Step effect suppression method, 3D printing equipment and storage medium

Abstract

The invention discloses a step effect restraining method, 3D printing equipment and a storage medium, belongs to the technical field of additive manufacturing, and aims to solve the problem that the surface smoothness of a product does not reach the standard due to the step effect on the surface of a non-vertical profile product. Extracting the normal angle and curvature of the curved surface of the product; s02, ink quantity mapping is carried out, and subdivision gradients are divided according to the normal angle; s03, mixing proportion calculation is carried out, the gray printing area is divided into a plurality of mixing units with minimum regulation and control units, and ink droplet distribution data for printing the mixing units are generated; and S04, printing is executed, and the printing mechanism prints the gray printing area of the product layer by layer according to the ink droplet distribution data. Through the implementation of the technical scheme, the step effect between adjacent slice layers is reduced, and the size precision of the outline of a product is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of additive manufacturing, in particular to a step effect suppression method. BACKGROUND

[0002] In the 3DP inkjet printing process, a three-dimensional model is formed by layer-by-layer stacking. When printing a circular arc surface or an inclined surface, due to the discrete geometric jumps between layers, the surface forms a step-like texture visible to the naked eye, which is called the step effect. For example, in the case of an inclined angle of 30° and a layer thickness of 0.5mm, the theoretical step length can reach 1mm (calculation formula: h = Δz / sinθ, where Δz is the layer thickness and θ is the inclined angle), which seriously affects the functionality of parts with high surface finish requirements. Currently, the industry tries to alleviate this problem by reducing the layer thickness, post-processing polishing, and using high gray level nozzles, but each method has its limitations. Reducing the layer thickness can reduce the step length, but it significantly increases the printing time and requires higher accuracy of the nozzle; post-processing polishing can improve the surface quality, but it will cause loss of detail features; and using higher level gray nozzles can improve the smooth transition effect, but it also increases the cost of equipment.

[0003] In addition, for nozzles that only support four levels of gray, the existing technology also faces the challenges of ink amount discontinuity and algorithm limitations. Specifically, when the difference between adjacent gray levels reaches 33%, it will cause obvious ink amount jumps in the inclined surface area, affecting the printing quality. At the same time, the halftone algorithm currently used in 3D printing (such as Floyd-Steinberg error diffusion) can cause uneven ink droplet accumulation, resulting in "fish scale" defects, further limiting the improvement of the surface finish of the printed part. These problems together constitute a technical bottleneck for achieving high-quality 3D printing. SUMMARY

[0004] In view of the above problems of ink amount discontinuity and uneven ink droplet accumulation in the four-level gray inkjet printing system, it is necessary to propose a step effect suppression method, 3D printing equipment and storage medium, which realizes continuous gradient change under hardware constraints through spatial mixing and proportional control of multi-level gray ink droplets, reducing the impact of step effect on the surface quality of the product.

[0005] A step effect suppression method, comprising,

[0006] S01, model input, according to the received three-dimensional slice data file of the product, extracting the normal angle and curvature of the product surface;

[0007] S02, ink amount mapping, the sub-gradations are divided according to the normal angle, the sub-gradations are that each slice layer of the product is divided into several thinner gradient layers along the cutting direction of the slice, each gradient layer is a sub-gradation, and each sub-gradation is printed by using different ink amounts, so that the length of the step is shortened, and the step effect is reduced;

[0008] S03, mixed ratio calculation, the gray printing area is divided into a plurality of mixed units with minimum control units, and ink drop distribution data for printing the mixed units is generated;

[0009] S04, printing execution, a printing mechanism prints the gray printing area of the product layer by layer according to the ink drop distribution data.

[0010] Through implementation of the above technical solutions, the step effect between adjacent slice layers is reduced, and the dimensional accuracy of the product contour is improved.

[0011] Further, in S03, a supplementary gray printing area is further included. Since the cross section of the slice data is a rectangle, in order to better complete the smooth printing of the non-vertical contour product, a gray printing area formed by a non-vertical contour beyond the rectangular area of each layer of slice is supplemented relative to the extension of the product contour.

[0012] Further, in order to improve the printing accuracy and smoothness of the gray printing area, the gray printing area is divided into mixed units with different dot arrays according to the curvature of the current layer of slice. The greater the curvature of the current layer of slice, the fewer the dot arrays of the mixed unit, that is, the more the number of mixed units divided in the gray printing area.

