Additive Technologies in Manufacturing Processes

January 4th 2021

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Economic Problems of Implementing Additive Technology

The course towards the advanced development of additive technologies determines the relevance of a thorough technical and economic analysis of the profitability of their implementation in each specific production. Economic issues are poorly reflected in statistics, which causes difficulties for specialists involved in the implementation of additive manufacturing.

At the same time, the world economy has taken a course towards the advanced development and implementation of additive technologies of dimensional shaping, which predetermines the relevance of a thorough technical and economic analysis of the profitability of additive manufacturing.

From a formal technological point of view, the introduction of additive technology at a particular enterprise is justified and expedient if, other things being equal, production costs per unit of output (specific resource costs) are reduced. Thus, it is important to calculate the difference between the workshop costs of manufacturing a part or assembly unit using two technology options:

The existing technology of manufacturing a product using the mastered methods of obtaining blanks and machining;
Technology for manufacturing a product-using additive shaping operations.

Before discussing the features of such a calculation, we will formulate some conditions, restrictions and assumptions:

A necessary condition for comparing the technical and economic efficiency of technology options is the identity of production results. Therefore, before carrying out a comparative analysis of the options, it is necessary to check the identity of the results in terms of the composition of the product, its quality, volume, and timing of the production assignment, time schedule and working conditions.
If the second option allows you to immediately obtain a component part of the product from n parts, then in order to ensure the identity of the result in terms of the composition of the product in the first option, the total unit costs for the manufacture of each of the m parts, plus the cost of their assembly, transport and storage, should be taken into account.
If the second option provides a reduction in the cycle of technological preparation of production and the production cycle, then for comparison it is necessary to ensure the identity of the options in terms of time. Reducing the delivery time of marketable products to the market is especially important in the manufacture of marketable products new in terms of consumer properties in conditions of fierce competition. This circumstance can be taken into account as a lost profit from the sale of products according to the additive option. Such a calculation often raises questions due to a possible change in the market situation, the level of prices for products, but it makes it possible to assess the important competitive advantage of additive technologies.
It is assumed that both options provide the same product quality, due to the technical conditions for manufacturing (identity in product quality). Otherwise, the change in the functional properties of the product must be assessed during the calculation, guided by the available recommendations. Thus, it is recommended to convert the number of products of higher quality into a larger number of products of ordinary quality with a change in the corresponding costs.

Considering the above, the structure of the cost of manufacturing and assembly:

1) According to the first version of the technology is presented in the form:

C1 = ∑ (C1зi + C1мi) + Cсб, i = 1

2) The second version:

С2 = Спр + Сад + Спс,

where C1, C2 are the total cost of manufacturing the final product according to the compared technology options, C1зi is the cost of obtaining a blank of the i-th part of an assembly unit, C1mi is the cost of machining the i-th part, m is the number of manufactured parts of an assembly unit, Cсб is the cost of assembling a component products, taking into account the cost of all other components according to the specification of the assembly unit, Спр - the cost of preliminary (previous) operations, Сад - the cost of the operation (operations) of additive shaping, Спс - the cost of subsequent operations of the final processing of the product.

Note that additive technologies of layer-by-layer growing of products from powder do not allow getting rid of residual porosity, which makes it necessary in some cases to use subsequent technologies, for example, hot isostatic pressing, infiltration, and heat treatment.

As shown above, only about 19% of additive manufacturing products are used as the final product. It is assumed that the starting materials for the second option; for example metal powder, are purchased and are not produced at the enterprise. For a technical and economic assessment of the effectiveness of two technology options, the method of direct cost calculation is used, according to which the choice of the best option is carried out according to two criteria:

Calculated coefficient of comparative economic efficiency Ер
Or according to the estimated payback period Tr.

The preference rule is expressed by inequalities of the form Eр> En, Tr <Tн, where the index "н" corresponds to the normative value of the corresponding criterion.

When finding these criteria, it is necessary to calculate the difference between the total workshop costs in the transition from the first option to the second (∆С = С1 - С2) where the difference between the costs of basic materials, wages, depreciation, and so on is compared.

In the general case, the difference in material costs ∆Cm is calculated using a well-known formula, knowing the wholesale prices per unit mass of material and waste, the rate of material consumption and the mass of waste per item according to options.

The given data make it possible to estimate the ratio of the cost of the material during additive shaping (cm2) to its cost during machining (cm1) of 0.5–5.

The peculiarity of comparative calculations in our case is as follows:

First, as a rule, the use of the additive shaping operation can significantly reduce the number of operations in the technological process of manufacturing a part.
Secondly, the piece-calculation time for the operation of additive shaping is, as a rule, tens of hours.

Since modern equipment has been operating in automatic mode for a long time, it is advisable to use multi-station service and combination of professions during its operation.

As a result, the machine and labor intensity of the operation are significantly different. Therefore, for each method of additive shaping, a calculated expression for machine or operational time is obtained based on the existing methodology for standardizing technological operations, taking into account the specifics of physicochemical processes for obtaining bulk solid forms in each case.

The main disadvantage of layer-by-layer synthesis of products of a spatially complex shape is the relatively large amount of machine processing time. This results in a high proportion of equipment depreciation costs in the costing. So, according to the available data, the share of costs for depreciation of the machine can in some cases reach 70% of the cost of the product.

