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Guidelines of making Plaster craft

Plaster craft is a complex process unless you are aware of its ins and outs. Given below are a few guidelines of making plaster craft.

Step – 1:
Cover your work surface with an old newspaper or a vinyl peace. As you may see from this photo plaster casting is a bit messy, so it is essential to protect your countertops.

Step – 2:
Check the mould to ensure it is clean and dry. Any dirt might show on the finished casting.

Step – 3:
Many moulds cannot sit flat on the counter, therefore, it is important to give them support while using. The most simple process is a zip lock bag filled with a few pounds of rice. Rice bags are convenient to pack and store when not being used and are made of common materials most people find handy. A box of sand will also work well but it is more difficult to store it when not being used.

Step – 4:
The surface tension of the water tends to trap air leading to pinholes in the finished casting. Airid is a product meant to break that surface tension, reducing the chances of trapped air. Spray or wipe a thin coat of Airid into the mould.

Step – 5:
Wiggle the mould down onto your rice/sand bag till it looks level. You are now ready to mix plaster.

Step – 6:
To find out how much plaster will it hold fill the mould with water. It is the exact amount of water you will need. Add a bit more and weigh it on scale.

Step – 7:
Plaster should always be added to water and never vice versa. Sprinkle it in slowly to allow it to absorb water.

Step – 8:
Let the mixture remain undisturbed for 2 minutes so the plaster absorbs all water.

Step – 9:
For coloring, pigments should be added now.

Step – 10:
Utilize a potato masher to mix thoroughly for about a minute. Small amounts can be mixed with a stick.

Step – 11:
Pour the plaster in a corner of mould and let it flow across the complete mould. On deeper moulds, pour it down the side of corner to avoid entrapped air.

Step – 12:
Once the mould is poured, wiggle it to dislodge any air which may have remained in the mould.

Step – 13:
Periodically feel the mould. When the mould is warm to touch, the plaster casting may be removed.

Step – 14:
Gently flex the edges of mould to break sides of casting loose.

Step – 15:
Hold the mould just above the rice/sand bag. Use pressure gently to take out the casting.

Step – 16:
After casting is out, set the mould to be cleaned.

Step – 17:
Utilize a knife to cut the sharp edges off the back of the casting. For fast drying it should be put where it gets air from all angles.

Step – 18:
When fully hardened, most of the plaster will flake off or breakout the plaster.

Step – 19:
Flex the blade of the plaster blender to flake the dried plaster off.

Step – 20:
Wipe off tools and moulds for final cleaning up.

Step – 21:
If you utilize a rice bag any drips may be removed by flexing the bag. For sand box, just pick out any plaster that has fallen on sand.

Step – 22:

Pack up your moulds, tools and plaster. Throw away the old newspaper with which you had covered the working area. If you had used vinyl piece, dust it and wipe with wet cloth.

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The New shock absorbers

A rigid motorcycle frame has a pair of spaced swingarms joined to a shock absorber that has a shock absorber casing pivotally mounted on the swingarms and has a shock absorber rod which is pivotally joined to the motorcycle at a point below the housing whereby the movement of the back wheel of the motorcycle makes the outer housing of the shock absorber to go upward relative to shock absorber rod which is fixed to the motorcycle frame and which is opposite from the normal operation of shock absorber. The shock absorber includes a spring means and/or hydraulic means to give the normal resistance given by a cushioning arrangement. In function the swing arms are moving downward, the shock absorber moves its mounting points closer together which is different from most shock absorbers who move their mounting points more apart.

Majority of the motorcycles in use these days utilize a swingarm to locate the back wheel relative to the motorcycle frame. The forward end of the swingarm; pivots around a bolt running crosswise through the motorcycle frame or through brackets attached to the motorcycle frame to let the back wheel move when it encounters a bump. The weight of the vehicle is supported by either one or two shock absorbers, which have a spring (mechanical or gas) and a way of damping movement.

Still there are motorcycles designs with two shock absorbers, with one shock absorber located on either side of the back wheel and extending upward from the swingarm to the rearward position of the frame. Recently, a large number of motorcycles utilizing only one shock absorber have given much better suspension performance. In these designs the shock absorber is located forward of the wheel and extends from the area of swingarm upward to an area under forward portion of the seat.

