Chapter: Testing Specimens
3-10 M10-16245-EN
Set the crosshead limit stops
The crosshead limit stops are two adjustable blocks mounted on the limit switch rod, which
is located inside the column of the machine, as shown in Figure 3-1 on page 3-11. Limit
stops have thumbscrews that you tighten and release by hand, and you can move them to any
position on the limit rod. Position these stops just beyond the test parameters to prevent
crosshead over-travel. When the crosshead reaches the maximum pre-set travel, the limit
switch actuator contacts one of these stops. Contact between the limit actuator and the limit
stop moves the limit switch rod and activates the limit switches. This stops crosshead
motion.
There is an additional, second level of crosshead limit stop that is activated if the first level
switch malfunctions. Activating a second-level limit switch disables the drive system so you
cannot move the crosshead. The second level limits are internal to the machine and cannot
be manually adjusted.
Set the crosshead limit stops:
1. Ensure that the crosshead is stationary and that the test parameters are set. The TEST IN
PROGRESS
indicator light on the control panel should not illuminate.
2. Set the upper limit stop at a position just above the expected maximum crosshead travel
in the upward direction when tension testing, or just above the test starting point when
compression testing. Tighten the stop securely on the limit rod.
3. Set the lower limit stop at a position just below the starting position when tension testing
or just below the expected maximum crosshead travel in the down direction when
compression testing. Tighten the stop securely on the limit rod.
Crush hazard - you must set the crosshead travel limits as protection against
unexpected crosshead movement.
Although Bluehill lets you set limits of travel in the software, you must set the crosshead
travel limits as well. These hardware limits provide an absolute limit of travel that operates
independently of the software.
Set the crosshead limits stops after you have established the crosshead starting position, but
before you start a test.
When setting limit stops, allow for an additional 3 mm of crosshead travel after the
actuator activates a limit stop. There is a small delay time from the point when the
actuator hits the limit stop and when the message relays to the limit switches
located in the frame base.
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