LINK Systems 5100-8 Tonnage & Analog Signal Monitor - Manual (Page 9)

Doc #: L-802-1110 Page 7 Rev. 02
2 DEFINITIONS AND TERMINOLOGY
This section will give some background and explain the meaning of various settings and readings in the
tonnage monitor. It is strongly recommended that this section be read in order to use the tonnage
monitor effectively!
2.1 Tonnage
The tonnage monitor reads forming forces (“tonnage”) from strain gages mounted on the machine
frame. Each strain gage is a “channel”. Tonnage monitors typically have two or four strain gages
depending on the type of machine. For example, OBI presses typically use two strain gages (one on
each side), while straight side presses typically use four strain gages (one on each corner). Sections 6.6
and 6.7 starting on page 55 covers strain gage location considerations and mounting procedures.
2.1.1 Channel Tonnage
A channel tonnage is the tonnage read from a single strain gage. A numerical channel tonnage reading
shown by the tonnage monitor is the highest tonnage exerted on that channel through the stroke or data
window (data windows are discussed in section 3.2). In addition, the tonnage monitor can show the
tonnage waveform for a channel. This waveform shows how the tonnage varies with press crankshaft
angle.
2.1.2 Total Tonnage
In addition to recording the maximum tonnage measured for each channel, the tonnage monitor module
calculates and records the instantaneous summation of all channels. It performs the same peak
measurement on this value as is performed on the individual channels. This value is displayed as the
total tonnage exerted on the machine frame at any single position in the stroke.
When forces occur on all channels at the same time, the maximum total tonnage is the summation of the
maximum channel tonnages. For example, the die shown in Figure 1contains two equally sharp punches
of equal cross-sectional area and equal length. This die is located in the center of an OBI press bed
equipped with a two channel tonnage monitor with strain gages mounted on both sides of the press
frame. If the tonnage required for each punch is 100 tons and both punches impact the material at the
same position in the stroke (at the same time) the graph in Figure 1 shows the forces applied to the left
and right sides of the machine frame along with the resulting total force. This process would result in
the tonnage monitor displaying 100 tons for the left channel, 100 tons for the right channel, and 200 tons
for the total.