In most case the performances benefits of single shock absorber are achieved by utilizing the mechanical links at top, the both, or bottom, which transmit the forces between these designs, either the upper end of shock absorber and/or linkage and brackets utilize space which would otherwise be utilized for an air filter box, a battery or some other purpose.

The present process is utilized on a motorcycle lock suspension and uses a shock absorber mounted on a swingarm which has a pair of spaced swingarm members. The piston rod of the shock absorber is fixed to a pivot on the lower end of the motorcycle frame and the housing or cylinder for the piston is attached to the swingarms. The shock pivots around a crosswise axis on the frame. The shock absorber tries to pull its mounting points closer together which is separate from most shock absorbers who try to push their mounting points further apart. Thus in the operation of devise when the back wheel is driven upward with the swingarms, the shock absorber piston rod travel downwardly in the casing, as the casing travels up with the swingarm.

Steps of plaster mould casting

In mould casting, melted aluminium is poured into a cavity in the required shape of product. When the hot aluminium comes into contact with mould its temperature goes down very fast. This causes the quick solidification of product being produced. Mould makers face the challenge of making sure that all the parts of mould cavity are properly filled, whatever the local temperature of aluminium might be or the hole might be narrow from which melted metal is to be filled.

Fluent goods give chance to mould designers to keep track of melted aluminium as it is poured into the mould. This gives them time to identify probable defects due to trapped air, extreme cooling of metal and possible defects of mould due to combined action of high temperature and high pressure. Mould designers are also able to detect folding free surface that can entrap air bubbles, break free surfaces which may cause excess oxidation of the metal and the progressive solidification of the aluminium.

What is plaster mould casting?
Plaster mould casting, it is also known as Rubber Plaster Moulding (RPM) is a system of making aluminium or zinc castings by pouring liquid metal into plaster (Gypsum) moulds.

Step – 1: Model or master pattern

1. Made from client’s drawing or CAD file.
2. Stereolithography, traditional hand made or machined.
3. Model is engineered to include:
1. Metal shrinkage
2. Mould taper (if needed)
3. Machine stock (if needed)
4. You may “clone” or adapt client supplied model if requested.

Step – 2: Foundry Pattern equipment

1. Negative moulds are made from model
2. Core plugs are made from moulds
3. A positive resin cope and drag design is now made from negative moulds.
4. Core boxes are made from core plugs
5. Gating, runner system and flasks are joined as needed.
6. Duplicate sets of tooling might be made from the master negative.

Step – 3: Plaster mould

1. A liquid plaster slurry is poured around the cope and drag pattern and into the core boxes.
2. The plaster mould is next removed from the cope and drag pattern.
3. The plaster mould and cores are then baked to remove moisture.

Step – 4: Pour Casting

1. Melted metal is made by degassing, and a spectrographic sample is taken to check the chemical analysis.
2. The melted metal is then poured into the assembled plaster mould.
3. The plaster is removed by mechanical knockout and high pressure waterjet.
4. After cooling of the casting, the gates and risers are then removed.

Step – 5: Secondary operations

1. The raw castings are inspected and serialized.
2. Castings may then need (as per client specifications):
1. Heat treatment
2. X-Ray
3. Penetrant inspection
3. After finish inspection, casting is ready for:
1. Machining
2. Chemical film, chromate conversion, paint or special finishes
3. Assembly
4. Form-in-place gasketing.

Plaster craft is a hobby, which gives you chance to make a few pennies worth of material into beautiful wall hangings and sculptures.

Plaster crafting is quite safe if you observe safety rules while mixing plaster. Once it is hardened three is little or no hazard from handling plaster things. Plaster is usually Plaster Of Paris. It is called by various names depending on its producer-viz.-Plaster Of Paris, casting plaster or just plaster.

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Having stylish door handles

Purchasing an antique style door handle may have your fingers trapped or you may get a door knob that does not work.

To avoid trapped fingers the first thing to check is the distance from the edge of door to the center of the hole drilled for the lock. Make certain that it is long enough not to trap your fingers on turning the door knob. If the distance looks rather short, get a lever door handle instead.

