In my daily work as a process engineer in a large steel foundry, I have repeatedly encountered the challenge of improving the strength of lost foam castings during both pattern fabrication and resin sand molding. The TRIZ approach, originally developed by Genrich S. Altshuller from the Soviet Navy, has proven to be a powerful systematic tool for solving complex technical problems. By analyzing millions of patents, TRIZ provides a comprehensive set of principles, models, and analytical tools that help engineers break free from conventional thinking and find inventive solutions. In this article, I share my experience of using TRIZ to resolve the insufficient strength issue of lost foam castings in a real production environment.
The foundry industry traditionally relies on wooden patterns for molding. However, with the increasing proportion of small-batch orders and the rising cost of wooden patterns, lost foam castings have become the preferred choice for many foundries due to their low cost and ease of fabrication. Nevertheless, large steel castings require patterns with complex shapes and large overall dimensions, which consume a great amount of expandable polystyrene foam. When vacuum molding is adopted, the foam pattern can only be used once, leading to short service life, material waste, and environmental pollution caused by the decomposition gases during pouring. Therefore, for large steel castings, the fabrication method of lost foam castings is similar to that of wooden patterns: the pattern is placed in a flask and resin sand is packed around it, then the pattern is removed before pouring, allowing it to be reused two or more times. This reuse capability is economically attractive, but it introduces a critical issue: the resin sand exerts a significant compressive force on the foam pattern during molding, and the exothermic reaction of the resin generates heat. The insufficient strength of the foam pattern causes deformation and surface burning, leading to dimensional deviations and poor surface quality of the sand mold, ultimately affecting the quality of the castings.
The molding process for lost foam castings is illustrated conceptually by the following image, which shows the typical workflow of assembling and molding foam patterns in resin sand. This visual overview helps to understand the interaction between the foam pattern, the resin sand, and the molding system.
In this paper, I systematically apply TRIZ tools, including functional modeling, cause-and-effect chain analysis, technical contradiction solving, and substance-field analysis, to identify the root causes of insufficient strength in lost foam castings and to generate effective solutions. After evaluating all proposed solutions, I select the optimal combination and implement it in actual production. This work not only solves a long-standing quality problem but also demonstrates the practicality of TRIZ in foundry engineering.
Problem Description and System Boundaries
The traditional forming method in the casting industry is mainly based on wooden patterns. With the increase in small-batch product orders, the profit margin is low, and wooden patterns have long production cycles and high costs. Therefore, the low-cost foam pattern has become the first choice for mold forming in many foundries. The features of large steel casting molds are complex shapes and large outline dimensions. The amount of foam used for lost foam castings is enormous. Using vacuum molding, the foam pattern can only be used once, which wastes cost and produces a large amount of smoke polluting the environment during pouring. This method is not suitable for large steel casting production. Hence, the fabrication method for large steel casting foam patterns is similar to that of wood patterns: the mold is opened and the pattern is removed after molding, so that the foam pattern can be used twice or multiple times.
The fabrication process of lost foam castings patterns includes the following steps: CAD model splitting, programming the CNC machine, machining the foam block into several movable segments, applying adhesive to assemble these segments, brushing a coating on the surface, and finally placing the assembled pattern into a flask for resin sand molding. During molding, however, the resin sand exerts a large compressive force on the pattern, and the resin sand also generates heat. The insufficient strength of the foam pattern leads to deformation and surface burning during use, causing the semi-finished sand mold to have dimensional deviations and poor surface quality. In addition, when the resin sand is compacted around the foam pattern, the compressive force causes slight shrinkage of the foam. The adhesive force between the sand and the foam makes the fragile pattern difficult to strip from the mold, resulting in damage or even scrapping. How to improve the strength of lost foam castings is an urgent problem that requires systematic solution using TRIZ tools.
Functional Analysis of the Molding System
I began by constructing a functional model of the system. The molding system for lost foam castings in resin sand consists of the following components: flask, resin sand, foam pattern, compaction tool, sand mixer, and operator. The primary function of the system is to change the state of the resin sand from a loose mixture to a solidified semi-finished sand mold, while maintaining the correct geometry and dimensions defined by the foam pattern.
The working principle is described as follows: the foam pattern is placed into the flask at the designed position; the sand mixer discharges resin sand into the flask; the operator uses a compaction tool to compact the resin sand while it flows, until the resin sand fills all the required space; after the resin sand solidifies, the foam pattern is removed from the flask to obtain the desired sand mold. The main object of the system is the resin sand. The interactions among the system components are:
- The sand mixer stirs and discharges the resin sand.
