DE102016108290B3 - WELDING TOOL AND PROCESS FOR WELDING PLASTIC PARTS - Google Patents

Abstract

The welding tool according to the invention comprises a lower and an upper punch of which at least one is movable, so that they can be moved towards each other. Between the punches a receiving space for at least two plastic parts to be joined together is formed. The welding tool further comprises a heating plate. The heating plate can be moved into the cavity and is arranged between the plastic parts, wherein the heating plate comes into contact with at least one contact surface of the plastic parts by the movement of the heating plate and of the stamp and heats this contact surface. In order to produce a second joint in addition to the welding, at least a first of the plastic parts comprises a rivet and a second of the plastic parts has a rivet hole, wherein the hot plate is modified to include a rivet for the rivet, and the upper or lower ram is modified in that a rivet support is formed for a rivet head of the rivet.

Description

Technical area

The present invention relates to a welding tool and a method for welding plastic parts with which larger structural structures can be constructed from individual parts, as e.g. needed in the automotive industry.

State of the art

In automotive engineering, plastic support parts for instrument panel, center console or door trim are used in large numbers. For this often different plastic parts must be joined together. Joining, welding, gluing, screwing or clipping are known as joining methods.

Even within the welding process, depending on the component, you can choose between ultrasonic, infrared or hot plate welding. In hot plate welding, a preheated hot plate is placed on contact surfaces of the plastic parts and these are melted before the melted contact surfaces are pressed together.

Are the plastic parts carrier for a decor, so visible in the vehicle interior parts, then the surface of the plastic parts should not be affected by welding. However, a melting of the plastic part leaves traces also on the surface back, so that ribs are provided on the plastic part, where then the weld is completed. However, this requires a certain minimum distance between the plastic parts to be joined, which is predetermined by the height of the ribs.

If the distance provided in the finished carrier part is less than that which can be achieved with ribs, it is necessary to make use of a hot caulking. When hot caulk both plastic parts can lie on top of each other, wherein one of the plastic parts must have a rivet, which is passed through a rivet hole of the other plastic part. By means of hot air, the rivet is heated and then reshaped so that a rivet head forms and both plastic parts are positively connected with each other. Since only the rivet must be heated, the surfaces can then be used for a decor.

For more complex geometries where the distance between the two plastic parts to be joined varies, both methods must be used in succession. However, this increases the production time and it requires two sets of tools for welding and hot calking.

The DE 199 57 042 A1 shows a method for forming a plastic body, such as a rivet, in which a quartz filament is pushed onto the plastic body and the plastic body can then be heated and formed. The DD 0 154 563 A1 shows an apparatus for performing Mehrfachverietungen with multiple heating loops and Formkopfstempeln. After the heating loops have heated the rivet shanks sufficiently, the forming head punches can punch out the rivet heads at the same time. From the JP S63-19227 A For example, a heating plate is known which is used to preheat a plastic before a punch pushes a part to be joined with a projection into the molten area of the plastic.

Description of the invention

An object of the invention is to provide a welding tool and a method for welding plastic parts, which reduces the manufacturing complexity of complex plastic parts.

The object is achieved by the welding tool and the method having the features of the independent claims. Advantageous developments of the invention can be found in the dependent claims.

The welding tool according to the invention comprises a lower and an upper punch, of which at least one is movable, so that they can be moved towards each other. Between the punches a receiving space for at least two plastic parts to be joined together is formed. The welding tool further comprises a heating plate. The heating plate can be moved into the cavity and is arranged between the plastic parts, wherein the heating plate comes into contact with at least one contact surface of the plastic parts by the movement of the heating plate and the die or stamps and heats this contact surface so far that the contact surface at least partially melts.

In order to also produce a second connection in addition to the welding, at least a first of the plastic parts comprises a rivet and a second of the plastic parts has a rivet hole, wherein the heating plate is modified such that it comprises a rivet receptacle for the rivet. The upper or lower punch is modified to form a rivet support for a rivet head of the rivet. This allows at the same time with a single tool welding the plastic parts in one place and the hot caulking of the plastic parts in another place respectively. The production can thus be significantly accelerated and also tool costs are saved.

