LIBRARY ı6ıul 0) - Cranfield University

Current: 500
Position: 234.5
5.7.3 Wire feed speed calibration
The calibration of the BDH550 wire feeder was checked off-line by measuring
the weigth of welding wire delivered during 10 seconds for different set-up wire feed
speeds and comparing with the weight of 1 metre of the same welding wire. Figure
5.5 shows the calibration curve obtained.
5.7.4 Robot Interface calibration
The robot interface was supplied with two analog inputs which were used to
set the desired level of welding voltage and wire-feed-speed. A 0-10 V signal in the
welding voltage input channel would correspond to 0-50 V output between the power
source terminals and a 0-10V signal in the wire-feed-speed input channel would map
from I m/min to 24 m/min in the wire feed unit. The reference values for voltage and
wire-feed-speed were issued in the control computer. Two conversions were
necessary: one from digital to analogue values, which was performed by an 8-bit D/A
converter in the control computer and another from analogue to digital values, which
was carried out by a 10-bit A/D converter in the robot interface. Due to the difference
in the resolution of each converter and also to some calibration error in the robot
interface, which was not possible to correct, calibration curves were obtained by
setting specific values in the control computer and reading the actual set values in the
power source display (see Figure 5.7 and Figure 5.8). These curves were programmed
in the control software along with the BDH 550 wire feeder calibration curve (see
Figure 5.5).
5.8 Experimental materials
Welding wire
The experimental materials consisted of
" Nominal diameter:
" Type:
" Specification:
" Wire material:
" Typical composition:
C 0.08%
Shielding gas
" Type:
Si 0.8%
Mn 1.4%
" Typical composition:
" Flow rate:
120
1.0 mm
BOHLER EMK 8A
BS 2901 pt. 1 GR. A18
Mild Steel
BOC Argonshield 5
93% Ar, 5% C02,2% O2
15 Umin