The most important factors in setting a cost for a MIM part are:
The MIM process does not have such an important variety of materials as other metal forming technologies. In the case of the Ecrimesa Group they are materials with commercial catalytic debanding.
The list of materials we can offer are:
The type of material has an important influence on the cost of the parts for two main reasons:
- Price of the material, which is more expensive in stainless steels (316L-174PH) than in carbon steels (42CrMo4-FN08), around 30%. In relation to the price of the materials, they are 10-15 times more expensive than the material coming from bar or ingot to melt.
- Sintering process, that must be at a slower rate in stainless steels, and in hydrogen atmosphere compared to carbon steels that are normally sintered in nitrogen atmosphere and with a sintering rate 30-40 % higher.
2.- Size and configuration of the part
The size is important, as it influences the weight mentioned above, as well as the sintering capacity, since the parts are processed in molybdenum trays of size 200*200 and the greater the number of parts that can be processed per box, the better the cost of this process, both in continuous furnace and in batch furnace.
According to our records, the optimum sizes of MIM parts are between 0.5 grms and 40 grms, although we have parts above 150 grms that, due to their configuration and the machining savings obtained, are profitable compared to other technologies.
On the other hand, and no less important, is the design of the part in order to adapt it to the limitations of the technology, to avoid secondary operations such as machining and to reduce its costs.
It is very important that the parts are not designed with sharp edges, and that they have as many radii as possible to facilitate the injection of the material, to avoid segregation during injection and to prevent cracks from appearing after the sintering process.
Likewise, they must have space for the placement of the injection point and homogeneous walls for a correct injection of the material (since it must be taken into account that steel powder will be injected with the difficulty that this entails since it is not an easy material to inject).
Designing the part with adequate areas for the part, to settle during the debanding/sintering process, also has a very important influence on the cost, since in case of not having flat support faces it forces to use special sintering supports, reducing the load on the furnaces and therefore not maximizing the cost advantage.
Finally, for carbon or low alloy steel parts that require heat treatments, it is of special importance to establish adequate placements for the performance of these heat treatments in order to avoid deformations during the heat treatments, or cracks generated by the heat treatment on the part. The Ecrimesa Group has its own facilities for heat treatments and adapts them to the requirements of the parts in order to maximize the cost and quality of the part.
Making a comparison between MIM and Microfusion of a potential part:
For an annual consumption of 45,000 pieces/year the cost study would be:
|PIECE||1 €||0,94 €|
|MACHINING TOOL||1.800 €||NO|
|MOLD||6.500 €||16.000 €|
Estimating the amortization of the tooling on the first 45,000 pieces, the result would be:
|1,72 €||1,29 €|
To learn more about this technology at Ecrimesa Group:
Even though the investment casting is an industrially fully developed process, its limits have been pushed during the last years towards producing larger and more complex pieces compared to the last decades. The following image shows the market positioning and development tendency of investment casting:
On the one hand, larger production volumes are being outsourced more and more to Asian countries, mostly because of the reduced prices for manual labour that still plays a very important role in the process. To cater to this necessity, Ecrimesa Group closed contracts more than 15 years ago with Asian providers and uses infrastructure in China in order to offer our clients this option if it benefits their projects. On the other hand, the area of application has expanded towards more complex pieces and smaller production volumes. Technological progress in both the materials and the machines has been crucial for this development, as well as simulation technologies that allow predicting the behavior of the pieces in the production process during th design phase and thus avoid problems in the production. As the size and complexity of the pieces has been evolving, the flexibility of production has increased in order to allow smaller series of complex parts. Ecrimesa Group offer projects of 20.000 pieces a week as well as smaller series of just 50 parts per year.
With these quipments, projects with pieces of more than 20 kgs with high metallurgic and dimensional requirements have been realized, for example for the energetic sector or oil and gas extraction, in stainless steel, certified according to AD2000 Merkblatt W0.
As well as aluminium parts.
Another relevant sector for investment casting is the automotive sector, where tha superficial and dimensional qualities reached through this technology allow for delivering fully-finished parts. This saves costs compared to other technologies and is applicable in a wide range of materials. In this manner, we develop projects for injection systems, in stainless steel:
EGR systems in stainless steel:
PowerTrain systems in carbon or low-alloy steel with heat treatment:
Locking systems for cabrios in carbon and stainless steel:
These are all fully-finished pieces, including machining, heat treatment and, if necessary, small assembling labors that allow the client to integrate the products seamlessly into their production processes, and with volumes of up to 1,000,000 parts per year. With our machining and heat treatment plants, we offer complete services to our clients for this type of projects, for stainless, carbon, or low-alloy steels. Currently, the machining sector is very important ofr our technology as well, as we can offer tailor-made solutions for designers in order to maximize the profit and efficiency of their facilities.
