CN104588649A - Process for directly forming metal part of cantilever structure through laser light - Google Patents

Abstract

The invention discloses a process for directly forming a metal part with a cantilever structure by laser. When forming to the cantilever layer, provide support according to one of the following three methods: ① Fill metal powder around the part, and scrape and compact the powder to be flush with the current cladding layer of the part; ② Lay the fine metal mesh To the formed part; ③ place the thin sheet made of powder on the level of the current cladding layer. Different ways of supporting one layer of the cantilever correspond to different forming processes: ①. Reduce the power of the laser and turn off the powder feeder, and sweep a layer over the scraped and compacted metal powder; ②. First scan the contour and melt the fine metal mesh On the substrate of the formed part, reduce the laser power, fill and scan one layer; ③, directly form according to the normal process. With the support provided by the previous layer, subsequent shaping can be carried out according to the normal process.

Description

Laser Direct Forming Technology of Cantilever Structure Metal Parts

technical field

The invention relates to laser additive manufacturing technology, in particular to a method for forming cantilever structural parts by using powder, fine metal mesh, and thin sheets pressed by powder to provide support in direct laser forming, and is mainly used to solve three-axis (or even five-axis) laser Forming problems of cantilever structural parts that cannot be solved in the system.

Background technique

Laser direct forming is an advanced manufacturing technology developed in the early 1990s that combines rapid prototyping technology and laser cladding technology. It is based on the "discrete-stacking" forming principle. First, the 3D CAD solid model of the functional parts is generated in the computer; then the 3D shape information of the parts is sliced and layered, converted into a series of 2D contour information, and the geometric information of the layers is fused The forming parameters generate the numerical control code of the scanning path. Under the control of the numerical control system, the laser cladding method of synchronous powder feeding is adopted to deposit layer by layer according to the scanning trajectory, and finally form a three-dimensional solid part. As a new technology subverting the traditional manufacturing industry, it can realize the toolless, fast, full-dense near-net shape of high-performance complex structural metal parts. It is regarded as the third industrial revolution and has set off an upsurge of research and application worldwide. It is especially suitable for special materials or metal parts with special shapes that are difficult to manufacture by traditional methods, and has broad application prospects in aerospace, automotive industry, mold design and manufacturing, biomedicine and other fields.

In fact, powder-spraying laser direct forming equipment cannot form arbitrarily complex metal parts. Taking the three-axis linkage forming equipment as an example, for parts exceeding the limit inclination angle and having a cantilever structure, support needs to be added to form, which reduces the forming efficiency, and it is difficult or even impossible to remove some supports. The five-axis linkage forming equipment can overcome the problem of large inclination angles, but it is still unable to form some complex cantilever structures (such as the forming of the top of the turbine blade of an aeroengine). It can be seen that the complex cantilever structure limits the wide application of laser direct forming technology.

Contents of the invention

Aiming at the problem that metal parts with cantilever structure cannot be formed in the existing laser direct forming technology, the purpose of the present invention is to provide a method using preset powder, metal fine mesh and thin sheet to provide support for subsequent cladding forming to form cantilever structure metal parts. Process of structural metal parts.

To achieve the above object, the present invention is achieved by taking the following technical solutions:

A process for directly forming a metal part of a cantilever structure by laser is characterized in that it comprises the following steps:

(1) When there is no cantilever structure in the metal part, the metal powder is directly clad according to the conventional laser forming process;

(2) When cladding to the first layer of the cantilever structure, provide support in one of the following three ways:

①. Fill the metal powder around the part, compact the powder, and make it flush with the current end face of the part;

②. Spread the fine metal mesh on the current end surface of the part;

③. Spread the prefabricated powder sheet on the current end face of the part, and the shape of the sheet is the same as that of the cantilever part;

(3) The cantilever layer is supported in different ways in step (2), corresponding to the following different forming processes:

①. For the support of step (2)①, reduce the laser power and close the powder feeder, and scan the metal powder flush with the current end face of the part according to the cantilever profile; partially melt the powder to form a sintered layer;

②. For the support in step (2)②, first scan according to the contour of the cantilever, and melt the fine metal mesh to the current end face of the part; reduce the laser power, and then fill and scan one layer;

③. For the support of step (2) ③, continue to form directly according to the conventional process;

(4) Subsequent forming only needs to continue cladding according to the normal process, and return to step (2) if the cantilever structure is encountered again.

In the above process, for the support form of the preset metal powder in step (2)②, after the cantilever structure is formed, the filled metal powder needs to be cleaned and recovered.

The particle size of metal powder for forming is 40-60 μm. The preferred material is Ti-6Al-4V, that is, TC4 powder.

In the laser direct forming, the present invention uses a layer of sintered powder, a fine mesh of the same metal, and a thin sheet pressed from the powder as supports to complete the forming of the cantilever structure and solve the problem of difficulty in direct laser forming of the metal parts of the cantilever structure. The present invention borrows from the selective laser sintering technology (SLM), the cantilever part of the three-dimensional model is supported by metal powder, instead of building a solid support for the model. In theory, any complex solid part can be formed, and due to the characteristics of laser direct forming parts, its strength is higher than that of laser selective sintering. The absence of unnecessary solid supports maximizes forming efficiency and saves powder.

The invention can quickly manufacture metal parts with a cantilever structure under the conditions of three moving shaft laser metal forming equipment, and is suitable for forming complex structures such as aeroengine blades and inner runners.

Description of drawings

Figure 1 is a schematic diagram of the laser direct forming system. In the figure: 1. Laser beam; 2. Carrier gas powder; 3. Atmosphere protection cover; 4. Numerical control workbench; 5. Powder feeding nozzle; 6. Substrate.