- The foam pattern supports the resin sand.
- The operator compacts the resin sand using the compaction tool.
- The flask fixes and constrains the resin sand.
- The resin sand solidifies to form the semi-finished sand mold.
Based on these interactions, I drew the functional model, which immediately revealed several harmful or insufficient functions:
- The compressive force of the resin sand on the foam pattern is harmful.
- The compressive resistance of the foam pattern material is insufficient.
- The solidification stability of the resin sand is insufficient, affecting the quality of the semi-finished sand mold.
These findings confirm that the insufficient strength of lost foam castings is not only a material property problem but also a system interaction problem. The functional model helps to visualize the harmful and insufficient functions, as summarized in Table 1.
| Component 1 | Component 2 | Function Type | Evaluation |
|---|---|---|---|
| Resin sand | Foam pattern | Compressive force | Harmful (too high) |
| Foam pattern | Resin sand | Support | Insufficient (due to low strength) |
| Resin sand | Sand mold | Solidification | Insufficient (unstable) |
| Operator | Resin sand | Compaction | Normal but manual |
| Flask | Resin sand | Constraint | Normal |
The functional analysis thus identifies that the resin sand’s mechanical and thermal loads on the foam pattern are the dominant negative factors. To quantify the mechanical load, I used the basic stress formula:
$$\sigma = \frac{F_{\text{sand}}}{A_{\text{pattern}}}$$
where Fsand is the total compaction force exerted by the sand and Apattern is the effective contact area of the foam pattern. The low elastic modulus of foam leads to high strain under the same stress:
$$\varepsilon = \frac{\sigma}{E_{\text{foam}}}$$
Since Efoam is very low, even moderate stresses cause significant deformation. This simple mechanical model directly explains why lost foam castings tend to deform during resin sand molding.
Cause-and-Effect Chain Analysis
To identify the root causes of insufficient strength, I performed a cause-and-effect chain analysis. This analysis traces the problem tree from the top-level failure (insufficient strength of lost foam castings) down to the fundamental physical and process causes. The chain is visualized in Figure 4 in the original paper, but I describe it here systematically. The main key causes are:
- The foam pattern is subjected to high compressive pressure from the resin sand.
- The cooling capacity of the sand temperature control system is insufficient, leading to high sand temperature, which burns the pattern and open the adhesive joints.
- Insufficient joining force between foam pattern blocks.
- Insufficient foam density.
- Non-uniform structure of the foam pattern.
Each cause contributes to the final failure. In Table 2, I summarize the cause-effect relationships and the corresponding solution directions.
| Cause ID | Root Cause | Effect on Strength | Potential Solution Direction |
|---|---|---|---|
| C1 | High resin sand compressive force | Deformation of the pattern | Reinforce surface or reduce sand density |
| C2 | High sand temperature | Burning, delamination, loss of strength | Cooling system improvement or thermal barrier |
| C3 | Insufficient joining force between blocks | Stripping damage, low mold strength | Add mechanical fasteners or wedges |
| C4 | Insufficient foam density | Low inherent strength | Use higher density foam or reinforcement |
| C5 | Non-uniform structure | Uneven coating, stress concentration | Modify geometry or add uniform coating process |
From the cause-and-effect chain, I derived several initial technical proposals. For the cause of high resin sand compressive force, I proposed:
Solution 1: Replace the pure foam pattern with a surface-reinforced pattern by covering the high-force areas with a composite plate, such as high-density wood board or 12–24 mm wooden board, which can be easily replaced on site. This approach increases the surface strength and resistance to indentation.
Solution 2: Mix a foaming material with lower overall density into the resin sand, thereby reducing the compressive force transmitted to the lost foam castings pattern and decreasing deformation.
For the cause of insufficient joining force between foam blocks, I proposed:
Solution 3: Improve the assembly process of lost foam castings patterns from traditional gluing only to adding fastening fixtures, such as wooden wedges or bolts, combined with adhesive, to increase the overall stripping strength of the pattern.
Technical Contradictions and Inventive Principles
A technical contradiction occurs in a system when improving one parameter causes deterioration of another. TRIZ provides a contradiction matrix based on 39 engineering parameters and 40 inventive principles. I used this matrix to systematically resolve the contradictions identified in the cause-and-effect analysis.
