CN112658208B - Printing method for spraying binder and catalyst according to requirements in 3DP process and spraying unit - Google Patents

Abstract

The invention relates to a method for spraying a binder and a catalyst as required in a 3DP process and a spraying unit, wherein the method comprises the steps of simultaneously spraying and printing two liquids of the catalyst and the binder on each layer of flat and compact raw sand, wherein an integrated spraying unit is used in the process of spraying the binder and the catalyst, nozzles are arrayed on the integrated spraying unit, the number of the nozzles is integral multiple of 3, each three rows of nozzles are a group, the three rows of nozzles in each group are respectively marked as a first nozzle, a second nozzle and a third nozzle, the types of materials communicated with the first nozzle, the second nozzle and the third nozzle are sequentially a binder-catalyst-binder, and in the reciprocating motion process of the nozzles, the liquids are sprayed on the surface of a sand bed sequentially according to the sequence of the binder-catalyst-binder. According to the printing method, the catalyst and sand grains do not need to be mixed in advance, the binder and the catalyst are only sprayed to the area of the workpiece in the droplet spraying process, the binder and the catalyst can be directly recycled without being cleaned, the liquid consumption is reduced, and the sand grain utilization rate is improved.

Description

Printing method for spraying binder and catalyst according to requirements in 3DP process and spraying unit

Technical Field

The invention relates to the field of 3DP processes in additive manufacturing, in particular to a method and a spraying unit for spraying a binder and a catalyst according to needs in the 3DP process.

Background

The 3DP process adopts a technology similar to that of an ink-jet printer, and the current technological process is as follows: firstly, mixing a catalyst and sand grains according to a proportion, then using the mixed sand grains to pave sand, selectively spraying a binder by a spray head according to a printing pattern when one layer of mixed sand is paved, and finishing the bonding of the sand grains by the cross-linking reaction of binder droplets and the coated catalyst sand grains. Repeating the steps, and bonding layer by layer to obtain a final printing model. However, the technical route has the following defects: (1) because the catalyst liquid is a liquid with certain viscosity, the fluidity of sand is poor after the catalyst liquid is mixed with sand grains, so that the difficulty of sand paving and leveling is increased; (2) when the mixed sand grains are reused, the strength of the sand mould is reduced, and the utilization rate of the used sand is lower; (3) the used sand needs to be washed by water to remove the catalyst on the surface layer of the sand grains in the post-treatment process, and the environmental pollution is serious.

The doctor paper of Du Shouhui, Qinghua university, is a method of printing by using a single nozzle spray head (i.e., one spray head has only one nozzle) to spray the binder and the catalyst separately without mixing the catalyst and the sand particles on the basis of the above process route. The technological process includes spraying adhesive and catalyst, spraying adhesive precisely to each layer of spread sand, spraying catalyst to the second nozzle along the same path, and curing sand layer by layer for deposition. However, the technical route has the problems that the content of the sprayed adhesive and catalyst is too high and the actual printing content requirement is difficult to meet, and the spray heads for spraying the adhesive and the catalyst need to perform complete spray printing in sequence, which is equivalent to performing two microdroplet spray printing tasks on the same layer, thereby reducing the forming efficiency to a certain extent.

The double-nozzle one-time composite spraying technology is proposed in Xudan doctor paper of Qinghua university. The technology is characterized in that a bonding agent spray head and a catalyst spray head are symmetrically and obliquely arranged (the liquid spray direction forms a certain included angle with a sand bed), two kinds of liquid are sprayed out from the nozzles at the same time, the two kinds of liquid are firstly converged at one point above the surface of the sand bed and are mutually mixed to form a liquid flow, then the mixed liquid flies in the air for a certain distance, finally falls on the surface of the sand bed and permeates into the sand bed, and a cross-linking reaction is generated to bond sand grains. The technical route firstly provides that the inclination angle of the spray head is changed and the binder and the catalyst are mixed before contacting the sand bed, thereby reducing the printing times of the same layer and improving the printing efficiency. But there are still deficiencies in actual printing: (1) the structure of the spray head is complex, the angle of the spray head needs to be strictly symmetrical and centered, and the debugging requirement is high; (2) the method has certain advantages for continuous printing, but has yet to be improved for discrete printing, for example, after the liquid drops are ejected from the nozzle, the two liquid drops collide in the air, and the flight path of the liquid drops is easily affected.

