WO2021001019A1

WO2021001019A1 - Device for detaching a 3d printed part, method for detaching and support structure

Info

Publication number: WO2021001019A1
Application number: PCT/EP2019/067681
Authority: WO
Inventors: Nicola Maria CERIANI
Original assignee: Siemens Aktiengesellschaft
Priority date: 2019-07-02
Filing date: 2019-07-02
Publication date: 2021-01-07

Abstract

Device for detaching a 3D printed part, method for detaching and support structure In order to free a 3D printed part (2) from a building plate (21), the support structures (23) must be cut or removed. A cable-based system (1) is disclosed which allows to easily detach the support structures from the build plate without having to cut, machine or manually remove them in other ways. The system comprises the following elements: A cable driver (1), that moves a cable (10) which works as detacher of the support structures (23). Secondly a method to detach the printed part (2) with the proposed cable driver (1). And finally, a special part of the support structure (23), preferably forming a channel (22), that allows properly placing the cable (10) and guides it during the detaching process

Description

Device for detaching a 3D printed part, method for detach ing and support structure

Most three-dimensional printing systems produce parts which are physically attached to a building plate. Usu ally, the building plate comprises a metal plate on top of which melted material is deposited layer by layer un til the complete part is obtained. Normally, support structures connect the printed part with the building plate .

These support structures are geometries which primarily allow a deposition of overhanging material during a printing process. Moreover, such structures hold a part in place during a printing process and remove heat from it during the process.

Support structures can assume different shapes such as columnar, lattice or block shapes. Their geometry is usually optimized to minimize the quantity of material used for their production, to control the temperature of the 3D printed material, to facilitate the removal of leftover raw material which remains inside of them at the end of the printing process and finally to facilitate their detachment from the printed parts in the post pro cessing phase.

In order to free the printed part from the building plate, the support structures must be cut or removed. In case of metal parts this is usually done using machine tools like band/wire saws, milling machines or electri cal discharge machines. As an alternative, the cut ting/removing can be done manually, using hand tools like pliers, chisels or hammers. Both methods, by machine or manually, are time consum ing, require skilled operators and, in the manual case, imply the risk of errors.

Moreover the manual removal of support structures generates health and safety problems due to the creation of powder and shavings and due to the risks of injuries connected with the use of the needed tools, can cause an uneven product qual ity and potential defects and is economically unfavora ble .

The invention proposed in the following will help to simplify the detachment of support structures and 3D printed parts from build plates after the completion of the 3D printing process .

The proposed solution considers 3D printing techniques that create support structures which connect printed parts with the build plate, namely the substrate that works as a base on top of which parts are additively manufactured. This is for example the case of SLM (Selective Laser Melting) , Stereo lithography or ME (Material Extrusion) . In all these tech niques the result of the 3D printing process is a substrate, also known as build plate, on top of which support structures and then the actual parts are built. In order to finish the parts, the first step is to detach the support structures from the build plate.

EP 18151831.7 discloses a support structure, where at least one part of the support structure is designed to change its outer shape when there is an external force on the support structure. Due to the changeability of the support structure the connection of the building plate to the printed part is breakable by means of an external force. Thereby, the supported printed part can be detached. An objective of the present invention is to facilitate a breaking of the connection between a part printed by means of a three-dimensional printing system and a building plate, the printed part is attached to.

Description of Invention

The problem is solved by a device according to the fea tures of claim 1

In addition, the problem is solved by a method of print ing a part three-dimensionally by means of a three- dimensional printing system according to claim 6.

Furthermore, the problem is solved by using a support structure for supporting a printed part and establishing a connection of a building plate to the printed part, which part is printed by means of a three-dimensional printing system, according to claim 8.

Advantageously, the printed part can be freed from the building plate without any cutting or breaking devic es/tools. There is no need of performing machining oper ations. Thus, the time needed for the removal of the printed part from the building plate can be reduced sig nificantly. More than this, manual supports removal op erations performed with hand tools, which can generate health and safety risks and constitute a source of vari ability in a quality of the printed part, are avoided.