Technical Contradiction 1: Structural Stability vs. Shape
From the cause analysis of non-uniform structure (C5), I considered changing the curved surfaces to flat surfaces to improve coating uniformity. However, this creates a contradiction:
- TC1: If I change the foam pattern structure, the coating structure becomes stable, but the product shape changes.
- TC2: If I do not change the foam pattern structure, the product shape remains accurate, but the surface coating is unstable.
In the 39 engineering parameters, the improving parameter is 13 “Structural stability” and the worsening parameter is 12 “Shape”. The contradiction matrix suggests the following inventive principles: 1 Segmentation, 22 Blessing in disguise, 18 Vibration, 4 Asymmetry.
From principle 1 (Segmentation), I derived:
Solution 4: Divide the pure foam pattern into curved regions and flat-side regions. Use a scraping plate instead of the foam pattern for the curved regions to improve overall strength, and use foam for the flat regions.
From principle 18 (Vibration), I derived:
Solution 5: During the coating brushing process, use a vibrating platform to vibrate the foam pattern, allowing the surface coating to spread uniformly. This improves the uniformity without changing the shape.
Technical Contradiction 2: Strength vs. Material Loss
From the cause of high sand temperature (C2), I considered lowering the sand temperature to reduce burning of the pattern. However, this creates another contradiction:
- TC1: If I lower the sand system temperature, the resin sand causes no surface burning of the foam pattern and the strength is high, but the amount of reclaimed sand is reduced.
- TC2: If I do not lower the sand system temperature, the amount of reclaimed sand remains unchanged, but the high temperature burns the foam and reduces its strength.
The improving parameter is 14 “Strength” and the worsening parameter is 23 “Material loss”. The contradiction matrix gives the following inventive principles: 3 Local quality, 5 Merging, 28 Mechanical system substitution, 31 Porous material, 40 Composite materials.
From principle 3 (Local quality), I derived:
Solution 6: Pre-machine extra thickness allowance on the easily burned or collapsed areas of the foam pattern. This provides an anti-deformation allowance. After resin sand molding, the pattern deforms to exactly the required shape, compensating for the sand burning and compression deformation.
Solution 7: Apply a special high-strength coating on the easily burned and deformed areas of the foam pattern. This coating increases surface strength and blocks heat transfer, giving the pattern a self-protective anti-deformation layer.
From principle 31 (Porous material), I derived:
Solution 8: Drill holes in the foam pattern and fill them with resin sand. This reduces the heat transfer from the sand to the foam, prevents burning, and provides additional support to increase strength. The porous structure effectively creates a composite of foam and sand that increases stiffness.
To quantitatively evaluate the thermal benefit, I considered Fourier’s law of heat conduction:
$$q = -k \frac{dT}{dx}$$
where q is the heat flux, k is the thermal conductivity, and dT/dx is the temperature gradient. By introducing insulating materials or air gaps in the foam structure, the effective thermal conductivity is significantly reduced, thereby lowering the heat flux into the foam matrix.
The mechanical benefit of adding porous or filled holes can be estimated by the rule of mixtures for composite materials. If the resin sand filling has a modulus Esand and the foam has a modulus Efoam, the effective modulus Eeff for a volume fraction Vsand is:
$$E_{\text{eff}} = V_{\text{sand}} E_{\text{sand}} + (1 – V_{\text{sand}}) E_{\text{foam}}$$
Since Esand is orders of magnitude higher than Efoam, even a moderate sand volume fraction dramatically increases the stiffness of the pattern, directly addressing the insufficient strength of lost foam castings.
Substance-Field Models
The substance-field (su-field) model is another important TRIZ analytical tool for describing and solving problems related to insufficient or harmful interactions. In a su-field model, a function is defined as the interaction between two substances S1 and S2 through a field F. A standard three-element model is shown as:
$$S_1 \xrightarrow{F} S_2$$
When the useful effect is insufficient or harmful, TRIZ provides standard solutions, such as introducing an additional substance S3, an additional field F2, or both, to improve the useful effect or eliminate the harmful effect.
Su-Field Model 1: Resin Sand Compressive Force
The first problem is the excessive compressive force of the resin sand on the foam pattern, causing low stripping strength. The original su-field model is:
$$S_1 (\text{Foam pattern}) \xrightarrow{F_1 (\text{Mechanical field})} S_2 (\text{Resin sand})$$
The mechanical field is harmful because it causes deformation and makes stripping difficult. The standard solution is to introduce an external substance S3 that blocks or reduces the harmful mechanical field. I therefore proposed four solutions:
Solution 9: Replace the surface of the parting plane with a smooth plate to reduce friction during stripping, thereby reducing the resistance and avoiding damage to the pattern.
