阅读说明：本技术 确定增减材复合制造中交替时机的方法 (Method for determining alternate time in material increasing and decreasing composite manufacturing ) 是由 白倩 杜巍 高英铭 求晓玲 乔国文 于 2019-11-08 设计创作，主要内容包括：本发明确定增减材复合制造中交替时机的方法,涉及金属增减材复合制造技术领域,尤其涉及一种确定增减材复合制造中交替时机的方法。本发明增材方式为铺粉式,减材铣削方式为三轴数控铣；确定增减材复合制造中交替时机的方法步骤包括：步骤1、获取刀轨；步骤2、建立刀具空间坐标模型；步骤3、提取待加工面密集点云；步骤4、碰撞分析；步骤5、确定最佳交替时机；步骤6、加工实施。本发明的技术方案解决了现有技术中的现有加工方法中存在增减材切换次数多,效率低,如采用较大的固定增材层数,无法保证对于复杂轮廓的刀具可达性等问题。(The invention discloses a method for determining alternation timing in material increase and decrease composite manufacturing, relates to the technical field of metal material increase and decrease composite manufacturing, and particularly relates to a method for determining alternation timing in material increase and decrease composite manufacturing. The material increase mode is a powder spreading mode, and the material reduction milling mode is a three-axis numerical control milling mode; the method for determining the alternate time in the material increasing and decreasing composite manufacturing comprises the following steps: step 1, obtaining a tool path; step 2, establishing a cutter space coordinate model; step 3, extracting dense point clouds of a surface to be processed; step 4, collision analysis; step 5, determining the optimal alternate time; and 6, processing and implementing. The technical scheme of the invention solves the problems that the existing processing method in the prior art has more times of material increase and decrease switching and low efficiency, and the accessibility of a cutter with a complex contour cannot be ensured if a larger fixed material adding layer number is adopted.)

1. A method for determining alternate time in material increase and decrease composite manufacturing is disclosed, wherein a material increase mode is a powder laying mode, and a material decrease milling mode is a three-axis numerical control milling mode; the method for determining the alternate time in the material increase and decrease composite manufacturing is characterized by comprising the following steps of:

step 1, obtaining a tool path: importing a three-dimensional model of a part to be formed into numerical control simulation processing software, setting parameters of a used cutter, determining cutting parameters according to the surface precision requirement of the part, generating a cutter path, and outputting a coordinate file of a cutter center track;

step 2, establishing a cutter space coordinate model: according to the selected cutter size parameters, expressing the spatial position of the whole cutter in the machining process in a coordinate mode by using the coordinate file of the cutter center track obtained in the step 1;

step 3, extracting dense point clouds of the surface to be processed: extracting point cloud data of the to-be-reduced material processing surface of the part, taking the extraction density as a principle that geometric profile features can be completely represented, and exporting text format files of point cloud x, y and z coordinates after extraction is finished;

step 4, collision analysis: judging the collision condition between the point cloud coordinate of the machined surface and the space coordinate of the cutter model, and sequentially recording interference points as P along the + Z direction₁To P_n；

Step 5, determining the optimal alternate time: the height of ith continuous material increase is less than P_iThe Z coordinate value of the point, the ith material reduction processing is reached to P_iStopping before the position, and then performing the additive forming for the (i + 1) th time; thus, the alternate timing of material increase and decrease is determined in sequence along the + Z direction, and the part is divided into n forming areas, which are marked as A₁To A_n；

Step 6, processing and implementing: according to the n forming areas divided in the step 5, sequentially finishing A from bottom to top_iPerforming material increase and material reduction processing on the area; firstly, high-energy beams are used for scanning/sintering powder layer by layer, and A is formed by additive forming_iThree-dimensional features of parts in the region, rear pair A_iAnd performing material reduction processing on the surface to be processed in the area to ensure that the required surface quality and dimensional precision are achieved.

2. The method of claim 1, wherein the method comprises the steps of: before planning the material reducing path in the step 1, a cutter is selected from a round nose cutter, a T-shaped cutter, a forming ball cutter, a drum cutter and a profiling cutter for processing according to the contour type of the part and the requirement of surface processing precision.

3. The method for determining the alternate timing in additive and subtractive composite manufacturing according to claim 2, wherein: the round nose cutter is mainly used for processing the upper surface of the part parallel to the substrate and the side surface vertical to the substrate so as to ensure large feeding amount; under the same condition, the cutter relieving space of the T-shaped cutter is larger than that of the forming ball cutter, but the residual height of the processing surface of the T-shaped cutter is small; due to the step effect in the material reducing process, the precision of the profile processed by the forming ball cutter is better than that of a T-shaped cutter; when machining the sidewall profile near the bottom surface, a drum knife is used.

