short answers to big questions, part 2

We continue to answer frequently asked questions about the application of selective laser melting technology.

How is a model prepared for 3D printing? What’s the best software to use?

To manufacture a part on a 3D printer, you first need to obtain an STL file. To do this, we convert the solid to a polygon model, and then perform the operations of fixing, improving, editing, platform preparation, nesting, support generation, measurements and analysis.

The next stage is slicing (division into layers), which consists in creating a control program for a 3D printer. The stages of work from converting to STL to slicing are performed in specialized software.

The printer firmware is only for the preparation of the control program and cannot perform analysis, correct errors, optimally position parts and create supports, etc. The most flexible and comprehensive solution is offered by Materialize, which has developed Magics software for 3D printing professionals. It allows you to create individual layers of components with high speed and accuracy from 3D CAD data or 3D scan data. The software provides a full cycle of additive manufacturing – from data import (in STL and other formats) and quality analysis to platform preparation and post-processing.

Using Materialize Magics Software in the Additive Manufacturing Cycle
Using Materialize Magics Software in the Additive Manufacturing Cycle

Is there a fundamental difference between Magics and software products such as Amphyon, Simufact, 3D Expert and the like?

Amphyon, Simufact, as well as similar Russian software – narrowly focused software products. They offer modules for solving specific tasks (simulation, topological optimization), and Materialize Magics – a complete turnkey solution for additive manufacturing.

Comparing with 3D Expert from 3D Systems, we can say that this software is very specific, sharpened mainly for printers of this company. In contrast, Materialize has partnerships with all of the major 3D hardware manufacturers, and Magics has a huge library of additive installations. The user can select a specific printer and along with it “pull up” all the settings for the platform, construction, etc. Speaking directly about the simulation, in the corresponding 3D Expert module there is no way to perform analysis after separating the product from the support.

How are the working parameters of a 3D printer adjusted?

Many people mistakenly believe that a 3D printer should produce a quality part at the touch of a start button. A specialist working on an additive machine, ideally, should be both a designer and, to a greater extent, a technologist – someone who understands the physics of the processes occurring and the influence of certain parameters on the quality of the resulting part. There are a lot of such parameters – more than one and a half hundred.

Each material and each additive setting requires adjustment of many parameters such as laser power, scan speed, bandwidth and focus parameters. This is an extremely complex process that requires high professionalism, experience and creativity.

However, as the skill level progresses, users still need to make some basic adjustments that are necessary for optimal printing results. These include, for example, construction speed, surface quality, porosity, and some physicochemical properties of metals.

Is there training in additive installations?

If you are planning to purchase a 3D printer, iQB Technologies will select the necessary configuration for your needs. We carry out the installation and configuration of the equipment and provide the necessary training on the use of both the printer and the software. As mentioned above, setting the print parameters directly depends entirely on the qualifications of the operator.

© SLM Solutions
© SLM Solutions

What are the requirements for the operation of 3D printers for metal?

Particularly stringent requirements are imposed on the premises and operating conditions of such equipment. Fine powders are hazardous when inhaled, therefore operators must both work in protective clothing and ensure tightness during operation of the machine.

SLM systems do not require a sterile environment, but they do require a relatively clean working environment to prevent contamination of laser optics. An office environment is not suitable as powder will be present and people in the vicinity must wear personal protective equipment when the machine is open. For this reason, the room in which the system is used must be locked when the machine doors are open.

Standard requirements for working with a metal 3D printer:

  • voltage of 3 phases 380 V, operating mode of consumption 7 kW, in peak up to 12 kW;

  • inert gas supply to the machine (3-5 cylinders);

  • air conditioning system in the room (from 18 to 23 ° C), optimally – in the air dehumidification mode;

  • a compressor or a line with a compressed air supply of 4 atmospheres;

  • industrial water for washing filters and products.

© addtivemanufacturing.media
© addtivemanufacturing.media

Is mechanical post-processing necessary for SLM products?

The selective laser melting process cannot be classified as a high-precision process, and the surface quality of parts is comparable to casting using burn-out and lost-wax patterns. Therefore, structural elements of parts with higher requirements for roughness and flatness of the surface must be subjected to subsequent finishing machining.

For this, various machines are used – milling, polishing, grinding, it is also possible to use electrical erosion and hot isostatic pressing.

Tell us about the heat treatment of printed products. In particular, how is the problem of relieving internal stresses solved?

The materials used in selective laser melting behave like conventional metals. The resulting blanks can be subjected to heat treatment both to relieve residual stresses (depending on the material, this is medium-temperature tempering or normalization), and to change the structure of the material, increase the mechanical properties – strength, hardness, plasticity.

Different metals require different heat treatments, and sometimes specially heated platforms are used for this. During the construction process, when the metal melts, a large amount of heat is generated, which must be removed. The role of heat sinks, which removes heat, is played by the supports used in the construction of products. In some cases, the part itself, without supports, is welded to the work table, as to a radiator.

Moreover, this task, which during mechanical processing is solved at each stage of production, is now replaced by one stage at the end of the production process. For example, a project that required 196 hours of machining is completed by means of additive manufacturing in 8 hours, plus 15 minutes for additional processing of seats.

What additional equipment is needed?

Metal 3D printing requires additional equipment to support the printing process, including an external cooler and powder sifter.

The coolant needed to cool the laser and optics is often placed in a separate room as it produces noise, heat and humidity. The cooled water is fed into the selective laser melting unit and there are special requirements for the minimum size and maximum lift of the corresponding pipes. The sifter is used to process the unmelted powder after each build, separating the fine particles that can then be reused from the larger particles and contaminants that are usually disposed of.

In terms of post-processing equipment, the minimum set includes:

  1. a muffle furnace for relieving the residual stress of the metal;

  2. dremmel, band saw or EDM machine for removing supports;

  3. shot blasting or sandblasting chamber for post-processing of the product and improving the surface quality.

Post-processing area with oven, table with extraction and blast chamber © SLM Solutions
Post-processing area with oven, table with extraction and blast chamber © SLM Solutions

How is the quality control of the printed product carried out? Is it possible in the printing process?

There are software products (for example, Materialize) that can predict changes in geometry during construction before printing starts, but direct control of the geometry is possible only after printing is completed.

Since all SLM printers are in the “Bed Deposition” group, it is impossible to control geometry during printing, since the printed part of the product is always in a layer of unsintered (unfused) powder. However, SLM Solutions machines use a powder layer control system throughout the entire printing process.

The accuracy and workmanship is checked, depending on the accuracy requirements, with standard tools – from a caliper to a 3D scanner. For internal control of porosity, continuity, density of the material, computed tomography and X-ray control are used. To control cracks on the surface of products, the luminescent control method is often used. The mechanical properties are confirmed by the joint manufacture of witness samples and their subsequent tests.

Interested in the issue of repair and maintenance of equipment. Are there such specialists in Russia?

Our company always trains its own engineers to work on 3D equipment and works very closely with suppliers – in the case of metal 3D printing, these are SLM Solutions and Sharebot. If we talk about SLM Solutions, despite the fact that it is a German manufacturer, it has engineers in Russia who completely solve the issues of repair, maintenance and very complex technical problems.

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