In summary, the existing industrial field implementation methods are: before printing, the catalyst and sand particles are mixed, and then sanding and bonding are carried out. Or firstly spraying the binder and then spraying the catalyst, under the control of a computer, a first spray head accurately sprays the binder on each layer of the flattened and compacted raw sand, and a second spray head sprays the catalyst along the same path, and the two penetrate into the porous sand grains to generate a crosslinking reaction.

Disclosure of Invention

In order to solve the above-mentioned disadvantages of the prior art, an object of the present invention is to provide a printing method and a jetting unit for jetting a binder and a catalyst on demand in a 3DP process. The printing method adopts an integrated spraying unit, so that the catalyst and sand grains do not need to be mixed in advance, the binder and the catalyst are sprayed only on a workpiece area in a droplet spraying process, and a non-workpiece area does not spray any liquid, so that the binder and the catalyst can be directly recycled without cleaning, the utilization rate of the sand grains is improved, and the pollution to the environment is reduced. In addition, the invention creatively uses the spraying unit to be equal to the printing breadth, the spray head can finish printing the whole layer in one movement process without circular reciprocating movement, and the spray head is in a working state in the movement process without idling (moving for returning to the initial position but not printing and spraying liquid drops), thereby improving the printing efficiency.

The technical scheme adopted by the invention is as follows:

a method for spraying a binder and a catalyst as required in a 3DP process is characterized in that the spraying and printing of two liquids of the catalyst and the binder are simultaneously finished on each layer of flat and compact raw sand, an integrated spraying unit is used in the process of spraying the binder and the catalyst, nozzles are arrayed on the integrated spraying unit, the number of rows of the nozzles is integral multiple of 3, each three rows of the nozzles are a group, the three rows of the nozzles in each group are respectively marked as a first nozzle, a second nozzle and a third nozzle, the types of materials communicated by the first nozzle, the second nozzle and the third nozzle are sequentially the binder-catalyst-binder, and in the reciprocating motion process of the nozzles, the liquids are sprayed to the surface of a sand bed sequentially according to the sequence of the binder-catalyst-binder.

An integrated injection unit for injecting a binder and a catalyst as required in a 3DP process is characterized in that the integrated injection unit comprises three rows of nozzles which are arranged in parallel, the arrangement direction is vertical to the advancing direction of the injection unit, and the distance between two adjacent nozzles in each row of nozzles is equal; the three rows of the nozzles which are arranged in parallel are respectively marked as a first spray head, a second spray head and a third spray head according to the rows in sequence, wherein the first spray head and the third spray head spray the adhesive, and the second spray head sprays the catalyst;

the width of the spraying unit is equal to the width of a printing breadth (printing area), the nozzles for spraying the adhesive and the nozzles for spraying the catalyst are arrayed on the spraying unit, the integrated spraying unit is used for printing, and the spraying unit can complete the spraying of two liquids of the catalyst and the adhesive at the same time by scanning along the whole breadth once, so that the printing efficiency can be improved.

The printing method comprises the steps that an initial position (A) and a middle position (C) of the integrated spraying unit are arranged on two opposite sides of a sand bed, an initial position (B) of a sand paving device and an initial position (A) of the integrated spraying unit are arranged on two adjacent sides of the sand bed, the sand paving direction is taken as the X direction, the moving direction of the integrated spraying unit is taken as the Y direction, and the integrated spraying unit is arranged in parallel to the Y axis and moves forwards or backwards along the X axis; the sand paving device is arranged perpendicular to the X axis and moves along the X axis direction;

the printing method comprises the following steps:

