hot and cold chamber die casting.pptx importance

hot and cold pressure die casting

1. PRESSURE DIE CASTING NAME: DIPIKA JAIN ROLL NO.: 23 SEC: B1 BRANCH: ITE

2. INDEX INTRODUCTION WORKING HOT CHAMBER PROCESS COLD CHAMBER PROCESS ADVANTAGES LIMITATIONS APPLICATION

3. PRESSURE DIE CASTING Die casting  is a  metal casting  process that is characterized by forcing  molten   metal  under high pressure into a  mould cavity . The mold cavity is created using two hardened  tool steel   dies  which have been machined into shape and work similarly to an  injection mold during the process.  the pressure die casting process consists of injecting under high pressure a molten metal alloy into a steel mold (or tool). This gets solidified rapidly (from milliseconds to a few seconds) to form a net shaped component. It is then automatically extracted. For example ,   Carburettor body made by  aluminum alloys

4. WORKING In Pressure die casting, the die consists of two parts. One called the stationary half or cover die which is fixed to the diecasting machine. The second part called the moving half or ejector die is moved out for the extraction of the casting. The casting cycle starts when the two parts of the die are apart. The lubricant is sprayed on the die cavity manually or by the auto lubrication system so that the casting will not stick to the die. The two die halves are closed and clamped. The required amount of metal is injected into the die. After the casting is solidified under pressure the die is opened and the casting is ejected. The die casting die needs to have the provision of ejectors to push the casting after it gets solidified . It will also have cooling channels to extract the heat of the molten metal to maintain proper die temperature.

5. The die casting machines are of two types: ● Hot chamber die casting ● Cold chamber die casting The main difference between these two types is that in hot chamber, the holding furnace for the liquid metal is integral with the die casting machine, whereas in the cold chamber machine, the metal is mehed in a separate furnace and then poured into the die casting machine with a ladle for each casting cycle which u also called ‘shot’

6. HOT CHAMBER PRESSURE DIE CASTING The hot-chamber process is applicable only for zinc and other low melting point alloys that does not affect and erode metal pots cylinders and plungers. The workings of a hot chamber process goes like this. The molten metal for casting is placed in the holding furnace at the required temperature adjacent to(sometimes as part of the machine itself) the machine. The injection mechanism is placed within the holding furnace and most of its part is in constant touch with the molten metal. When pressure is transmitted by the injection piston, the metal is forced through the gooseneck into the die. On the return stroke, the metal is drawn towards the gooseneck for the next shot. This process ensures minimum contact between air and the metal to be injected. The tendency for entrainment of air in the metal during injection is also minimised .

7. HOT CHAMBER PRESSURE DIE CASTING

8. SCHEMATIC PROCESS OF HOT CHAMBER PRESSURE DIE CASTING

9. COLD CHAMBER PRESSURE DIE CASTING The difference of this process with the hot-chamber process is that the injection system is not submerged in molten metal. On the contrary, metal gets transferred by ladle, manually or automatically, to the shot sleeve. The metal is pushed into the die by a hydraulically operated plunger. This process minimises the contact time between the injector components and the molten metal. Which extends the life of the components. However the entrainment of air into the metal generally associated with high-speed injection can cause gas porosity in the castings. In the cold chamber machine, injection pressures over 10,000 psi or 70,000 KPa is obtainable. Generally steel castings along with aluminium and copper based alloys are produced by this method.

10. COLD CHAMBER PRESSURE DIE CASTING

11. SCHEMATIC PROCESS OF COLD CHAMBER PRESSURE DIE CASTING

12. ADVANTAGES Die casting is an economical process for large scale production Because of the use of the movable cores, it is possible to obtain fairly complex castings than that feasible by permanent mould casting. Very small thicknesses can be easily filled because the filled because the liquid metal is injected at high pressure. Inserts can be readily cast in place Reduces or eliminates secondary machining operations. Die casting fluid length is unaffected by solidification range, unlike permanent molds, sand castings, and other types. Corrosion rates for die castings are slower than those for sand castings due to the smoother surface of the die castings.

13. LIMITATIONS The maximum size of the casting is limited.The normal sizes are less than 4Kg with a maximum of the order of 15Kg because of the limitation on the machine capacity. The process is limited to high-fluidity metals. Increased scrap rates can be caused by fluidity failure, and scrap costs in die casting are high. Die casting involves a large number of parts, so questions of repeatability are particularly important. The air in the die cavity gets trapped inside the casting and is therefore a problem often with the die castings. The dies and the machines are very expensive and therefore, economy in production is possible only when large quantities are produced

14. APPLICATIONS A utomotive parts like wheels, blocks, cylinder heads, manifolds etc. Aerospace castings. Electric motor housings. Kitchen ware such as pressure cooker. Cabinets for the electronics industry. General hardware appliances, pump parts, plumbing parts.

15. THANK YOU NAME: DIPIKA JAIN ROLL NO.: 23 SEC: B1 BRANCH: ITE