The concept of a 3D printer printing metal with high resolution and great speed
Once again, glad to welcome, dear community!
A couple of years ago, I began to search for a simple technology for the production of precision metal products. So in the "background" I studied various metal processing technologies, different methods for creating metal products, from casting to photolithography, from a lathe to installing an ECHO.
Not finding the technology that meets all my requirements (mainly because of the price), I decided to think over my own, which I submit to your court, under the cut. I draw your attention to the fact that this is still just a concept, and not a finished product.
I also invite everyone to participate in a project to implement this concept, details at the end of the article.
To date, the author knows several ways to produce metal products from metal powders. All these methods have their advantages and disadvantages.
The purpose of this work was to develop a device that incorporates all the advantages of the following production methods, while eliminating all the disadvantages.
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The technology of manufacturing products from metal powders (or their compositions with non-metallic powders). In general, the technological process of powder metallurgy consists of 3 main stages: mixing of powders, compaction (pressing, briquetting) and sintering.
Advantages:
- relatively simple technology.
Disadvantages:
- it is not possible to produce products of complex shape;
- equipment is required (molds for pressing);
- relatively low resolution and accuracy.
When using MIM technology, a mixture of fine metal powder and a binder is injected into injection presses, which are almost identical to the presses used to inject thermoplastics. The raw material for the MIM technology is a mixture of the binder and fine metal powder, the so-called feedstock.
Advantages:
- it is possible to produce products of complex shape;
- rather high accuracy and resolution.
Disadvantages:
- difficult and expensive equipment;
- the equipment is required (molding forms);
- there is an additional process step - burning polymer;
- there is a consumable (which increases the cost of the final product) - polymer;
- sintering is required in furnaces with protection against oxidation (vacuum, inert gases).
In SLS technology, the powder is sprayed with a uniform layer over the entire area, after which the laser bakes only those areas that correspond to the cross section of the model on this layer at this height. In the SLM, metal particles are brought to a state of melting and welded together, forming a rigid frame.
Advantages:
- it is possible to produce products of complex shape;
- sufficiently high accuracy and resolution;
- does not require tooling;
- it is possible to make single copies.
Disadvantages:
- complex and expensive equipment;
- low manufacturing speed.
(also while in the project)
The system uses layer-by-layer deposition of metal powder and photopolymer. The powder is applied in a continuous layer, and the photopolymer only along the contour of the cut of the product. Then the photopolymer is exposed to ultraviolet light. So It turns out a metal-polymer product surrounded by powder. Then the polymer is burned and the powder is sintered in a furnace.
Advantages:
- high production speed,
- high resolution and accuracy,
- does not require tooling,
- relatively cheap equipment.
Disadvantages:
- requires consumable material - photopolymer,
- there is an intermediate stage - polymer burning.
The device presented in this paper also uses powdered metals as a starting material.
The principle of creation of the product consists in the formation of 2 component layers, i.e. Each layer will contain 2 types of powder: base and backfill.
The basis is a metal powder from which the product will be formed.
Backfilling is powder filling the voids, with a sintering temperature greater than that of the Foundation.
Thus, each layer (being a cut of the product, that is, two-dimensional) will be “printed” as follows: the base is the product, the backfill is the background.
After each layer is applied, the roller is pressed.
After creating all the layers, the resulting mass is sintered in a furnace. Since in the base powder, the melting point (and, consequently, the sintering temperature) is lower, then only the particles of this powder will sinter, and the backfill will remain loose.
2 component layers are applied using the so-called. electrography.
Electrography (xerography) is a reprography method that uses an electric charge to transfer toner (dry ink). On the principle of electrography work laser printers and copiers.
More information about electrography and the principle of operation of laser printers can be found in this Wikipedia article.
For applying 2 components at once, 2 identical sequential electrostatic transfer systems are used.
After the next layer is applied and compacted, the table on which the “printing” is made makes 1 step (the step size depends on the required resolution) down.
After applying all layers, the product is baked in the oven. It does not require protection against oxidation (vacuum or inert gas), because air penetration to the metal of the product is prevented by backfilling.
Advantages of development
1) The ability to use mass-produced components (used in laser printers), significantly reduces the cost of the device.