the method comprises the following steps: the sand paving device moves forward along the X axis to discharge and pave sand and compact the sand bed 1, when the sand paving device sweeps all areas of the sand bed, the sand paving device stops working and rapidly returns to the initial position (B) of the sand paving device along the negative direction of the X axis to finish the sand paving work of one layer,

step two: the integrated spraying unit sweeps a sand bed in a printing area along the positive direction of a Y axis from an initial position (A) of the integrated spraying unit and finally stops at a middle position (C) of the movement of the integrated spraying unit, and adhesive and catalytic liquid drops are sprayed as required in the moving process to finish the printing task of the whole forming area in one movement;

step three: the sand bed descends by the height of a sand paving layer to wait for sand paving of the next layer;

step four: repeating the step one, wherein the sand paving device performs blanking and sand paving along the positive direction of the X axis and compacts the sand bed, and returns to the initial position (B) of the sand paving device along the original path;

step five: repeating the second step, but the moving direction is opposite, the integral spraying unit sweeps the sand bed of the printing area along the Y-axis negative direction from the middle position (C) of the movement of the integral spraying unit and returns to the initial position (A) of the integral spraying unit again, and the binder and the catalyst liquid drops are sprayed as required in the moving process to finish the printing task of the second layer of the whole forming area;

step six: repeating the third step;

step seven: and repeating the first step to the sixth step until all printing tasks are completed.

Compared with the prior art, the invention has the beneficial effects that:

1. the method of spraying the adhesive and the catalyst by the spray head as required is adopted for printing, the catalyst and sand do not need to be mixed in advance, and the process steps are simplified; raw sand is adopted in the sand paving process, so that the difficulty in sand paving caused by the humidity change of mixed sand is reduced; because the binder and the catalyst are sprayed according to the requirement, the utilization rate of the binder and the catalyst is greatly improved, and the consumption of the catalyst and the binder is reduced; after printing is finished, sand grains of the sand bed, which are not sprayed with the binder and the catalyst, still keep dry sand, so that the work of post-treatment such as sand removal and the like is facilitated, and the production efficiency is improved.

2. The computer is used for respectively controlling the dosages of the adhesive and the catalyst sprayed by different spray heads, so that the content and the proportion of the adhesive and the catalyst are effectively controlled. The physical parameters of the binder and the catalyst are different, the binder belongs to an organic solution, the viscosity is high, the permeability in the porous medium sand bed is poor, the control of a permeation unit is easy, the catalyst belongs to an inorganic solution, the viscosity is low, the fluidity in the porous medium sand bed is high, the permeation of the catalyst is difficult to control, and the mode of spraying the binder, the catalyst and the binder can enable the liquid with high viscosity to be coated outside the liquid with low viscosity in the process of permeating into the sand bed, so that the control of the form of a condensation unit body is facilitated, and the precision of a finished piece is improved.

3. The integrated jet unit is equal to the printing area in width, and the printing task of the whole printing area can be completed by one-time movement. The integrated jet unit comprises three nozzles which form a complete whole, the width of one line printed each time is enough to cover the whole forming area, the printing task of one layer can be completed only by printing once, and the printing efficiency is high; compared with the mode of successively printing two nozzles in the doctor thesis of Du Shough of Qinghua university, the movement paths of the three nozzles of the spraying unit are always kept consistent in the movement process, the accurate control of the two paths is not required to be considered, and the control requirement is reduced to a certain extent.

4. The integrated spraying unit only moves in a single direction (from the area A to the area C or from the area C to the area A) in the printing process of each layer, the initial position (the area A) does not need to return after each spraying, the printing time is shortened, and the printing efficiency is improved.

5. The integrated injection unit comprises three rows of spray heads, when the integrated injection unit is positioned in a printing area, the three spray heads all work normally, the integrated injection unit is different from the existing multiple spray heads, and only two spray heads work and the other spray head stops working when the three spray heads are positioned in the printing area.

