CN101081388B - Method for reducing light-cured rapid prototype component surface roughness - Google Patents

Abstract

The present invention discloses one kind of physical and chemical method to lower the surface roughness of stereo optically cured body. The method includes the following steps: compounding resin paint through adding surfactant not more than 0.1 %, active diluent in 5-30 % and leveling agent not more than 1 % into resin and regulating the viscosity of the resin paint to 0.25-0.70 Pa.S; and coating the resin paint to the surface of the body to form homogeneous coating of thickness within 300 micron, so as to reduce the roughness from 6-15 micron to 3 micron. The method can eliminate the step effect of stereo optically curing, and has excellent application foreground.

Description

A Method for Reducing Surface Roughness of Light-cured Rapid Prototype

technical field

The invention relates to a post-processing method for photocured three-dimensional molding prototypes, in particular to a method for reducing the surface roughness of photocured rapid prototypes. The method treats the surface of the prototypes by physical and chemical methods to quickly reduce the surface roughness of the prototypes Spend.

Background technique

Rapid prototyping technology is a processing and forming method based on material accumulation. Rapid prototyping technology can speed up product innovation and shorten product design and production cycles. Stereolithography is currently the most widely used and most precise method among various rapid prototyping methods. It has the advantages of high production efficiency and material utilization rate close to 100%, and it can form particularly complex shapes (such as hollow parts), Extra fine parts. However, there will still be precision deviations caused by the step effect during the molding process on the surface of the prototype after molding. This is related to the working principle of the stereolithography material additive molding and is inevitable.

At present, the accuracy of the prototype is basically improved by optimizing the software, hardware, molding materials and parameters in the molding process at home and abroad, but the cost of these optimizations is the increase in cost, and can only reduce the impact of the step effect. But can not fundamentally eliminate the step effect. The prototype can be processed by the post-processing process, which can make up for the formed step effect and reduce the error caused by the step effect. Compared with the method of increasing the accuracy by increasing the number of layers, the production cost is greatly reduced and the manufacturing process is shortened. time. At present, the commonly used post-processing methods include grinding, mechanical secondary processing and other mechanical processing methods. The disadvantage is that it is necessary to reserve a machining allowance during molding. Using mechanical processing for secondary processing requires a lot of manpower and material resources, which further increases Processing costs, and it is not suitable for parts with complex surface shapes.

According to the data retrieval conducted by the applicant, there are no related literatures and patents about treating the surface of the prototype by physical and chemical methods to reduce the surface roughness of the prototype.

Contents of the invention

The object of the present invention is to provide a method for reducing the surface roughness of a photocured prototype by using a physicochemical method. In the method, the stereolithography prototype is post-processed through the preparation of the resin coating and the adjustment of the coating process, and a uniform coating is formed on the surface of the stereolithography prototype. The coating is extremely thin without affecting the dimensional accuracy of the prototype, and can reduce the manufacturing error caused by the inevitable step effect in the molding process in a short time, and reduce the surface roughness of the prototype; no pre-treatment is required during molding. The machining allowance is reserved, the cost is saved, and the dimensional accuracy of the parts is guaranteed; compared with machining processes such as grinding, this method has no influence of secondary errors.

In order to realize above-mentioned task, the present invention takes following technical solution:

A physical and chemical method for reducing the surface roughness of stereolithography rapid prototypes, characterized in that it comprises the following steps:

First prepare the resin coating, the preparation method of the resin coating is to add the following raw materials into the resin according to the mass percentage of the photocurable resin: surfactant: ≤0.1%, reactive diluent: 5% to 30%, leveling agent ≤1%; And adjust the resin coating viscosity between 0.25Pa.S～0.70Pa.S;

Apply the resin coating on the surface of the stereolithography resin prototype by brushing, soaking or spraying;

Then, a uniform coating with a thickness of no more than 300 μm is formed on the surface of the stereolithography prototype through a curing process.

The method of the invention can reduce the surface roughness of the stereolithography rapid prototype from the original 6 μm to 15 μm to within 3 μm. It eliminates the step effect produced by the stereolithography method, is easy to operate, and greatly saves production costs without affecting the dimensional accuracy of the stereolithography rapid prototype. It has a good application prospect and makes rapid prototyping better. in the production process.

Description of drawings

Fig. 1 is a schematic diagram of reducing the surface roughness of the prototype by coating with resin coating;

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

Detailed ways

The invention provides a physical and chemical method for reducing the surface roughness of a stereolithography prototype based on photocuring stereolithography technology. The method firstly prepares a photocuring or normal temperature curing resin coating. The coating has a low viscosity and has a certain Wettability and leveling can form a thin uniform coating on the surface of the prototype; secondly, the resin coating is applied (soaked, brushed or sprayed) on the surface of the light-cured resin prototype, and through a certain process (inverted blowing) After drying or spin-drying) to make the excess resin on the surface flow out, the surface coating is cured through the corresponding curing process.