In order to protect surfaces of the plastic parts, the contact surfaces are advantageously arranged on ribs of the plastic parts, wherein the ribs have a height of 3 to 9 mm, preferably 5 to 7 mm. The ribs protrude from the respective plastic part in the direction of a connection point of the two plastic parts and thus form a thermal insulation of the heating with respect to the remaining plastic part. The higher the ribs, the better the insulation, but the larger the space required. The specified ranges have proven to be a good compromise between space requirements and thermal insulation.

Furthermore, it is advantageous if the rivet receptacle of the heating plate has a larger diameter than the rivet and only one tip of the rivet comes into contact with the heating plate. This prevents sticking of the rivet receptacle and only melts the area of the rivet needed for forming a rivet head.

As an advantageous material for the heating plate brass has been found, alternatively, another good heat-conducting material can be used, but then with a non-stick coating, e.g. Teflon, is provided.

Depending on the desired shape of the rivet head (overhanging or not), the punch will comprise a counter-holder for a protruding rivet head or a rivet support for a rivet head which terminates flush with the plastic part. Furthermore, it is advantageous if the rivet encloses a cavity. In this case, the likelihood of sinking in the plastic part, which are due to the production of the plastic part by injection molding decreases. With the tool, a variety of materials can be molded, it has been found that in particular plastic parts made of a thermoplastic material, e.g. PA, PBT, PC, PE, POM and PP can be particularly well connected to each other, wherein also a proportion of reinforcing fibers may be included.

The inventive method for welding the plastic parts provides as a first step, the plastic parts in a welding tool ready. The welding tool comprises a lower and an upper punch and a heating plate, wherein at least one of the punch is movable relative to the other punch and between the punches a receiving space for receiving the plastic parts is clamped. In a second step, the heating plate is moved into the cavity and between the plastic parts. In a third step, the heating plate and punch are moved towards each other, so that the heating plate comes into contact with at least one contact surface of the plastic parts and heats this contact surface. The heating leads to at least partial melting of the plastic, so that the contact surfaces are deformable. After heating, the heating plate is removed from the receiving space and the plastic parts are pressed by means of the stamp before the plastic parts can be removed from the welding tool.

According to the invention, at least one of the plastic parts comprises a rivet and a second of the plastic parts has a rivet hole, the rivet being guided through the rivet hole into the rivet receptacle during the relative movement of the heating plate and punch. The heating plate is modified to include a rivet receptacle for the rivet. Furthermore, a modification of the upper or lower punch is provided so that a punch comprises a rivet support for a rivet head of the rivet.

This can be done on the same plastic parts in the same tool and in common steps a welded joint and a hot-caulking.

The method may be advantageously developed by moving the hot plate and die towards one another (eg, the hot plate is stationary during this step and the punches move from both sides towards the hot plate) comprising at least two phases, first a rapid movement to the first Contact surfaces and then a slower movement until the contact surfaces have deformed. This results in a controlled deformation without breaks due to the slower movement. Subsequently, a cooling of the plastic parts takes place and a stamp is removed.

In the deformation of the contact surfaces is advantageously based on the fact that the movement of hot plate and stamp each other to ribs of the plastic parts, on each of which a contact surface are deformed such that a height of the ribs by 1 to 3 mm, preferably about 2 mm , shortened. Thus, sufficient material is melted and deformed in the sense of process reliability, in order to guarantee a durable durable connection of the plastic parts with each other.

The movement of the heating plate in the receiving space is advantageously a horizontal movement and the movement of the stamp on the heating plate to a vertical movement.

It has been found that in the materials used for the plastic parts of polypropylene or polyamide, if necessary with an admixture of reinforcing fibers, the heating plate should advantageously be heated to a temperature of 300 to 450 ° C, in particular about 400 ° C, and the contact surfaces remain in contact with the heating plate for about 2 to 8 seconds. This ensures a good connection with minimal process time.