To reduce the spending of this cost item, it is recommended to maximize the load, operate the equipment seven days a week, preferably in 2-3 shifts.

Due to the rapid obsolescence of such equipment, the payback period should not exceed 5 years. According to experts, in the coming years, a noticeable reduction in prices for equipment for SLS and SLM should be expected, which will have a favorable effect on the sales conjuncture and the pace of implementation of relevant technologies.

To improve economic performance when introducing Additive technologies in production, it is recommended to equip the additive forming section with several machines with different capabilities, for example, SLM 50 + SLM 300 (400 W):

SLM machines with powerful lasers are more efficient and provide a lower technological cost. Machines with a less powerful laser and a smaller spot diameter provide a better quality of the surface layer of products;
The distribution of the range of products of different standard sizes between machines with different dimensions of the working area leads to saving powder and reducing auxiliary time.

Benefits that can also be taken into account in the feasibility study also include a reduction in the number of workers and the cost of ensuring life safety, a decrease in shop and plant overhead costs due to cheaper logistics.

Organizational and Technical Aspect s

When mastering technologies, the description of their characteristics and conditions for implementation becomes an urgent task. The conceptual apparatus is specified, the relationship is established between the parameters of physical and chemical processes that ensure the synthesis of a solid of a given configuration, and the technological characteristics of additive shaping operations.

Such work will lead in the near future to the creation of a regulatory and reference base for additive technologies. The factors holding back the development of additive technologies in production include the following:

Material properties
Manufacturing precision and surface quality of parts
Relatively low performance
High capital investments
The equipment is still imperfect
Differences in geometry and properties between identical parts manufactured in different installations
Closed architecture of most Additive machines, which does not allow researchers and technologists to vary the processing conditions.

Along with the listed, organizational and technical factors limiting the development and implementation of additive manufacturing, include the following:

1. Standardization of additive manufacturing processes started and actively developed by the American Society for Testing Materials (ASTM). A number of important standards have already been created, but the development of a fairly complete set of international standards, the development of national standards will take time.

2. Equipment certification is a fundamentally important factor for the implementation of Additive Manufacturing and is a prerequisite for product certification. The main problems of equipment qualification can be formulated as follows:

Lack of standards for materials, technologies and equipment;
A large number of equipment of different design and principles of operation;
Insufficient experience of its industrial operation and lack of statistics;
The absence in some cases of the results of testing products in real conditions, reliable data characterizing the physical and mechanical properties of products;
Weak metrological support;
closed architecture of equipment;
the existing business model of sales and after-sales service of equipment actually turns the installation into a black box, restricts the ability of technologists and plant operators to increase the efficiency of Additive technologies;
Time and money for the certification procedure.

3. The factors listed above make it difficult to certify Additive Products. So far, applications have typically been accompanied by extremely rigorous testing to ensure that product properties meet specifications, greatly reducing the benefits and efficiency of additive manufacturing.

4. It should be emphasized that the creation of technologies and equipment of the third and fourth classes requires not only the rapid development of the scientific foundations of mechanical engineering technology in relation to new processes and methods of shaping, but also advanced training of engineering and technical personnel capable of solving new design and technological problems .

Main Directions of Development

An effective way to increase the productivity of equipment for additive shaping is the development of new methods, different from layer-by-layer synthesis.

Thus, we note the emergence of an additive shaping method based on the bulk synthesis of the required shape from a liquid interface. This method - continuous liquid interface production (CLIP) - provides a high speed of forming (in 25–100, and in the future, according to experts, up to 1000 times higher than methods of layer-by-layer synthesis).

It is also characterized by isotropy of the structure and properties of the object of production, low surface roughness, and high resolution when printing the product. It is expected to receive a spatially complex object, the functional properties of which correspond to the requirements for the finished product, in real time.

Let us note the trend towards the development of combined technologies and equipment of the fourth class. Such technologies will provide a further reduction in the duration of the technological cycle and will allow using the advantages of both subtractive and additive technologies.

For example, Solidica has developed the UAM (Ultrasonic Additive Manufacturing) technology, based on which Fabrisonic produces hybrid machines of the SonicLayer R200 type, which provide additive-subtractive processing of products made of plastic metals and composite materials with a metal or polymer matrix. Mitsubishi LUMEX has begun supplying the Avance ‑ 25 Integrated System, which combines SLS technology and milling.

The preparation for production of the MPA-40 complex, which integrates the capabilities of 5-axis milling and 3D gas-dynamic spraying, was announced by Hermle. The use of such technologies and associated machine tool systems will also require a feasibility study, taking into account the above features.

Conclusion

The development of additive manufacturing was accompanied by excitement and overestimated expectations. Despite the fact that many consider Additive Technologies to be breakthrough and key in the transition to the sixth technological order, so far, their impact on the scale of global production remains moderate.

A realistic approach and analysis of the experience of the industrial "nano revolution" that has recently swept the world allow us to hope that Additive Manufacturing in the foreseeable future will occupy its rather extensive niche in world production.

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Sergey Golubev (Сергей Голубев)