Features of examples of the present disclosure will be come apparent by reference to the following detailed de scription of the drawings. For the sake of brevity, ref erence numerals or features having a previously de scribed function may or may not be described in connec tion with other drawings in which they appear. Fig. 1 illustrates the device for detachment, cable driver, contained in a box, with closed lid (above) and an open lid (below) ;

Fig. 2 illustrates the cable spool with a motor and a torque sensor and the cable wound thereon;

Fig. 3 represents the clamping system with clamping fingers, actuator and presence sensor;

Fig. 4 shows a support structure according to the in vention on a build plate with channel;

Fig. 5 illustrates the channel of a support structure comprising channel openings to allow the detachment;

Fig. 6 illustrates an enlarged cross-section of the support structure according to Fig. 4;

Fig. 7 shows the channel according to Fig. 5 with a cable inserted (above) and with the openings breaking due to the cable pressure (below);

Fig. 8 shows the same view as Fig. 6 with the cable already breaking a part of the support structure.

The invention solves the problem by introducing a cable-based system which allows to easily detach the support structures from the build plate without having to cut, machine or manu ally remove them in other ways.

The system comprises two elements:

A device 1, also called cable driver, that moves a cable 10 which works as detacher of the support structures 23.

Special parts of the support structures 23, preferably form ing a channel 22 that allows properly placing the cable 10 and guides it during the detaching process. Other forms to hold the cable such as a channel, eyelets, loops, chutes, ... are possible.

Cable driver 1

The invention proposes to perform the detachment of support structures 23 from the build plate 21 using a cable 10 as a tool to physically break the connections with the build plate. The first element of the invention is therefore the device 1 that drives the cable. Figure 1 shows two views of the cable driver, above with the lid closed and below with the lid opened showing its parts.

One element of the device is a cable spool 14, preferably mo torized with a motor 15, shown in more detail in Figure 2, which drives the cable back and forth. The cable is sliding and can be made for example of a metal wire rope. In another favorable embodiment, the motor can further be equipped with a torque sensor 17 to detect possible cable blocking. The ca ble spool 14 is covered by a guide housing 16 which allows pushing the cable as is typically made in Bowden cable sys tems. The cable features further a clampable tip 11 that can be inserted into the clamping system 13, shown in Figure 3, which holds it during the cable pulling phase. Such system uses two clamping fingers 191, 192 moved by an actuator 193 to hold the cable tip 11 and is equipped with a presence sen sor 18 to detect the cable tip 11.

The operating steps of the cable driver 1 are as follows:

1. The tip 11 of the cable 10 is inserted in the cable en trance 261 of the channel which is part of the support struc tures 23.

2. The operator activates the device which unrolls the cable 10 from the cable spool 14, pushing it through the above- mentioned channel 22 or other suitable cable cradle.

3. When the tip of the cable 11 reaches the cable exit of the channel 262, it is inserted into the clamping system entry

12. 4. The clamping system detects the cable tip through the presence sensor 18 and stops the cable movement

5. The clamping system is activated and blocks the cable tip.

6. The pulling phase is started: the spool 14 rolls back the cable and by doing so breaks the support structures 23, 24.

7. The pulling phase stops if one of the following conditions applies :

- The operator manually stops the phase.

- The spool 14 reaches the end position.

- The safety torque threshold of the motor is exceeded.

Support structures

Another element of the invention is a special type of support structure which can be detached from the build plate using the described cable driver. This support structure shows at least these features:

1. A channel or other suitable cradle structure that guides the cable along a suited path along the support structure and that breaks in a controlled fashion when the cable is re tracted, allowing it to move through the support structures detaching them from the build plate.

2. Breaking points that allow a controlled breaking of the supports when the cable hits them.

Figures 4 and 5 show, using a simplified example, how a chan nel 22 according to the invention is formed. The channel 22 is 3D printed together with the support structures 23 along the external perimeter of their bulk, in order to encircle them. In Figure 4 it can be noticed that the channel 22 is placed as close as possible to the build plate, allowing to detach the support structures almost in their entirety. In Figure 5 the structure of the channel 22 alone is shown in more detail: on its inner side the channel has openings 25 whose height is equal to the diameter of the cable. The open ings are separated by small elements that are made to break when the cable 10 applies a pressure on them. Figure 6 shows the conformation of the support structures 23: at the same height of the channel 22 a sharp reduction of their width (break point 24) make them easy to break when the cable 10 applies pressure on the break points, as shown in Figures 7 and 8.

