(on behalf of a UKSMA Member)
- Model: LTM1-100
- Manufactured: 2010
- Price: £3,000
DESCRIPTION (Automatic Machine)
This automatic, computer controlled machine enables rapid, precision measurement of a broad range of compression and extension springs. The machine incorporates a wide array of standard features designed to make spring load testing both efficient and accurate. The LTM1 comprises 4 main elements:
- Rigid loading frame.
- Measuring system incorporating state-of-the-art load and length transducers.
- Industry standard embedded controller.
- Custom written control software.
Accurate spring load testing can only be accomplished if the basic loading frame (including the load cell system) is rigid and does not deflect under the applied loading from the spring under test. Although some calculated compensation can be applied on computer-based testers, the adjustment can never be exact under all test conditions. The amount of compensation must therefore be kept to an absolute minimum by careful attention to the load frame design.
The bench mounted loading frame on the LTM1 is of the proven “C” type design, comprising two substantial guide pillars, which precisely align the aluminium moving crosshead.
The loading platens are made from steel hardened to 58 Rc min. to minimise wear and maintain accuracy over many years of continuous operation. After hardening, the platens are ground, and lapped to minimise out-of-flatness and a built-in adjustment mechanism enables the platens to be exactly aligned and fixed for parallelism at the assembly stage.
In order to facilitate load testing of extension springs, a set of standard loading hooks are fitted to the machine. The loading pins on which the spring hooks are seated are easily interchanged to enable the use of specially machined pins for particular spring hook dimensions.
All these loading frame design features combine to provide absolute confidence that the load test results obtained are to the highest possible standard of accuracy.
At the heart of any spring load tester are the load and length measuring systems, and if measurement accuracy is the goal, no compromise can be accepted with the components used. In particular, budget load cells designed for dead weight measurement are not acceptable in spring tester applications.
On the LTM1, spring load is measured using a high precision load cell mounted to the bottom of the loading frame. The type of load cell selected was specifically chosen for its rigidity and high level of insensitivity to non-axial spring forces. The result is a machine that minimises the effect of spring position and orientation upon the measured load.
The output signal from the load cell is fed to the computer via a single range amplifier and a 20-bit A-D converter. This combination provides stable load reading over a wide temperature range.
The loadcell system on the LTM1-100 has a capacity 100N and has a calibrated accuracy of 0.5% of reading from 1.0% to full scale giving a working range of 1-100N. This arrangement provides the highest possible accuracy across the widest possible load range on a single machine. The display software, enables the load to be displayed in units of either N, Kg, gm, or lbf.
The load cell incorporates a mechanical overload device to provide a high level of damage protection due to incorrect use.
Spring length is measured using a 5µm (~0.00025inch) digital linear transducer. The type chosen was developed for use on positioning systems of CNC machine tools and is fully resistant to grease, cutting fluids and dirt. The LTM1 is therefore suitable for use in industrial environments. The output signal from the transducer is fed to associated processing and interface electronics to produce a displayed resolution of 10µm (~0.0005 inch.), for accurate setting and measuring of spring length. The operator can select the spring length to be displayed in either millimetres or inches
The motive power to drive the crosshead on the LTM1 is provided by a hand wheel, driving a rack and pinion, enabling fast positioning of the crosshead. The weight of the crosshead is counter balanced a gas spring giving a smooth damped operation.
All manual IST spring load testers come complete with an embedded controller that is used to control the operation of the tester and to analyse, display and store test data. An optional printer (dot matrix) can be supplied as standard with the machine enabling rapid printout of results in the form of data and statistics. The printout is personalised with your own company details appearing at the head of each test certificate.
The controller has a 240 x 128 pixel backlit graphics display enabling easy to read operation.
All manual operator controls and data input are entered via the 16 key keyboard. Apart from the on-off switch no other user manual controls are present.
Loading frame deflection is compensated for by the controlling software, which provides the highest possible accuracy when measuring high rate springs.
The unique Menu driven programming language - specifically designed for spring load testing applications provides the operator with simple and quick set up for any spring part.
The major features of the software are described below:
- All data and control inputs are made via the keyboard to call up menus and commands. Each current command key and its function are displayed on the graphics display to provide the operator with a constant monitor of the machine status.
- The operator may tare the spring and/or jig weight at any time.
The length reading may be zeroed or pre-set at any crosshead position. This facility enables the operator to easily set the length display when spring jigs or hooks are being used.
- The software enables any combination of units to be used, such as kgf for the load with the spring length in inches.
The operator can set two toleranced test lengths. This then enables automatic spring rate measurement.
- All measured test parameters may be toleranced with max. and min. values. During a test, any measured parameter found to be outside the set tolerance band is indicated by the reading and associated tolerance being highlighted on the LCD. The calculated Cp, Cpk, max, min, x(bar), Std dev, number Hi and number Lo are also calculated against each toleranced test position.
- A spring counter is displayed on the screen to register the number of springs tested from a current batch.
- During a test run the computer automatically backs up the current test data and macro program so that should a power failure occur the results up to that point will not be lost. On resumption of power the data and machine can be reset and testing continued.
- The optional printer (Dot matrix) and associated software enables the test data and statistical data to be printed out as a test certificate. This routine has the user-selectable option of printing out any or all of the following, the header information, tolerances, data or statistics.
Important machine siting details
The very low capacity of this machine means that it is sensitive to environmental conditions such as vibrations and fast air movements. Thus it is important that it is sited on a sturdy bench and floor and away from sources of external disturbance.
- Load Range: 1-100N / (0.2-22lbf)
- Load Resolution: 0.001N / (0.0002lbf)
- Maximum Length: 300mm / (12inch)
- Length Resolution: 0.01mm / (0.0005inch)
- Repeatability and Accuracy on Load: to BS EN ISO 7500-1:2004: Grade 0.5
- Repeatability and Accuracy on Length: ±0.03/300mm travel / (±0.0015/10inch)
- Platen Diameter: 60mm / (2.3inch)
- Machine Dimensions (excluding printer): 400 wide x 230 deep x 550 high mm (16 x 9 x 22 inch)
- Machine Weight: 25kg / (65lbf)
- Finish: Natural/Grey/Black
Power Requirements: 110/230, 1amp, 50/60Hz
Temperature Range: 10 - 35 Deg C
Relative Humidity: less 80% (non condensing)
The high precision of this machine will enable calibration to BS EN ISO 7500-1:2004: Grade 0.5. However, this must be carried out after installation at the customer works by an independent calibration company at the customer’s cost.
Calibration is accomplished via a specific routine in the operating software. Access to the routine to enable adjustment is only available via a security password system.