2) High resolution and accuracy.
3) High print speed.
4) Lack of equipment.
5) No additional consumables (backfill can be used repeatedly).
6) Can the manufacturer of products of complex shape.
7) Protection against oxidation is not required when baking.
8) It is not necessary to use powders with spherical particles.
Possible problems and solutions
1) Rapid wear of the fotovalo.
Solution a) Apply wear-resistant materials.
Solution b) Do not use foval at all, i.e. charge the layer directly.
Solution c) Split process: the fotoval transfers the desired electrostatic pattern to the previous layer, then the powder is applied.
2) Development of a universal charge suitable for baking powders of various brands.
3) Different grades of powders may react differently to electrostatics.
Solution a) applying some kind of coating (shell) on a particle of powder
Solution b) use, instead of electrostatics, other physical effects. For example, backfilling is applied by electrostatics, and the foundation is driven by the “spatula” method into the formed recesses.
At the end of the post I want to remind once again that this is just a concept and much that can change during the design and testing process. The main thing in this article is the technology of creating a 3D figure itself (layer-by-layer deposition of 2 powders, bases and backfill).
1) Is the technology patented?
Not. The technology is not patented, because Firstly, it is still too early to patent at this stage, and secondly, I consider it a waste of time (my opinion is that the Institute for the Protection of Intellectual Property in the Russian Federation, as in most countries, does not work).
2) Why only powder metallurgy is discussed in the article?
I consider powder metallurgy to be the most promising, and also the most suitable for precision production.
3) Why spread the technology in free access?
I cannot do this project alone. Therefore, with the help of this article, I hope to find enthusiasts who, perhaps, will come up with an idea and create a community for its implementation, on a voluntary basis. Let it become an open project accessible to everyone who wants to realize themselves.
In this regard, I have suggestions to all interested professionals from different fields of science and technology: If you are interested in the project and you want to take part in it, write in the comments (so that your messages are available to the entire nascent community).
PS I plan to continue to talk about their developments. Subscribe not to miss!
If someone missed here is the first article in this series.
A couple of years ago, I began to search for a simple technology for the production of precision metal products. So in the "background" I studied various metal processing technologies, different methods for creating metal products, from casting to photolithography, from a lathe to installing an ECHO.
Not finding the technology that meets all my requirements (mainly because of the price), I decided to think over my own, which I submit to your court, under the cut. I draw your attention to the fact that this is still just a concept, and not a finished product.
I also invite everyone to participate in a project to implement this concept, details at the end of the article.
Introduction
To date, the author knows several ways to produce metal products from metal powders. All these methods have their advantages and disadvantages.
The purpose of this work was to develop a device that incorporates all the advantages of the following production methods, while eliminating all the disadvantages.
')
Classical powder metallurgy
The technology of manufacturing products from metal powders (or their compositions with non-metallic powders). In general, the technological process of powder metallurgy consists of 3 main stages: mixing of powders, compaction (pressing, briquetting) and sintering.
Advantages:
- relatively simple technology.
Disadvantages:
- it is not possible to produce products of complex shape;
- equipment is required (molds for pressing);
- relatively low resolution and accuracy.
MIM technology
When using MIM technology, a mixture of fine metal powder and a binder is injected into injection presses, which are almost identical to the presses used to inject thermoplastics. The raw material for the MIM technology is a mixture of the binder and fine metal powder, the so-called feedstock.
Advantages:
- it is possible to produce products of complex shape;
- rather high accuracy and resolution.
Disadvantages:
- difficult and expensive equipment;
- the equipment is required (molding forms);
- there is an additional process step - burning polymer;
- there is a consumable (which increases the cost of the final product) - polymer;
- sintering is required in furnaces with protection against oxidation (vacuum, inert gases).
SLS and SLM (3D printers)
In SLS technology, the powder is sprayed with a uniform layer over the entire area, after which the laser bakes only those areas that correspond to the cross section of the model on this layer at this height. In the SLM, metal particles are brought to a state of melting and welded together, forming a rigid frame.
Advantages:
- it is possible to produce products of complex shape;
- sufficiently high accuracy and resolution;
- does not require tooling;
- it is possible to make single copies.
