DE1704210A1 - Oscillation friction welding - Google Patents

Description

Keyword: Oszl.Reibschweiß # s Oscillation friction welding # s The oscillation friction welding # s of plastics is a special type of friction welding.

Friction welding is known of the type in which the relative movement, that generates the frictional heat, is a pure rotary motion, and that with each other parts to be welded are welded in congruent rotating surfaces, e.g. Am Circular, circular or truncated cone surfaces.

Another type of friction welding of plastics is also known in the form of a subtype of ultrasonic welding, with certain relative movements are carried out in the welding area.

The disadvantage of friction welding, which is carried out with pure rotary motion is, in particular, is that it is limited to rotationally symmetrical Work pieces. The part of the tool that makes the rotary motion directly on the workpiece executes, must - in order to be able to remove it from the work piece - be in two parts, if after the weld has been carried out, it does not go over the welded axis in the direction of the axis of rotation Part can be pushed over lengthways and thereby removed.

The disadvantages of ultrasonic welding are in particular: that ultrasound is mechanical vibration energy with frequencies above 20 kHz, and the ultrasonic waves propagate well in the weld, i.e. in the plastic. In general, therefore, only very short distances can be achieved from the shaped sonotrode (this is the end of the ultrasonic tool on the workpiece side) to the one to be welded Plane can be bridged without excessive loss of ultrasonic energy. tEt ultrasound are therefore generally only wall thicknesses of a few millimeters - in general only 1 - 2 mm - penetrable, i.e. on the side of the wall facing away from the sonotrode weldable. Can be welded very well with ultrasound, even over larger distances of the sonotrode is polystyrene; which are very much used in industrial applications Plastics used and welded to be welded with a wall thickness greater than 2 - 3 mm, such as polyethylene len, polypropylene, polyvinyl chloride but cannot be welded if greater distances from the sonotrode must be bridged.

The object of the invention is a method for joining workpieces made of materials that become soft plastic as a result of an increase in temperature, in which largely regardless of the shape of the surface pieces in which the work pieces are welded are intended to weld with simple means in quick and only short clamping times requiring manner is possible.

According to the invention it is proposed that at least two workpieces are placed flat against each other and pressed against each other, these workpieces while reciprocating movements are given relative to one another in an oscillation-like manner. and these movements are ended after the weld plastic state has been reached, the surface pressure possibly changing during the welding process will.

The welding process according to the invention does not require any rotary movement of the workpieces to be connected and within the workpieces no transfer of Vibrations, which - like in ultrasonic welding - could be dampened.

It works with a simple oscillating movement and pressing against each other of the individual workpieces. The surfaces to be welded should expediently be parallel to each other and congruent. The congruence is but not absolutely necessary, and there is just one advantage of the finding in that e.g. 10 pipes could be welded onto one plate at the same time. If the surfaces to be welded are not exact and parallel to the surface, you can these small bumps are evened out during the first oscillating movements. Advantageously, the lighter one of the gels to be welded, e.g. B. the Lid or bottom of a container, permanently or slowly changing against the other pressed and by an oscillating device in rapid to and fro movements offset with relatively small deflections.

The frequency of the oscillation of this translational movement can depend on the material and the shape of the workpiece between 5 and 1000 Hz, and the size the deflection can be between 0.01 and 5 mm, optionally also 10 mm.

By the oscillating movement of the second workpiece part suitably metered and / or time-altered pressure on the first workpiece part Frictional heat is generated at the contact surfaces of the two parts. This frictional heat flows primarily into the two workpiece parts, starting from the contact surfaces, and leads to an increase in temperature in the two workpiece parts, which then increases the temperature is of course highest in the contact areas and with increasing distance each is lower. The heating and temperature increase in the run Over time, the plastic begins to be soft, starting at the contact surfaces to become. Is it softened in a sufficient layer thickness, i.e. plastically weldable, the oscillating movement of the second workpiece part is ended. The part is through Suitable measures in the desired welding position opposite the little resting held first workpiece part and pushed in this position with a suitable gradually increased contact pressure held by the oscillating movement warmed and softened layers that merged into one during movement, i.e. welded, cooled down and solidified. The composite part welded in this way is then removed from the vibration welding device and new ones to be welded Parts can be used.