Drawings

FIG. 1 is a schematic top view of an embodiment of an integral injection unit of the present invention;

FIG. 2 is a schematic three-dimensional view of an embodiment of the integrated injection unit of the present invention;

FIG. 3 is a schematic diagram of a printing path of the printing method of the present invention;

FIG. 4 is a schematic diagram of the structure of the 3DP printing apparatus of the present invention;

FIG. 5 is a schematic view of an integrated spray unit of the spray head with a honeycomb grid arrangement;

FIG. 6 is a schematic diagram showing the positional relationship between the sand bed and the integrated injection unit body at the time t;

FIG. 72 t is a schematic view showing the positional relationship between the sand bed and the integrated injection unit body;

FIG. 83 t is a schematic view showing the positional relationship between the sand bed and the integrated injection unit body;

FIG. 9 is a schematic diagram of a zigzag printing method according to the present invention.

In the figure, a sand bed 1, an integrated injection unit 2, a powder spreading roller 3, a blanking bin 4, a first spray head 5, a second spray head 6, a third spray head 7, a target path 8 and a transition path 9, wherein A is the initial position of the integrated injection unit, B is the initial position of a sand spreading device, C is the middle position of the movement of the integrated injection unit (the position where the integrated injection unit is temporarily parked in the printing process), M is a reference point, N is a binder, and D is a catalyst.

Detailed Description

The present invention is further explained with reference to the following examples and drawings, but the scope of the present invention is not limited thereto.

The invention relates to a binder and catalyst printing method in a 3DP process by spraying as required, wherein the spray printing of two liquids of a catalyst and a binder is simultaneously finished on each layer of flat and compact raw sand, an integrated spraying unit is used in the binder and catalyst spraying process, nozzles are arrayed on the integrated spraying unit, the number of rows of the nozzles is integral multiple of 3, each three rows of the nozzles are a group, the three rows of the nozzles in each group are respectively marked as a first nozzle, a second nozzle and a third nozzle, the types of materials communicated by the first nozzle, the second nozzle and the third nozzle are sequentially the binder-catalyst-binder, and in the reciprocating motion process of the nozzles, the liquids are sprayed on the surface of a sand bed sequentially according to the sequence of the binder-catalyst-binder.

According to the integrated spraying unit 2 for spraying the adhesive and the catalyst according to the needs in the 3DP process, as shown in figure 1, the integrated spraying unit comprises three rows of nozzles which are arranged in parallel, the arrangement direction is vertical to the advancing direction of the spraying unit, and the distance between two adjacent nozzles in each row of nozzles is equal; three rows of a plurality of nozzles which are arranged in parallel are respectively marked as a first spray head 5, a second spray head 6 and a third spray head 7 according to rows in sequence, wherein the first spray head and the third spray head spray adhesives, and the second spray head sprays catalysts;

the width of the spraying unit is equal to that of a printing breadth (printing area width), the nozzles for spraying the adhesive and the nozzles for spraying the catalyst are arrayed on the spraying unit, the integrated spraying unit is used for printing, and the spraying unit can complete spraying of two liquids of the catalyst and the adhesive at the same time once along the whole breadth in a scanning mode, so that the printing efficiency can be improved. The number of the nozzles in each row is set according to the width of the spray head, and the distance between every two adjacent nozzles is equal. In the single-layer printing process, three spray heads all execute droplet spraying tasks in a printing area, and the three-dimensional schematic diagram of the integrated spraying unit is shown in FIG. 2.

The layout of the printing device using the integrated ejection unit is: as shown in fig. 3, a region a is an initial position of the integrated ejection unit, a region B is an initial position of the sanding device, and a region C is an intermediate position of movement of the integrated ejection unit (a position where the integrated ejection unit is temporarily parked during printing). A. B, C areas are respectively arranged around the sand bed 1, wherein the areas A and C are located on opposite sides of the sand bed 1, the areas B and A are located on two adjacent sides of the sand bed 1, and the sand bed 1 is rectangular.

