Chapter One Introduction to Lost Foam 1.2 Applicability and Economy of Lost Foam Casting


1.2.1 Applicability of lost foam casting

 

Lost Foam Casting andThe comparison of V method, paraffin casting and sand casting process is shown in the figure.1-2shown.

 

(a) Lost Foam Casting Process

(b) V"Casting process flow

 

(c)Paraffin wax casting process

 

d) Sand casting process

Figurel-2  Comparison of Lost Foam Casting and Several Other Casting Methods

 

The biggest feature of lost foam casting is the use of polystyrene(EPs)or copolymer(stMMA)Foam is materialMaterial, after pre-development, molding, combined into a pattern unit, buried in dry sand, after vibration, pouring under the action of negative pressure.Liquid metal, high-temperature liquid metal gasifies the pattern and discharges it through the coating layer and dry sand. The liquid metal is replaced and solidified to become cast.pieces. From Figure1-2It can be seen that compared with other casting processes, the lost foam casting process has the following advantages:

① The appearance material isEPSorstMMA;

② There is no core process, eliminating the need to make core boxes, core, baking core and other work;

③ There is no need for complicated work such as mold drawing, modification and box closing in the modeling section;

The production of castings without flash burrs, greatly reducing the amount of cleaning;

 

 ⑤ flexible process, can achieve a box of multiple casting, casting, etc.

It is the above points that make it have great advantages in the consumption of mold making materials, modeling man-hours and cleaning man-hours.

 

(1)Applicability to casting materials Generally speaking, all alloys that can be cast can be cast in lost foam, with super adaptability.Sand casting. Ordinary sand mold can not cast titanium alloy, but the lost foam is used.Si(: Titanium alloy can be poured after sand, which is currently usedLost mold casting production, the material is ordinary cast steel, heat-resistant alloy steel, stainless steel, nickel-iron alloy, ordinary gray cast iron, anti-wear casting.Iron, white iron, heat-resistant and corrosion-resistant cast iron, ductile iron, aluminum alloy, copper alloy, etc., for high melting point casting alloy materials, tableThe surface is less sticky sand, no flash burr, easy to clean, and the casting matrix is uniform.

 

(2)SUITABILITY FOR CASTING SIZESize of working face and sand box of vibrating table(Long× width × height)Directly decide to disappearThe size and quantity of castings cast by the mold, so the applicability of castings is much wider than that of sand casting, which can be used in vibrating bench work.Different sizes of sand boxes are placed on the surface, making it easy to arrange various castings in the sand box.(Including small pieces of strings, stringsArrangement of groups), can pour a few kilograms(The following group string)Casting, can also be pouredlt(Above)Castings(Intermediate frequency furnace capacityand fixed), such as support(zG 35)Small hammerhead, stove bar andltMultipleHT250Table top, etc., cylinder base, etc. Anyway, bigAccording to the capacity of smelting intermediate frequency furnace, the arrangement of small pieces in series and series of castings is flexible and changeable according to the size of sand box.

 

(3)Applicability to various structures of castings  The process characteristics of lost foam casting are especially suitable for complex structures.(ComplicatedInner cavity interlayer, blind hole, bending and turning cavity, etc.), it is difficult to classify the appearance and shape, so as to avoid the difficulty of facing up on the large plane.Difficult, ordinary sand casting is more difficult core, parting surface complex castings, more such as long sleeve, cylinder, propeller,Water pump impellers, shells and castings with more complex structures and more cores, such as automobile engine blocks, cylinder heads, intake manifolds, etc.

 

(4)Suitable for single and mass production of castings  Lost foam casting consumes a foam for each casting poured.Material appearance(EPS,EPMMAorstMMA)For mass production, the mold cost of producing plastic white molds must be considered,For example, the production of highway guardrail brackets(zG35)The demand is large, tens of tons, hundreds of tons and constantly needs, soEPSParticle foam mold into the best appearance, anti-wear parts of high chromium cast iron hammer head is the same;2Pieces,3pieces or moreA small but small casting is used.EPSIt is appropriate to cut and bond the blank into a white mold. Because of appearance(white mold)Can be made-The white mold is produced in large quantities by hand or particle foaming mold molding, and its applicability is flexible.

 

(5)Quality advantages of lost foam castings  From the production process can be seen, lost foam casting its molding process is similar to the lossWax precision casting, pouring is similarVMethod casting, modeling type is the same as real casting. So the combination of modern lost foam casting technologythe real type,VThe advantages of the three methods and precision casting.

 

Due to the unique characteristics of lost foam casting, the dimensional error caused by core combination is reduced, and the dimensional accuracy of castings is reduced.and surface roughness upCT5~CT7,Ra63125μm, between sand casting and lost wax investment casting. Due to the use of dry sand for filling sand, the defects caused by moisture, adhesives and additional substances are eliminated, the reject rate of castings is reduced, and the quality of castings is clear.significantly improved. Table1-2Comparison of surface roughness of lost foam castings with castings produced by several other casting processes.

 

TableComparison of Surface Roughness of 1-2 Casting Castings

 

Category ordinary sand casting resin sand casting lost foam casting precision casting
Ra/μm Approximately 50 12.5-25  6.3-12.5    3.2-6.3

(6) Lost foam casting is easy to achieve clean production  Polystyrene at low temperatures(EPS)Organic emissions accounted for only pouringquality of liquid iron0.3%, self-hardening sand is5%. At the same time, the generation of organic emissions is short, concentrated and easy to collect,Can use negative pressure suction combustion purification treatment, combustion products after purification of environmental pollution-free, old sand reuse rate in.95% inOn. Compared with the traditional casting method,EPSThe noise and dust hazards of the casting method are significantly reduced, and the labor intensity of the workers is greatly reduced,The working environment has been significantly improved, and it is easy to realize mechanization, automation and clean production.

1.2.2lost foam casting economy

casting tonnage consumptionEPS costs are more economical. According to the statistics of the relevant manufacturers, the average consumption per ton of castings.EPSMold processingCost100150yuan, includingEPSslab stock(or small amountStMMA,EPMMASheet metal andEPS, orEPMMA,stMMA))The particle foaming mold is formed into a pattern, and the coating is prepared according to the alloy material, the size and structure of each piece.Average consumption per ton of castings.50100dollar cost. Table1-3Lists the lost foam casting process and sand casting process productioneconomy compared to castings.

Process

Advantages

Disadvantages
type

Simplify plant engineering design

No sand binder

No sand core

Mold can be repeated sand mold

Increase pattern pouring system glue

Appearance can only be used once

Pouring

Saving the amount of metal and alloy gating system

Ductile iron can be solidified without riser equalization

Additional sand casting cooling and conveying equipment
Cleaning

Reduce the workload of casting surface cleaning

No casting burr flash

No removal of riser for ductile iron parts

Add special tools for appearance

String removal gate

Machining

Reduced machining allowance for castings

Casting is easy to automate

 
Environmental protection

Reduced environmental pollution

Simplified environmental facilities

 
Mold tooling

Reduce the traditional mold production

Simple and dedicated mold for easy maintenance

Long mold life

High initial mold cost due to complex design and long cycle time
Investment

Factory design level is highly flexible

Overall with economic scale

To facilitate the transformation of the old workshop into a lost foam casting process.

Low degree of mold automation

 

 

 

 

 

 

 

 

 

 

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