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| Specifications for the TCA Series of |
| Tension/Compression Testing Machines |
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| Revised: Feb. 3, 2002 |
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| Introduction |
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| The TCA series of low cost bench mounted tensile testers was designed for test applications requiring tension or compression capabilities but which still demand the accuracy usually available in much higher priced testing machines. These machines feature a limited stroke length mechanical loading actuator for applications not requiring the long stroke length capability and larger clearances featured in our TTD and TTS series of testing machines. The machines available in the TCA series consist of the following models and their testing capacities: |
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| TCA-IOKN (10 kN / 2,200 lb Capacity) |
| TCA-5KN ( 5 kN / 1,100 lb Capacity) |
| TCA-2KN ( 2 kN / 500 lb Capacity) |
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| The TCA series feature a short stroke loading actuator and an adjustable crosshead which can be adjusted vertically on a pair of parallel chrome plated solid steel loading posts. The loading actuator is driven by a DC gearmotor drive system. Its motion is controlled by front panel mounted Down/Up and Stop/Start switches. The test speed is set between 0 - 100 % of the maximum speed using a front panel mounted single turn potentiometer. The nominal speed range is between 0 - 100 mm/min (0 - 4.0 in/min). Figure 1 shows an overall view of the TCA-2KN machine. Figure 2 shows a closeup view of the load cell and the optional roller type tensile grips mounted on the machine. Figure 3 shows the Power Control and Motor Control switches on the front panel. Figure 4 shows the digital display used for load indication. Figure 5 shows the major parts locations of these machines and their dimensions. |
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| For loading applications, the lower loading grip to be used with the system is mounted on the loading actuator. The top grip is attached directly to the machine load cell which is an electrical device which is used to determine the load applied to the system. The load cell is attached to the lower surface of the crosshead. The load cells used on the TCA Series are from the same line of high precision full Wheatstone bridge load cells used on the higher priced series of ATM's machines. The crosshead may be vertically adjusted along the loading posts by loosening off the socket head cap screws which compresses the crosshead in place on the vertical loading posts. |
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| Motor Control System |
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| The motor control system for the TCA series of testing machines utilizes a 90 VDC permanent magnet gearmotor which is coupled to the input of the loading actuator with a timing belt drive. The gearmotor is lubricated for life and should not require servicing in normal operation. The motor control is provided by a solid state DC motor speed controller. |
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| The electrical control circuitry to control the loading actuator consists of the following control elements. The Down/Up selector switch setting determines the movement direction of the loading actuator when the motor is running. The Stop/Start selector switch will start the motor which drives the loading actuator at the speed set by the Speed control potentiometer. The loading actuator speed is scaled from 0 - 100% from the minimum to maximum Speed potentiometer setting. The Speed potentiometer adjusted fully clockwise will result in 100 % of the maximum speed (ie. 100 mm/min or 4.0 in/min). With the potentiometer rotated fully counter clockwise the motor speed is off. |
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| Load Display System - General Information |
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| The microprocessor display board utilizes a precision DC conditioner for the functions of excitation and amplification of the load cell signal. In addition, the system allows for the scaling and display of the calibrated load cell signal in one of three Operator chosen Engineering Units, continuous monitoring of the maximum compressive and tensile loads applied to the load cell, monitoring the status of the upper and lower crosshead travel limit settings, and the operation of taring or zeroing of the load cell if any changes in the grips or test setup have been made. The load cell signal is measured using a 12 bit A/D converter whose sampling rate is controlled by an on board microprocessor. The microprocessor also serves the |
| functions of monitoring the front panel push button switches, monitoring the test maximum and minimum load cell signal, and monitoring and indication of the load cell capacity limits. |
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| Detailed Description of Load Display System |
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| The load display system was designed to overcome some of the shortcomings of the various displays which are commercially available for amplification and display of load cell signals. These displays typically calculate and display the maximum and minimum loads at the same low speed rate of approximately 3 / second (ie. 3 Hz). The ATM display externally updates at approximately 3 Hz but internally updates at a conversion rate of over 800 Hz. The high speed conversion rate ensures that peak loads are accurately calculated at the time of sample failure which is usually a high speed event. Displays which convert at a rate of approximately 3 Hz. tend to inaccurately calculate the failure load in situations of rapid load changes. |
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| The ATM display board has also been designed to allow Operator input of lower load limits than the load cell capacity for test situations where a test is to be stopped after a preset test load has been applied. If the preset load limit is reached the crosshead motion will stop. The load can then be decreased by reversing the test direction. The Operator can set the display to indicate load in Units of lb, kg, or N for test applications requiring different testing Units. The Operator may also tare the load cell to zero out a, non-zero load reading due to load grips setup changes or during the initial system warmup. |
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| Main Display Function Key Descriptions |
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| A) Single Key Input Operations |
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| The single key input operations are described as follows: |
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| a) Cal Check |