A schematic structural diagram of a 3D printing apparatus to which the integrated ejection unit of the present invention is applied is shown in fig. 4. A discharging bin 4 and a powder paving roller 3 are parked in the area B, the integrated injection unit 2 is parked in the area A, the length direction of the area B is taken as the Y direction, the length direction of the area A is taken as the X direction, the discharging bin and the powder paving roller are arranged in parallel to the Y axis, the discharging bin and the powder paving roller reciprocate along the X direction (sand paving is carried out along the positive direction of the X axis, and the discharging bin and the powder paving roller immediately return to the initial position along the original path after the sand paving is finished), and a sand paving task is executed; the integrated spraying unit is arranged in parallel to the X axis and moves along the positive direction or the reverse direction of the Y axis (the first movement executes a droplet spraying task along the positive direction of the Y axis, after the whole printing breadth is printed, the integrated spraying unit is temporarily stopped at the middle position C, and when the next layer sanding task is completed, the integrated spraying unit moves for the second time and returns to the initial position A after executing the droplet spraying task along the reverse direction of the Y axis), and the printing task (the binder and catalyst droplet spraying task) is executed.

Referring to fig. 3 for explanation, the printing and jetting process of the integrated jetting unit is as follows:

the method comprises the following steps: the sand paving device (comprising a blanking bin 4 and a powder paving roller 3) moves forwards along the X axis to carry out blanking and sand paving, compacts the sand bed 1, stops working when the sand paving device sweeps all areas of the sand bed 1, rapidly returns to the initial position B of the sand paving device along the negative direction of the X axis to complete the sand paving of one layer,

step two: the integrated spraying unit 2 sweeps the sand bed 1 in the printing area along the positive direction of the Y axis from the initial position A of the integrated spraying unit and finally stops at the middle position C of the movement of the integrated spraying unit, and adhesive and catalytic liquid drops are sprayed as required in the moving process to finish the printing task of the whole forming area in one movement;

step three: the sand bed 1 descends by the height of a sand-laying layer to wait for sand laying of the next layer;

step four: repeating the step one, wherein the sand paving device performs blanking and sand paving along the positive direction of the X axis, compacts the sand bed 1 and returns to the initial position B of the sand paving device along the original path;

step five: repeating the second step, but the moving direction is opposite, the integral spraying unit 2 sweeps the printing area sand bed 1 along the Y-axis negative direction from the middle position C of the movement of the integral spraying unit and returns to the initial position A of the integral spraying unit again, and the binder and the catalyst liquid drops are sprayed as required in the moving process to finish the printing task of the second layer of the whole forming area;

step six: repeating the third step;

step seven: and repeating the steps from one to six until all printing tasks are completed.

In the movement process of the integrated spraying unit, a certain point above a sand bed is taken as a reference, three rows of spray heads sequentially pass through the reference point, the spray heads sequentially pass through a first spray head 5, a second spray head 6 and a third spray head 7 (shown as a path a in figure 3) or a third spray head 7, a second spray head 6 and a first spray head 5 (shown as a path b in figure 3), and because the first spray head and the third spray head spray the adhesive, the sequence of liquid drops colliding and permeating into the sand bed is always 'adhesive-catalyst-adhesive', so that the catalyst is sprayed into the two layers of adhesive, the two layers of adhesive are more favorable for a cross-linking reaction, and a high-quality condensation unit body is formed.

