The circular welding (ZS) is placed under the rubric „friction-welding“. This industrial serial production is unthinkable, especially in the automotive- and supply industry.

The circular-rivet is a cold rivet procedure which is effected without any change on a machine for welding.

A separate information gives details about the tools and use of treatment.

The advantages and disadvantages of the linear friction welding are known, the dominant welding direction has its limit in dividing profiles.

At the circular welding there are no precedence’s in the welding directions, it is a double-dimensional system without spring-centring. With the welding ends, the part adaption can be centred in the mid, within extreme short time and without an after swinging.

Due to this reason the joining zone can enter into a homogeneous connection during the cool-off phase.

At all press-welding procedures as well as at the circular welding all joining parts of thermoplastic synthetics are moved together due to the circulating kinematics, and are welded together under pressure, whereas the motional distance is equally the swing-width. The starting point before and after the welding is the centre of the machine.
With corresponding parameters for the joining-pressure, welding-frequency, swing-width and welding-time, the parts in the joining area heat up until plasticize of the joining areas and then crystallize again under the pending joining pressure to a solid connection with the best welding factor (Wf until 1,0 possible). In this welding phase the stages of the solid matter-friction pass non-stationary- and stationary melting formations.

These phases are shown in the following diagram.

Phase 1: solid matter friction,
Phase 2: transitional friction,
Phase 3: stationary melt

DEMANDS AT THE MACHINES

A solid finish of the machine is necessary for the friction welding procedure. Due to the chosen circular welding kinematics the vibration generator and the transmission take place without pulsating accelerating reverse. There are harmonic torsional vibrations resulting into a low noise process.
The machine construction guarantees an anti-polluting and easily accessible working place for a manual operation and for automation without additional charges for the operator.
This system works at 100 Hz welding frequency underneath 80 dB (A) working noise.

The digital adjustable parameters are:

welding frequency in Hz
the oscillation radius is convertable, independent from masses and frequency
the welding time in s, or the welding way from zero of the machine or of the workpiece surface
several press-profiles over the welding phases, with cold holding pressure afterwards welding in bar
the holding-time, a delay in welding and the supervisor time of the process-all in sec

WELDING CHARACTERISTICS OF SYNTHETICS

All thermoplastics as well as elastomeric are weldable if they can be count in the group of GF-materials and filled materials.
Good weldable thermoplastics are: ABS,PA,PC,PMMA,POM,PP,PS,PVC,PVC-U,SAN, and their reinforced modifications.
We consider basic-welding for new materials suggestive, these can with the help of test-plates be welded in the standard sizes of 50 x 40 mm and they reduce the expense considerable compared to the part of the mould-sample which at least makes a simple acceptance-tool necessary.
Thin wall parts and thin joint-flanges are ideal to connect.
The welding oscillation operates to all sides also in the direction of the thin wall part and transverse of it. Due to these rotating oscillations the walls remain thin and instable against the friction strength in its position.
Wall reinforcements are only necessary at instable work-pieces.
The welding flow of the melt is reduced due to the circular welding kinematics but not removed. A small visible welding flow is the proof for the root-penetration in the joint connection.

QUALITY DEMANDS TO THE ASSEMBLY-PARTS

Good welding connections can be achieved with parts which are according to the geometry of the parts adapted joining zone and shaped for the friction welding. No special seam-shaping is necessary for circular-welding if the shaping is constructed to RS.

Equal vibrations to all sides are allowed, even smaller welding flanges and therefore exact welding at precision-parts.

Opposite to the linear oscillation welding the same welding rapidity is about 35% less at the circular oscillation (comparable with amplitude).
The welding extras – depending on the part-size- should be chosen between 02, + 0,8 mm
A homogeneous joint seam shows, also at any double-dimensional course, an even root-penetration with small welding flow. By shaping the joint-flanges a covering of the joint seam can take place at the out- and inside.
The joint area should be free from any separating-agents, varnish and impurities.

CONSTRUCTIVE SHAPING OF THE ASSEMBLEY-PARTS

Depending on the demand of the building component concerning appearance and function different joining zone-geometries can be chosen.

WELDING END AND CRYSTALLIZATION IN THE COOL-OFF PHASE

The welding process is more effective if the subsequent cool-off phase is immediately in an „at ease position“ of the dividing haft to each other at a contiguous cool pressure. It is important that the welding oscillation is stopped very shortly to enable the plastic/synthetic to crystallize calmly. This can be achieved in little ms with the circular welding spindle and without any after swing masses. With the initiation of the driving-brake a braking moment is given and with its help the oscillation system is automatically steered into the zero position.
With this short seek-time t pos and optimal passing of the melt to the crystallization of the welding deposit is given (Picture 2). 

With the short position time t pos an optimal passing of the melt to crystallization of the welding deposit is given