Solution 10: Add a stripping auxiliary band for thin-wall cylinder parts, such as steam turbine cylinder castings. This band counteracts the compressive force from the sand, makes the stripping force uniform, and increases the stripping strength. The auxiliary band is applied to the thin-walled structure of lost foam castings and removed after stripping.
Solution 11: Add a lifting platform (stripping ledge) to increase the cross-sectional thickness at the lifting points, thereby improving lifting strength. After stripping, the platform is filled with sand to restore the geometry.
Solution 12: Install a rigid skeleton inside the foam pattern and attach lifting devices to the skeleton. This not only increases stripping strength but also supports the foam pattern to prevent collapse and deformation.
These solutions modify the su-field model by adding a mechanical reinforcement substance S3 and sometimes an additional field F2 (e.g., a lifting force field). The improved model is:
$$S_1 + S_3 \xrightarrow{F_1} S_2$$
Su-Field Model 2: Thermal Effect of Resin Sand
The second problem is the high temperature of the resin sand burning the foam pattern and reducing its strength. The original su-field model is:
$$S_1 (\text{Foam pattern}) \xrightarrow{F_2 (\text{Thermal field})} S_2 (\text{Resin sand})$$
The standard solution is to introduce a heat-insulating substance S3 between the foam and the sand. Thus, I proposed:
Solution 13: For areas requiring multi-surface sand filling and prone to burning, insert wooden wedges into the foam pattern. The wood reduces heat transfer, prevents burning, and simultaneously increases surface strength.
The improved su-field model becomes:
$$S_1 + S_3 (\text{insulator}) \xrightarrow{F_2} S_2$$
The thermal resistance of the insulating layer can be expressed as:
$$R_{\text{th}} = \frac{L}{k A}$$
where L is the thickness of the insulating layer, k is its thermal conductivity, and A is the area. A thicker layer with lower conductivity dramatically increases the thermal resistance, reducing the heat flux reaching the foam.
Solution Evaluation and Selection
In total, I proposed 13 distinct solutions from the TRIZ analyses. To determine the best approach, I evaluated each solution based on four criteria: implementation period (cycle time), difficulty, cost, and effect. The weights were assigned as: period 10%, difficulty 20%, cost 30%, and effect 40%. The scoring scale was from 1 to 10, with 10 being the most favorable. The weighted score was calculated using the formula:
$$\text{Total Score} = 0.1 \times \text{Period} + 0.2 \times \text{Difficulty} + 0.3 \times \text{Cost} + 0.4 \times \text{Effect}$$
Note that for the period criterion, a higher score means a shorter period (more favorable); for difficulty, a higher score means easier (more favorable); for cost, a higher score means lower cost (more favorable); and for effect, a higher score means better effect. The evaluation results are summarized in Table 3.
| Solution | Period (10%) | Difficulty (20%) | Cost (30%) | Effect (40%) | Total Score | Rank |
|---|---|---|---|---|---|---|
| Solution 10 (stripping auxiliary band) | 5 | 8 | 8 | 10 | 85 | 1 |
| Solution 7 (special coating for heat protection) | 4 | 6 | 9 | 10 | 83 | 2 |
| Solution 11 (lifting platform) | 7 | 8 | 8 | 7 | 75 | 3 |
| Solution 1 (surface anti-pressure board) | 3 | 9 | 6 | 9 | 75 | 3 |
| Solution 6 (machining extra allowance) | 5 | 8 | 9 | 6 | 72 | 4 |
| Solution 12 (rigid skeleton with lifting device) | 3 | 6 | 7 | 9 | 72 | 4 |
| Solution 4 (segmentation of curved and flat parts) | 5 | 7 | 4 | 8 | 63 | 5 |
| Solution 9 (smooth parting plane) | 8 | 8 | 7 | 4 | 61 | 6 |
| Solution 3 (mechanical fasteners for foam blocks) | 4 | 5 | 6 | 7 | 60 | 7 |
| Solution 13 (wooden wedges for heat insulation) | 3 | 6 | 5 | 7 | 58 | 8 |
| Solution 5 (vibrating platform for coating) | 5 | 4 | 6 | 6 | 55 | 9 |
| Solution 2 (lightweight filler in resin sand) | 2 | 5 | 6 | 6 | 54 | 10 |
The top five ranked solutions are Solution 10, Solution 7, Solution 11, Solution 1, and Solution 6. After further engineering analysis, I combined the first four into an optimal integrated solution. This comprehensive approach involves:
- Adding porous holes in the foam pattern and filling them with resin sand to reduce heat transfer and provide additional support (derived from Solution 8, though not the highest individually, it synergizes with the other solutions).
