Twenty-Seven Reasons To Choose Lostfoamtechnology To Produce Castings

PRODUCTION COST

The metal mould can be used for more than 100 thousand times,which reduce the maintaining cost.

Combination casting, one box with multiple pieces, improves the process yield and production efficiency of castings.

The sand processing system was simlifed, the molding sand can be completely reused.

High degree of automation,reducing manual labor

Reduce pollution, improve working environment, reduce labor intensity, and lower investment costs for personnel wages.

lt is easy to realize mechanic auto-assembly line production with great flexibility and different lloys, shapes, sizes of castings can be produces in a production line

Plant design can be simplifed with fix investments being reduced by 30-40%，floor area and covered area by 30-50%,power consumption by 10-20%，production cost was reduced.

Combination casting in dry sand,sand drop off easily and the temperature of sand and casting are synchronous, therefore waste heat can be used for heat treatment. especially the high manganese steel casting water edge processing and the solid

solution treatment, the effect is very ideal, with much energy saved and processing cycle shortened.

CASTING QUALITY

The castings are precision with the characteristics of accurate size and shape, good reproductive.

Castings are highly polished on the surface with the roughness reaching Ra3.2-12.5 u m.

There are no fins and rags on castings, which make the work load in dearing process half reduced.

The maximum allowance is 1.5-2mm,reducing the weight of the casting.

The cost of machining was reduced greatly, compared with the traditional sand casting methods,the mechanical processing capacity can be reduced 40-50%

No mould assembling and delivery greatly simplifed molding process, eliminating casting flaws and waste products caused by mould assembling and delivery.

PROCESS DESIGN

Lost foam casting technology is widely applied in producing steel castings,iron castings. copper castings and aluminum castings.

lost foam castng technology is not onty for casting of simple geomelry, but also for mmult- part, multl core casting of compley geometny.

Core and core aking sectons are canoeled, which eliminates casting fars and waste products.

The design is flexible, and the shape of the parts is not limirted by the traditional casting process, which prowides sufficient freedom or the structurel design of the castings and liberates the mechanical designers. They can design the most ideal casting shape according to the service performence of the parts. and can combine highy complex castings through toam plestic molds.

Reasonable shaped gating and rser can be sat in the idea position without being constrained by traditional factors such as parting and mold taking. reducing the intemnal defects of castings.

Adopting a dry sand molding without binder, moisture, and any additives, it eliminates various casting defects and waste caused by moisture, additives, and binders.

Easy sand shekeout greatly reduced the work loed and labor strength.

Patterm draft can be canceled, it removes the cisting defects and wast products caused by casting material, shrinkage rate and friction castings.

Negatiwe pressure pouring ls more condudive to the stamping and shrinkage of liquid metal, and improves the density of the casting structune.

Lost foam casting technology can realize micro-viberation pouring. which enhance the formaian o metlographic structure with specia reguirements and internal quaity of the castings.

The complex casting is easy which can realize the production of different parts and different material castings.

The inlay casting way is corvenient. we can put the metal inlay block in advance.

LOST FOAM CASTING PROCESS

Production principle of LFC,First of all, white foam models are made according,to requirements of the product design.Second, after dipping with refractory coating and drying,models are embedded into specially designed sandboxes with dry,sand to carry out three-dimensional solid moulding and molten liquid pouring under vacuum state,Then models are gone because of gasification with the molten liquid replaced,Thus, qualified castings are produced.

White area of LFC is used to make white foam models through pre-foaming, ripening, molding, cutting and bonding Raw materials includes EPS, STMMA, EPMMA and other expandable foam materials

Take the commonly used EPS beads as example,EPS beads are used for castings of non-ferrous metals, grey iron and general cast steel,EPS beads characteristics:semitransparent, preforming rate: 40~60 times,beads diameter: 0.18 to 0.80 millimeters,6 different sizes,generally, original beads diameter should be less than,1/9~1/10. or equal to 1/9 to 1/10 of the minimum wall thickness of the castings,Raw material prefoaming follows right beads selection,Raw material prefoaming follows right beads selection.

Prefoaming

Before fed into mould,EPS beads need to be pre expanded to a certain size,The prefoaming process determines the density,dimension accuracy and stability of the models,There are mainly two kinds of equipment for EPS bead prefoaming:electric steam prefoaminq machine,and pure steam prefoaming machine,both of which are equipped with the most advanced PLC technology.

Ripening

Pre-foamed EPS beads are placed,in a dry and ventilated silo for a certain period of time,making inside and outside of beads pressure balanced,optimizihg the elasticity and the expandability,and removing water on the bead surfaceThen sent to curing storage hopper through automatic feeding system.

Foam modeling

After curing ripening,EPS beads are fed into lost foam mould cavity by pressure feedinq system and heated,so that the beads are expanded again and fused together,filling the cavity and forming a smooth surface,Models should be cooled and settled before ready,After modeling, there should be enough time for models drying and stabilization,The white model is wet on the surface,and contains moisture inside,so it must be thoroughly dried.

There are mainly two types of forming equipment: hydraulic forming machines and screw forming machines.The lost foam mould-die is made of aluminum alloy,and designed according to different product structure,Model cutting and bonding,Modeling products may only be part of the model or initial forminq blanks,which need further processing such as cutting and bonding,This process is to combine multiple white foam models with gating,and riser models by lost foam special glue to make model clusters.