The present invention adopts following technological process (as shown in Figure 1):

1) Prepare the resin coating. The preparation method of the resin coating is to add the following raw materials in the resin according to the mass percentage of the photocurable resin: surfactant: ≤0.1%, reactive diluent: 5% to 30%, leveling agent ≤1 %; and adjust the resin coating viscosity between 0.25Pa.S～0.70Pa.S;

2) Applying the resin coating to the surface of the stereolithography prototype by brushing, soaking or spraying;

3) Let the excess resin on the surface flow out;

4) The surface coating of the stereolithography prototype is cured by light curing (normal temperature curing), and a layer of extremely thin uniform coating is formed on the inner and outer surfaces of the stereolithography prototype, thereby reducing the influence of the step effect. Reduce the surface roughness of the prototype. The method of the present invention does not require secondary machining, saves cost, and enables the surface of the prototype to achieve industrial-grade precision.

The curing process of the invention can cure the surface coating of the resin prototype in a short time. Through the adjustment of the curing process, the curing of the coating does not affect the dimensional accuracy of the prototype itself. High-pressure mercury lamps are used for light curing. The curing time is short, the quality is good, and the resin is cured in depth; after curing, the surface layer is cured by low-pressure ultraviolet lamps, and the coating quality is guaranteed by controlling the curing time. Curing at room temperature adjusts the curing time through the preparation of the resin coating, and can be accelerated by slight heating (not exceeding the deformation temperature of the resin prototype).

The following are specific examples given by the inventors, taking the photocurable coating as an example.

Example 1:

1. Deploy resin paint

(1). The resin coating is prepared by the following aspects:

1) Add the surfactant JFC (polyoxyethylene ether compound, the addition amount does not exceed 0.1% of the mass of the photocurable resin) to the existing photocurable resin, heat and stir or use other chemical methods to chemically modify the photocurable resin. sex.

2) Add commercially available reactive diluent HDDA (1,6-hexanediol diacrylate, the addition amount is 10% of the mass of the resin) to the photocurable resin to reduce the viscosity of the resin.

3) Add commercially available UV leveling agent 4325 (the amount added should not exceed 1% of the mass of the resin) into the photocurable resin to improve the fluidity of the resin.

4) Adjust the viscosity of the resin coating within 0.70Pa.S to optimize the performance of the resin coating. It can completely fill up the step surface and form an extremely thin layer of coating, and there is a certain gap between the coating coating and the step surface. of adsorption. After preparing the resin coating, leave it for more than 30 minutes, and proceed to the next step after the bubbles in the resin disappear.

2. Coating and hanging process

Coating and hanging on the surface of the formed stereolithography prototype, the basic process of forming the stereolithography prototype is:

First, use CAD 3D modeling software to design resin parts, and then use special computer slicing software to cut the 3D CAD model into several thin-layer plane graphic data.

At the beginning of photo-curing rapid prototyping, the lifting platform usually drops to less than 0.1mm (about a few tenths of a millimeter, equivalent to the thickness of the bottom slice of the CAD model) from the liquid surface, and then the x-y laser scanner according to the first layer ( That is, the plane graphic data of the bottom layer) slices scan the liquid surface, and the part of the liquid resin that is irradiated by the laser on the liquid surface is solidified on the lifting platform due to photopolymerization. Then the lifting device drives the lifting platform to lower it to a height equivalent to the thickness of the second slice, and the x-y laser scanner scans the liquid surface according to the plane graphic data of the second slice, so that a new layer of liquid resin is solidified and adhered tightly. On the previous layer of cured resin, the resin parts are formed layer by layer.

The coating and hanging process is to coat a certain thickness of coating on the surface of the stereolithography rapid prototype, which can be achieved in the following ways:

1) Brushing process

The brushing process is mainly suitable for the outer surface that is simple to deal with and does not require high precision. The process step is to use a fine brush to evenly brush the prepared resin coating on the surface of the stereolithography rapid prototype to be processed with an appropriate thickness , Cured after being placed at a temperature not higher than 50°C for 10 minutes.

2) soaking process

The impregnation process is suitable for all surfaces, the specific operation is as follows:

Take out the formed prototype from the molding machine, remove the support, and remove the residual resin on the surface of the stereolithography prototype (mainly use alcohol, acetone and other chemical reagents to clean the stereolithography of the prototype); then put the stereolithography rapid prototype The parts are placed in the pre-prepared resin coating and soaked for a certain period of time (about 5 minutes), so that the surface of the stereolithography rapid prototype can be completely soaked and an appropriate amount of resin coating is hung on the surface of the stereolithography rapid prototype. Take out the stereolithography rapid prototype, and hang it upside down to blow dry or spin dry, so that the excess resin coating on the surface flows out, and after the excess resin coating on the surface of the stereolithography rapid prototype flows out, paint the surface of the stereolithography rapid prototype. layer is cured.

