Order casting using burnt wax models: quickly and accurately 

Order casting using burnt wax models: quickly and accurately

The turnaround time for precision investment casting in our production ranges from 7 to 14 working days for pilot batches, which allows us to reduce the time to market (Time-to-Market) by almost half compared to standard foundries. If you needзаказать литьё по выжигаемым восковым моделям: быстро и точно, the key factor is not just the speed of metal pouring, but the optimization of the entire chain: from 3D printing of master models to finishing machining with IT6-IT7 tolerances. We work with aluminum, steel and titanium alloys, providing geometric precision unattainable with sand casting.

In our practice, we encountered a situation where a client in the oil and gas industry lost three months trying to obtain a shipment of valves from a supplier who promised “quickly” but did not have an in-house waxing facility. The result was a melt leak and 40% of the batch was rejected. This incident taught us that speed without quality control at the wax assembly stage is a direct path to financial losses. Therefore, in this article we will analyze the technical nuances that allow us to guarantee deadlines and quality at the same time, based on real production data, and not marketing slogans.

Technological process: where speed and accuracy lie

The accuracy of the final metal part is established at the stage of creating the wax model, and this is where the main difference between our approach and traditional methods lies. Classic technology involves the use of molds for wax injection, which requires time to manufacture metal tooling (from 3 to 5 weeks). We use a hybrid approach: for prototypes and small series (up to 500 pieces), we use direct 3D prototyping of wax models or printing injection molds on photopolymer printers, followed by filling with special casting wax. This shortens the preparation phase from months to just a few days.

The process starts with a digital CAD model. Our engineers conduct an analysis of foundry technology (DFM - Design for Manufacturing), identifying areas of probable shrinkage or hot cracks. After the model is approved, a wax knot is created. The critical parameter here is the coefficient of linear expansion of the wax. In our laboratory, we control the injection temperature with an accuracy of 0.5°C, since a deviation of even 2 degrees can lead to a change in the geometry of the part by 0.1 mm, which is unacceptable for precision components.

Next comes the process of building up the ceramic shell. We use multilayer technology, where the first layer is formed from electrocorundum with a grain fraction of no more than 0.063 mm. This ensures perfect copyability of the metal surface. The number of layers varies from 6 to 9 depending on the mass of the casting and the type of alloy. A mistake at this stage that competitors often make in the pursuit of speed is insufficient drying between layers. In our practice, there was a case when residual moisture in the shell led to gas holes in a batch of turbine blades made of a heat-resistant alloy. We now use automated drying chambers with humidity control, eliminating human error.

Burning of wax and calcination of the mold occur in a single cycle in ovens with a programmable atmosphere. The temperature schedule is selected individually for each alloy. For aluminum alloys, the mold is heated to 850-900°C, for steels - to 1000-1100°C. The metal is poured in vacuum induction furnaces, which prevents oxidation and gas saturation. It is vacuum melting that allows us to achieve mechanical properties of castings close to those of forged metal.

Every stage of the process is verified. Before being sent for machining, each casting undergoes visual inspection and geometry testing on coordinate measuring machines (CMMs). Only after confirmation of compliance with the drawing, the part enters the CNC workshop. This tight vertical integration of processes allows us to truly deliver on our “fast and accurate” promise, as we are not dependent on third-party contractors for critical steps.

Key parameters influencing accuracy

• Material shrinkage:Each alloy has its own shrinkage coefficient (for example, aluminum AL9 - 1.3%, steel 30KhGSA - 1.8%). Our model makers make these adjustments directly into the digital wax model.
• Cooling deformation:The design of the gating system is calculated to compensate for the warping of thin-walled elements during cooling.
• Surface roughness:Thanks to fine-grained ceramics, we achieve roughness Ra of 1.6–3.2 µm, which often eliminates rough machining.

Understanding these physical processes distinguishes professional casting from artisanal production. If you're planning a complex project, make sure your supplier can explain exactly how they compensate for shrinkage in the specific alloy you've chosen.

Selection of materials and alloys for precision casting

The ability to work with a wide range of alloys is one of the main advantages of the investment casting method. However, the choice of material directly affects the cost and production time. Our portfolio includes more than 40 alloy grades, from structural steels to exotic nickel-based superalloys. It is important to understand that not every alloy performs equally well in thin-wall castings.

Our experience is especially in demand in the energy and petrochemical sectors, where material requirements are maximum. As a companyWuxi Kaisheng Electric Power and Petrochemical Equipment Co., Ltd., specializing in the design and production of high-pressure heat transfer equipment, we are faced with the need to use corrosion-resistant and high-temperature alloys every day. Our core products—Titanium Shell and Tube Heat Exchangers, Corrugated Tube Bundles in 316 Stainless Steel, C46400 Marine Brass, C70600 Copper-Nickel Alloys and N06625 Nickel Alloys—require impeccable quality raw materials. The ASME and PED standards to which our equipment is certified dictate the strictest control over every element, be it 321 steel tube sheets or complex air cooler assemblies.

