A Functional Test Bench for Power Tools

Author(s):
-
Mondeep Duarah - Captronic Systems
Sukesh Kumar - Captronic Systems

Industry:
Machines/Mechanics

Products:
LabVIEW

The Challenge:
Designing and developing a single test bench to inline functionally test commercial power tools.

The Solution:
Using National Instruments sensors, signal conditioning, and data acquisition devices to create load on the power tool and acquire various parameters such as current, voltage, vibration, rpm, temperature, and sound.

Functional Test Using Flexible, Powerful NI Products
We selected LabVIEW to develop a functional power tool test, using an NI SCXI-1530 device as the front end for vibration and noise, an NI SCXI-1102 device for conditioning temperature data, and an NI SCXI-1125 device to measure the voltage (230 VAC) and current drawn by the tool. We installed a computer with an NI PCI-6527 card to control the sequence of operations. The operator interfaces use LabVIEW graphical support, and the LabVIEW Report Generation Toolkit and LabVIEW SQL Toolkit create custom reports.

To use the system, a user logged in with a valid password. Prior to the load test, the user selected the tool to be tested and enters the tool serial number. The load test screen displayed the present system status.

We performed the functional test by placing the tool on a holding fixture and conducting the test in two parts – the first without applying any load to the tool, and the second by applying load onto the tool. The no-load test measured the starting current, running current, rated voltage, no-load power, vibration, noise, speed, and temperature of the tool when no load is applied to it.

The load test involves running the tool for a specified time without load, gradually applying the specified torque through the eddy-current-based dynamometer, and measuring running current, power, voltage, vibration, noise, speed, torque, and rise in temperature on the housing of the tool.

We used the Magtrol WB-20 eddy current dynamometer, capable of generating 20 Nm torque, as the load. We connected the dynamometer to the corresponding tool through a coupler and gradually applied the set torque to the tool.

System Configurations Based on Multiple Tools
The test system is intended to test different kinds of tools, such as drill guns, angle grinders, miniangle grinders, and marble cutters, to determine whether the tool is meeting specifications. Each type of tool is mounted on a different fixture. Some of the sensors, such as thermocouples and accelerometers, are attached to the fixture in order to make necessary contact to the power tool. Other sensors, such as a Hall Effect sensor (LEM), a microphone, infrared temperature sensor, proximity sensor, and the dynamometer, are common to the bench.

We generated torque using a Magtrol WB-20 eddy current dynamometer, which is controlled by the NI PCI-6035 E analog output data acquisition card. A B&K accelerometer measured vibration, and a B&K Falcon microphone measured sound level. A National Instruments SCXI-1530 signal conditioning device conditioned the ICP-based accelerometer and microphone signals.

While executing load test, t-type thermocouples mounted onto the fixtures measured the rising power tool temperature. The speed sensor and LVDT (part of the dynamometer) gave the corresponding tool speed and torque values, which were acquired and logged into an MS Access database. The NI PCI-6527 digital I/O card defined the control strategy, which included turning the tool on and off, controlling the water cooling dynamometer circuit, turning on the alarm, reading back the emergency conditions, and shutting down the bench.

Hardware Functions Together to Create Flexible System
Each hardware component is assigned a functional role:

Hardware	Functional Role
SCXI-1000	Chassis for mounting SCXI modules
SCXI-1530	Conditioning accelerometer and microphone inputs
SCXI-1125	Isolated analog input module
PCI-6035E	Multifunction data acquisition card for acquiring analog signals
PCI-6527	Digital I/O card for defining control strategy
T-Type Thermocouples	Tool casing temperature rise measurement
Endevco 751/10	Accelerometer for measuring vibration
Falcon Microphone 4188	Acquires the sound level generated by the tool
Isotron Amplifier	Microphone preamplifier
Magtrol WB-20	Eddy current dynamometer for generating torque
Fixtures	Different fixtures for each type of tools
Infrared Temperature Sensor	To measure rise in chuck temperature
Hall Effect Sensors (LEM)	To measure current drawn by the tool

User priority includes administrator, engineer, and operator. Operators are restricted from configuring tool parameters and diagnostic operations. Engineers can use these features, but are restricted from creating new users. Administrators are allowed to use all system features.

The diagnostic features are available only for engineers and administrators. This feature helps to troubleshoot the system in case of any system failure.

The result window appeared at the end of the test, and the alarm indicated test completion with a buzzer.

Because the user defines reporting criteria based on the tool, the tool serial number tracked the tool parameter details in an historical database. The database can be exported to spreadsheet-format reports.

Customized Test at One-Third of the Cost of Noncustomized
We implemented a high-performance, functional test bench at a power tool manufacturing unit. With this system, the testing accuracy has become better than the previous manual testing methods, which were error-prone. The tool test parameters can be tracked very easily based on tool number, which was not possible before. This was all accomplished at a much faster rate of testing, with one test bench for different types of tools at one-third the cost of a ready-made tool tester.

For more information, contact:
Captronic Systems Pvt. Ltd.
#19, Alif Arcade 7th Main Road
I Block Koramangala
Bangalore-560034 Karnataka
capsys@vsnl.com

Browse All Case Studies »