3) Spraying process

The spraying process is suitable for the outer surface of the stereolithography prototype and the inner surface of the wide mouth. The process method is to install the prepared resin coating in the designed spraying device, and spray the resin coating on the stereolithography rapid prototype. Surface, spray again after curing; spray several times until the coating surface meets the requirements.

3. Curing process

The photocuring process is to soak the cleaned stereolithography prototype in the photocuring resin coating for about 5 minutes. After soaking, take the stereolithography prototype out of the photocuring resin coating and invert it for 3 minutes (the inversion time can be seen The size and shape complexity of the stereolithography prototype should be adjusted), when the excess resin on the surface of the stereolithography prototype flows out, and when the coating is stable, immediately place the coated stereolithography prototype under a high-pressure mercury lamp Curing, the curing time is 150 seconds, deep curing; then put it under a low-pressure mercury lamp for curing for more than 3 hours to cure the surface layer, and the curing is completed.

Example 2:

The difference between this embodiment and Example 1 is: add commercially available reactive diluent HDDA (1,6-hexanediol diacrylate, the addition amount is 8% of resin quality) in photocurable resin, add surface active Agent JFC (polyoxyethylene ether compound, the addition is 0.5% of the photocurable resin mass), adjusts the viscosity of the resin coating at about 0.60 Pa.S, and the rest are the same as in Example 1.

Example 3:

The difference between this embodiment and Example 1 is: add commercially available reactive diluent HDDA (1,6-hexanediol diacrylate, add-on is 15% of resin quality) in photocurable resin, add surface active Agent JFC (polyoxyethylene ether compound, the addition is 0.8% of the photocurable resin quality), adjusts the viscosity of the resin coating at about 0.40Pa.S, and the rest are the same as in Example 1.

Example 4:

～The difference between this embodiment and embodiment 1 is: add commercially available reactive diluent HDDA (1,6-hexanediol diacrylate, add-on is 20% of resin quality) in photocurable resin, add surface Activator JFC (polyoxyethylene ether compound, added in an amount of 0.7% of the mass of the photocurable resin), adjusts the viscosity of the resin coating at about 0.35 Pa.S, and the rest are the same as in Example 1.

Example 5:

The difference between this embodiment and Example 1 is: adding commercially available reactive diluent HDDA (1,6-hexanediol diacrylate, the addition amount is 30% of the resin mass) in the photocurable resin, adding surface active Agent JFC (polyoxyethylene ether compound, the addition is 0.5% of the photocurable resin quality), adjusts the viscosity of the resin coating at about 0.25Pa.S, and the rest are the same as in Example 1.

Claims (5)

1. a physical and chemical method for reducing the surface roughness of stereolithography rapid prototype, is characterized in that, comprises the following steps: First prepare the resin coating, the preparation method of the resin coating is to add the following raw materials in the photocuring resin according to the mass percentage of the photocuring resin: surfactant polyoxyethylene ether compound: ≤0.1%, reactive diluent 1,6-hexanedi Alcohol diacrylate: 5% to 30%, UV leveling agent 4325 ≤ 1%; and adjust the resin coating viscosity between 0.25Pa.S to 0.70Pa.S; Apply the resin coating on the surface of the stereolithography prototype by brushing, soaking or spraying; Then through the photocuring process: first put it under a high-pressure mercury lamp to cure for 5 minutes, and then put it under a low-pressure ultraviolet lamp for more than 3 hours to form a uniform coating with a thickness of no more than 300 μm on the surface of the stereolithography prototype; The brushing method is: use a fine-haired brush to evenly brush the resin coating to an appropriate thickness on the surface of the stereolithography prototype, and then cure it after placing it at a temperature not higher than 50°C for 10 minutes; The soaking method is as follows: taking the formed stereolithography prototype out of the molding machine, removing the support, and removing the residual resin on the surface of the stereolithography prototype; then placing the stereolithography prototype in the resin coating and soaking for 5 minutes , so that the surface of the stereolithography prototype can be completely soaked and an appropriate amount of resin coating is coated on the surface of the stereolithography prototype, and then the stereolithography prototype is taken out, and hang upside down to blow dry or spin dry, so that The excess resin coating on the surface flows out, and the surface coating is cured after the excess resin coating on the surface of the stereolithography prototype flows out. 2. The method according to claim 1, wherein the spraying method is: the resin coating is installed in a spraying device, directly sprayed on the surface of the stereolithography prototype to form a layer of resin coating, and the resin coating is treated Spray again after curing; until the coating surface meets the requirements. 3. The method according to claim 1, characterized in that, the treatment time for hanging upside down to blow dry or spin dry to make excess resin coating on the surface flow out is 3 minutes. 4. The method according to claim 1, wherein a uniform coating with a thickness of no more than 300 μm is formed on the surface of the stereolithography prototype by using room temperature curing or heating curing instead of the photocuring process. 5. The method according to claim 4, characterized in that, the temperature in the heating and curing mode does not exceed 50°C.

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