4. The method of claim 1, wherein the method comprises the steps of: after the alternation time is determined, overlapping tool paths exist in the two adjacent material reducing areas in the axial direction of the tool, so that the surface quality is ensured to be smooth; the axial feeding amount of the cutter for the material reducing machining and the additive forming allowance can control the size precision and the surface quality of the part.

Technical Field

The invention relates to the technical field of metal material increase and decrease composite manufacturing, in particular to a method for determining alternate time in material increase and decrease composite manufacturing.

Background

The traditional manufacturing method is difficult to process deep grooves, deep holes, large inflection points, closed cavity structures, inverted buckle surfaces and other characteristics, but the emerging multiple additive manufacturing modes expand the range of the processing characteristics, wherein selective laser melting forming is particularly suitable for processing precise curved surface parts, but the surfaces of the parts which are formed only by additive manufacturing generally have the defects of step effect, powder bonding, spheroidization and the like.

The additive manufacturing process and the subtractive manufacturing process are combined, namely, the alternative forming and processing process is adopted, metal powder with a certain number of layers is melted/solidified through high-energy beam scanning, then milling is carried out, and additive forming is carried out again after subtractive manufacturing is finished. Therefore, the surface precision can be improved, and the accessibility problem of the cutter in the post-processing of the complex additive part can be improved.

However, in the conventional material increase and decrease process, the single continuous additive height, which is the time for material increase and decrease to alternate, is usually set as a fixed parameter, and the maximum continuous additive layer number at each position is not determined according to the part characteristics, so that the efficiency of material increase and decrease composite manufacturing is not improved. For example, in the patent (a material increase and decrease composite manufacturing equipment and method for metal parts, publication number: CN106735216A) applied by Huazhong university of science and technology, the time for material increase and decrease alternation is not described; patent application (layered molding apparatus, publication No. CN107363259A) by Sadick corporation mentions: "the surface of the sintered layer is cut by a rotary cutting tool every time a predetermined number of sintered layers are formed". The method also comprises the steps of dividing the part into a plurality of blocks according to the outline of the part, and adopting different continuous material increase heights for each block, but the method can only realize qualitative and can not realize quantitative determination, does not fundamentally avoid the interference problem in subsequent material reduction processing, and does not reach the maximum benefit.

The material increasing and decreasing composite manufacturing is carried out by adopting the fixed sintering layer number, namely the additive layer number, so that the cooperative control of the accessibility and the processing efficiency of the cutter is difficult to realize, and the accessibility of the cutter can be ensured by adopting a smaller fixed additive layer number for parts which comprise complex profiles such as a space curved surface and the like and simple profiles such as a vertical surface and the like, but the efficiency is low because the material increasing and decreasing switching times are more; the accessibility of the tool to complex contours cannot be guaranteed by adopting a larger number of fixed additive layers.

In view of the above problems in the prior art, it is necessary to develop a novel method for determining the alternation timing in the additive and subtractive composite manufacturing process, so as to overcome the problems in the prior art.

Disclosure of Invention

The conventional machining method proposed by the prior art has the technical problems that the number of times of material increase and decrease switching is large, the efficiency is low, and the accessibility of a tool to a complex contour cannot be ensured if a large fixed material increase layer number is adopted, and the like, and provides a method for determining the alternate time in material increase and decrease composite manufacturing. According to the method, the material reducing path planning is required to be carried out according to the profile characteristics of the part, and the maximum continuous additive layer number in different areas is determined on the premise of meeting the requirement of non-interference machining, namely the alternative time of additive and material reducing machining forming is determined, so that the coordinated control of cutter accessibility and machining efficiency maximization is realized.

The technical means adopted by the invention are as follows:

a method for determining alternate time in material increase and decrease composite manufacturing is disclosed, wherein a material increase mode is a powder laying mode, and a material decrease milling mode is a three-axis numerical control milling mode; the method for determining the alternate time in the material increase and decrease composite manufacturing is characterized by comprising the following steps of:

step 1, obtaining a tool path: importing a three-dimensional model of a part to be formed into numerical control simulation processing software, setting parameters of a used cutter, determining cutting parameters according to the surface precision requirement of the part, generating a cutter path, and outputting a coordinate file of a cutter center track;

step 2, establishing a cutter space coordinate model: according to the selected cutter size parameters, expressing the spatial position of the whole cutter in the machining process in a coordinate mode by using the coordinate file of the cutter center track obtained in the step 1;

step 3, extracting dense point clouds of the surface to be processed: extracting point cloud data of the to-be-reduced material processing surface of the part, taking the extraction density as a principle that geometric profile features can be completely represented, and exporting text format files of point cloud x, y and z coordinates after extraction is finished;

step 4, collision analysis: judging the collision condition between the point cloud coordinate of the machined surface and the space coordinate of the cutter model, and sequentially recording interference points as P along the + Z direction₁To P_n；

