The Relationship Between Lost Foam Casting Process And Mold Manufacturing

Abstract: This paper describes the lost foam casting process for die design and manufacturing impact, but also analysis of the domestic EPC status and mold manufacturing industry, impetuous, through case analysis and explanation, resulting not only the relationship between process and castings, but also leads to the lost foam casting mold industry forward.

Key words：LFC process, lost foam mould, case, direction

Introduction

LFC (also known as EPC) is the same size and shape with the casting foam models adhesive to form cluster models, fire-resistant paint and brush after drying, buried in the dry sand of vibration modeling, casting under vacuum in a vacuum, the model gasification, liquid metal occupy models, formed after casting solidification cooling emerging casting method, is the foundry industry's most "green" casting process, but also the twenty-first century foundry industry trends.

Lost foam casting process abroad pace slightly ahead of the country, but it does not mean that the level of domestic EPC enough. Looking at the domestic EPC industry, regardless of whether or not advanced foundry business equipment, corporate culture is the same, but the idea of technology as the core, the industry is still the soul, which affects the EPC industry and mold the future of manufacturing.

1. Lost foam casting process developments

Lost foam casting process from research and development has so far successfully contained more than fifty crossed the last century in the late sixties, China has also begun EPC technology research, as process of continuous improvement annd innovation, it has developed into a more mature casting process, to meet the needs of most industrial production, but with the technology and the continuous development and updating technology, based on current industry conditions, in order to better promote the development of EPC technology, seize opportunities, and even lead the pace of the times, we must continue to explore the potential lost foam casting process energy, releasing intrinsic value, in order to better serve the industry and contribute to society for the benefit of mankind.

2. The domestic current situation of the lost foam casting industry and mould industry

Since the 1990s, China's EPC if springing up, showing vigor, many manufacturers have to learn and committed foundry lost foam casting this one, along with the enthusiasm after the part with the production technology and the strength of the casting manufacturers continue to ride in this fertile land, the other part casting manufacturers gradually withdraw EPC industry, the reason can be summarized from the following aspects: First, the introduction of EPC carefully enough, lack of professional personnel, lack of on EPC-depth understanding of the lack of a complete feasibility study report, the blind project; Second, some foundries have purchased equipment and mold itself can not meet its production processes and performance requirements; finally, that the interests and pursue maximization, send drawings to contact with a number of mold manufacturers, mold manufacturers choose the lowest bid, casting manufacturers and mold manufacturers were not the product of potential process failure analysis, blind investment, resulting in poor product stability, high production costs, qualified rate.

These aspects fully confirmed the truth: do technology must be down to earth, rigorous. Engaged in the EPC staff, we must first make the product is reliable process analysis, in order to produce high quality castings.

3. Lost foam casting mold development and manufacturing case studies

3.1 Heavy-duty engine exhaust pulse Case Study

This long and thin wall casting body (as shown in Figure 3.1-1), so easy to produce LFC white mold casting product variations and leakage of the adhesive seam area, it is difficult to ensure the dimensional accuracy between the branch pipe, the end will lead to the manifold and the engine can not be precise fit, resulting in poor exhaust, noisy and other defects, and the casting process requirements with the competent branch pipe flange faces must guarantee a certain vertical, apparently lost foam casting mold ordinary difficult to meet its process requirements.

Figure 3.1 1 product three-dimensional entity graph

Based on their casting structure itself and the use of technology requirements, we design comes pouring system and self-positioning of the mold (Figure 3.1-2 below). In this mold will runner and white mold fused together to make a white mold pattern (Figure 3.1-3 below), its main runner serve to prevent deformation and ensure the branch pipe size precision role, and because each tube was ingates support necessary to ensure the branch pipe flange and head flange between the verticality. And we in the sub-section made on the cross snap tabs, it can be fitted uniform; this is also to avoid the thin wall generated variants, but also play a leak-proof effect.

