Diy metal 3d printing

And then I thought, what if I spray metal in the place I need, gradually increasing the thickness? I looked for information about whether someone did this - I did not find it.

Registered on a forum where sprayers gather together and began to disturb them with questions like: is it possible to build up a “film” with a thickness of 1 or more millimeters. To which I caught a lot of misunderstanding what it was for, but received a positive answer.

General information received, you can begin to prepare for experiments.

It is known from various articles and documents that a vacuum of no more than 10⁻² Pa is needed. For comparison, the order of magnitude - the pressure that gives a household vacuum pump (Value and others) - about 4 Pa ​​(measured value), i.e. pressure is 400 times greater than necessary. How to deal with it and what to do? To achieve low pressures, turbomolecular vacuum pumps are used, they work in parallel with the foreline pump and, literally by molecules, capture the remaining air from the chamber. The process is not fast. The pump looks like this.

We installed a pump, it pumps out air and everything seems to be fine, but how to find out the pressure? For this I chose an ionization vacuum gauge.

In fact, nothing else is needed, except for the chamber and evaporator. I did not find a ready-made affordable (in terms of finances) camera, therefore, I decided to make my own. It is of a small volume (about 8-10 liters) in order for the air to be pumped out faster. Usually, the chambers have a spherical shape, in my case it is, on the contrary, elongated, in order to be able to set the “target” (the place where the metal is deposited) at different distances from the evaporator. In addition, the camera has a lot of flanges for connecting all kinds of inputs/outputs and sensors. I modeled the camera in a well-known CAD program, drew drawings and transferred it to production.

Current leads and conductors I made from a brass bar and a brass rod, bought on the local market. (Juno, who is from St. Petersburg).

In the photo below, a tungsten boat is fixed between two conductors.

The bottom part looks like this. The photo shows the cooling tubes of the current leads. Subsequently, I abandoned them, due to the simplification of the system.

Assembling the camera did not take much effort and complexity. It is much more difficult to achieve vacuum retention in this chamber. To do this, I polished the flanges and all mating surfaces to avoid the slightest leakage through the rubber seal (in the photo below, I processed only the top flange).

As it turned out later, the weld is not airtight at all (meaning for low vacuum). I, out of inexperience, assumed that by pumping a pressure of 300 kPa into the chamber and immersing it in a bath of water, I would carefully find all the leaks and eliminate them. Yes, at the first stage I did just that, but the pressure in the chamber did not fall below 10-2 Pa, there were leaks. Interestingly, before the start of the test, at a pressure in the chamber of 300 kPa, bubbles emerged from the welds with an intensity of approximately 1 bubble (diameter 2-3 mm) in 30-40 seconds. And those were big losses that I eliminated. But what to do with minimal vacuum losses that cannot be tracked in "kitchen" conditions?

The solution was close. To do this, all you need is a mass spectrometer.

The idea is simple – the investigated chamber or container is connected to the vacuum chamber of the spectrometer. Air is pumped out, on the graph they look for extraneous peaks of any gases. After that, helium is supplied locally, to the places of possible leakage. It is helium, because its penetrating power is higher and the helium peak can be easily tracked on the spectrum. As soon as helium enters the chamber through a micro-hole, it is immediately visible on the spectrum.

I drove twice and looked for leaks twice. Now the chamber with the installed pump is hermetic and it is possible to carry out experiments further, having previously assembled all the components of the system on the rack.

General view of the incredible installation.

Starting up the plant and checking it comes down to maintaining the lowest possible pressure. The foreline pump is started first.

The pressure after the operation of the foreline pump can be seen in the picture below.

After the pressure is established (does not change). You can launch "heavy artillery" - a turbomolecular pump. It reduces the pressure by another 3 orders of magnitude.

The time has come for experiments, what I have been going for so long and what I have been waiting for so long.

First experiment.

Place a small amount of silver into the boat fixed between the conductors. Above the boat I install a steam conduit - a soldered tin cylinder, which, as I thought, should limit the spread of metal through the chamber. Above the steam conduit there is a lid with a hole of 2 mm, behind the lid there is a target on which the metal should condense. It is a pity that there are no photos left, but the vacuum chamber was completely dusty. There was not a single place where there was no applied layer of metal. In the photo below, it’s not a different planet at all, but silver sprayed onto the inner surface of the wall.