The particular advantages of friction welding according to the invention over Friction welding by means of pure unidirectional rotary motion are beyond those mentioned in the introduction The following disadvantages of rotary friction welding: In the oscillation friction welding according to the invention every surface element of the oscillating moving part has the same in every moment Relative speed to the resting part, even if it changes from moment to moment Moment increasing and decreasing in the interplay, changes. This will, at the same large contact pressure of all surface elements with each other, in each surface element the same amount of frictional heat is generated in the same time elements, and the temperature apart from other influences, increases in the same way in all surface elements at.

In contrast, with rotary friction welding, only those have at any given moment Surface elements have the same relative speed to the stationary part, the same Distance from the axis of rotation.

Although the rotary motion is carried out at a constant speed what may be simple and technically desirable to a certain extent are natural the relative speeds of the various Surface elements proportional to their distance from the axis of rotation, and thus is also the production of frictional heat proportional to this distance from the axis of rotation greater. Therefore, the temperature also decreases faster the greater the distance from the axis of rotation to. This means that especially when there is a relatively large ratio on the workpiece between the largest and smallest diameter of the e.g. circular welding surface is present, the outer area of the welding surface is more soft and plastic than the one further inside. Because the innermost area is also well welded during welding must be, otherwise there would be a sharp ring notch, must be turned and with it overheated until the innermost area is soft and plastic, i.e. in a welded state is brought.

But this can hardly be seen from the outside. Until then, however, are also the outer areas have been heated higher and there is a risk that these too have been exposed to too high a temperature for a long time. The material can thereby thermally damaged and the weld no longer flawless in these areas be.

Such a risk of overheating as in rotation friction welding Due to the other process, oscillation friction welding cannot occur or can be easily avoided.

In a further development of the invention, it is proposed several straight lines Oscillation movements, which are preferably perpendicular to each other, each other to overlay. There is thus the possibility of oscillating relative to one another Moving workpieces the moments of the relative rest position in the end points which only oscillates in one direction should be avoided.

According to a further proposal, the oscillation movement is carried out Workpieces along an arc of a circle. This is particularly advantageous when e.g. spherical bodies with each other connected or e.g. a pipe branch is to be welded to another pipe.

To adapt to the welding process, it is advantageous to and to change reciprocation in frequency and / or amplitude. The frequency change serves to avoid overheating. By changing the amplitude, the Oscillation adapted to the changing plasticity of the parts to be welded and under certain circumstances can be regulated in such a way that this happens when the welding table is reached State is zero.

According to a further proposal of the invention, between the to connecting surfaces ein'Zusatzwerkstoff z. B. in the form of a disk-shaped intermediate layer arranged. In this way, materials can be welded under certain circumstances, which normally do not connect in a weld-plastic state. The reasons, why no connection is usually established has not yet been clarified. It but it has been found that when a neutral additive is used, a compound takes place, the two first-mentioned materials each for themselves with the Connect additional material.

The device for carrying out the method according to the invention is characterized by separate receiving devices for the to connecting workpieces, with the devices in the welding surfaces and perpendicular for this purpose are movable relative to each other, an oscillation drive to achieve the Back and forth movements of at least one receiving device in the welding surface and a pressing device assigned to at least one receiving device for pressing against one another of the workpieces.

Further details of the device and the implementation of the method are described in more detail below with reference to one shown in the drawing Embodiment example, Fig. 1 shows a plan view of the device below Continuation of the one receiving device, FIG. 2 shows a section through the two Pick-up devices according to line A-A in FIG. 1.