Figure3.1-2 upper mould and white mould          lower mould and white mould

Figure 3.1-3 White mold foam molding appearance and slices

White mold casting system make mainly to avoid a "gating system and the appearance of white mold caused by internal casting plus adhesive coating film defects" to reduce the manual work and reduce the casting cost of production.

Figure 3.1-4 shows, the pieces do "potential process failure analysis," summed up - the two biggest problems are the casting wall thickness of 4.5mm, easy to produce variants and parting seam leakage. As shown below, the mold development manufacture, does not consider the variant and parting seam leakage problems, so click on the icon for the system out of the mold casting production, eventually leading to low yield.

3.1-4 Common exhaust pipe mold design

3.2 The tractor rear axle shell case analysis

Casting products for process analysis (product shown in Figure 3.2-1), known from its use of oil-filled pieces belonging to the sealing requirements are extremely stringent. For its oil piece using the EPC should avoid fragmentation forming, because the adhesive fragments are more prone to oil leakage at the problem, according to its process requirements, we design the mold shown in Figure 3.2-2, the axle housing interior molding surface design into six loose piece, although increased the difficulty of making the mold, but this white mold can be integrally formed to ensure that the casting will not appear genotyping oil leakage phenomenon.

Figure 3.2-1 white mould                  Figure 3.2-2  mould based on technology

Figure 3.2-3 pour syetem design      Figure3.2-4 mould and white foam

In order to avoid leakage of casting, we adopt bottom gating system (shown in Figure 3.2-3), since the end of injection-type runner is likely to cause the upper surface of the casting shrinkage, slag and other issues, we increased the pouring cup root white mold with the highest surface pressure head difference (generally for antes style runner, pouring cup root and white mold highest surface pressure head difference of not less than 260mm), so also ensure that the entire cast oil leakage phenomenon does not occur.

Figure 3.2-5 Common design and appearance of white mold gating system design

Shown in Figure 3.2-5 mold design analysis, we can see that there are two fatal problems, one: because white mold fragments forming, in its sub-type prone to leakage problems at castings; Second: Gating System design is unreasonable, although the design of a ladder-type casting system, but apart from the two inner runner too close not play a relevant role in two ingates same water, prone to shrinkage, re-skin, slag and other issues . Although this scenario is simple mold, no loose piece of hot metal utilization is high, if applied to actual production, will eventually lead to lower yields.

3.3 Plow drive shaft housing case analysis

The casting process requirements analysis shows (Figure 3.3-1), to ensure its symmetry is very important. Since casting larger and structural compact enough die deformation, do not take appropriate measures to ensure that two die hard symmetry; respectively as separate casting, casting uneven cooling rate and other factors, will inevitably lead to geometry deviations affect assembly and product appearance.

Figure3.3-1 Plow drive shaft looks like white mold      Figure3.3-2  mould

Figure3.3-3 White mold and pour system

Based on the above analysis of the technology, we have designed out of the mold (as shown in Figure 3.3-2,3.3-3), do highlight the symmetry plane intersection of the plane buckle (as shown in Figure 3.3-4), the two die can be fitted symmetrically, so you can ensure that the two die symmetry. At the same time cast into the housing box casting, casting while the casting due to water stress mutual restraint, greatly reducing distortion, meet the product requirements.

Figure 3.3-4 Two white mold appearance and flat cross buckle

3.4 Small castings in EPC skillfully efficient use of case studies

EPC in the industry jargon is called "fear of fear complex simplicity", for some simple small castings, lost foam is always difficult to efficiently produce high-quality products. But everything is not absolute, the following will introduce small castings in EPC successfully used the case:

Bow mold design

On the bow structure analysis shows (Figure 3.4-1), because the appearance is white mold has a high plasticity, and this casting without the constraints of their own, so be sure to bow perspective on LFC white mold appearance is extremely difficult, and this casting foundry manufacturers high quality requirements.

Figure 3.4 1 blank (a) product (2)                  Figure 3.4 2 mould and model