Second experiment.

I thought it was because of the large gaps between the boat and the steam line. The solution was born immediately and quickly. I took two boats and combined them so that a shell was obtained. I placed silver inside, and cut a hole with a diameter of 2 mm in the upper half.

And he began to heat up the whole thing. But, I did not take into account the rigidity of the boats and the rigidity of the current leads. The shells parted a little and a gap formed between them, through which steam also flew in all directions.

As a result - spraying in the entire volume of the chamber. In the photo below there is a viewing window, the boat in which was slightly above half, but the window was completely dusty.

Third experiment.

After a little thought and grief, I thought that the container with the evaporated metal should be airtight and with only one outlet, but how and what to make it. From tungsten - very expensive and difficult to process. The way out has been found! Graphite is an excellent material for making a crucible, let's call it that. On the ad site, I found an ad for the sale of graphite bars from the contact whiskers of a trolleybus, cut out a bar with a hole in the center and made a cover for it. In the photo below - just a bar with a hole for the material (without a cover).

And in this photo already in the chamber with the lid installed (the hole in the lid is 1 mm in diameter).

Under the spoiler are a few photos with a short period of time, from which you can see how dusty the viewing window is.

Loss of transparency

It is obvious that in this case, too, there was no success, to my great regret. All three experiments were carried out with a gradual increase in temperature from the state when evaporation does not occur.

A small video in which the information is presented in a slightly different way, in a different form and volume.

Video link

www.youtube.com/watch?v=4yWQOWIG1qw

Unfortunately, it was not possible to get what was intended, but, on the other hand, invaluable experience was gained in the design and manufacture of vacuum equipment. Most of this experience I have shared with you and I would be very grateful if you express your opinion on this issue.

Thank you all and good luck.

3D metal laser printer: do-it-yourself metal 3D printer

Metal 3D printing is increasingly competing with traditional production methods. 3D printers can print metal nuts and wrenches, screws, bolts, car and aircraft parts, decorative items, cutlery and almost any product whose dimensions correspond to the dimensions of the printed surface of the printer. Larger objects can be printed as separate components and then assembled together.

The main problem of metal 3D printing is the high cost of consumables. Many products are still easier and more profitable to manufacture using traditional production methods. This article will review the process of metal 3D printing using SLM and DLMS technologies, provide an overview of the most popular printers, and assess the prospects of technology in industry and at home.

SLM vs DMLS: What's the difference?

Both of these technologies are actively used today for metal 3D printing. SLM involves selective laser melting of metal powder, while DMLS involves direct laser sintering of metal. In both cases, a laser is used to selectively melt metal powder grains, bind these grains together and create products in layers.

The difference between the technologies is:

• Metal powder is melted in SLM.
• DLMS uses lower temperatures so the metal does not liquefy. Powder particles simply sinter together.

Both technologies are protected by patents.

How does metal 3D printing work?

Metal 3D printing today requires an impressive amount of money. The cost of printers is measured in hundreds of thousands of dollars, and to this we must also add the cost of maintaining and maintaining them, purchasing consumables, training employees and remunerating them.

At the same time, these costs are offset by the efficiency of the production process. Thus, traditional production methods in the aviation industry lead to the fact that up to 90% of raw materials turn into waste. With 3D printing, no more than 5% of the material is sent to waste. Unused powder is sifted, mixed with new and reused for printing.

WARNING : Support area elements are usually waste.

The power consumption of 3D printers is much lower than traditional equipment. The mass of printed components is half that of traditional analogues. This is especially important for the aviation and space industries, as it saves millions of dollars in aircraft fuel.

Using 3D technology, you can print the following products:

How a metal 3D printer works

SLM and 9DMLS 3D printers print using the same algorithm:

3 Inside the build chamber, argon or another inert gas is launched so that the metal powder does not oxidize so much.

The finished object will be powder coated and secured to the work surface with supports. Supports are made of the same material as the object itself - otherwise they can be distorted or deformed under the influence of high temperatures.

The build chamber is allowed to cool to room temperature, the remaining powder is manually removed. The printed object is first heat treated to remove residual stresses and then the supports are removed. Once separated from the print platform, the parts are ready for use.

Key features SLM & DMLS

In SLM devices, the laser melts each layer of metal powder individually. Temperatures change drastically, which causes internal stresses in the parts. This may adversely affect the quality of the product, although it will in any case be higher than when casting. Products printed on SLM printers are superior to DLMS counterparts in terms of safety margin and solidity.

