ZVAC is the name given to a simple, reliable and economical vacuum die casting technique.

To discuss how to implement ZVAC, email its originator via the contact form below:

 TOP 

The basic ZVAC method was designed in November 1990, and applied in January 1991 for a zinc product for IBM. The castings required high temperature powder coating, and vacuum enabled them to be made without imperfections like micro blisters or porosity. Today, it is being used for a diverse range of 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

• Consumer goods
• Computer components
• Bathroom fittings
• Door handles and furniture
• Lighting enclosures
• Electronic housings and heatsinks

ZVAC is 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.

 TOP 

TO GET ZVAC

To get ZVAC, email Chris Hoskyns, who is a UK registered Chartered Engineer (CEng) with over 40 years of hands-on foundry experience of diecasting processes.

PROJECT PRACTICALITIES:

Vacuum projects usually have 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
• Implementation and commissioning
• Proving trials and production with vacuum

 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 

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.