The workpieces to be welded together are designated by 1 and 2. They are to be welded in flat patches that lie in plane 1a. Workpiece 1 is resting in the lower receiving part 3 against forces in the welding plane 1a and held perpendicular to it. Receiving part 3 lies on the rigid base 3a and is supported by the side brackets 4 against forces in the welding plane 1a held. Workpiece 2 is snugly attached to the upper receiving part 5 Packed at the top and sides, pressed onto the workpiece 1 and against the stationary one Workpiece 1 in the welding surface pieces in plane 1a by moving to and fro of the upper receiving part 5, which takes the workpiece 2 back and forth, rubbed. This generates friction heat in the areas that are parallel to the weld surfaces Layers the temperature is thereby increased, and gradually the welding of workpieces 1 and 2, desired soft plasticity are achieved.

The reciprocating movement of the upper receiving part 5 is controlled by the oscillating connecting rod 6 generated, which is driven by an eccentric 21 and a motor 33. That Oscillation connecting rod 6 is connected to the receiving part 5 by a joint 7, the The axis of rotation is perpendicular to the longitudinal axis of the oscillating element 6 and parallel to the welding plane 1a lies. The distance of the axis of rotation of the joint 7 from the welding plane 1a is kept quite small, so that the receiving part 5 with the workpiece 2 as possible tends not or only insignificantly to tilt and thereby the pressure on the workpiece 2 makes the workpiece 1 unevenly as little as possible, although the want to tilt by the return and pressure forces of the oscillating rod 6, interacting with the Frictional forces Sn of the welding plane 1a and the changing acceleration forces the reciprocating masses to the oscillatingly moved receiving part 5 together generally inherent with the workpiece 2.

The pressing of the workpiece 2 against the workpiece 1 is ultimately caused by the changeable weight 14.. The power flow from the workpiece 2 backwards up to the weight 14 goes through some intermediate links of a special kind: The upper receiving part 5 must on the side where it receives the workpiece 2, a have a special shape adapted to this part.

This shape depends on the workpiece to be welded. On the upper side facing away from the workpiece 2, the receiving part 5 always has the same shape and thus fits into the short fitting part 8. Un the contact pressure of to transfer the vibrating parts 5 and 8 to the practically stationary part 10, the relatively long pressure transmission part 9 is interposed therebetween. Its bottom end 9a swings completely parallel to the horizontal welding plane 1a, its upper collar 9b, on the other hand, practically only vibrates vertically and at a rate that is orders of magnitude smaller Rashes. The two ends 9a and 9b of the Drucküberrabungteils 9 are as spherical heads designed to tilt movement in all directions in the ball sockets of parts 8 and 10 easily to enable. Instead of the ball heads and ball sockets, e.g. two crossed cutting edges and prismatic sockets act as opposing surfaces. For vertical straight guidance of the part 10 and to absorb the small horizontal forces that the part 10 in the Direction of vibration parallel to the direction of movement of the upper receiving part 5 seek to move, the part 10 is slidable between the fixed guides 11a and lib held. A compression spring 12 is inserted above part 10; with her the contact pressure can meet the requirements during friction heating and welding and then cool down accordingly. This can be done by changing the vertical position of the lever 13, which is fixedly mounted in the pivot point 13a is, on a short lever arm the receiving plate 13b for the upper end of the compression spring 12 has and on a long lever arm, at joint 13c, carries the attachment arm of the weight 14. By turning the cam 15 into a suitable position, the height of the weight 14 to adjust the pressure force of the spring 12 appropriately.

The transmission of the drive power of the electric motor 33 over several Intermediate members up to the eccentric 21, from where the rotary movement in the back and forth forward movement of the oscillating rod 6 is not set, happens on the following Way: To the motor 33 is a gear 31 with continuously variable output speed connected; this output speed is changed with the adjusting lever 32. from the point of departure of the transmission, a V-belt drive 27 transmits the rotary power of the rotor on a strong countershaft 24, which is in two strong bearings 25 and 26 is running, on the shaft sits a rotating bracket 23 in which the eccentric 21 is radial is slidably mounted, so that the eccentricity / make can be adjusted as required can. A ring sits around a strong roller bearing on the eccentric pin. This ring and the oscillating connecting rod 6 are through a joint 22, the axis of rotation of which is perpendicular to the connecting rod longitudinal axis and perpendicular to the eccentric axis of rotation, connected to each other.