Step 5, determining the optimal alternate time: the height of ith continuous material increase is less than P_iThe Z coordinate value of the point, the ith material reduction processing is reached to P_iStopping before the position, and then performing the additive forming for the (i + 1) th time; thus, the alternate timing of material increase and decrease is determined in sequence along the + Z direction, and the part is divided into n forming areas, which are marked as A₁To A_n。

Step 6, processing and implementing: according to the n forming areas divided in the step 5, sequentially finishing A from bottom to top_iPerforming material increase and material reduction processing on the area; firstly, high-energy beams are used for scanning/sintering powder layer by layer, and A is formed by additive forming_iThree-dimensional features of parts in the region, rear pair A_iReducing the material of the surface to be processed in the area to ensure that the surface to be processed reaches the required surface quality and dimensional precision; after completion, A is carried out_i+1Additive and subtractive formation of the regions. Attention needs to be paid to that overlapped tool paths exist in the two adjacent material reducing areas in the axial direction of the tool, so that the surface quality is ensured to be smooth; the axial feeding amount of the cutter for the material reducing machining and the additive forming allowance can control the size precision and the surface quality of the part.

Further, before planning the material reducing path in the step 1, a cutter is selected from a round nose cutter, a T-shaped cutter, a forming ball cutter, a drum cutter and a profiling cutter for machining according to the type of the part profile and the requirement of surface machining precision.

Further, the round nose cutter is mainly used for processing the upper surface parallel to the substrate and the side surface vertical to the substrate in the part so as to ensure large feeding amount; under the same condition, the cutter relieving space of the T-shaped cutter is larger than that of the forming ball cutter, but the residual height of the processing surface of the T-shaped cutter is small; due to the step effect in the material reducing process, the precision of the profile processed by the forming ball cutter is better than that of a T-shaped cutter; when machining the sidewall profile near the bottom surface, a drum knife is used.

Further, after the alternation time is determined, coincident tool paths exist in the adjacent two material reduction areas in the axial direction of the tool, so that the surface quality is ensured to be smooth; the axial feeding amount of the cutter for the material reducing machining and the additive forming allowance can control the size precision and the surface quality of the part.

Compared with the prior art, the invention has the following advantages:

1. the method for determining the alternate time in the material increasing and decreasing composite manufacturing can determine the optimal alternate time of material increasing and material decreasing by providing a basis for selecting the number of continuous material increasing layers of a three-axis material increasing and decreasing system, minimize the alternate times of material increasing and material decreasing, reduce the material increasing and decreasing switching time in the forming and processing process, shorten the whole processing period of metal material increasing and decreasing composite manufacturing, improve the production and manufacturing efficiency of material increasing and decreasing composite manufacturing equipment, and maximize the processing benefit on the premise of ensuring the precision;

2. according to the method for determining the alternate time in the material increasing and decreasing composite manufacturing, provided by the invention, material increasing and material decreasing parameter setting are combined, so that two parameters can be dynamically adjusted according to the geometric shape of a curved surface part, and the accessibility of a cutter and the contour processing integrity in the process are ensured;

3. the method for determining the alternate time in the material increasing and decreasing composite manufacturing provided by the invention provides a specific method and a theoretical basis for the preparation of the composite material increasing and decreasing manufacturing process, shortens the preparation time and the processing period of the process, and ensures the processing precision of the complex curved surface profile and the consistency of the roughness of each part of the part.

In conclusion, the technical scheme of the invention solves the problems that the material increasing and decreasing switching times are more, the efficiency is low, and the accessibility of the cutter to a complex contour cannot be ensured if a larger fixed material increasing layer number is adopted in the existing processing method in the prior art.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a flow chart of a method for determining alternate timing in additive and subtractive composite manufacturing in accordance with the present invention;

FIG. 2 is a schematic diagram illustrating the interference position determination when the T-shaped knife processes the inverted buckle surface according to the present invention;

FIG. 3 is a diagram illustrating the corresponding parameters of the round nose cutter of the present invention;

FIG. 4 is a schematic diagram of the corresponding parameters of the T-knife of the present invention;

FIG. 5 is a schematic diagram of the parameters of the forming ball cutter of the present invention;