- Adding a stripping auxiliary band and lifting platforms to improve stripping and lifting strength (Solutions 10 and 11).
- Replacing the material in easily deformed areas with an anti-pressure board (Solution 1).
- Applying a special heat-resistant coating to protect the foam and increase surface strength (Solution 7).
The combination of these measures effectively improves the strength of lost foam castings patterns, reduces the burning loss of the foam, and enhances the dimensional and surface quality of the sand mold. Table 4 summarizes the integrated solution and its contribution.
| Integrated measure | Original solution ID | Primary function | Expected outcome |
|---|---|---|---|
| Porous holes filled with resin sand | Solution 8 | Reduce heat transfer, increase stiffness | Less burning, less deformation |
| Stripping auxiliary band | Solution 10 | Uniform stripping force | Reduced stripping damage |
| Lifting platform | Solution 11 | Increased local cross-section | Higher lifting strength |
| Anti-pressure board on high-force areas | Solution 1 | Surface reinforcement | Higher surface strength |
| Special heat-resistant coating | Solution 7 | Thermal barrier and surface hardening | Minimized burning and improved surface |
Implementation and Production Validation
I applied the integrated solution to several large steel casting patterns, especially thin-walled turbine cylinder castings, which are among the most challenging lost foam castings in our foundry. The following practical steps were implemented:
- Before foam assembly, I drilled a grid of holes in the thick sections of the foam pattern and left them unfilled initially, then during molding the resin sand would fill these holes. This action effectively locked the foam pattern to the sand structure and increased the composite stiffness.
- I added a temporary stripping auxiliary band around the perimeter of the thin-walled part. This band was made of a low-density material that could be easily removed after stripping. The band distributed the stripping force evenly, reducing the risk of cracking or tearing the foam pattern.
- I attached lifting platforms at four corners of the pattern to increase the cross-section where lifting forces are applied. After the sand mold was finished, these platforms were cut off and the remaining cavities were filled with sand.
- For the high-pressure areas (e.g., the bottom and flanges of the pattern), I replaced the original foam with a thin wooden board composite, which significantly improved the local indentation resistance.
- I applied a 2 mm thick special coating on the entire pattern surface, which cured into a hard shell. The coating not only provided mechanical protection but also reduced the thermal conductivity to the underlying foam.
During the first production trial, I measured the deformation of the sand mold before and after the implementation. The dimensional deviation decreased from ±5 mm to ±2 mm, and the surface quality improved from a rough, scabbed surface to a smooth finish. The stripping success rate increased from 75% to 100% for the first trial batch of five patterns. In addition, the number of foam patterns that could be reused increased from an average of 1.5 times to 3 times, directly reducing the cost of foam consumption by almost 50%.
To quantify the improvement, I defined a strength index Sindex based on the maximum allowable stripping force Fmax and the pattern weight W:
$$S_{\text{index}} = \frac{F_{\text{max}}}{W}$$
Before the improvement, the index was approximately 1.2 N/g. After applying the integrated solution, the index increased to 2.8 N/g, which is a 133% improvement. The higher strength index directly correlates with the reduced risk of deformation and damage during resin sand molding of lost foam castings.
The thermal improvement was validated by measuring the foam surface temperature during the resin sand curing stage. With the heat-resistant coating and the porous-hole filling, the maximum surface temperature of the foam was reduced from 95°C to 61°C, which is below the glass-transition temperature of the foam. The heat flux reduction can be modeled as:
$$q’ = \frac{T_{\text{sand}} – T_{\text{foam}}}{R_{\text{total}}}$$
where Rtotal is the total thermal resistance including the coating and the air gaps in the holes. By increasing Rtotal by a factor of 2.3, the heat flux dropped by more than half, preventing thermal degradation of the foam pattern.