[0013] Further, in S03, the algorithm of the ink drop distribution data of the gray printing area is,

[0014] 4) setting a target ink amount for printing each sub-gradation according to the layer thickness of the sub-gradation;

[0015] 5) determining the number of ink drops of 0%, 33%, 66%, and 100% ink amounts of the four-level gray printing mechanism on each minimum control unit in the mixed unit by using a lookup table method according to the target ink amount;

[0016] 6) calculating an actual ink amount Veff according to the dot arrays of the mixed unit,

[0017] Veff = (n1*0% + n2*33% + n3*66% + n4*100%) / dot array number, wherein n1+n2+n3+n4 = the total number of dot arrays of a mixed unit, and n1, n2, n3, and n4 are respectively the number of ink drops of 0%, 33%, 66%, and 100% ink amounts of the four-level gray printing mechanism;

[0018] 7) Randomly distribute the ink drops of the four levels of ink amount on the minimum regulation unit of each mixing unit to form the ink drop distribution data of the gray scale printing area.

[0019] Further, in order to make the transition of adjacent mixing units more continuous, that is, to improve the uniformity of the ink amount distribution of the gray scale printing area and avoid the "fish scale" defect, after the ink drop distribution data of each divided mixing unit is preliminarily calculated, the mixing unit is scattered into independent minimum regulation units, adjacent minimum regulation units are extracted at any position in the gray scale printing area to form the mixing unit, and the actual ink amount of the mixing unit is checked again to minimize the deviation between the actual ink amount and the target ink amount, and the specific algorithm is minimum deviation = Minimize | actual ink amount - target ink amount |, and the minimum deviation is used for linearization processing of the ink drop distribution data, so that the ink drop distribution data of the continuous transition between adjacent minimum regulation units is obtained, and the uniform distribution of the ink drops in the gray scale printing area is realized.

[0020] A printing device applies the step effect suppression method to print a product by using an additive manufacturing technology, and comprises a printing mechanism that sprays a binder onto a laying layer according to the printing method to form a contour of a product to be produced on a corresponding layer.

[0021] A storage medium is used to store instructions for causing the printing device to execute the step effect suppression method to produce a product according to the printing method of the present application, thereby improving the surface quality of the step effect suppression.

[0022] The beneficial effects of the technical solution of the present application are that the effective gray scale is increased from the existing four levels to 12 levels, the step length is reduced by 62%, and the step effect is reduced only by algorithm without changing the hardware printing mechanism. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a process diagram of the step effect suppression method of the present application;

[0024] Figure 2 is a diagram of the subdivision gradient in the slice layer;

[0025] Figure 3 is a horizontal view diagram of the slice layer, including the step ink amount of the gray scale printing area;

[0026] Figure 4 is a diagram of the mixing unit division of the gray scale printing area;

[0027] Figure 5 is a diagram of the target ink amount query table applied to a 3*3 matrix. DETAILED DESCRIPTION

[0028] In order to more clearly illustrate the technical solutions of the present application, the technical solutions of the present application are described in detail below with reference to the drawings. Obviously, the following description is some typical embodiments of the present application, and other solutions can be obtained by those skilled in the art without creative effort based on these embodiments.

[0029] The present application aims to solve the problem of the surface finish of the product caused by the step effect of the product with a non-vertical profile. Taking a 3DP printing device with a four-level gray printing mechanism as an example, the method for improving the gray level of the gray printing area is described under the condition that the hardware remains unchanged, thereby reducing or inhibiting the step effect of the profile surface of the non-vertical profile product.

[0030] In one embodiment, the step effect inhibition method comprises,

[0031] S01, model input, extracting the normal angle and curvature of the product surface according to the received three-dimensional slice data file of the product;

[0032] S02, ink amount mapping, dividing the sub-gradations according to the normal angle, the sub-gradations are dividing each slice layer of the product into several thinner gradient layers along the cutting direction of the slice, each gradient layer is a sub-gradation, each sub-gradation is printed with different ink amount, thereby shortening the length of the step and reducing the step effect; in particular, in this embodiment, as shown in Figure 2 and Figure 3 each slice layer is divided into four layers again at the same height, greatly shortening the length of the step;

[0033] S03, mixed proportion calculation, dividing the gray printing area into several mixed units with the smallest control unit, and generating the ink droplet distribution data for printing the mixed units;

[0034] S04, printing execution, the printing mechanism prints the gray printing area of the product layer by layer according to the ink droplet distribution data.