Disadvantages:
- complex and expensive equipment;
- low manufacturing speed.
The “Production system” from the company “Desktop metal”
(also while in the project)
The system uses layer-by-layer deposition of metal powder and photopolymer. The powder is applied in a continuous layer, and the photopolymer only along the contour of the cut of the product. Then the photopolymer is exposed to ultraviolet light. So It turns out a metal-polymer product surrounded by powder. Then the polymer is burned and the powder is sintered in a furnace.
Advantages:
- high production speed,
- high resolution and accuracy,
- does not require tooling,
- relatively cheap equipment.
Disadvantages:
- requires consumable material - photopolymer,
- there is an intermediate stage - polymer burning.
Development Description
The device presented in this paper also uses powdered metals as a starting material.
Technology
The principle of creation of the product consists in the formation of 2 component layers, i.e. Each layer will contain 2 types of powder: base and backfill.
The basis is a metal powder from which the product will be formed.
Backfilling is powder filling the voids, with a sintering temperature greater than that of the Foundation.
Thus, each layer (being a cut of the product, that is, two-dimensional) will be “printed” as follows: the base is the product, the backfill is the background.
After each layer is applied, the roller is pressed.
After creating all the layers, the resulting mass is sintered in a furnace. Since in the base powder, the melting point (and, consequently, the sintering temperature) is lower, then only the particles of this powder will sinter, and the backfill will remain loose.
Work principles
2 component layers are applied using the so-called. electrography.
Electrography (xerography) is a reprography method that uses an electric charge to transfer toner (dry ink). On the principle of electrography work laser printers and copiers.
More information about electrography and the principle of operation of laser printers can be found in this Wikipedia article.
For applying 2 components at once, 2 identical sequential electrostatic transfer systems are used.
After the next layer is applied and compacted, the table on which the “printing” is made makes 1 step (the step size depends on the required resolution) down.
After applying all layers, the product is baked in the oven. It does not require protection against oxidation (vacuum or inert gas), because air penetration to the metal of the product is prevented by backfilling.
Advantages of development
1) The ability to use mass-produced components (used in laser printers), significantly reduces the cost of the device.
2) High resolution and accuracy.
3) High print speed.
4) Lack of equipment.
5) No additional consumables (backfill can be used repeatedly).
6) Can the manufacturer of products of complex shape.
7) Protection against oxidation is not required when baking.
8) It is not necessary to use powders with spherical particles.
Possible problems and solutions
1) Rapid wear of the fotovalo.
Solution a) Apply wear-resistant materials.
Solution b) Do not use foval at all, i.e. charge the layer directly.
Solution c) Split process: the fotoval transfers the desired electrostatic pattern to the previous layer, then the powder is applied.
2) Development of a universal charge suitable for baking powders of various brands.
3) Different grades of powders may react differently to electrostatics.
Solution a) applying some kind of coating (shell) on a particle of powder
Solution b) use, instead of electrostatics, other physical effects. For example, backfilling is applied by electrostatics, and the foundation is driven by the “spatula” method into the formed recesses.
At the end of the post I want to remind once again that this is just a concept and much that can change during the design and testing process. The main thing in this article is the technology of creating a 3D figure itself (layer-by-layer deposition of 2 powders, bases and backfill).
FAQ
1) Is the technology patented?
Not. The technology is not patented, because Firstly, it is still too early to patent at this stage, and secondly, I consider it a waste of time (my opinion is that the Institute for the Protection of Intellectual Property in the Russian Federation, as in most countries, does not work).
2) Why only powder metallurgy is discussed in the article?
I consider powder metallurgy to be the most promising, and also the most suitable for precision production.
3) Why spread the technology in free access?
I cannot do this project alone. Therefore, with the help of this article, I hope to find enthusiasts who, perhaps, will come up with an idea and create a community for its implementation, on a voluntary basis. Let it become an open project accessible to everyone who wants to realize themselves.
In this regard, I have suggestions to all interested professionals from different fields of science and technology: If you are interested in the project and you want to take part in it, write in the comments (so that your messages are available to the entire nascent community).
PS I plan to continue to talk about their developments. Subscribe not to miss!
If someone missed here is the first article in this series.
Source: https://habr.com/ru/post/348628/
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