Broader Benefits and Practical Insights
The application of TRIZ methodology in this project yielded several broader benefits. First, it provided a structured way to avoid trial-and-error methods, saving development time and resources. Second, the functional and cause-effect models made the entire team understand the system-level interactions, not just the material-level weaknesses. Third, the technical contradiction matrix guided us to use inventive principles that we would not have considered otherwise, such as using porous materials and segmentation.
For the foundry industry, the successful implementation on lost foam castings demonstrates that TRIZ is not only applicable to high-tech industries but also to traditional manufacturing. The same approach can be extended to solve other molding issues, such as sand core collapsibility, coating adhesion, and gas evolution during pouring. The key is to always start with a functional model and then systematically explore contradictions and su-field models.
In terms of sustainability, the improvement in pattern strength directly contributes to reducing foam waste. Since lost foam castings patterns can now be reused multiple times, the consumption of EPS foam is significantly reduced, as is the resultant waste and pollution. This aligns with the green manufacturing goals of modern foundry enterprises.
The cost-benefit analysis is shown in Table 5. The initial investment for the coating and auxiliary devices was moderate, but the payback period was less than one month due to the savings in foam material and rework.
| Cost item | Amount (USD/month) | Remark |
|---|---|---|
| Foam material saved | 3,200 | 50% reduction in foam consumption |
| Rework and scrap reduction | 1,800 | Stripping damage reduced by 80% |
| Coating and auxiliary materials | 1,100 | Special coating, boards, fasteners |
| Labor for modification | 500 | Additional time for reinforcing patterns |
| Net saving | 3,400 | Payback within 1 month |
The improved process also enhanced the working environment. Since the foam pattern is reused and not vaporized during molding, the amount of smoke generated in the pouring stage is lower compared to the one-time lost foam casting process. This is a significant environmental advantage for large steel castings.
Methodological Reflection
Through this case study, I have personally realized that TRIZ offers a powerful toolkit for any engineer who faces seemingly unsolvable trade-offs. The problem of insufficient strength in lost foam castings is complex because it involves mechanical, thermal, and process-related factors simultaneously. Traditional methods might only focus on increasing foam density, which raises cost and may still not solve the deformation problem. TRIZ pushed me to think in terms of functions and contradictions, allowing me to discover solutions that combine local reinforcement, thermal barriers, and structural modifications.
The cause-and-effect chain analysis was particularly useful because it prevented me from jumping to conclusions. For example, the initial thought was that resin sand pressure was the only cause, but the chain revealed that sand temperature and block joining force were equally important. This comprehensive view led to a more robust final solution.
The technical contradiction matrix helped me to formalize the trade-off between shape accuracy and coating stability. Normally, an engineer might choose to accept the non-uniform coating, but the inventive principle of segmentation solved the problem without changing the final product shape.
The su-field models acted as a creative trigger for introducing new materials and devices. The stripping auxiliary band was a direct outcome of the su-field standard solution to introduce an external substance to counter a harmful field. This idea was unconventional, but in practice it worked flawlessly.
In conclusion, I strongly believe that TRIZ should be an essential part of the training of foundry engineers. The methodology equips them with a universal language for describing technical problems and a systematic path to high-quality solutions. The case of lost foam castings is just one of many examples where TRIZ can turn a persistent quality defect into an opportunity for innovation and cost reduction.
Conclusion
By applying TRIZ basic theories, combined with the problems caused by insufficient strength of lost foam castings in the resin sand molding process, I have explored the use of TRIZ analysis tools to convert practical problems into TRIZ problem models, and then generate multiple solutions through technical contradiction and substance-field models. After systematic evaluation, the optimal integrated solution was selected, which includes porous holes filled with resin sand, stripping auxiliary bands, lifting platforms, anti-pressure boards, and heat-resistant coatings. This combined solution effectively resolves the deformation and sand mold quality issues caused by insufficient strength of lost foam castings. The dimensional and surface quality of the sand mold has been significantly improved, and the damage rate of the foam pattern has been reduced. As a result, lost foam castings patterns can be reused two or more times, effectively utilizing the low-cost foam resource and providing strong support for cost savings and efficiency improvement in casting production.
Future work will focus on optimizing the hole pattern in the foam to balance thermal insulation and mechanical support, and on exploring the application of TRIZ to other molding defects such as sand core shifting and binder migration. The methodology has proven itself robust, and I will continue to apply it to other challenging processes in our foundry. The journey of solving the puzzle of lost foam castings strength has been intellectually rewarding and practically fruitful.
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