The most popular are aluminum alloys of the AK (AL9, AK7ch) and AB series. They have excellent fluidity, which allows filling complex cavities with a wall thickness of 1.5 mm. For parts operating in aggressive environments or under high pressure, we recommend stainless steel grades 12Х18Н10Т (analogous to AISI 321) or 20Х13. These materials require higher pouring temperatures and special care when forming the gating system to avoid cold junctions.

Heat-resistant alloys, such as KhN77TYUR (EI437B) or imported analogues of Inconel 718, deserve special attention. Casting these materials is the aerobatics of metallurgy. They are prone to segregation and the formation of carbide networks. In our practice, we have introduced a special technology for modifying the melt with rare earth elements, which made it possible to increase the service life of gas turbine engine parts by 30%. One of our clients, an industrial burner manufacturer, was faced with the problem of cracks in the combustion chambers after 500 hours of operation. Switching to our casting using a modified alloy solved the problem completely.

When choosing a material, it is necessary to take into account not only operational requirements, but also casting properties. For example, magnesium alloys have an excellent strength-to-weight ratio, but require special fire safety measures when melting, which makes the process more expensive. Titanium alloys (VT6, VT20) provide maximum strength with minimal weight, but their casting is possible only in vacuum furnaces with a consumable electrode or induction melting in graphite crucibles with a protective atmosphere. It is our ability to work with complex materials such as titanium and nickel alloys that allows us to supply components for waste heat boilers and seawater desalination equipment where conventional steel is not suitable.

The choice of alloy should be based on the technical specifications, and not on the price of the material per kilogram. A cheap alloy may require such complex post-processing or have such a high percentage of defects that the final cost of the part will exceed the cost of a product made from an expensive but technologically advanced material. Our engineers always carry out cost-effectiveness calculations before launching a series.

Quality control and compliance with international standards

In the industrial B2B sector, trust is built on documents and repeatability of results. Our production is ISO 9001:2015 certified, which guarantees that we have documented control procedures at every stage. However, for the Russian and Eurasian markets, compliance with GOST requirements and the availability of EAC (Eurasian Compliance) certificates are critical.

We understand that a certificate is just paper if there is no real control system behind it. Therefore, each batch of castings is accompanied by a quality certificate, including the results of chemical analyzes and mechanical tests. We use spectral analysis to check the chemical composition of each heat. Deviation from the nominal composition of even one element (for example, the sulfur content in steel is above 0.02%) leads to rejection of the entire melt, regardless of the appearance of the castings.

For critical parts operating under load, we always carry out non-destructive testing (NDT). Basic methods include:

• Radiographic control (RC):Allows you to identify internal defects: gas pores, shrinkage cavities, non-metallic inclusions. We use digital detectors that allow us to see defects smaller than 0.5 mm.
• Penetrant control (PVC/PT):Detects surface cracks and lack of penetration. Particularly relevant for welded assemblies and parts of complex shape.
• Ultrasonic testing (UZK/UT):Used for massive castings to assess the integrity of the internal structure.

In 2024, we introduced a statistical process control (SPC) system. This allows us to monitor parameter trends before they go beyond acceptable limits. For example, if the size of a certain characteristic on five parts in a row shifts to one side, although it remains within the tolerance range, the system signals the need to adjust the process. This is a proactive approach that prevents the release of defective products.

Compliance with GOST 15150 (climatic conditions) and GOST 9.301 (coatings) standards is also within our area of responsibility. We can provide castings with various types of coatings: anodizing for aluminum, galvanizing or nickel plating for steels, polymer coatings. All processes are carried out in-house or with trusted partners with full control of incoming and outgoing quality.

The customer must clearly formulate control requirements in the technical specifications. The phrase "inspection by drawing" is often interpreted in different ways. It is better to indicate specific standards (for example, “defects are not allowed according to GOST R 53872 level A”) and the percentage of parts subject to complete control. This will save both parties from claims in the future.

Economic efficiency: when casting is more profitable than machining

The main question that buyers ask is: “Why should I order casting if I can mill the part from a solid blank?” The answer lies in the plane of metal utilization factor (MCM) and labor intensity. When machining from rolled stock, CMM often accounts for 30-40%, that is, more than half of the expensive material goes into chips. When investment casting, CMM reaches 85-90%.

Let's look at a specific example. We received an order to produce a gearbox housing made of stainless steel. The manufacturing option from round bars with a diameter of 200 mm required 18 hours of machine time on one CNC center and consumed 12 kg of metal. The cost of the workpiece plus labor was approximately 500 euros per unit. Casting the same part required 4 kg of metal and only 2 hours of finishing (only seats and threads). The cost of casting was 280 euros. Savings for a batch of 1000 pieces amounted to 220,000 euros.

However, casting is not always profitable. For simple parts such as flanges, washers or small diameter shafts, machining will be cheaper and faster due to the elimination of the cost of creating wax assemblies and ceramic molds. The economic threshold for the profitability of investment casting usually occurs when the part is complex, requiring more than 5-6 machining operations, or when expensive alloys are used (titanium, Inconel, bronze).