Yellow area of LFC

Mainly used to brush special coating on white model clusters and to dry in drying rooms,The main functions of coating in LFC are to insulate metal liquid and model,to discharge model gasification waste gas,to ensure surface quality of castings,to improve the strength and stiffness of models and to prevent damage or deformation of the models to a certain extent.

This requires the coating to be air permeable, fireproof coating suspension adhesive in order to reduce the defects on castings such as blowholes, sand burning so as to ensure the rate of finished produtts generally, there are generally four methods for coating and hanging: brushing, dipping, sprinkling, and spraying.

According to the characteristics of different models,several methods can be applied comprehensively in actual production,After coating, models are moved to drying rooms with 45~55℃,circulating hot air for drying,During drying, models should be placed reasonably and supported to prevent deformation,At the meantime, temperature and humidity should be strictly controlled to get thoroughly dryout,After thoroughly dried, model clusters are eady for pouring.

Black area process is the stage of solid casting,Dry model clusters are placed in sand boxs,Special dry sand is fed to sandbox by movable showerfeeding machine for moulding,Molten liquid is poured under negative pressure state,Models gasified with molten liquid replaced,Models gasified with molten liquid replaced,Thus, qualified castings are produced.

The black area of the lost foam casting process is to replace white foam models with molten iron and form casting,There are three steps:vibration moulding,casting replacement fand sand treatment.

The vibration molding process includes four steps: bottom sand feeding,model clusters placing-sand feeding and moulding,film covering and surface sand feeding.

The moulding is completed by vibration platform and a shower sand feeding machine,

Sand boxes move to position under sand storaqe hopper;sThe rain shower sander adds bottom sand to the sand box,After the bottom sand is added, the model cluster is put into the sand box, and the rain shower sander moves again to add sand to the flat gate position;During the whole sand fillinq process,vibration table keeps vibrating to ensure molding,sand is filled to hollow section around foam model cluster,After vibration completed,vibrating table lowers to relocate sand box track,Then sand box is pushed away by hydraulic pusher to make,space for next sandbox moulding,sandboxes reach to surface,sand feeding station of shower,feeder one by one to cover plastic films and finish moulding.

Plastic film is used to seal from top of sanbox,During casting, negative pressure system is automatically butted with sandbox,making a relative vacuum environment in the sandbox.

The sand particles are "bonded" together by the pressure difference between,the atmosphere and the internal moulding,which ensures that the casting process is not broken or scattered.

The neqative pressure system has a second compaction effect on the molding sand improving the static friction force between the sand particles,making a stable negative bressure field in sandbox,forcing the dry sand to set under the action of atmospheric pressure.

When pourinq, it absorbs the gas generated by the EPS model gasification,avoiding blow hole in the casting,increasing the flow speed of the liquid metal,Also it accelerates the flush type, and thus improves the qualified rate of the castings.

After moulding,sandboxes are moved to the pouring section one by one,This section is equipped with negative pressure automatic butt-joint machine,When pouring, EPS model is vaporized under the heat of liquid metal,The gasified gas enters negative pressure system through the coating and molding sand.Liquid metal continuously occupies the position of EPS model and occurs the replacement process of liquid metal and EPS model,Finally, qualified castings are formed.

After pouring, the castings need to be cooled down for a certain time in sandbox,then be turned over out of box,Automatic turnover machine is used to seperate castings from molding sand.

Molding sand goes to sand treatment system,while castinqs qo to shot blasting machine to remove surface coating,Molding sand can be reused after treatment,which reduces production cost,This is also one of the advantages of lost foam process.This is also one of the advantaqes of lost foam process.

Sand treatment system is a very important production process of LFC,Molding sand after box turnover is primarily cooled by water cooling and sand shakeout machine,Then it is separated from casting residue and sundries by screening conveyor,The screeninq conveyor is equipped with air cooling system,which could reduce sand temperature quickly and efficiently,The residue is taken out by the slag lifting machine while the molding,sand is lifted by elevator to horizontal cooling machine for major cooling,hen by elevator, the molding sand is sent to temperature requlator for further cooling,After all these process,the sand is transferred to storaqe hopper for production.

In thelwhole sand treatment system,each node usesdust collector to ，removeldust from production process,On the one hand, this helps production be clean and pollution-free,On the other hand, the dust in the molding sand is removed,which improves the air permeability,of the sand and reduces casting defects,Thanks to advanced PLC technoloay,the whole process is equipped with sand temperature control,automatic temperature requlation,and frequency modulation to finalize sand screening,dust removal and cooling, so that molding sand can be recycled,

The commonly used equipment in dust removal system,is pulse bag type dust removal,which mainly deals with the dust treatment of each node in LFC sand treatment system,GuoNing company has also developed exhaust gas treatment system,which is mainly used to purify the benzene compound gas produced,by the white model gasification during pouring,It uses activated carbon adsorption,light oxygen type,adsorption desorption catalytic combustion and so on to purify the exhaust gas,to meet qreen production and environmental requirements,and to quarantee smooth production.