|Cuts on the forward stroke using gravity cutting load|
|No blade lift off on return stroke|
|Main pivot of bow on the same axis as crank drive shaft|
|Stroke||153mm ± 1mm|
|Selection of 2 cutting speeds||35/70 strokes/min ± 2 380/415 Vac 3ph|
|Typical test time||
Automatic 25 min
Manual 40 min (including calculation)
BS 1919 describes the specification for a cutting performance test and the requirements for a powered hacksaw machine suitable for executing the mechanical testing. These requirements are normally met by the refurbishment/conversion of a standard engineers power saw (Rapidor Manchester 6" saw illustrated as the basic manual version) or using a new machine of the equivalent specifications.
A standard power hacksaw is converted by CATRA with the addition of electro-pneumatic/hydraulic actuators to the bow raise/lower, bar feed and clamp mechanisms such that the sequencing of repeat cuts and bar feed can be run automatically. Cutting speed selection is also made electronically, with the stock feed increment being set by mechanical adjustment. The control system is based on a PLC with the operator having both manual and auto functions accessed from a push button control panel. The system is capable of being run through auto tests from this panel but requires operator attendance.
With a host computer (housed in a free standing enclosure beside the machine) connected to the machine controller operation of the machine in automatic test mode can be controlled from specially developed software and left to complete test unattended save for the loading of new test bar.
This purpose written application runs under WinNT on a Pentium >600MHz PC with 64Mb RAM / 100Mb hard drive free space. It provides a user-friendly visual tool for the configuration and operation of hacksaw tests. All the necessary parameters of the blade and the tests are stored with a suitable file name, in a MS Access compliant database. Results can be viewed and printed out in the standard report format.
Additional useful features in the software are a display of test cutting times in real time graphical format whilst the test is in progress and the ability to search the test results database, via any field, to pick out individual or groups of tests. All of this data can be saved to a file in MS Excel format for more in depth analysis and presentation.
The blade is manually fitted into the machine bow at the prescribed attitude and secured under a specific stress by means of a screw-tensioning device. According to the style of blade being tested a "pack" of standard test bar (comprising of strips of 25mm wide 305 type austenitic stainless steel on edge) is clamped in the machine vice. The blade is then set to make repeated "cuts" through this media and the "number of strokes to cut through" is logged. This media and procedure produces an accelerated wear test and each blade must complete a predetermined amount of work as set by the number of cuts through the bar.
The operator records the stroke/cut on the manual version and can either manually calculate the wear rate and total time or enter the details into a spreadsheet software for a quick calculation and graphical display.
With the automatic version the wear rate and total cutting time for the test is as prescribed by BS1919 and are calculated automatically at the end of the test and there is an option to print these out in the form of a report sheet and are compared with the pre-stored limits laid down in BS1919.
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