It is also important to consider the size of the batch. Pre-production (making molds or setting up 3D printers) requires fixed costs. For a batch of 10 pieces, these costs per unit will be high. For a batch of 10,000 pieces they become insignificant. However, thanks to additive manufacturing, our minimum economic run quantity has dropped to 50 pieces for complex parts.

We recommend carrying out a comparative calculation for each new product. Our designers are ready to analyze your drawing free of charge and suggest the optimal manufacturing method: casting, rolled processing, or a combination of these methods (for example, casting a workpiece with allowances only on critical surfaces).

How to place an order and minimize risks

The process of interaction with us is structured in such a way as to eliminate misunderstandings and technical errors. Toзаказать литьё по выжигаемым восковым моделям: быстро и точно, follow a simple algorithm that we have developed over years of working with international clients.

1. Preparation of technical documentation.We need a drawing in PDF format indicating all tolerances, roughness and material requirements, as well as a 3D model in STEP or IGES format. The lack of a 3D model significantly increases the cost and slows down the process, since we will have to restore the geometry manually.
2. Preliminary audit (DFM).Our engineers examine the model for casting defects. We may suggest changes to fillet radii, wall thickness, or sprue placement to improve quality without compromising part function. This stage is free and takes 1-2 days.
3. Calculation of cost and timing.We provide a commercial offer broken down by cost item: cost of equipment, price per unit of product, production time for a pilot batch and a serial order. We fix the price in the contract currency for the entire duration of the contract, protecting you from market fluctuations.
4. Manufacturing and approval of a prototype.Before launching a series, we make 3-5 samples. You receive them along with the quality control report. Only after your written approval (“golden sample”) mass production begins.
5. Serial production and logistics.We take care of packaging (wooden boxes, polystyrene foam, anti-corrosion protection) and organizing delivery to your warehouse anywhere in the world, including customs clearance for export.

A common mistake customers make is trying to save money at the prototyping stage by abandoning the pilot batch. This is a false economy. Correcting an error in a series of 1000 parts will cost tens of times more than reworking one mold at the preparation stage. We insist on the mandatory production of a control batch for any new products.

Another important point is packaging. Precision castings often have thin features that can become deformed during transportation. We use individual cells made of polyethylene foam and rigid wooden sheathing. There was a case in our history when a client independently organized delivery and received a shipment with bent brackets. Since then, we have included "professional export packaging" service as a basic standard for all fragile products.

Frequently Asked Questions

What is the minimum order quantity?

Благодаря использованию 3D-печати восковых моделей, мы можем изготовить партию от 1 штуки (для прототипирования) без затрат на дорогостоящую металлическую оснастку. Для серийного производства с использованием пресс-форм экономически целесообразно начинать от 50-100 штук, но технически мы готовы лить и меньшие объемы.

Какие допуски точности вы гарантируете?

Стандартный класс точности по ГОСТ 26645 составляет 5-7 класс (CT5-CT7 по ISO 8062). Это соответствует допускам примерно ±0.1 мм на 100 мм длины. Для особо ответственных узлов мы можем достичь допусков IT6 за счет дополнительной механической обработки критических поверхностей.

Сколько времени занимает изготовление первой партии?

При использовании 3D-моделей цикл составляет 7-10 рабочих дней. При необходимости изготовления металлической пресс-формы для инжекции воска срок увеличивается до 20-25 дней. Срочные заказы на прототипы могут быть выполнены за 5 дней с применением экспресс-технологий.

Работаете ли вы с давальческим сырьем?

Да, мы принимаем давальческое сырье, однако рекомендуем использовать наши материалы. Это связано с тем, что мы несем полную ответственность за химический состав и механические свойства отливок только пр и использовании сертифицированного сырья из нашей базы. При работе с материалом заказчика ответственность за его качество разделяется.

Можно ли получить отливки сразу с нужной шероховатостью?

Да, поверхность отливок после удаления керамической оболочки имеет шероховатость Ra 3.2-6.3 мкм. При использовании специальных мелкозернистых смесей для первых слоев оболочки можно достичь Ra 1.6 мкм, что во многих случаях исключает необходимость механической обработки поверхностей.

Conclusion

Литье по выплавляемым моделям остается безальтернативной технологией для создания сложных, высоконагруженных и точных металлических компонентов. Возможность сочетать высокую скорость прототипирования с качеством серийного производства делает этот метод идеальным выбором для современных промышленных задач. Мы доказали на сотнях реализованных проектов, что соблюдение технологической дисциплины и использование передового оборудования позволяют избегать компромиссов между скоростью и точностью.

Не позволяйте некачественным отливкам тормозить развитие вашего продукта. Доверьте производство профессионалам, которые понимают физику процесса и ценность вашего времени. Свяжитесь с нами сегодня для получения бесплатного аудита вашего чертежа и расчета стоимости. Мы готовы показать, какзаказать литьё по выжигаемым восковым моделям: быстро и точнои получить результат, превосходящий ожидания.