system with huge receivers and large powerful Chinese reciprocating piston dry vacuum pumps.
- 2008, introduction of ZVAC to The South America.
Now are you interested? :
Send your questions via form below:
TOP
TO GET ZVAC
To get ZVAC, invite its creator to your company, to transfer the techniques to your die designers, tool makers and production staff.
You will need to install a vacuum pump and some other standard commercial pipe mounted vacuum valves and filters, which would be specified to suit one or all of your machines.
The ZVAC vacuum method has to be 100% integrated with the die construction, but can often be retrofitted to existing dies without much modification.
There are variations to the ZVAC method, which would be applied depends upon how much vacuum is needed to satisfy the quality needs and die-mould construction.
Each vacuum project is different, but usually has three stages:
- STAGE 1
- Presenting the principles of the method
- Examining existing or planned new dies and machines
- Show how to adapt dies and machines to ZVAC
- Specify and order equipment
- STAGE 2
- Purchase equipment
- Vacuum system preparation
- Machine preparation
- Die design, manufacture or modification
- STAGE 3
- Commissioning
- Proving trials and production runs with vacuum
Contact Chris Hoskyns for on site instruction and engineering help.
Chris Hoskyns is a UK registered Chartered Engineer (CEng) , fully qualified, highly trained and with over 37 years of hands-on diecasting process experience.
Fees for the consultancy service are agreed with the client before instruction commences.
TOP
GUARANTEE
You are guaranteed that ZVAC® will give an enormous and consistent improvement to die casting quality.
TOP
BENEFITS OF VACUUM
Vacuum diecasting techniques enable porosity and surface appearance standards to exceed those possible by the ordinary high pressure die casting process. Which ever vacuum method is used, if it works well, it will always improve quality and reduce scrap. Vacuum reduces porosity. Vacuum produces cleaner looking castings with less lube stains. Vacuum can reduce occurrence of cold laps. Vacuum reduces need for overflow pockets. Vacuum reduces need for high pressures, and so enables larger parts or more impressions per given machine size. Vacuum enables the die designer to sidestep gating conundrums. Vacuum eliminates blister defects in painted and polished parts. Vacuum increases process yield. Higher yield means the die lives are longer. Vacuum reduces the load on inspection personnel, by producing good parts of consistent good quality. Vacuum can enable parts to be made thinner. Castings made with vacuum are stronger.
TOP
ADVANTAGES OF ZVAC
The main advantage of ZVAC over traditional vacuum die casting methods is reliability. You won't have to buy expensive stand-by vacuum valves. You won't have to buy expensive chillvents. You won't have to make big pockets in the outer peripheries of your holder blocks to accommodate chillvents, so holders retain their stiffness. In operation, the vacuum gallery around the die in conjunction with the ZZVs, draws residual lubricants on the parting faces, away from the mold cavity, so reducing porosity caused by lubricant liquids. Overflow volumes can be reduced or eliminated. Economical implementation costs, allow ZVAC vacuum technique to be used simultaneously on every die and machine in a foundry. ZVAC® uses standard stock vacuum equipment, which means you can buy valves and pumps from your local high vacuum equipment suppliers. The ZVAC method can show you the vacuum pressure actually in the die cavity before each shot, not just at some remote point on the supply pipe or tank. Very rapid vacuum pull down is achieved by using standard large high flow vacuum valves, filters and pipes. Most existing dies can be easily and successfully converted to ZVAC venting and vacuum, even those with lots of sliding cores.
TOP
TECHNICAL OUTLINE
The ZVAC technique uses a new concept of deep channel venting named Zig Zag Vents (ZZVs) combined with large bore high flow vacuum channels and sealing techniques using binary silicone rubbers.
To significantly reduce die casting porosity by using vacuum, the air pressure in the die cavity has to be reduced to better than 90% of full vacuum; i.e. lower than 100 millibar absolute before injecting metal.
The lower the pressure, the better the cast part will be. In some instances, pressures lower than 10 mbar are possible.
The relationships between porosity volume, pore diameter and vacuum, and leaks and vacuum, are shown by graphs.
In the die-casting foundry, ZVAC enables very low pressures to be reliably achieved, by using a comprehensive sealing strategy together with large area vents, large pipes, large filters and large valves.
Primary sealing is on the holder block (bolster) parting face, and is accomplished by a very practical method, with precision made high temperature silicone rubber cord. The most frequently asked question is, "Does it survive die flashing?" The answer is, "Yes".
Secondary sealing is internal, by two alternative ways:
(a): injecting special non-corrosive liquid RTV silicone rubber,
or
(b): fitting silicone foam or solid cord. or strategically placed silicone, PU or PTFE O_rings.
The sealing method is tolerant of gross die face contamination, corrosion and distortion of the die and slide abutments; and, has proven to be reliable and durable on hundreds of dies since 1990.
The cavity and slide ways are entirely surrounded by a large vacuum channel, which has large bore ports to large bore pipes and valves(25 to 50 mm ID). The peripheral vacuum channel draws lubricant residues away from the die-mold cavity, and intercepts any inward air leakage.
Vacuum is directly connected to the mould cavity by multiple deep Z_Vents (ZVs or ZZVs).
To maximise evacuation rate, ZVs can also be connected to main metal feed runners.
Total vent area can be much more than that possible with poppet valves and chill vents, so enabling maximum vacuum to be realised very quickly.
ZVs are self cleaning and do not block up like corrugated chillvent block inserts or poppet valves, which are impossible to clean without removal from the machine.
As well as maximising vacuum in diecasting, ZVs were found to be very effective when used in non-vacuum dies.
When the mould has filled, metal flows into the ZVs and starts to freeze as its flow is repeatedly reversed upon itself, which progressively chokes the path of the metal.
Vacuum within the die cavity is directly measured before and throughout each shot, which gives more accurate data than measuring it on the supply side of the valve, as in commercial systems.
In the ZVAC method, air and fumes are extracted at maximum rates during the plunger slow and fast injection plunger strokes, up to complete filling of the die cavity.
All features use robust fundamental engineering. See example of basic vacuum die technique from training material on CD.
ZVAC® vacuum diecasting technique can be used with semi solid, rheocasting and thixotropic casting technologies, to maximise cast feature integrity.
ZVAC® vacuum die casting technique can be used on machines with extremely fast (7m/s) and very slow injection plunger speeds.
ZVAC® has used pumps, valves and filters from Balzer, Pfeiffer, Northey Technologies, BOC-Edwards, SMC Pneumatics, Huntington Mechanical Laboratories Inc., Kanglia, manufactured in Brazil, China, Germany, Japan, Russia, USA and UK.
|
