System concept:
The Wegener pipe bending facility has been developed to manufacture elbows of extruded pressure pipes, primarily of PE-HD. The facility processes different pipe diameters, various pressure levels and produces elbows up to an angle of 90°.
The ends of the pipes remain cold during the process and thus comply with the standard pipe. They can be joined to the piping immediately by socket or heated tool welding. The facility realises a bending movement that is controlled in three axes. The elbow can be drawn or compressed during bending. Preheating is by means of IR radiation whereby the pipes rotate beneath the radiator field. The width and intensity distribution of the radiator field can be adjusted. Additional internal heating (hot gas) is used for pipe diameters over 140 mm. The machine works with special automatic protruding and retracting bending cores in the pipe and a female mould around which the pipe is bent. The facility is fully automated on the highest configuration level.
The unique, special process engineering that has been realised in the facility leads to unmatched product features.

Product features:

Cold pipe ends
The ends of the pipes (elbow) do not achieve temperatures higher than around 45 °C throughout the entire production process. This means that they are neither deformed nor thermally affected. Deviations in diameter compared to the extruded base pipe are possible on account of the effects of temperature and the clamping of the pipes during bending and are usually around +/- 1 %. Every standard joining technology can thus be employed with no finishing work. The elbows can be connected to the next section of piping by means of sockets for resistance welding, heating sword sockets or heating sword butt welding.

Bending radius
The elbows are shaped with a standard bending radius of R = 1.5 *D. The special kinematics of the facility keeps the ratio of bending radius to pipe diameter constant in the design range of all diameters.

Wall thickness
The wall thickness of the elbow can be varied by stretching or compressing the pipe during bending. Depending on the requirements or customer's wishes, the neutral bending line can be shifted relative to the centre axis of the pipe, i.e. the elbow can be compressed or stretched within certain limits during bending, with a corresponding effect on the wall thickness. The bending speed (angular velocity) is another parameter that can be infinitely adjusted.
The wall thickness naturally decreases at the outer radius and increases at the inner radius. Unpublished creep-depending-on-time tests under internal compression show that the creep strength of the bends under internal compression corresponds to that of the straight pipe with no reduction factor.

Rebound
The maximum machine bending angle is 105°. This over-bending compensates the unavoidable rebound of the elbow and produces a true-to-size final product. 
Optional retaining clips that are attached immediately after ejection can shorten the cycle time and greatly increase the productivity of the facility with some products.

Technical description:

Pre-heating system
The pre-heating system consists of a clocked, automatically transporting continuous flow heater with infrared heating technology.
The pipes are heated up to the forming temperature in several successive stations with an infrared radiator field. The pipes are forwarded from station to station with an automatic transporting device. The pipes rotate beneath the radiator field in the individual stations and are heated up to the necessary forming temperature. The width of the heating zone for the pipes can be precisely adjusted. The heating system also offers the opportunity of realising different pipe wall temperatures along the length of the pipe. This setting is used to adjust the wall thickness distribution in the elbow.
A separate pyrometric temperature measurement is integrated in each pre-heating station and is used to both control the heating and monitor the safety of the facility. No contact is made at any time with those parts of the pipe that are to be heated to forming temperature so that their excellent surface quality is retained. The facility is largely shielded against radiation losses. It is characterised by its high efficiency, extreme stability and great ease of maintenance.
Additional internal pipe heating by means of hot gas is used for pipes with very thick walls in the last pre-heating station.

Bending facility
The bending facility works with negative female bending moulds in the inner radius of the elbow, two holding tools as hydraulic clamps in the cold area of the pipe ends and slit full cores of polypropylene. The basic bending station consists of a two-legged bending machine with a vertical bending axis. The bending axis can be adjusted relative to the centre axis of the pipe and is set depending on the pipe diameter to be manufactured in such a way that an R/D ratio of 1.5 is achieved. The two bending legs are moved by a central drive along symmetrical paths and angles. The travelling clamps of the pipe holders are mounted on the two bending legs and are hydraulically driven. The clamps move towards each other during bending around the fixed bending axis. The numerical control system of the main drive and the two clamp drives allow the elbow to be specifically stretched or compressed during bending. The neutral fibres in the pipe bend can thus be moved.
The clamps to hold the cold pipe ends are designed as single-shear, hydraulically operated clamping elements. They consist of a master clamp with corresponding reducing inserts for smaller pipe diameters. The master clamp simultaneously acts as a holding tool for the biggest pipe.
A centrally arranged negative mould, the so-called female mould, produces the inner radius of the elbow. The pipes are bent around the female mould and are pressed against this. The contact pressure for the female mould can be varied. This prevents creasing and the wall thickness can be altered. The female moulds have cooling bores for compressed gas cooling so as to minimise the facility's cycle times and set a constant working temperature for the tool. 
The extension and retraction drive for the bending core is mounted on one of the bending legs. The bending core is designed as a laminar  core that is compression-proof but flexible. The bending core is inserted into the straight pipe before the start of bending and withdrawn from the elbow at the end of the cooling time. The bending core prevents any collapses and an oval deformation of the elbow in the deformation range.

Cooling ( optional )
The elbows should have ducted cooling in the interests of economical cycle times. The cooling system works with compressed air. The elbow's cooling time is split into two parts, cooling time with core and cooling time without core. The outer surface of the elbow is cooled with compressed air immediately at the end of the bending process. Compressed air blowing heads cool the outer bend, cooling air bores in the female mould rinse the inner radius of the elbow and raise it slightly from the female mould. The bending core is withdrawn after a defined time and the inside of the pipe is also rinsed with compressed air.
In order to further reduce the cycle time (cooling time) in the event of thicker walls, the elbow can be removed before the end of the actual necessary cooling time and left to cool in special holding clamps outside the facility. We can offer these holding devices as optional extras.

Pipe removal ( optional )
The finished elbows can be removed automatically. A pneumatic, two-dimensional linear axis with a vacuum head is used for this purpose. The vacuum head removes the elbow from the opened and positioned pipe clamp and places it in the discharge channel in connection with a slideway. A conveyor belt removes the elbow from the facility.

Interlinking ( optional )
An interlinking from the supply magazine before the pre-heating system through to the discharge channel to the conveyor belt can be realised to allow fully automated operation. With this set-up a pipe is transferred from the supply magazine to the pre-heating system and another pipe simultaneously transferred from the pre-heating system to the bending machine in sync with the overall facility's bending and cooling cycle. The facility is equipped for fully automated operation with the interlinking option.

Operation, control system / monitoring :
The facility's control system is divided up into three main sections,
a) Pre-heating system
b) Bending facility
c) Set-up, automation
The control and adjustment of the pre-heating system is designed as a standalone unit and communicates with the central system for reasons of plant safety and quality assurance. The desired temperature profile for the pipe is set symmetrical to the middle of the pipe with a potentiometer control and is adjusted and monitored pyrometrically. The heating is controlled within a minimum to maximum range so as to ensure the optimum processing temperatures.
The bending facility is operated from a central control desk. The individual functions can be activated and called by hand in the set-up mode. Following successful set-up, the entire bending cycle runs automatically through to the end of the cooling time after a two-button activation.

Download the technical Data of the Pipe Bending Facility
as a *.pdf Document (80kb) here.