The integrated spraying unit can integrally move in a zigzag manner and spray liquid drops in a printing area, the integrated spraying unit moves from an initial position to the starting point of a target path, then moves along the target path to perform first line on-demand spraying printing, moves along a transition path 9 to the starting point e of a next target path after completing a printing task of a target path 8, does not perform spraying printing in the moving process of moving from the transition path to the next target path, then moves along the next target path to perform second line on-demand spraying printing, and only horizontally moves without rotating in the moving process; repeating the steps until the printing task of the whole layer is completed; the spray head moves out of the forming space from the termination position f, the integrated spraying unit returns to the initial position, and a printing task of the next layer is waited; the target path is perpendicular to the direction of travel of the nozzle, and the transition path is perpendicular to the target path. When the zigzag printing is carried out, the width of the integrated injection unit is far smaller than the printing breadth, the first spray head, the second spray head and the third spray head respectively start to work after entering the forming space, the spray head which is not in the forming space does not work, and the first spray head, the second spray head and the third spray head are different in position, so that the working starting time and the working finishing time are different; in the printing process of each target path, the liquid is always sprayed according to the sequence of the binder, the catalyst and the binder, when the integrated spraying unit moves through a certain point above the sand bed, the three rows of spray heads can spray the liquid in sequence, the three rows of spray heads entering the forming space spray simultaneously, the simultaneous spraying can be implemented at the reference point and the front and back positions of the reference point, the material is sprayed to the reference point and the front and back positions of the reference point according to the sequence of the binder, the catalyst and the binder by one-time spraying, the material is sprayed to the reference point and the front and back positions of the reference point according to the sequence when the next reference point is sprayed, the binder, the catalyst and the binder can be formed in an overlapped mode after the same reference point is overlapped for three times, and the liquid with higher viscosity is coated on the outer side of the liquid with low viscosity in the process of penetrating into the sand bed by the binder, the catalyst and the binder are sprayed in an overlapped mode, the method is more favorable for controlling the form of the condensation unit body, improves the precision of the finished piece and obviously improves the printing efficiency.

In the invention, printing is carried out by spraying the binder and then spraying the catalyst. Two types of nozzles are designed, wherein one type of nozzle sprays the adhesive, the other type of nozzle sprays the catalyst, and because the volume ratio of two liquids required in the 3DP process is different (generally, the catalyst occupies about 50% of the volume of the adhesive) and the physical parameters such as fluid viscosity, surface tension and density of the two liquids are different, parameters such as the aperture and inlet conditions of the corresponding nozzles need to be adjusted, different nozzle sizes are designed for different liquids, in the embodiment, the apertures of the nozzles for spraying the adhesive and the nozzles for spraying the catalyst are preferably the same, and are both 20-27 μm, and the adhesive liquid drop and the catalyst liquid drop are 20-27 pL.

Examples

For each nozzle in the integrated spray unit: the nozzle adopts the inverted circular truncated cone pattern of putting vertically for liquid drop drippage track does not receive the angle influence, and the debugging requires lowly.

In the 3DP process, the volume content of the binder is required to be 2% of the total weight of the sand, and the volume content of the catalyst is required to be about 50% of the binder. In general application, the catalyst and sand particles are mixed and then sand-paved. The sand grains in the sand bed are coated with the catalyst, the bonding of the sand grains can be completed by spraying the bonding agent through the spray head, and the volume of the liquid drop of the bonding agent is about 50 pL.

According to the printing process provided by the invention, the integrated spraying unit is adopted to print in a printing mode with a spraying sequence of 'binder-catalyst-binder'. The catalyst (strong acid) drop of about 25pl was determined approximately from the current parameters (binder (furan resin) drop of about 50pl, nozzle orifice diameter of about 50 um). The integrated spraying unit is designed to adopt a three-row structure, two rows on the outer side are adhesive nozzles, and one row in the middle is a catalyst nozzle. Because two rows of spray heads spray the adhesive, the spray amount of each row of adhesive spray heads is approximately half of the required adhesive amount, which is about 25pl, and is the same as the spray amount of the catalyst spray heads, and the caliber of the spray heads is about 25 um.

During droplet ejection, the flight path of the ejected droplets is affected by the distance between the nozzles. In order to avoid the liquid drops colliding in the air and reduce the adverse effect of the nozzle spacing on the formed liquid drops, all the nozzles of the three rows of the spray heads are arranged in a honeycomb grid, as shown in fig. 5.

The honeycomb grid is transversely arranged according to overlapped regular hexagons, six vertexes and the center of each regular hexagon are respectively provided with a nozzle, four vertexes on the upper edge and the lower edge of each hexagon are provided with adhesive nozzles, and two vertexes on the horizontal center line of each hexagon and the center of each hexagon are provided with catalyst nozzles. The arrangement method can ensure that the intervals between every two adjacent nozzles are all equal, and can reduce the situations of flight path deviation of the droplet flow, increase of the cross-linking reaction time and the like caused by different nozzle intervals to the maximum extent.

