Monthly Archives: November 2017

InvestigationofWaxPatternsforAccuracyImprovementinInvestmentCastParts

Investment casting is referred to as a near net shape casting process and it is often preferred over other casting processes because of its many advantages(Some of them are mentioned below),

  • Application to parts with intricate geometry combined with high accuracy
  • Relative ease of producing components with internal cavities
  • Good surface finish, and good cast-ability with a large variety of alloys
  • The investment casting process has number of smaller processes and has its own complexities. There are three major stages in investment casting:

    • The production of wax patterns,
    • The production of the ceramic moulds and
    • The metal casting

    Dimensional changes occurs at every above mentioned stages, It needs to be addressed by applying shrinkage allowances so that the required final dimensions of the cast part can be achieved as accurately as possible.
    As the demand for tighter tolerances from investment casting grows, it becomes economically and competitively important for the investment caster to be able to have the best possible control of the factors that affect the accuracy of the final cast component.
    Modelling the Wax Pattern Contraction Process
    Because of the change in temperature occurring in the pattern material as it cools from injection temperature to room temperature there is an associated change in volume that can be accurately predicted if the material properties are known. However, there are a large number of factors such as injection parameters, die cooling regime, part size and geometry, which affect the degree of the changes in this ideal behaviour of the material.
    Above things needs to be addressed for getting accuracy in investment casting at every stages of processes apart from thes wax pattern also plays important role for achieving accuracy so we need to choose a wax pattern which have some properties for making the pattern like lowest thermal expansion, low melting point, low shrinkage, good surface finish, eco friendly etc.
    We at Saffroshine Pvt. Ltd. manufacture and supply all types of waxes across the world, which helps you to achieve accurate desired results in investment. Please connect with our wax expert for getting customized consulting solutions for your requirement at sales@saffroshine.com or call us at +91-217-2357272.

UnderstandingofInvestmentCastingWaxes

Investment Casting Waxes

Pattern Waxes:
In investment casting waxes are widely used as a pattern material with few exceptions. As the ultimate quality of castings in this process depends primarily on quality of wax patterns, so it is necessary to understand how best performance of wax – blend can be achieved. For the purpose, we will understand basics of wax moulding process.

Process of pattern – making needs either gravity pouring of molten wax or injection moulding of wax under pressure.

Gravity pouring is practiced when it is not possible to exert pressure on the mould (or only nominal pressure is permitted). In this case pouring is at comparatively high temperature to ensure proper fluidity. Mould material must be specially formulated to achieve low shrinkage values and cavitation to account for this high temperature.

Injection moulding in general, is preferred with semi-liquid or paste form of wax. To replicate the die for wax pattern, it should be filled at as low a temperature as possible to contract minimum on solidification.

Although for special requirements, billet injection is carried out by pressurizing solid blocks in to die, practically, considering mechanical set-up requirement etc. semi-liquid or the paste form is the best choice.

Selection of a wax blend for pattern – making must consider below mentioned points,

  • Should be suitable for injection and other processes in current plant set-up
  • Quality requirement of castings should be fulfilled by pattern performance on injection

While understanding the waxes we should know how the wax will perform in the shop floor condition and what is required to achieve its optimum performance, so it is very important to understand the nature of formulation of pattern – waxes.

Straight, Resin-filled & Water Emulsified Waxes

Normal straight formulation of pattern – wax is prepared from constituents, each of them
melting and forming a homogeneous melt.

When molten wax solidifies, it sets with dimensional shrink and cavitation or dishing effect, to reduce shrinking effects, a component may be added which is called filler and it does not melt but remains in the fine particulate suspension in the wax melt. Filler reduces the tendency to shrink of liquid wax thereby reducing the shrinkage percentage.

For this application, several natural or synthetic chemical entities have been tried in past. But research have resulted in the choice of synthetic resins, often styrene based homo or copolymers till date.
Water emulsified waxes are prepared by making slightly changes in normal straight formulation of pattern waxes so that with suitable emulsifiers, water added in the molten wax forms emulsion in the melt and fine droplets remain dispersed throughout the wax volume.

Water reduces the proportion of liquid which solidifies, reducing the shrinkage by that ratio hence it act as filler also these waxes are also called resin-filled waxes.
Due to function of water as a fillers in water emulsified waxes we can eliminate high initial cost of resin filler and later filler replenishment cost in subsequent cycles for reuse of wax after dewaxing.

Concept of Wax Conditioning:
Homogeneity of wax melt is very important to get good patterns.
The process to achieve the thoroughly homogenized phase of wax is called as ‘conditioning’ Need of wax conditioning arises due to poor thermal conductivity of waxes.
Total wax mass must attain the same physical form viz. semi-liquid, paste etc. and throughout maintain the same temperature. Generally, it is attained by slowly cooling wax molten at higher temperature under continuous agitation. Care must be taken to prevent air entrapment in the process of conditioning.
Conditioning is a very slow process and should be carried out before feeding into injection machine.

For achieving pattern quality is depend on function of injection conditions, wax conditioning, die design considerations, dedicated shop floor practice and very important quality of waxes, We, Saffroshine Organics Pvt,Ltd. is a leading investment casting wax manufacturer our waxes are available in the world market like India, Taiwan, China, Turkey, Germany, USA and other leading countries.

LostWaxInvestmentCastingAdvantages

Lost Wax Investment Casting

Lost Wax Casting:
Lost wax casting is also called as investment casting and is one of the oldest technique carried out to obtain precision casting. Today it is widely used in each and every sector of casting so as to reduce machining cost and obtain fine surface finish because of many impactful advantages and few are listed below:

Design Advantage:

  • Lost Wax investment casting helps to form intricate forms even forms with undercut.
  • Production of wide variety of products across different industries is only possible in lost wax investment casting. (Examples are like a larger-sized product that can be made using investment casting is turbine blades with complex shapes for power generation industries, Blades can be single-crystal, directionally solidified, or conventional equated blades and another example is The firearm industry where investment casting is used for smaller precision parts like firearm receivers, triggers, and hammers.

ACCURACY ADVANTAGE:

  • The accuracy of lost wax investment casting is second to none,
  • Parts with the highest precision can be cast with little to no machining or detailing required.
  • superior surface finish on the castings ( 120 to 150) RMS. Grater alloy selection
  • Helps to enhance performance of casted part.
  • Close tolerances of ± .005” (This is not possible with other types of casting processes.

Cost Reduction Advantage:

  • Lost wax investment casting provides exact shapes which leads to lower material cost.
  • Lost wax investment casting reduces the expensive machining operations that reduces initial tooling cost

The most impactful advantage of lost wax investment casting is environment friendly as it is produced from wax patterns which in most cases can be reclaimed and used again. Because of wax pattern one can eliminate expensive revisions and reducing metal scrap as we can see our part before it get casted.

Now it is very essential to use lost wax in investment casting industry to save environmental changes. We, Saffroshine organics Pvt,Ltd. are leading manufacturer of pattern wax, Our wide range of waxes are economically friendly as they can be used 3 to 5 times without losing any of their properties. and are easiest recyclable wax available in the world market like India, Taiwan, China, Turkey, Germany, USA and other leading countries.