There are a few sets of matching reclaimed door knobs available these days. If you have time to look around you might be lucky enough to find them. If not then you can always buy new ones. Companies like Drummonds produce exact replicas of beautiful original pieces.

There is a mouth watering quality of designs to select from if you are planning to purchase antique knobs. For that you do have to go out and search. And you also need to make sure that the antique door knobs will work. New door knobs are much simpler to install and naturally works better.

Style of door knobs is a matter of personal preference. You have to ask yourself whether you want the style of door knob to conform to the rest of house, or you wish the door knob to conform to the style just the door on which it is installed or you simply want to select the doorknob that you like whether it matches with its surroundings or not.

Door knobs and handles made of brass are the best. Brass has a big plus of not rusting or rotting. It is decorative and when polished acquires an attractive patina over time you can easily plate it for a silver or copper finish. Well polished knobs will get a wonderful patina if they are not lacquered.

Iron knobs need protecting except for pure black which is slow to rust. The most popular form of protection is to paint them, but ailing or waxing look more natural and wear to a nice patina over time.

Ebony and fruitwoods are traditional but modern looking; hardwoods are mainly utilized these days, often stained to look like ebony. Cracks in these knobs are generally not serious problems and mix with surroundings.

Ceramic or glass knobs generally have brass parts. You should watch for hairline cracks. Small cracks are harmless but serious cracks can cause lot of damage.

There is a Rim lock type of lock. In this a box is planted on the door that catches in a box on the door frame. The benefit of Rim lock is that it has knobs on both sides of the door. You have to be sure in your mind that this is the type of knob you want for your lock. If you wish slight alteration can be made.

As a device door handles are necessary to lock the doors and facilitate your entry inside or outside the house. Entering and exiting is comfortable with door handles around, so there is a premium attached to there being reliable 24/7.

Die casting Manufacturer in India? ? ? ? |? ? ? ? Die castings in aluminium alloys? ? ? ? |? ? ? ? Aluminium rain water guttering? ? ? ? |? ? ? Locomotive Brake components

Best pressure die casting

This relates to a pressure die casting machine and in particular to an apparatus and method for moving a die of a pressure die casting machine.

Pressure die casting is the injection of melted metal or plastic under high pressure into a mould cavity.

Before injecting the melted metal into the cavity, the mould is “closed” i.e. the two halves of the mould, called dies are brought together, after which dies are held together while the melted metal is forced into the cavity they form. The metal is allowed to solidify in the shape of mould cavity and then the dies are pulled apart so that solidified object may be ejected and the cycle repeated.

To manufacture die castings free of pores and shrink holes it is normal practice to fill the mould at high pressure and to let the metal solidify while under high pressure so as to effect compression of die casted metal. The apparatus which closes the dies and holds them together needs to have capacity to withstand this high pressure and it is required to work for long hours.

To simplify the clamping procedure for holding the dies together the apparatus uses a die casting machine which has one die fixed on the machine base and second die half is removable into and out of apparatus. Thus movement and control apparatus might be given for one half of die. This has an additional advantage that the hot melted metal can be fed into the mould cavity or chamber between the dies through a sprue in the fixed die.

Aluminium and copper alloys that attack and erode machine components with which they are in regular contact are generally produced in what is called cold chamber machine, whereas tin, lead and zinc die castings are processed in a chamber called hot chamber machine. The pressure die casting machine is equally well used in hot and cold chamber pressure die casting.

A die casting machine uses a fixed and moveable die. Four tie bars or guideways are rigidly connected to two plates upstanding from the machine lease; one die is placed on one plate while the other die is slidably mounted on the tie bars. Pressure oil is given to an operating cylinder containing an operating piston which is linked to a displacement yoke linked in turn with guide spars these are externally threaded to receive nuts between which the yoke is clamped.

The dies are closed and melted metal is entered into cavity of dies from the sprue in the fixed die and required pressure is given. After the metal solidifies the pressure on the dies is released and two halves of dies are separated and finished product is taken out and process of pressure die casting is repeated.

The same process of pressure die casting is used in plastic moulded die casting products the only difference being that instead of melted aluminium, melted plastic is poured into the die from a sprue fixed in lower die and required pressure is given. After the plastic cools down and solidifies the pressure is released, and die opened and finished product is taken out and process repeated.

