Thixoforming : Semi-solid Metal Processing

392j 10 Thixoforging and Rheoforging of Steel and Aluminium Alloys
Table 10.1 Hydraulic press main parameters.
Parameter Value
Nominal press load 6.3 MN
Maximum press ram velocity 120 mm s 1
Maximum press ram stroke 600 mm
Stroke accuracy 0.1 mm
Auxiliary cylinder load 1 MN
Auxiliary cylinder maximum piston velocity 100 mm s 1
Auxiliary cylinder maximum piston stroke 300 mm
10.3.6.2 Robot with Gripper
To increase the reproducibility of the thixoforming process, a industrial six-axis robot
(KUKA KR 15/2) is used to transport the heated billet from the induction furnace to
the hydraulic press. The robot has to place the billet in the cavity. Therefore, the
gripper tongs were elongated to avoid damage to the drives or cables by radiation or
contact. Furthermore, the gripper tongs are equipped with ceramic inlays, which
reduce the radiation losses, and with an inert gas rinsing that prevents oxidation of
the skin.
10.3.6.3 Forming Aggregates
To perform the thixoforging experiments, a hydraulic press with a nominal load of
6.3 MN was used (see Table 10.1). The lower plunger movement is controlled by an
auxiliary cylinder, which is positioned under the lower tool frame. The press ram and
auxiliary cylinder piston velocities, working load, press ram and auxiliary cylinder
piston strokes and also time delay during the forming process are controlled by the
press CNC programme. Electrically heated tool frames that can be heated to 500 C
are equipped with tool inserts, which can be easily changed.
10.3.6.4 Sequence Control of the Plant
The production of semi-solid parts is very sensitive to disturbances or changes in the
production conditions. To assure constant boundary conditions and to minimize
disturbances, the automated production plant connects the following components
with a master process controller [20] (Figure 10.20):
1. feedstock magazine
2. robot with gripper
3. induction furnace
4. hydraulic forging press with tools
5. unloading unit for forged parts.
10.3.6.5 Master Process Controller
The production process is controlled by a master controller using the programmable
logic controller (PLC) of the robot controller. The automation components are
connected with a remote I/O, which itself is connected with the robot controller