Short description of the figures

1 shows a connection of two plastic parts according to the prior art,

2 shows stamps according to the invention,

3 shows a heating plate according to the invention,

4 shows the plastic parts to be joined together,

5 shows the three steps of the welding process,

6 shows the plastic parts of stamp, hot plate and three plastic parts according to a first embodiment during heating,

7 . 8th show the step of pressing according to the first embodiment at the beginning and the end,

9 shows the manufactured component consisting of three plastic parts,

10 shows the interaction of stamp, hot plate and three plastic parts according to a second embodiment during heating,

11 . 12 show the step of pressing according to the second embodiment at the beginning and at the end,

13a , b show two variants of the manufactured component consisting of two plastic parts,

According to the prior art plastic parts 5 . 6 . 7 corresponding 1 connected in two separate steps with each other, if the design-related distance of the plastic parts shown above 6 . 7 for the plastic part shown below 5 at least partially very small. In this case, part of the connection (between two plastic parts 5 and 6 ) about welding and another part of the connection (between two plastic parts 5 and 7 ) are made by hot caulking. For the connection with hot caulking involves a plastic part 5 a rivet 52 passing through a rivet hole 72 within another plastic part 7 is performed before by means of hot air heating and forming by means of special tools a rivet head is formed.

According to the invention - see 2 - an upper and a lower stamp 2 . 3 a welding tool 1 modified from aluminum. Surfaces of the stamp 2 . 3 , which show the plastic parts provided later, are shaped to be flush with the surface of the plastic parts and to exert a compressive force on these plastic parts can. Between the stamps 2 . 3 becomes a recording room 4 clamped, which can then accommodate a hot plate and the plastic parts.

In this embodiment, the upper punch 3 modified so that in addition to the surface of a rivet 63 is integrated. This rivet pad 63 is a sink which serves as a counter-holder for forming a rivet head and is positioned so that it faces a rivet of a plastic part shown later.

An in 3 shown heating plate 8th of the welding tool 1 has surfaces facing the plastic parts adapted to the geometry of these plastic parts. In one of these surfaces is a rivet recording 81 introduced as a deep depression, which is smaller in depth than the length of the rivet, but larger in diameter than the rivet. This is to ensure that the rivet is only at the top by the heating plate 8th is heated and not within the rivet receptacle 81 can stick together. The heating plate 8th Made of brass, it can be dispensed with a non-stick coating, which would be necessary with other materials.

The plastic parts to be joined together 5 . 6 . 7 are in 4 shown. A held by the lower punch first plastic part 5 includes a rib 55 at the top of a contact surface 51 is arranged. The rib 55 has a height h1 over the plastic part 5 , Furthermore, the first plastic part comprises 5 a rivet 52 with a rivet point shown 54 , A second plastic part 6 also includes a rib 65 a height h2 with contact surface 61 at the top and should with the first plastic part 5 be connected by means of a welded joint. A third plastic part 7 contains for attachment to the first plastic part 5 a rivet hole 72 , The plastic parts 5 . 6 . 7 are made of polypropylene (PP), but other thermoplastics can be used as well.

The connection of the three plastic parts 5 . 6 . 7 will be after a in 5 shown method performed. In a first step S1, the provision of plastic parts takes place 5 . 6 . 7 in the welding tool 1 , The plastic parts can 5 . 6 . 7 to the stamp 2 . 3 held by vacuum nozzles become. In a second step S2, the heating plate 8th horizontally in the cavity 4 and between the plastic parts 5 . 6 moved before in a third step S3, the hot plate 8th and the stamps 2 . 3 be moved vertically towards each other, leaving the heating plate 8th something at the same time on the contact surfaces 51 . 62 the plastic parts 5 . 6 and the rivet point 54 touches down.

With this contact, heating S4 sets the contact surfaces 51 . 61 but also the rivet 52 one. At a temperature of the heating plate 8th from 400 ° C, this heating phase lasts only 2 to 8 s, before in a further step S5 the heating plate 8th out of the recording room 4 removed and in a sixth step S6 the stamp 2 . 3 the plastic parts 5 . 6 . 7 Press together. This will be the ribs 55 . 56 from an original height h1, h2 of 5 mm each to a height h1, h2 of 3 mm compressed, whereby a material closure between them arises. The rib 55 of the first plastic part 5 is slightly wider than the rib 65 the second plastic part, so that the adhesion is even more pronounced.

In a seventh step S7, first at least one stamp 3 from the plastic parts 5 . 6 . 7 moved away before the plastic parts 5 . 6 . 7 from the tool 1 be removed.

Based on 6 to 9 this process will be clarified once more.