When working with DLMS technology, internal stresses are not created, so the quality of products is incommensurably higher than that of analogues made by stamping or casting. This is especially required for the aerospace and automotive industries, since the components used in them must be extremely durable.

Printer parameters

The parameters of metal 3D printers are usually:

• The layer thickness ranges from 20 µm to 50 µm.
• Dimensional accuracy is approximately ± 0.1 mm.
• The average printable area is 250 mm × 150 mm × 150 mm.

Devices are usually sold pre-configured so that the user does not have to change anything.

Adhesion between coats

Products printed on SLM and DMLS printers are almost identical in their isotropic thermal and mechanical properties. They are solid, their internal porosity does not exceed 0.5%. Compared to conventionally manufactured parts, these parts are usually stronger and more flexible, but are more prone to fatigue.

Support area and part orientation

Support for metal parts is a must in 3D printing as their processing temperatures are extremely high. To build such supports, a lattice structure is usually used.

In the production of metal objects, support takes on the following tasks:

• to provide the next layer with a secure platform;
• fix the element to the build platform and prevent its deformation;
• remove heat from the product and allow it to cool at a controlled rate.

To minimize the risk of deformation and increase strength in critical directions, products are usually oriented at an angle. Because of this, the printing time and material consumption increase, the cost of production increases, and the area of ​​\u200b\u200bsupport required expands.

CAUTION : To avoid warping, it is acceptable to use random random scan patterns. Such a sequence of laser passage through the sections of the layers will remove the residual stresses remaining in a particular direction.

Simulations are used to predict product behavior during printing. Continuous optimization algorithms can be used to produce lightweight parts and improve their performance. These algorithms also reduce the risk of deformation and reduce the required support area.

Hollow sections and lightweight constructions

Removing support areas for metal parts requires considerable effort, so hollow sections are avoided. Instead, products are designed to have a core and a shell. They are treated with a laser at different powers, with different scanning speeds. As a result, different areas of parts have different properties.

This approach is particularly useful for the production of objects with large solid sections. The risk of their deformation is minimized, the printing time is reduced. The finished objects are exceptionally stable and their surfaces are extremely high quality.

WARNING : To reduce the mass of the object, metal 3D printing often uses a lattice structure.

SLM and DMLS consumables

These technologies print on aluminum, titanium, inconel, cobalt chromium and other metals and metal alloys. The scope of powders of these metals is extremely wide: from medicine to the aerospace industry. Silver, gold, palladium and platinum are printed mainly in the jewelry industry, these materials are not in great demand outside of it.

WARNING : prices for metal powders remain high and can be in the region of $400 per kg. Therefore, today in 3D it is advantageous to print primarily small metal parts that are too difficult or expensive to create using traditional methods.

Cobalt-chromium or nickel superalloys are extremely difficult to work with conventional methods. 3D printers, on the other hand, create products with an almost clean surface from such a powder, which can then be refined using more familiar methods.

Post-processing

Parts are post-processed to improve their accuracy, mechanical properties and appearance. Support areas are removed from them, the remnants of the powder are cleaned off, and then subjected to thermal firing. During heat treatment, residual stresses are removed from the products.

If the product needs to be given a complex geometric shape, to create threads or holes on it, CNC machines are used for this. To improve surface quality and increase fatigue strength, products are pressure treated, metallized, polished and micromachined.

Metal 3D Printer Overview

Below are the technical specifications and brief descriptions of the four most used metal 3D printers in industrial production. The exact price is given for one model only, since prices for such units are usually announced upon request. In any case, we are talking about hundreds of thousands of dollars.

HP Metal Jet

MJF powder sintering technology delivers up to twice the printing speed of laser technology. Metal powder is applied to the working surface of the device, leveled and filled with a printing compound according to the shape of the part, which binds the powder grains together. Each layer is fixed at a high temperature, then the remaining powder is removed from the working surface and the entire object is sintered.

HP Metal Jet 3D Printer

• Material Metal powder
• Print resolution 1200x1200 dpi
• platform type Stainless steel
• Working chamber area 430x320x200 mm

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The service life of the device, according to the manufacturer, is at least 100,000 parts. In a spacious workspace, you can produce several objects in one go, and their height can be different. The products printed on the printer comply with the international ASTM standard. Density index after sintering exceeds 93%.