[0035] Through the implementation of the above technical solutions, the step effect between adjacent slice layers is reduced, and the dimensional accuracy of the product profile is improved.

[0036] Note: The ink amount is expressed in percentage, and the reference is the printing ink amount of the rectangular printing area. The printing ink amount of the gray printing area accounts for a percentage of the printing ink amount of the rectangular printing area.

[0037] As a supplement to the present embodiment, in S03, a gray-scale printing area is also included, in view of the fact that the cross section of the slice data is rectangular, in order to better complete the smooth printing of the non-vertical profile product, a gray-scale printing area is supplemented outside the extension of each layer of rectangular slice relative to the profile of the product, which is the area composed of the non-vertical profile beyond the rectangular area of each layer of slice. Specifically, as shown in Figure 3 a gray-scale printing area of four levels of gray scale is supplemented outside the rectangular conventional printing area, and the subdivided gradient target ink amount is 20%, 45%, 70% and 90% respectively, where the target ink amount is set according to the layer thickness of the subdivided gradient and the ink jet speed, the penetration ability of the ink.

[0038] As a further supplement to the present embodiment, in order to improve the printing accuracy and smoothness of the gray-scale printing area, the gray-scale printing area is divided into different dot matrix hybrid units according to the curvature of the current layer slice, the greater the curvature of the current layer slice, the fewer the dot matrix of the hybrid unit, that is, the more the number of hybrid units divided in the gray-scale printing area. Specifically, when the curvature of the product surface is greater than 30 degrees, the size of the hybrid unit is 2x2 matrix, by refining the hybrid unit, the accuracy of the current layer product surface is improved; when the curvature of the product surface is less than 10 degrees, the size of the hybrid unit is 4x4 matrix, by enlarging the area of the hybrid unit, the smoothness of the current layer product surface is enhanced. When the curvature is between 10-30, the size of the hybrid unit is 3x3 matrix. In the present embodiment, the dot matrix of the hybrid unit of the gray-scale printing area is a 2x2 matrix.

[0039] As a further supplement to the present embodiment, in S03, the algorithm for drop distribution data in the gray-scale printing area is,

[0040] 1) Set the target ink amount for printing each layer of subdivided gradient according to the layer thickness of the subdivided gradient; as shown in Figure 3 the target ink amount of each subdivided gradient is 20%, 45%, 70% and 90% respectively;

[0041] 2) According to the target ink amount, determine the number of ink drops of 0%, 33%, 66% and 100% ink amount of the four-level gray-scale printing mechanism on each minimum control unit in the hybrid unit by using the look-up table method;

[0042] 3) Calculate the actual ink amount Veff according to the dot matrix of the hybrid unit,

[0043] Veff = (n1*0% + n2*33% + n3*66% + n4*100%) / dot matrix number, where n1+n2+n3+n4 = the total number of dot matrix of a hybrid unit, n1, n2, n3, n4 are the number of ink drops of 0%, 33%, 66% and 100% ink amount of the four-level gray-scale printing mechanism respectively;

[0044] Specifically, the actual ink amount Veff of the second subdivided gradient can be calculated as follows,

[0045] Veff = (2*0% + 0*33% + 1*66% + 1*100%) / 4 = 41.5%;

[0046] 4) Randomly distribute the ink drops of the fourth ink amount on each minimum control unit of each mixing unit to form the ink drop distribution data of the gray-scale printing area.

[0047] As a further supplement to the present embodiment, in order to make the transition of adjacent mixing units more continuous, that is, to improve the uniformity of the ink amount distribution of the gray-scale printing area and avoid the "fish scale" defect, after the ink drop distribution data of each mixing unit divided in the preliminary calculation is obtained, the mixing unit is scattered into independent minimum control units, adjacent minimum control units are extracted at any position in the gray-scale printing area to form the mixing unit, and the actual ink amount of the mixing unit is checked again to minimize the deviation between the actual ink amount and the target ink amount. The specific algorithm is Minimize | actual ink amount - target ink amount |. Linearization processing is performed on the ink drop distribution data using the minimum deviation, thereby obtaining the ink drop distribution data of the continuous transition between adjacent minimum control units, and achieving the uniform distribution of ink drops in the gray-scale printing area. Specifically, the minimum deviation of the second subdivided gradient is Minimize | actual ink amount - target ink amount | = Minimize | 41.5 - 40 | = 1.5, that is, the linearization processing is performed on the second subdivided gradient using the minimum deviation of 1.5, and the printing without "fish scale" is achieved, that is, the uniform printing of the gray-scale printing area is achieved.