When the integrated injection unit moves to pass a certain point above the sand bed, the three rows of spray heads can sequentially spray liquid, and in the reciprocating motion process of the spray heads, the liquid is always sprayed on the surface of the sand bed according to the sequence of 'binder-catalyst-binder':

in the movement process of the spray heads, the three rows of spray heads spray liquid (the first row sprays adhesive, the second row sprays catalyst and the third row sprays adhesive) at the same time, and the sizes and the intervals of liquid drops are the same. Due to the integral movement of the integral type spray heads, for a certain point M on the sand bed, the integral type spray unit has a height h from the sand bed, and the three rows of spray heads of the integral type spray unit pass above the point in sequence at a movement speed v. At the time t (as shown in fig. 6), the first spray head passes right above the reference point, and the adhesive is sprayed right above the reference point; at the moment of 2t (as shown in FIG. 7), the second spray head passes right above the reference point, and the catalyst is sprayed right above the reference point; at time 3t (see fig. 8), the head 3 passes directly above the reference point, and the adhesive is sprayed directly above the reference point. After the droplet spraying process is finished, three droplets above the reference point M sequentially impact and penetrate into the sand bed according to the sequence of the binder, the catalyst and the binder, and the bonding process of the condensation unit body is finished. Because the binder spray head and the catalyst spray head are arranged in a staggered way, the sprayed binder liquid drop and the catalyst liquid drop have certain amount of position deviation, and the sand bed can be covered more effectively. Therefore, according to the sequence of the adhesive, the catalyst and the adhesive, the uniform mixing of the catalyst and the adhesive among sand grains is facilitated, the cross-linking reaction is generated, the curing time is shortened, and the shape precision of the condensed unit body is improved.

The invention is applicable to the prior art where nothing is said.

Claims (9)

1. A3 DP process sprays adhesive and catalyst printing method as required, characterized by that, spray printing of two kinds of liquid of catalyst and adhesive is finished on each layer of flat and compact crude sand at the same time, in spraying adhesive and catalyst, use the unitary to spray the unit, the array arranges the spray nozzle on the said unitary to spray the unit, the line number of the spray nozzle is an integral multiple of 3, every three rows of spray nozzles are a group, three rows of spray nozzles in each group are marked as first shower nozzle, second shower nozzle, third shower nozzle separately, the kind of the first shower nozzle, second shower nozzle, third shower nozzle communicating supplies is adhesive-catalyst-adhesive sequentially, in the course of reciprocating motion of the shower nozzle, will spray the liquid to the surface of sand bed sequentially according to the order of "adhesive-catalyst-adhesive";

the printing method comprises the following steps: the integral type spraying unit moves integrally in a zigzag shape and sprays liquid drops in a printing area, the integral type spraying unit moves from an initial position to the starting point of a target path, then moves along the target path to perform first line of on-demand spraying printing, after the printing task of the target path is completed, the integral type spraying unit moves along a transition path to the starting point of the next target path, the integral type spraying unit does not perform spraying printing in the moving process of moving from the transition path to the next target path, then moves along the next target path to perform second line of on-demand spraying printing, and the integral type spraying unit only performs horizontal movement without rotation in the moving process; repeating the steps until the printing task of the whole layer is completed; the spray head moves out of the forming space from the end position, the integrated spraying unit returns to the initial position, and a printing task of the next layer is waited; the target path is perpendicular to the row direction of the nozzles, and the transition path is perpendicular to the target path.

2. The printing method according to claim 1, wherein the first head, the second head, and the third head start to operate after entering the molding space, and the head not in the molding space does not operate, and the first head, the second head, and the third head are different in position and thus start to operate and end to operate at different times; when the integrated injection unit moves past a certain point above the sand bed, the three rows of spray heads can sequentially inject liquid.