6 shows stamp 2 . 3 , Plastic parts 5 . 6 . 7 and hotplate 8th at the moment of heating the contact surfaces 51 . 61 on the ribs 55 . 65 and the heating of the rivet 52 in the rivet 81 that is, fourth step S4. A touch of hot plate 8th with the plastic parts 5 . 6 . 7 is limited only to these precisely specified areas, so that no deformation of the plastic parts is to be feared on the other surfaces, which could otherwise adversely affect the functionality and aesthetics. This is also the height h1, h2 of the ribs, the effective heat insulation of the heating points of the remaining plastic parts 5 . 6 enable. Likewise, the heating plate 8th through a column to the rivet 52 (except at the rivet point 54 ) and the third plastic part 7 thermally insulated.

7 shows the beginning of pressing S6, the heating plate 8th is already removed and the contact surfaces of the ribs, as well as the anvil 63 of the upper stamp 3 and the rivet 52 touch each other. Until this time, the stamps 2 . 3 From this point on, the movement slows down until a deformation of the ribs 55 . 65 and the rivet 52 corresponding 8th has exposed. To 8th the ribs are deformed so that their height is now about 3 mm, also has by the anvil a complete rivet head 53 emerged, the third plastic part 7 completely encloses behind the rivet hole and brings about a positive fit.

Be the stamp 2 . 3 away from each other and that from the three plastic parts 5 . 6 . 7 existing component (carrier component for an instrument panel, center console or door trim) taken (seventh step S7) so get the component after 9 which contains both a welded joint and a hot-caulking joint and was produced in a joint joining process.

An alternative method, relating to the fact that not three, but two plastic parts are joined together, is in the 10 to 13 shown. How out 10 There is a rivet hole 62 directly in the second plastic part 6 that at least two places with the first plastic parts 5 to be connected.

The warming ( 10 ) and pressing ( 11 and 12 ) as previously explained. The resulting and in 13a However, shown component consists only of two plastic parts 5 . 6 ,

An alternative regarding the rivet shape is in 13b shown. Should the rivet head 54 flush with the second plastic part 6 complete is a conical rivet hole 62 in the second plastic part 6 intended. In addition, in the upper stamp 3 as rivet pad 64 a smooth rivet pad chosen that contains no sink. Thus, the entire material of the rivet is in the rivet hole 62 pressed and a conical rivet head 54 develops.

As an additional variance can be added that the rivet 52 inside is hollow, so a cavity 56 having. This has the advantage that the otherwise massive rivet 52 Cools faster, but even that already in an injection molding of the plastic parts, here the first plastic part 5 , no sinks appear, as less material in the shape of the rivet 52 must be injected.

LIST OF REFERENCE NUMBERS

 1

 welding tool

 2

 Lower stamp

 3

 Upper stamp

 4

 accommodation space

 5, 6, 7

 Plastic parts

8th

 heating plate

 51, 61

 contact surfaces

 52

 rivet

 53

 rivet head

 54

 rivet tip

 55, 65

 ribs

 56

 cavity

 62, 72

 rivet hole

63

 Rivet pad, counterholder

64

 Rivet pad, rivet pad

81

 rivet receptacle

 h1, h2

 Height of the ribs

Claims (12)