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| A quick calibration check of the load cell may be performed by use of this key. Load cells provided by ATM are of a full Wheatstone bridge type which utilizes four strain gauges for measurement of the load. Pressing the Cal Cheek switch places a resistor in parallel with one of the four strain gauges which results in an unbalanced bridge and a known load cell output reading. The Operator can then |
| compare this reading to that taken when the load cell was initially calibrated. |
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| b) Set Units |
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| The Set Units key switch allows the Operator to select between the Units lb, kg, or N for load display. Pressing the Set Units key will cause the red light emitting diode (LED) next to the indicated Unit to turn on and the displayed reading to be updated to the selected Unit. |
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| c) Max |
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| The Max key switch is used to display the internally stored maximum tensile load or smallest compressive load (ie. closest to zero load) since the Clear button was last pressed. This load is calculated by sampling the load cell signal at over 800 Hz. The load will be displayed in the Engineering Unit which has been selected. |
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| d) Min |
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| The Min key switch is used to display the internally stored maximum compressive load or smallest tensile load (ie. closest to zero load) since the Clear button was last pressed. This load is calculated by sampling the load cell signal at over 800 Hz. The load will be displayed in the selected Engineering Units. |
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| e) Clear |
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| The Clear key switch is used to reset the display to start recording the maximum and minimum load cell readings. This switch would typically be pressed before the start of a test to ensure that the correct Maximum and minimum load readings have been stored during a test. |
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| f ) Tare |
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| The Tare key switch is pressed to zero the load cell if a change in the loading grips arrangement has been made or if the system electronics are in the warmup period. This is a software tare and is not recorded by the microprocessor display board memory when the AC power switch is turned off. |
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| B) Combined Key Operations |
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| The four combined key operations are used to change the Operator settable load limits. If these limits are exceeded during a test, the crosshead movement will stop and an Error messsage will be displayed. If the maximum load limit or the upper crosshead travel limit setting is reached the Error message E HI will be displayed. If the minimum load limit or the lower crosshead travel limit setting is reached the Error message E LO will be displayed. The combined key operations to change the load limits are described as follows. |
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| a) Max and Clear |
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| Simultaneously pressing and holding the Max and Clear key switches will increment the Operator settable maximum load limit from the present setting. |
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| b) Max and Tare |
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| Simultaneously pressing and holding the Max and Tare key switches will decrement the Operator settable maximum load limit from the present setting. |
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| c) Min and Clear |
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| Simultaneously pressing and holding the Min and Clear key switches will increment the Operator settable minimum load limit from the present setting. |
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| d) Min and Tare |
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| Simultaneously pressing and holding the Min and Tare key switches will decrement the Operator settable minimum load limit from the present setting. |
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| Optional Features |
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| Additional features may be added to the TCA Series of machines for special applications. Some of these options are listed as follows: |
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| a) Safety Shields for Front and Rear (Option TCAxxxx.SAF) |
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| The TCA series machines may be supplied with clear safety shields for the front and/or rear working area of the systems. The safety shield package consists of two side panels and two front hinged panels of 3/8 in (9.5 mm) thick clear polycarbonate sheet. This design ensures a large enclosed working distance for specialized setups. The side panels are approximately 4 in (10 cm) wide and do not open. The hinged doors are secured in place by two sliding bolts. |
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| The safety shield package includes two hinged door panels, two side panels, and mounting hardware. A complete package is used to enclose each of the front and rear working areas of the system. Price of each package includes factory installation of the safety shields on the machine when ordered with the TCA series machine. |
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| b) Bellows Covers on Actuator (Option TCAxxxx.BSC) |
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| For dusty environments, ATM can supply the TCA Series machines with a bellows cover over the Loading Actuator rod to prevent dust from coating the linear bearing guiding the actuator rod through the top of the base. This option is a factory installed modification and should be ordered with the system. |
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| In addition to the listed options, ATM can provide other modifications to the standard machines to accommodate specific requirements. Some of these options included safety door mounted limit switches to shut off the motor, increased working distance between the loading posts, longer actuator travel length, and other speed ranges. Please contact us with your additional requirements. |
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| Accessories |
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| A wide range of accessories such as test grips and fixtures can be provided by ATM to allow testing of many different sample types or customer products. Please contact us with your requirements for test grips and/or custom designed fixtures for testing your products. |
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