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Plaster casting

Plaster casting is similar to sand moulding the difference being that plaster is used in place of sand. Plaster is 70-80% gypsum and 20-30% strengthener and water. Normally it takes 4-6 days to prepare after which a production rate of 1-10 units/hr. mould is possible with items as big as 45kg and as small as 30 grams having very high surface resolution and fine tolerances.

Once used and cracked, it cannot be easily recast. Plaster casting is generally utilized for nonferrous metals like aluminium, zinc or copper based alloys. It cannot be utilized to cast ferrous metals because sulfur in gypsum slowly reacts with iron. Before mould is prepared the pattern is sprayed with a thin film of parting compound to prevent the mould from sticking to pattern. The unit is shaken so that the plaster fills the small cavities around the pattern. The form is extracted after the plaster sets. Plaster casting means a step up in sophistication and needs skill. The automatic functions may be given to robots but the higher precision pattern designs need even greater level of direct human assistance.

In plaster mould casting, a plaster, usually gypsum or calcium sulfate, is mixed with talc, sand, asbestos, sodium silicate and water to form a slurry. This slurry is sprayed on the polished surfaces of pattern halves (generally brass). The slurry sets in less than 15 minutes to form a mould. The mould halves are removed carefully from the pattern and dried in oven.

The mould halves are carefully joined, along with the cases. The melted metal is poured in moulds. After the metal cools down, the plaster is broken and cores cleaned out.

Parts cast are generally small to medium size, having weight of 30 grams to 7kg. the section thickness maybe as small as 0.6mm and tolerances are 0.2% linear. The draft allowance is 0.5-0.1 degree. The surface finish is 1.25 ?m to 3 ?m (50 ?m to 125 ?m) rms.

Low temperature melting materials like aluminium, copper, magnesium and zinc may be cast utilizing this system. This system is utilized to make fast prototype components as well as limited production parts.

Plaster casting as a sculpture system is of three types. One uses a waste mould, another a piece mould (both Plaster Of Paris) and the third a gelatin mould, all remake the original clay or wax model made by the sculptor. The waste mould is broken to free the hardened cast, which was poured in as a liquid plaster. The gelatin mould being reusable may be sprung from the cast with care and extracted intact and utilized for replicas. The piece mould can also be utilized again, being so divided as to be easily drawn away from the undercutting of the cast without damaging either of them. Plaster casts are utilized not only for creations of new sculptures, but also for the many replicas of famous marble and stone statues. The ancient Egyptians utilized models of plaster made directly from human body. The Romans cast in plaster many thousands of copies of Greek Statues. In another sense of the term, plaster casting refers to the surgical process of encasting in a Plaster-Of-Pairs cast any part of body in which bones are broken so that the bones set well without interference of motion or jarring or physical shock.

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The zinc-aluminium die casting alloys

New high performing zinc-aluminium ZA casting alloys (zA-8, ZA-12, ZA-27) give superior mechanical properties which designers can apply utilizing die casting technology. In general the ZA alloys are stronger, harder and offer more creep resistance than standard zinc alloys and can be used where bearing properties are important.

Aluminium alloys with 0.5-0.9% Fe content have largely replaced 1350 EC alloy for making electrical circuits because the latter continuously suffered from gradual loosening at terminals, which led to overheating. This problem has been totally removed in new conductor alloys without sacrifice of conductivity.

To get economic benefit of weight advantage of aluminium wire should be capable of attaching securely to standard fixtures without special handling techniques. But EC wire on binding screw terminals tightened to a standard torque may become loose, when the wire heats due to being overloaded. The wire gets expanded more than the Cu-alloy fixture and creeps to relax the added stress.

On getting cool it contracts to a smaller dimension, whereby the area of contact is reduced and it permits oxide to form at interface. On a subsequent current overflow, the overheating increases which leads to further loosening of wire. EC wire annealed for adequate bend ability gets sub structurally loosened at 200°C and ultimately fails due to repetitions of these cycles.

The new alloys (800 series) of 0.5-0.9% Fe have much better microstructural stability and creep resistance and, therefore, they are not prone to these failures.

While annealed to the same ductility or bend ability, the high Fe alloys are double strong. This capability has been established by practical field use of many years in USA, Europe and South Africa after these alloys were introduced in 1968.