Other industrial examples for the appliaction of investment casting are machinges for the food industry. The high superficial quality reached through investment casting and the materials comply with the sanitary standards of the sector:
And lastly, a promising sector in the last year has been the defense sector, both military and civil, with diverse alloys.
Ecrimesa Group has the know how of more than 50 years and 9,000 projects developed for diverse industrial sectors, making us the perfect partner for any projects our clients might want to realize.
What is additive manufacturing?
Additive manufacturing, also known as 3D printing or rapid prototyping, is the fabrication of metal parts by using a 3D model and applying several layers of material to it.
Fabricating metal parts through additive manufacturing has become one of the most interesting technologies of the sector throughout the last decade – one the one hand, because it offers the possibility of prototyping for process and case studies, on the other hand through the option of fabricating complex geometric pieces directly. Additive manufacturing is the speerhead of an industrial revolution in different sectors, especially in aviation, heavy industries and the health sector, but also in automotion and the energy economy.
There are two groups of fabrication technologies for metal parts in additive manufacturing : fusion-based technologies, where the final part is produced by directly melting the primary material, and technologies that rely on sintering, where a green part is produced first, while the final product is obtained through de-binding and sintering. The following image shows the classification of additive manufacturing technologies according to ISO / ASTM 52900.
Depending on the pre-defined objectives, either FDM (Fused Deposition Modeling) or Binder Jetting technologies are selected to implement additive manufacturing.
Definition of FDM and Binder Jetting technologies
FDM and Binder Jetting are forms of additive manufacturing the most resemble the MIM process in terms of the specifics of the process and the final products.
When fabricating metal parts through FDM, powdered materials (metal and polymeres) are applied layer by layer through a jet. This technology can use filaments, pellets, or bars as primary material. After creating obtaining the green shape, de-binding and sintering are necessary to obtain the final product.
In Binder Jetting, layers of metal powder are applied to a printing model and mixed with polymeric materials which are applied through a jet. These polymeric glues have to dry and harden after each layer. After finishing the printing, a so-called “de-powder” process is necessary to remove the excess material and obtain the green part. Then, de-binding and sintering are necessary to obtain the final product. The de-binding process is less critical than usual in the Binder Jetting process as very little gluing material has to be applied between the layers. This makes it easier to remove the binders, but in turn also amkes the green shape more fragile and complicated to handle.
The heightened economic interest in additive manufacturing has resulted in the development of a very competitive market for 3D printers. At Ecrimesa Group, we have conducted an extensive benchmarking process over the last few years in order to evaluate providers of 3D printers and implement the technology in our facilities. After the comparative study based on characteristics such as the resilience of the green shape, surface quality, porosity, deformation and the costs of the printer, we selected the Studio System printer by Desktop Metal in order to implement additive manufacturing in the company. This enables us to explore new markets and create more added value for our customers.
STUDIO SYSTEM PRINTER BY DESKTOP METAL
|Main characteristics Studio System Desktop Metal|
|Primary material||Bars (cartridges)|
|Available materials at Mimecrisa||17-4PH, 316L, 4140|
Flowchart foe the fabrication of prototypes with the printer Desktop Metal:
How to use additive manufacturing in the fabrication of metal parts
The design of the pieces has to be adapted to the technology used for their fabrication. As with traditional technologies, additive manufacturing too has certain limits that have to be respected when designing the piece. This is why Desktop Metal has developed a set of ground rules for the design that have to be applied when developing the metal parts. These rules are recommendations – if the limits shown in the following table are not respected, problems might arise in different steps of production.
The Studio System printer is equipped with two printing heads for different printing qualities: a standard jet with a diameter of 400µm and a high definition jet with a diameter of 250µm. The design recommentations in the following table are sorted per jet.
|Standard jet 400µm||High definition jet 250µm|
|Maximum size of the parts||X 240mm Y 150mm Z 155mm||X 60mm Y 60mm Z 60mm|
|Minimum size||X 6mm Y 6mm Z 6mm||X 3mm Y 3mm Z 3mm|
|Minimum wall thickness||1mm||0.6mm|
|Maximum wall thickness||10mm||10mm|
|Minimum drill size||1.5mm||0.75mm|
|Minimum pin diameter||3mm||1.5mm|
|Minimum overhang angle||40º||40º|
|Thickness of layers||0.15-0.3 mm||0.05-0.15 mm|
|Minimum elevation||X/Y W 0.45mm H 0.50mm |
Z W 0.25mm H 0.50mm
|X/Y W 0.30mm H 0.30mm |
Z W 0.15mm H 0.30mm
|Min engraving size||X/Y W 0.45mm H 0.50mm|
Z W 0.25mm H 0.50mm
|X/Y W 0.30mm H 0.30mm|
Z W 0.15mm H 0.30mm
|Empty space between components||0.3mm||0.2mm|
In terms of the dimensional tolerances that can be reached with the printer, Desktop Metal guarantees the following values for the standard printing profile. The characterisation of the other printing profiles has yet to be determined.