About the rotary drive of the k = 3enter 21 and thus also the oscillation of the moving workpiece at the right moment of the welding process to be able to sit on the countershaft 24, a friction clutch 28, which normally is kept engaged by the compression springs 29. The linkage 30 with the in Actuating lever 30a, which can be locked in certain positions, is used to operate the clutch 28.

Thus, after becoming soft plastic, the one adjacent to the friction plane overheated layers of the two workpieces and the subsequent setting down of the oscillation drive the workpieces before these layers cool down and the Solidification of the weld in the correct welding position to each other, the compression springs 41 and 42 are used.

A shift across the direction of vibration is caused by the guide surfaces 43a and 43b avoided.

A possibility for acceleration within the scope of this invention The process of plasticizing consists in that the workpieces are introduced before they are introduced are preheated in the receiving parts and / or the receiving devices themselves are designed to be heatable.

A variant of the welding process included by the invention is that a workpiece is held in rest position and on several sides This workpiece 'simultaneously welds are carried out according to the invention.

So can accordingly arbitrarily combined on two opposite one another Sides of a plate each have a part, e.g. B. a ring, be welded, or to each Side of a cube each a rod or along the circumference of a tube of large diameter several tubes corresponding to small diameter.

There is another variant embodiment of the method according to the invention in keeping two workpieces still, e.g. two pipes, and a third oscillating one, z. 3. to weld a pipe bend or a straight piece of pipe to the pipes and so that the longer pipe sections can be connected by means of a short pipe section.

Claims (14)

Claims 1. A method for joining workpieces made of materials, which become soft plastic as a result of the increase in temperature and in this state on the Softened areas can be welded together by pressing them together are, e.g. made of thermoplastics, characterized in that-at least 2 workpieces are laid flat against each other and pressed against each other, these workpieces, running back and forth in an oscillation-like manner relative to one another Xer movements granted and the movements after reaching the schafeissplastischen State in the welding surface pieces are ended, with the surface pressure may be changed during the welding process. 2. The method according to claim 1, characterized in that the to be welded Surface pieces are essentially congruent. 3. The method according to claim 1 or 2, characterized in that the Weld patches are parts of flat surfaces that are in one plane or with each other lie parallel. 4. The method according to claim 1 or 2, characterized in that the Pieces of welded surface are parts of flat surfaces that are only one set to each other contain parallel straight lines. 5. The method according to claim 1 or 2, characterized in that the weld surface pieces parts of cylinder surfaces, preferably of circular cylinder surfaces, which have surface lines parallel to each other. 6. The method according to claim 1 or 2, characterized in that the weld surface pieces are parts of spherical surfaces with a common center. 7. The method according to any one of claims 1 to 6, characterized in that that the surface pressure between the weld surface pieces pressed against one another is changed during the welding process according to a certain program. 8. The method according to any one of claims 1 to 7, characterized in that that at least one workpiece is kept stationary, and that or the other workpieces be moved in a straight line swinging. 9. The method according to any one of claims 1 to 3, 6, 7, characterized in that that at least one workpiece is kept stationary, and that or the other workpieces simultaneously in several, preferably two mutually perpendicular directions, which are parallel to the parallel welding surface pieces, each in a straight line be moved in a swinging manner. 10. The method according to claim 1 or 2, characterized in that at least one workpiece is held stationary, and that or the other workpieces are set in movements on a circular arc. 11. The method according to any one of claims 1 to 10, characterized in, that the back and forth movements during the welding process in the oscillation frequency and / or can be changed in amplitude. 12. The method according to any one of claims 1 to 11, characterized in that that between the welding surfaces of the workpieces a filler material in the form of a Interlayer is provided. 13. Device for performing the method according to one of the claims 1 to 12, characterized by separate receiving devices for the workpieces to be joined, the devices in the welding surfaces relative are movable to each other, an oscillation drive to achieve back and forth movements at least one receiving device in the welding surfaces and at least one Anpreßeinrichtnng associated with the receiving device for pressing the Workpieces, 14. The device according to claim 14, characterized by one in the Device for return associated with welding surfaces movable receiving devices the receiving devices in the welding position after the end of the oscillating movement.