Better and latest alloys which not only provide high integrity to terminations but are suitable for magnet wire after normal hot annealing have been made after adding a third alloy to improve its performance examples are 0.5% Fe with 0.5% Co and 0.5% Fe with 0.2-0.4% Si.

Processing and microstructure:
In continuous casting a bar of 50cm2 is made at 16 m/min on a 2.5m diameter copper wheel. The quick solidification results in a 20 ?m dendrite arm spacing and eutectic red cpacing of about 0.2 ?m with a supersaturation of about 0.1% Fe. These very fine particles play a significant role in giving stability to substructure while being incapable of nucleating crystallization.

The presence of sub grains has been known in hot worked aluminiums but without quantitative determinations of the dimensions or the effects on properties. As the temperature rises from 200-450°C, the cold yield strength of the hot worked product decreases greatly from the strengthening made by 97.5% cold rolling.

As has been seen in many hot worked metals, the yield strength is inversely proportional to sub grain diameter. Because the temperature is less and strain rate is high in a given pass than those in the previous one, substructure “inherited” from i.e., carried forward from, the latter is altered by dislocations to the existing walls to raise their density and by formation of new walls to subdivide the sub grains lessening their size.

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Magnesium alloy castings

Magnesium alloy castings can be made by almost all methods of castings. The casting method to be used depends on to what use magnesium is going to be put. Some of its casting processes are as given below:

Sand casting:
Magnesium alloy’s sand castings are used in aerospace uses because of clear advantage they have in weight over aluminium and other metals. A great deal of research and development on these alloys has led to terrific changes in general properties compared with earlier AZ types. There has been and still a very large amount of castings for aerospace uses being made in AZ type alloys, the trend is for making maximum share of aerospace castings in latest zirconium types.
Though, the magnesium-aluminium and magnesium-aluminium-zinc alloys are generally easy to cast they are limited in certain respects. They show microshrinkage when sand cast and they are unsuitable for uses where temperatures of 95°C are felt. The magnesium rare earth-zirconium alloy do in fact show very good pressure tightness. The greater tendency of zirconium containing alloys to oxidize is overcome by utilizing special melting processes.
The two magnesium-zinc-zirconium alloys originally developed ZK51A and ZK61A show good mechanical properties, but they suffer from heat shortness cracking and are unweldable.
When a demand arose in aerospace engine uses for having metal of high mechanical properties at high elevated temperature (up to 205°C), thorium was replaced for rare earth metal content in alloys of the ZE and EZ type, giving rise to the alloys of the type ZH62A and HZ32A. Not only the mechanical properties improved greatly at elevated temperatures but they also retained their features of good castability and welding. The thorium containing alloys however showed a greater tendency for oxidation, requiring greater care in meltdown and pouring. A further development aimed at improving both room temperature and elevated temperature mechanical properties produced on alloy named QE22A. In this alloy silver replaced some of the zinc, and high mechanical properties were obtained by grain refinement with zirconium and by a heat treatment to the full T6 condition. But problems were experienced with both these alloys.

Permanent mould casting:
Normally alloys which are sand cast can also be permanent mould cast. The exception to this are the alloys of magnesium-zinc-zirconium type which show strong hot-shortness tendencies and are therefore unsuitable for processing by this method.

Die casting:
The alloys from which die castings are normally made are of magnesium- aluminium zinc type. Two versions of this alloy which were die cast for many years are AZ91A and AZ91B. The only difference in these two alloys is higher copper impurity in AZ91B.

The most important reason for using magnesium castings is their lightweight. Due to this magnesium castings have been greatly in use since World War II in aircraft and aerospace industry both military and commercial. The latest trend is magnesium’s use in auto field basically as die castings due to demand for lightweight cars to save petrol.

Magnesium has other important casting advantages over other metals:

1. It is an abundantly available metal
2. It is easier to machine than aluminium
3. It can be machined faster than aluminium, preferably dry.

In die casting process it can be cast four times quicker than aluminium. Die life is much more than with aluminium alloys because there is very little welding on the die surfaces. When protected correctly, especially against galvanic effects it behaves in a very satisfactory way. Modern casting methods and by applying protective coatings ensure long life for well designed components.

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