|Diameter of pivot point||D||<65 mm||± 0.5 mm|
|Length||L||>65 mm||± 0.8% L mm|
|Distance between pivot points||S||>65 mm||± 0.8% S mm|
The obtained tolerances depend directly on the printing, de-binding and sintering processes. Dimensions of less than 65mm result in dimensional tolerances of ±0.5mm, bigger dimensions result in dimensional tolerances of ±0.8% of the measured height. These tolerances can be guaranteed when sticking to the design rules described here.
The surface finish is one of the most important aspects of additive manufacturing. As it is one of the main limits of the technology, further processes are necessary in many cases to obtain the desired surface quality. The roughness of the printed objects depends on the size of the jet as well as the thickness of the printed layers.
Business development strategy for additive manufacturing
These are the main goals of Ecrimesa Group in the implementation of additive manufacturing:
- Manufacturing of prototypes prior to the production of the mould with characteristics as close as possible to MIM-fabricated pieces
- Possibility of design studies with the client prior to the production of the mould
- Increase the speed of the MIM process through studies on prototypes (positioning during sintering, deformation studies, defects, etc.)
- Production of short series of metal parts with complex geometry that would be too costly to fabricate by MIM or whose form is too complex to produce by MIM
Metal Injection Moulding (MIM) is a suitable technology to fabricate small or medium-sized pieces with complex geometry. A variety of materials can be used (stainless steels, low-alloy steels, soft magnetic, tooling steel or ceramic materials). MIM combines the technique and versatility of plastic injection with sintering in order to fabricate metal pieces with high density and narrow geometric tolerances.
The following image shows the MIM process.
First steps. Fabrication of the mold: The molds employed in the MIM process are made of highly resilient steel, of complex geometry and more challenging than the molds used for plastic injection. When fabricating the hollow form, it is important to fator in the contraction of the material that will be injected, which means the hollow form has to be bigger than the actual desired piece. It is vital to stick to the design rules of the technology in this step in order to obtain a stable and immaculate product.
The number of hollow forms in the mold depends on the geometry and dimensions of the esired piece and can vary between one and ten hollow forms in total. The usual number of hollow forms lies between two and four, production time can vary between 15 and 60 seconds.
Feedstock or primary material: The primary material consists of a metal powder with a particle size of maximum 32 micrometers (at least 80% of the material must be smaller than 22 micrmeters), mixed with binders, and normally comes in the shape of pellets. The binders are made of thermoplastic, waxes, polymeres and other substances.
The characterization and control of the feedstock is crucial in order to calibrate the parameters of the following processes, especially the injection and sintering, and obtain the desired tolerances and repeatability.
Injection: Now, the feedstock is injected into the mold. The most important parameters in this step are precision, the flow volume and temperatures (of the injection head and the mold). The parameters of the injection have to be adapted to the geometry of the desired piece. The manufacturer’s know-how is vital for obtaining intact parts without internal defects. The piece obtained in this production step is called the “green part”. During the extraction from the hollow form, the material normally contracts for the first time (0.7 – 0.9% when using carbon or low-alloy steels, about 0.4% when using stainless steels).
De-binding: The binder that was necessary for the injection process now has to be removed. This de-binding can take place in several different ways: 100% thermical, water-based, with solvents or through a catalytic reaction. At Ecrimesa Group, we use catalytic feedstock, because it offers several advantages compared to other methods – especially the speed of the process. The catalytic reaction is produced under controlled conditions with N2 and nitric acid with a temperature of 120ºC. During this proces,s the main component of the binder, POM, passes from a solid to a gaseous state and leaves the green form in a very fragile state, called the “brown” state.
The de-binding process can be carried out in vaccum batch furnaces or continuous furnaces. The advantages of using continuous furnaces are that manual handling is avoided and the brown state can be transferred directly to sintering. During this process, the piece is especially unstable and very susceptible to deformation and other damages, which makes the absence pf manual handling an important factor for the reliability of the process. Ecrimesa Group have both types of facilities at our disposal.
During this phase, a small part of “secondary” binders remains in the brown state, keeping it in its shape. These secondary binders are removed an the begining of the sintering process.
Sintering: The sintering is the last steps of the process, during which the desired density is aquired by interdiffusion of the metal particles due to thermal reactions and fase (H2 or N2, depending on the type of alloy). The pieces can be sintered in vacuum batch furnaces (especially suitable for small production volumes or special materials) or in continuous furnaces (more suitable for bigger production volumes). At Ecrimesa Group, we have 3 continuous furnaces and vacuum batch furnaces at our disposal. The positioning of the parts during the de-binding and sintering can alter the dimensional results, which is why the phase of definition and industrialisation is very important to obtain a robust and reliable process.