Figures 7 and 8 show the process of breaking the channel 22 or cradle structure and the support structures 23 (these are not depicted in figure 7 for clarity reasons) :

1. As a first step the cable 10 is inserted in the channel entrance 261 and fed until it reaches the channel exit 262.

2. The cable is then drawn by the cable driver 1, shown by the arrow on the left - possibly also on both ends of the ca ble. The pressure applied by the cable on the internal sur face of the channel breaks the openings 25 as shown on the bottom of Figure 7, represented by the two arrows directing away from the break 27. The cable then exits the channel and presses on the break points of the support structures detach ing them from the build plate 21.

Figure 8 shows a detail of the breaking process with the ca ble 10 halfway through the support structures volume. The small arrows symbolize again the direction in which the cable is moving while drawn by the cable driver, as described above. On both sides the support structures are already bro ken 28, as well as the channel 27.

As compared to state-of-the-art techniques for the detachment of support structures from build plates, the presented tech nique features several advantages: firstly, it avoids the use of machine tools and consequently reduces the health and safety risks entailed with such technology and does not need skilled personnel to be used. Secondly the cable driver is significantly cheaper than conventional machine tools and therefore gives also an economical advantage.

Finally, the presented device and method allows a planned de tachment of support structures, this means that it makes it possible to determine in advance where and how they will break .

The special conformation of the support structures with the breakable channel to guide the cable and the break points contribute to avoiding machine tools and allow a controlled, deterministic detachment of the support structures from the build plate. Both features build up a very simple process that can be performed also by non-skilled personnel.

While one example has been described in detail, it is to be understood that the disclosed example may be modified. There fore, the foregoing description is to be considered non limiting .

Reference Character List

1 Device for detachment, Cable Driver

10 Cable

11 Clampable Cable Tip

12 Cable Entry

13 Clamping System

14 Cable Spool

15 Motor

16 Cable Guide

17 Torque Sensor

18 Presence Sensor

190 Clamping Finger Movement

191, 192 Clamping Finger

193 Clamping Finger Actuator

2 3D Printed Part

21 Build Plate

22 Channel

23 Support Structure

24 Break Point

25 Channel Openings

261 Cable Entrance

262 Cable Exit

27 Channel Break

28 Support Structure Break

Claims

Patent claims

1. Device (1) for detaching a part (2), produced by a three-dimensional printing system, from a build plate (21), whereby the part comprises a support structure (23), for supporting, the device including

- a cable (10) with a cable tip (11),

- a cable spool (14) suitable for winding up the cable (10),

- a clamping system (13, 191, 192)

characterized in that

the cable (10) is aimed to first surround the part (2) in the area of the support structure (23) , preferably in a channel shaped receiving element (22),

the cable (10) is then fixed in the clamping system (13) and rolled back by the cable spool (14) working as detacher.

2. Device (1) according to claim 1,

characterized in that

the cable spool works motorized.

3. Device (1) according to claim 1 or 2,

characterized in that

the cable is made of a metal wire rope.

4. Device (1) according to one of the previous claims, characterized in that

the device comprises a torque sensor.

5. Device (1) according to one of the previous claims, characterized in that

the cable (1) is heatable to a temperature that is sufficient for melting the material using which the part (2) is pro duced .

6. Method of detaching a part (2) that has been produced by means of a three-dimensional printing system, the part (2) comprising a support structure (23) and a cable receiving element (22), with the steps: - insertion of a cable (10) in the cable receiving element

(22), thereby encircling the part (2) almost entirely,

- clamping the cable (10) at the loose end

- start pulling the cable at least at one end,

until the support structure (23) has been cut through.

7. Method of detaching a part (2) according to claim 6, characterized in that

the pulling of the cable is done by a motor, and

the pulling of the cable is stopped if a threshold value of torque at the motor is crossed.

8. Support structure (23) for supporting a printed part (2) and establishing a connection of a building plate (21) to the printed part (2), which part (2) is printed by means of a three-dimensional printing system, the support structure

(23) being arrangeable on the building plate (21) of the three-dimensional printing system,

characterized in that

special parts of the support structures (23) form a cable re ceiving element, preferably channel-shaped (22) that allows properly placing a cable (10) and guides it during a detach ing process according to one of the methods of claims 6 or 7.

9. Support structure (23) according to claim 8,

characterized in that

the cable receiving element (22) has openings (25) that form a predetermined breaking point when the cable (10) exerts force by being pulled.

10. Support structure (23) according to claim 8 or 9,

characterized in that

the cable receiving element (22) is placed as close as possi ble to the building plate (21) .