Farsoon FS121M

This model features high speed and extreme construction accuracy, which provide an individualized laser scanning algorithm. For inert gas, a supply and filtration system has been developed, which increases the safety of work and the quality of manufactured objects. The software of the device was created in open source and is constantly being improved. Due to this, the user gets maximum access to all configurable printer settings.

• Dimensions, mm 780×1000×1700
• Software FarsoonMakeStar
• Producing country USA
• Weight, kg 1000

• Laser spot diameter 40～200 µm
• Shielding gas Argon / Nitrogen
• Laser power 200 W
• Seal SLM
• Laser type Yb fiber laser
• File format STL
• Working chamber area 120×120×100 mm
• Speed 5 cm3/h
• Layer thickness from 20 µm
• Scan speed 15. 2 m/s

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Russian SLM 250

Russian The Russian-made SLM 250 from 3DSLA is compatible with both native and third-party consumables. If necessary, the manufacturer is ready to create custom-made powders. The device prints with powders with fractions of no more than 60 microns, fusing them layer by layer with a laser in the presence of an inert gas. Triangulatica's own software was developed for the printer, which not only processes the loaded models and generates support for them, but also controls all phases of the printing process (laser power, inert gas state, layer thickness, and so on). If desired, the device can be supplemented with a powder sifting station and a fractional division unit for it, a layer-by-layer video control system for printing with an archive for data storage, a shielding gas generator with a purity of up to 99.99% (this figure is given for nitrogen). If you plan to use not the entire printer platform at once, it would be wise to purchase a powder saving module as well.

3D printer SLM 280 2.0

• File formats STL
• Dimensions, mm 2600 x 1200 x 2700
• Software SLM AutoFabMC
• Producing country Germany
• Weight, kg 1300

• Laser spot diameter 80 - 115 µm
• Minimum wall thickness 150 µm
• Laser power 1x400/2x400/1x700/2x700/1x700 + 1x1000 W
• Seal SLM
• Performance 55 cm³/h
• Shielding gas consumption during construction, l/min. Ar 2.5
• Shielding gas consumption during purge (start of operation), l Ar 70 l/min
• Laser type IPG fiber
• Working chamber area 280 x 280 x 365 mm
• Layer thickness from 20 µm
• Display yes
• Interfaces Ethernet 10/100/1000
• Scan speed 10 m/s

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Concept Laser X line 2000R

• Technology: LC
• Print surface dimensions: 800 mm x 400 mm x 500 mm
• Weight: 8000 kg
• Layer thickness from 2 µm0160

The abbreviation LC stands for LaserCusing and is the manufacturer's own design. This technology is close to laser sintering, but is carried out using high power fiber lasers. Thus, there is no sintering, but a complete fusion of powder grains to a homogeneous mass. This allows you to create products of the most complex geometry with outstanding technical characteristics. The device is equipped with a vacuum unit and can also work with reactive materials (eg titanium). Marcam AutoFab M2 software allows you to create models of jewelry and dental products for printing, and 3Shape CAMbridge automates the production of metal orthopedic structures.

Do-it-yourself: metal 3D printer for the home

Outside the production environment, it is better to print not with metal, but with plastic filament with the addition of metal particles, such as bronze. For this, an FDM printer is suitable, whose cost is significantly lower than that of machines for printing with metals. FDM devices do not need to be heated to such high temperatures as industrial metal printers, the level of noise and unpleasant smell from them is much lower. In this way it is very convenient to print interior objects, household items and jewelry.

Products printed from plastic filament with metal particles look and feel indistinguishable from metal counterparts, and also have a comparable mass. Unlike metal, they will never rust. For their manufacture, it is not necessary to install a heated table on the printer, and when cooled, such products will give minimal shrinkage. However, it requires post-processing in the form of grinding and polishing, and the nozzle temperature and filament feed rate must be fine-tuned. In addition, metal particle filaments are extremely abrasive, which accelerates nozzle wear.

WARNING : It is not recommended to create objects with plastic filament using metal that will come into contact with food.

3D printing with metal powder allows you to create products with much more complex geometries than analogues produced by traditional methods. The finished product has excellent physical characteristics, even if it was made from superalloys that are difficult to process traditionally.

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