During the sintering, the second and definite cotraction occurs, resulting in the final dimensions defined before the beginning of the process. With carbon and low-alloy steels, the contraction factor between mold and final piece amounts to 1.2165, and 1.205 between the green form and the final piece. With stainless steels, the contraction factor is 1.166 between mold and final piece, and 1.160 between green part and final product.
Last steps and termination: After sintering, the product might require further operation of machining in ordr to meet the requirements of the client. Ecrimesa Group owns a modern facilty for heat treatment, allowing us to offer completely finished products. The machining can be processed in-house as well, for instance when pickling or polishing should be needed.
Our ample experience of more than fifty years in this area enables us to find synergies between the MIM and investment casting process.
Investment casting is among the oldest industrial manufacturing processes still being applied today. Its history can be traced back to 4,000 BC. At this time, bee wax and other animal greases were used instead of synthetic waxes employed today. Samples of sculptures crafted with investment casting have been found in Europe, Asia, Africa, and South America. It took until the 20th century to develop the technology industrially – 400 patents were registered between 1900 and 1940, especially in the defense and health sectors.
Many materials are suitable for investment casting: stainless steel, alumnium, carbon steels, brass or glass. The process is based on inverting the desired material in a hollow mould inside the breaking material. This hollow mould is an exact copy of the desired final piece. Due to certain characteristics of the breaking material, the superficial quality of the piece is very high, reducing the need for secondary operations.
The first step consists in fabricating a metallic mould (mostly made of aluminium or steel), into which wax is injected in the form of the desired final piece. In order to maximize the yield, this form is then melted together with other identical units, allowing to continue working with conjunctions of units. The configuration of these conjunctions is crucial to control the process and cost across the whole production.
The conjunctions are then coated with several ceramic shells until they have reached the necessary resilience for the following process steps. The integrity of the process depends on the employed materials as well as the temperature and air moisture in the work rooms and the drying process of each ceramic shell.
As soon as the desired ceramic structure is reached, the wax is removed with an autoclav, using the correct pressure and temperature settings and taking care that the ceramic shell is not damaged – creating the ceramic hollow mould. The desired final material is injected into the hollow mould and, after it has hardened, the ceramic shell is removed by vibration and shaking processes. Eventually, the single units are separated and the necessary end operations effectuated to correspond to the clients’ wishes.
The main advantages of investment casting are:
- Freedom of design: Produce complex pieces, even wit complex inner structures.
- Cost advantage: Produce pieces with precise finish and tailor-made design, lowering the weight of the pieces.
- Repeatability: By repeating the production units, homogeneous quality can be safeguarded.
- Versatility: Produce an ample variety of alloys.
- Flexibility: With investment casting, you can produce very small volumes of a few hundred pieces as well as higher unit numbers up to several millions.
Maybe, you can count among the disadvantages of investment casting that you need to produce a mould for each final piece, as well as high working efforts. Compared to other, faster technologies such as MIM, investment casting takes more time. These factors, as well as the limits of the pieces’ sizes that the technological equipment of the manufacturer can impose, make it necessary to examine in detail which tecnology is apt for producing a certain piece.
The Ecrimesa Group is looking back at more than fifty years of experience in the realm of investment casting. With more than 2,000 projects in our portfolio, we have a rich experience in producing carbon and stainless steels.
We have our own office for any adjustments of the design and the fabrication of prototypical moulds, enabling us to offer our clients complete consulting services in order to adapt their design perfectly to the process of investment casting. Our designers and metallurgic engineers use simulation softwares like Magma Soft and Inspire Cast.
We use 3D printing for rapid prototyping without having to produce the mould directly, which is very beneficial at the beginning of the process, when the customers’ vision of the desired piece is not complete yet and different samples have to be examined before making the final decision on the mould. This avoids the necessity of producing a mould for each sample, avoiding extra costs.
We have our own metallurgic laboratory with more than eight technicians, where me conduct continuous controls if the melting process and heat treatments. Moreover, we can conduct X-Ray scans, digital tomography, corrosion controls and material examinations.
In 2005, we incorporated a machining plant into our company group in order to offer our clients fully finished pieces. Internalizing all machining processes enables us to offer more versatility in the design phase as well as the finished yields.
Following this philosophy, we also have our own facilities for heat treatments, with 4 lines for hardening and tempering, including stanradized carbon control, 3 lines for hardening and a line for aluminium T6 treatments, all of them CQi-9 certified. With us, the customers receive everything out of one hand, from the design and planning up to the final piece – always with maximum quality.