Fig. 2 is an example of the laser direct forming cantilever part of the present invention. Among them: (a) the metal part does not contain the part of the cantilever structure, which is directly formed on the substrate; (b) a layer is sintered on the preset metal powder; (c) the final formed metal part. In the figure: 6, base plate; 7, parts without cantilever structure; 8, preset metal powder; 9, a layer sintered on preset powder; 10, powder container; 11, final formed metal parts.

Fig. 3 is a topographic photo of another example of the laser direct forming cantilever part of the present invention. Among them: (a) using metal mesh as support; (b) the final formed TC4 cantilever structural parts.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Referring to Fig. 1, the laser direct forming system of the present invention includes a laser, a computer, a three-coordinate numerical control workbench 4, a protective gas and a powder feeder, a powder feeding nozzle 5, an atmosphere protection cover 3, etc., and the laser generates and conducts a laser beam 1 to the processing area , the three-coordinate CNC workbench realizes the relative movement between the laser beam and the forming sample, the powder feeder transmits the carrier gas powder 2 to the four-way powder feeding nozzle, so that the powder flow coincides with the laser beam, and the atmosphere protection cover 3 ensures that the forming chamber The oxygen content meets the processing requirements.

Embodiment one

(1) Material selection for laser direct forming cantilever structure metal parts: The metal powder used in the experiment is usually Ti-6Al-4V (TC4) powder, the powder particle size is 40-60 μm, and the material of substrate 6 is TC4 substrate.

(2) Before the experiment, heat the powder in a vacuum drying oven to 150°C and keep it warm for 24 hours to remove moisture and enhance the powder fluidity; after polishing the surface of the TC4 substrate with fine sandpaper, remove the grease and stains on the surface of the substrate with acetone solution, and finally Clean the substrate surface with ethanol solution.

(3) During the forming process, when the height is less than 3cm, it is normally formed on the TC4 substrate. The main process parameters are laser power 200W, scanning speed 10mm/s, powder feeding amount 4g/min, Z-axis lifting amount 0.1mm, two The lapping distance between roads is 0.30mm.

(4) When the height is 3cm, the contour shape of the part is a rectangular surface, and the middle part of the rectangular surface is not supported, so it cannot be formed directly [Fig. 2(a)]. Therefore, fill the metal powder 8 around the part, and scrape it flat after compaction, so that the powder is flush with the upper surface of the part. When forming the cantilever layer, close the powder feeder to prevent the powder feeding nozzle from blowing the compacted powder away. Reduce the laser power to 150W, so that the powder is partially melted, connected together (one layer 9 sintered on the pre-set powder), and provides support for the next layer [Fig. 2(b)].

(5) When the height is greater than 3mm, it can be formed according to the normal process parameters: open the powder feeder and increase the laser power to 200W. After the forming is completed, the powder is cleaned and recovered, and the final formed titanium alloy parts are shown in Figure 2(c).

Embodiment two

(1) When the forming height is less than 3cm, use the same process as Example 1; when forming to a height of 3cm, use titanium mesh instead of powder as support [Figure 3(a)].

(2) When forming on the titanium mesh, first scan the contour according to the normal power, and fuse the titanium mesh to the formed part substrate. Then reduce the laser power to 100W, turn on the powder feeder, and fill and scan one layer.

(3) On the support of the formed layer, it can be formed according to the normal process, and the final formed part is shown in Figure 3(b).

In this example, the metal fine mesh with the same element as the metal powder is used as a support, which can also provide support for subsequent forming. Compared with metal powder as a support, there is no additional sticky powder at the bottom of the cantilever layer during metal fine mesh cladding, so it has higher forming accuracy.

Embodiment Three

The prefabricated powder sheet is used instead of the fine metal mesh in Example 2, and it is spread on the current end surface of the part. The shape of the sheet is the same as that of the cantilever part, and it can be directly formed on the sheet according to the normal process.

Claims (4)

1. a technique for Laser Direct Deposition cantilever design metal parts, is characterized in that, comprises the steps:

(1) when metal parts does not exist cantilever design, by the direct deposited metals powder of laser forming common process;

(2), when cladding is to one deck of cantilever design, provide support by one of following three kinds of methods:

1., by metal dust be filled into around part, and by powder pressing, and with part when front end face is concordant;

2., metal fine-structure mesh is laid in part and works as front end face;

3., prefabricated powder thin slice is laid in part works as front end face, chip shape is identical with bracketed part;

(3) cantilever layer is according to the support of step (2) different modes, corresponding following different forming technology:

1., to step (2) support 1., reduce laser power and also close powder feeder, with part when the metal dust that front end face is concordant presses cantilever profile scan; Powder fractions is melted and forms sinter layer;

2., to step (2) support 2., first press cantilever profile scan, metal fine-structure mesh is molten to part and works as front end face; Reduce laser power, recharge scanning one deck;

3., to step (2) support 3., directly conveniently technique continues to be shaped;

(4) follow-up shaping only need continue cladding by normal process, if run into cantilever design again, is then back to step (2) again.

2. the technique of Laser Direct Deposition cantilever design metal parts as claimed in claim 1, is characterized in that, the described supporting form to step (2) preset metal dust 2., and cantilever design needs the metal dust that clearing and retrieving is filled after being shaped and terminating.

3. the technique of Laser Direct Deposition cantilever design metal parts as claimed in claim 1, it is characterized in that, forming metallic powder size is 40 ~ 60 μm.

4. the technique of Laser Direct Deposition cantilever design metal parts as claimed in claim 1, it is characterized in that, forming metallic powder the selection of material is Ti-6Al-4V, is also TC4 powder.