Welding tool ( 1 ) with - a lower and an upper punch ( 2 . 3 ), wherein at least one of the punches ( 2 . 3 ) with respect to the other stamp ( 2 . 3 ) is movable and between the stamps ( 2 . 3 ) a recording room ( 4 ) for receiving at least two plastic parts to be joined together ( 5 . 6 . 7 ), - a heating plate ( 8th ), which enter the cavity ( 4 ) and between the plastic parts ( 5 . 6 ) is movable and in the cavity ( 4 ) in contact with at least one contact surface each ( 51 . 61 ) of the plastic parts ( 5 . 6 ) and this contact surface ( 51 . 61 ), characterized in that • at least a first of the plastic parts ( 5 ) a rivet ( 52 ) and a second of the plastic parts ( 6 . 7 ) a rivet hole ( 62 . 72 ), • the heating plate ( 8th ) a rivet receptacle ( 81 ) for the rivet ( 52 ), and • the upper or lower punch ( 2 . 3 ) a rivet pad ( 63 . 64 ) for a rivet head ( 53 ) of the rivet ( 52 ). Welding tool ( 1 ) according to claim 1, characterized in that the contact surfaces ( 51 . 61 ) on ribs ( 55 . 65 ) of the plastic parts ( 5 . 6 ) and the ribs ( 55 . 65 ) have a height (h1, h2) of 3 to 9 mm, preferably 5 to 7 mm. Welding tool ( 1 ) according to one of the preceding claims, characterized in that the rivet receptacle ( 81 . 82 ) of the heating plate ( 8th ) has a larger diameter than the rivet ( 52 ) and only one tip ( 54 ) of the rivet ( 52 ) in contact with the heating plate ( 8th ) occurs. Welding tool ( 1 ) according to one of the preceding claims, characterized in that the heating plate ( 8th ) is made of brass and / or provided with a non-stick coating. Welding tool ( 1 ) according to one of the preceding claims, characterized in that one of the punches ( 2 . 3 ) a counterholder ( 63 ) or a rivet pad ( 64 ). Welding tool ( 1 ) according to one of the preceding claims, characterized in that the rivet ( 52 ) a cavity ( 56 ) encloses. Welding tool ( 1 ) according to one of the preceding claims, characterized in that the plastic parts ( 6 . 7 ) consist of a thermoplastic material. Method for welding at least two plastic parts ( 5 . 6 . 7 ), comprising the following steps: - providing (S1) the plastic parts ( 5 . 6 . 7 ) in a welding tool ( 1 ), a lower and an upper punch ( 2 . 3 ) and a heating plate ( 8th ), wherein at least one of the punches ( 2 . 3 ) with respect to the other stamp ( 2 . 3 ) is movable and between the stamps ( 2 . 3 ) a recording room ( 4 ) for receiving at least two plastic parts to be joined together ( 5 . 6 . 7 ), - moving (S2) the heating plate into the cavity ( 4 ) and between the plastic parts ( 5 . 6 ), - moving (S3) of heating plate ( 8th ) and stamps ( 2 . 3 ) towards each other, so that the heating plate ( 8th ) in contact with at least one contact surface each ( 51 . 61 ) of the plastic parts ( 5 . 6 ) and this contact surface ( 51 . 61 ) (S4), - removing (S5) the heating plate ( 8th ) from the recording room ( 4 ) and pressing (S6) the plastic parts ( 5 . 6 . 7 ) by means of the punches ( 2 . 3 ) before the plastic parts ( 5 . 6 . 7 ) from the welding tool ( 1 ) (S7), characterized in that at least a first of the plastic parts ( 5 ) a rivet ( 52 ) and a second of the plastic parts ( 6 . 7 ) a rivet hole ( 62 . 72 ), the heating plate ( 8th ) a rivet receptacle ( 81 ) for the rivet ( 52 ) and the upper or lower punch ( 2 . 3 ) a rivet pad ( 63 . 64 ) for a rivet head ( 53 ) of the rivet ( 52 ), and - during the movement of heating plate ( 8th ) and stamps ( 2 . 3 ) to each other on the rivet ( 52 ) through the rivet hole ( 62 . 72 ) in the rivet receptacle ( 81 . 82 ) to be led. Method according to claim 8, wherein the movement of the heating plate ( 8th ) and stamps ( 2 . 3 ) comprises at least two phases, first a fast movement until the contact surfaces ( 51 . 61 ) and then a slower movement until the contact surfaces ( 51 . 61 ) have deformed. Method according to one of claims 8 to 9, wherein the moving (S3) of hot plate ( 8th ) and stamps ( 2 . 3 ) to rib one another ( 55 . 65 ) of the plastic parts ( 5 . 6 ), on which the contact surfaces ( 51 . 61 ) are deformed such that a height (h1, h2) of the ribs ( 55 . 65 ) shortened by 1 to 3 mm, preferably about 2 mm. Method according to one of claims 8 to 10, wherein the movement (S2) of the heating plate ( 8th ) in the reception room ( 4 ) a horizontal movement and moving (S3) the punches ( 2 . 3 ) on the heating plate ( 8th ) is a vertical movement. Method according to one of claims 8 to 11, wherein the heating plate ( 8th ) is heated to a temperature of 300 to 450 ° C, in particular about 400 ° C, and the contact surfaces ( 51 . 61 ) for about 2 to 8 seconds in contact with the heating plate ( 8th ) stay.

Images