3. The printing method according to claim 1, wherein the computer is used for controlling the dosages of the binder and the catalyst sprayed by different spray heads respectively, so that the content and the proportion of the binder and the catalyst are effectively controlled; the integrated injection unit is only needed to be debugged in the direction vertical to the sand bed, and is also suitable for continuous injection printing and discrete injection printing.

4. An integrated injection unit for injecting a binder and a catalyst on demand in a 3DP process, wherein the integrated injection unit is used for printing by adopting the printing method for injecting the binder and the catalyst on demand in the 3DP process of claim 1, the integrated injection unit comprises three rows of nozzles which are arranged in parallel, the arrangement direction is vertical to the advancing direction of the injection unit, and the distance between two adjacent nozzles in each row of nozzles is equal; the three rows of the nozzles which are arranged in parallel are respectively marked as a first spray head, a second spray head and a third spray head according to the rows in sequence, wherein the first spray head and the third spray head spray the adhesive, and the second spray head sprays the catalyst; the width of the spraying unit is equal to that of the printing breadth, and the spraying of the catalyst and the adhesive can be simultaneously finished by the spraying unit scanning along the whole breadth once.

5. The spray unit of claim 4, wherein the nozzles are in a vertically oriented rounded table pattern.

6. The spray unit according to claim 4, wherein the nozzle diameters of the spray head for spraying the binder and the spray head for spraying the catalyst are the same and are 20-27 μm, and the binder droplet and the catalyst droplet are 20-27 pL.

7. The spray unit of claim 4, wherein all the nozzles of the three rows of spray heads are arranged in a honeycomb grid, the honeycomb grid is arranged in a transverse direction according to overlapping regular hexagons, one nozzle is arranged at each of six vertices and the center of the hexagon, adhesive nozzles are arranged at four vertices located at the upper and lower two sides of the hexagon, and catalyst nozzles are arranged at two vertices and the center of the hexagon located at the horizontal center line of the hexagon.

8. The spray unit of claim 7 wherein the adjacent nozzles are spaced apart by 250 um.

9. A printing method of binder and catalyst on demand in 3DP process using the spray unit according to any one of claims 4 to 8, wherein the initial position (a) and the middle position (C) of the integrated spray unit are provided on opposite sides of the sand bed, the initial position (B) of the sand-spreading device and the initial position (a) of the integrated spray unit are provided on adjacent sides of the sand bed, the sand-spreading direction is X-direction, the moving direction of the integrated spray unit is Y-direction, and the integrated spray unit is arranged in parallel with the Y-axis and moves forward or backward along the X-axis; the sand paving device is arranged perpendicular to the X axis and moves along the X axis direction;

the printing method comprises the following steps:

the method comprises the following steps: the sand paving device moves forward along the X axis to discharge and pave sand and compact the sand bed 1, when the sand paving device sweeps all areas of the sand bed, the sand paving device stops working and rapidly returns to the initial position (B) of the sand paving device along the negative direction of the X axis to finish the sand paving work of one layer,

step two: the integrated spraying unit sweeps a sand bed in a printing area along the positive direction of a Y axis from an initial position (A) of the integrated spraying unit and finally stops at a middle position (C) of the movement of the integrated spraying unit, and adhesive and catalytic liquid drops are sprayed as required in the moving process to finish the printing task of the whole forming area in one movement;

step three: the sand bed descends by the height of a sand paving layer to wait for sand paving of the next layer;

step four: repeating the step one, wherein the sand paving device performs blanking and sand paving along the positive direction of the X axis and compacts the sand bed, and returns to the initial position (B) of the sand paving device along the original path;

step five: repeating the second step, but the moving direction is opposite, the integral spraying unit sweeps the sand bed of the printing area along the Y-axis negative direction from the middle position (C) of the movement of the integral spraying unit and returns to the initial position (A) of the integral spraying unit again, and the binder and the catalyst liquid drops are sprayed as required in the moving process to finish the printing task of the second layer of the whole forming area;

step six: repeating the third step;

step seven: and repeating the steps from one to six until all printing tasks are completed.

Images