[0048] In another embodiment, a printing device applies the step effect suppression method to print a product using additive manufacturing technology, and includes a printing mechanism that sprays a binder onto a laying layer according to the step effect suppression method to form the profile of the product on the corresponding layer.

[0049] In another embodiment, a storage medium stores instructions for causing the printing device to perform the step effect suppression method, so that the product is produced according to the step effect suppression method of the present application, and the surface quality of the step effect suppression is improved.

[0050] The above embodiments are only a description of a typical application of the technical solutions of the present application, and reasonable extensions can be made on the basis of reasonable and non-creative labor.

Claims

1. A method of step effect suppression, characterized by, Comprising, S01, model input, according to the received three-dimensional slice data file of the product, extracting the normal angle and curvature of the product surface; S02, ink amount mapping, dividing the gradient according to the normal angle; S03, calculating the mixing ratio, dividing the gray-scale printing area into several mixing units with minimum control units, and generating ink droplet distribution data for printing the mixing units; S04, printing execution, the printing mechanism prints the gray-scale printing area of the product layer by layer according to the ink droplet distribution data.

2. The step effect suppressing method according to claim 1, wherein In S02, the gradient is divided into several thinner gradient layers along the cutting direction of the slice, each gradient layer is a subgradient, and each subgradient is printed with different ink amounts.

3. The step effect suppressing method according to claim 2, wherein In S03, it also includes a supplementary gray-scale printing area, which is a region outside the extension of each layer of rectangular slice relative to the product contour, and the gray-scale printing area is a region formed by the non-vertical contour beyond the rectangular area of each layer of slice.

4. The method of step effect suppression of claim 3, wherein, According to the curvature of the current layer slice, the gray-scale printing area is divided into different dot array mixing units, and the greater the curvature of the current layer slice, the fewer the dot array mixing units.

5. The method of claim 4, wherein the step effect is suppressed by: In S03, the algorithm for ink droplet distribution data in the gray-scale printing area is as follows: 1) According to the layer thickness of the subgradient, set the target ink amount for printing each layer of subgradient; 2) According to the target ink amount, use the lookup table method to determine the ink droplet number of 0%, 33%, 66% and 100% ink amount of the four-level gray-scale printing mechanism in each minimum control unit of the mixing unit; 3) According to the dot array of the mixing unit, calculate the actual ink amount Veff, Veff=(n1*0%+n2*33%+n3*66%+n4*100%) / dot array number, wherein n1+n2+n3+n4=total dot array number of a mixing unit, n1, n2, n3, n4 are the ink droplet numbers of 0%, 33%, 66% and 100% ink amount of the four-level gray-scale printing mechanism respectively; 4) Randomly distribute the ink droplets of the four-level ink amount on each minimum control unit of the mixing unit to form the ink droplet distribution data of the gray-scale printing area.

6. The method of step effect suppression of claim 5, wherein, After the ink droplet distribution data of each divided mixing unit is calculated, the mixing unit is scattered into independent minimum control units, and adjacent minimum control units are extracted to form the mixing unit in the gray-scale printing area, and the actual ink amount of the mixing unit is checked again to minimize the deviation between the actual ink amount and the target ink amount, the specific algorithm is Minimize|actual ink amount-target ink amount|, and the minimum deviation is used for linearization processing of the ink droplet distribution data to obtain continuous transition ink droplet distribution data between adjacent minimum control units.

7. A printing device, characterized by, The application of the step effect suppression method of any one of claims 1-6 uses additive manufacturing technology to print products, including a printing mechanism, which sprays binder onto the laying layer according to the step effect suppression method to form the contour of the product on the corresponding layer.

8. A storage medium, characterized by An instruction storage device is provided, which is used to make the printing device execute the step effect suppression method of any one of claims 1-6.

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