FIG. 6 is a schematic view of the corresponding parameters of the drum knife of the present invention;

FIG. 7 is an isometric view of a selected area laser fusion formed curved surface part according to an embodiment of the present invention;

FIG. 8 is a cross-sectional view of a selected area laser fusion formed curved surface part in accordance with an embodiment of the present invention;

FIG. 9 is a schematic view of an embodiment of the present invention illustrating tool paths on the inner surface of a machined part;

FIG. 10 is a schematic view of a tool path for machining the outer surface of a part according to an embodiment of the present invention;

FIG. 11 is a partial content of a coordinate text file of a tool center trajectory according to an embodiment of the present invention;

FIG. 12 is a point cloud extraction of a machined surface of a part with reduced material in accordance with an embodiment of the present invention;

FIG. 13 is a partial contents of a point cloud data file of a part material reducing machining surface according to an embodiment of the present invention;

FIG. 14 is a sectional view of additive manufacturing in accordance with an embodiment of the present invention.

In the figure: D. the diameter H of the cutter, the thickness L of the cutting edge, the clearance length T of the cutter, the number R of the cutting edges and the radius of the round corner of the cutter point.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

In the description of the present invention, it is to be understood that the orientation or positional relationship indicated by the directional terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc., are generally based on the orientation or positional relationship shown in the drawings, and are used for convenience of description and simplicity of description only, and in the absence of any contrary indication, these directional terms are not intended to indicate and imply that the device or element so referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore should not be considered as limiting the scope of the present invention: the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of the present invention should not be construed as being limited.

As shown in the figure, the invention provides a method for determining alternate time in material increase and decrease composite manufacturing, wherein a material increase mode is a powder laying mode, and a material decrease milling mode is a three-axis numerical control milling mode; the method for determining the alternate time in the material increase and decrease composite manufacturing is characterized by comprising the following steps of:

step 1, obtaining a tool path: importing a three-dimensional model of a part to be formed into numerical control simulation processing software, setting parameters of a used cutter, determining cutting parameters according to the surface precision requirement of the part, generating a cutter path, and outputting a coordinate file of a cutter center track;

step 2, establishing a cutter space coordinate model: according to the selected cutter size parameters, expressing the spatial position of the whole cutter in the machining process in a coordinate mode by using the coordinate file of the cutter center track obtained in the step 1;

step 3, extracting dense point clouds of the surface to be processed: extracting point cloud data of the to-be-reduced material processing surface of the part, taking the extraction density as a principle that geometric profile features can be completely represented, and exporting text format files of point cloud x, y and z coordinates after extraction is finished;

step 4, collision analysis: judging the collision condition between the point cloud coordinate of the machined surface and the space coordinate of the cutter model, and sequentially recording interference points as P along the + Z direction₁To P_n；

Step 5, determining the optimal alternate time: the height of ith continuous material increase is less than P_iThe Z coordinate value of the point, the ith material reduction processing is reached to P_iStopping before the position, and then performing the additive forming for the (i + 1) th time; thus, the alternate timing of material increase and decrease is determined in sequence along the + Z direction, and the part is divided into n forming areas, which are marked as A₁To A_n。

Step 6, processing and implementing: according to the n forming areas divided in the step 5, sequentially finishing A from bottom to top_iPerforming material increase and material reduction processing on the area; firstly, high-energy beams are used for scanning/sintering powder layer by layer, and A is formed by additive forming_iThree-dimensional features of parts in the region, rear pair A_iAnd performing material reduction processing on the surface to be processed in the area to ensure that the required surface quality and dimensional precision are achieved.

Before planning the material reducing path in the step 1, a cutter is selected from a round nose cutter, a T-shaped cutter, a forming ball cutter, a drum cutter and a profiling cutter for processing according to the contour type of the part and the requirement of surface processing precision.

The round nose cutter is mainly used for processing the upper surface of the part parallel to the substrate and the side surface vertical to the substrate so as to ensure large feeding amount; under the same condition, the cutter relieving space of the T-shaped cutter is larger than that of the forming ball cutter, but the residual height of the processing surface of the T-shaped cutter is small; due to the step effect in the material reducing process, the precision of the profile processed by the forming ball cutter is better than that of a T-shaped cutter; when machining the sidewall profile near the bottom surface, a drum knife is used.

After the alternation time is determined, overlapping tool paths exist in the two adjacent material reducing areas in the axial direction of the tool, so that the surface quality is ensured to be smooth; the axial feeding amount of the cutter for the material reducing machining and the additive forming allowance can control the size precision and the surface quality of the part.