Transcript
Design & Engineering Services
DIRECT CURRENT HANDHELD INDUSTRIAL SANDERS ET12SCE1030 Report
Prepared by: Design & Engineering Services Customer Service Business Unit Southern California Edison August 2012
Direct Current Handheld Industrial Sanders
ET12SCE1030
Acknowledgements Southern California Edison’s Design and Engineering Services (DES) group is responsible for this project. It was developed as part of Southern California Edison’s Emerging Technologies Program under internal project number ET12SCE1030. DES project manager Neha Arora conducted this technology evaluation with overall guidance and management from Paul Delaney. For more information on this project, contact
[email protected]. Disclaimer This report was prepared by Southern California Edison (SCE) and funded by California utility customers under the auspices of the California Public Utilities Commission. Reproduction or distribution of the whole or any part of the contents of this document without the express written permission of SCE is prohibited. This work was performed with reasonable care and in accordance with professional standards. However, neither SCE nor any entity performing the work pursuant to SCE’s authority make any warranty or representation, expressed or implied, with regard to this report, the merchantability or fitness for a particular purpose of the results of the work, or any analyses, or conclusions contained in this report. The results reflected in the work are generally representative of operating conditions; however, the results in any other situation may vary depending upon particular operating conditions.
Southern California Edison Design & Engineering Services
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Direct Current Handheld Industrial Sanders
ET12SCE1030
INTRODUCTION Compressed air is very expensive to create and maintain and is often an inefficient means to operate portable air tools in manufacturing facilities. One of the common applications of compressed air is to fine-finish products at industrial and commercial facilities. The random orbital sander is a handheld tool that uses compressed air for its operation in wood manufacturing, auto body shops, sheet metal shops, and fiberglass manufacturing. However, these tools can prove to be more efficient and economical if run on electric power. Such sanders are called “electric sanders”. This field assessment evaluates the energy efficiency potential of electric random orbital sanders in comparison to pneumatic random orbital sanders for manufacturing plants. In addition, overall performance and features such as noise reduction, lightweight and throughput of this technology are factored in this evaluation.
BACKGROUND The random orbital sander is a handheld power tool that combines the advantages of belt sanders with portability. The sanding action is a random orbit that proves very useful in fine finishing product surfaces, especially around curves and hard to reach places. Traditionally, random orbital sanders are pneumatic and use compressed air to operate. These sanders do not contain any motor and the pressure of compressed air rotates the sanding disk. Modulation of compressed air supply to the tool controls the speed of the sanding disk. The unique random orbit sanding pattern is the result of simultaneous spinning of the sanding disk while creating an ellipse. This motion ensures that no part of the abrasive material or the sandpaper travels the same path twice and the tool does not leave swirl marks on the product surface. This makes it useful when sanding or finishing two pieces that meet at a right angle. Random orbital sanders use sandpaper disks that are attached to the tool using either a pressure sensitive adhesive or a Velcro hook and loop tape. Some models are also equipped with a dust collection system. On such models, a vacuum effect sucks sanding dust through holes in the paper and pad and feed it to a bag or a canister. A typical compressed air system in a wood manufacturing plant consists of a 50-75 horsepower rotary screw single stage compressor, a storage tank for compressed air, a filter, 2 inch supply pipe from the compressor and a 1 inch pipe for the compressed air supply to the sanders. The operating pressures of these compressors usually range within 100 to 140 pound-force per square inch gauge (psig). Electric random orbital sanders are an enhancement over traditional pneumatic sanders and use electric power to operate. These sanders contain a brushless Direct Current (DC) motor that provides smooth operation and reduces noise level. Electrical supply to the sander is provided via a plug and receptacle. The Alternating Current (AC) power passes through the transformer-rectifier box of the sander and is converted to DC power. This DC power runs the motor of these sanders and modulation of DC power varies the speed of the sander. Sanding action of electric sanders is very similar to the pneumatic sanders. Therefore, the look and feel of the end product surface is the same.
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PROJECT DESCRIPTION This field evaluation occurred at a wood manufacturing plant located in Paramount, California. This site was selected because it uses random orbital sanders on a large scale to fine finish wooden doors and cabinets. Random orbital sanders are used at a constant rate during the regular shift hours of this facility. The existing pneumatic sanders used at the test site were 5 inch sanders with a 3/16 inch random orbit. Maximum speed of these sanders is 12,000 Revolutions Per Minute (RPM) with an air pressure of approximately 135 psig (supply pressure to 12 sanders). The electric sanders tested at this facility were of same physical dimension with a maximum speed of 10,000 RPM. Nominal power draw of these electric sanders is 90-240 volts AC and the supply power to the sander is a constant 24 volts DC. Two pneumatic sanders were replaced by two electric sanders to evaluate the energy savings potential of electric sanders. Monitoring of the facility occurred before and after the installation of electric sanders. The difference in electric consumption during both monitoring periods is the energy savings potential of electric sanders. In addition to electric consumption, other parameters such as airflow, pressure, and Cubic Feet per Minute (CFM) were monitored to observe impact on the consumption of compressed air at the facility when electric sanders were in use. These parameters were recorded at: Point of entrance of compressed air to the facility next to compressed air storage tank. End use point at which air is distributed to the sander stations. This set-up enables detection of leaks in the system and any variation in demand caused by air leaks that can be adjusted during energy savings calculations. This methodology provides accurate results for air usage at the facility before and after the installation of electric sanders. Figure 1 displays the monitoring setup.
FIGURE 1. MONITORING SETUP FOR COMPRESSOR AND END USE AT TEST FACILITY, RESPECTIVELY
The facility was monitored for its energy and air use for a month (baseline monitoring) before changing out the sanders. After the completion of baseline monitoring period, Southern California Edison Design & Engineering Services
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pneumatic sanders were replaced with electric sanders. Electric sander monitoring used the same test setup. The electric sanders ran slower compared to their pneumatic counterparts and could not keep up with the production demand. This resulted in a 20% production rate loss. As a result, use of electric sanders was discontinued. To investigate further, two additional electric sanders (different manufacturer/model) were tested. However, both sanders were rejected due to excessive heat and ergonomic issues. Because of the challenges associated with the electric sanders tested, none of them were used for more than a few hours and the energy savings potential could not be calculated for this technology.
PROJECT FINDINGS Overall, testing of three different electric sanders revealed that this technology is still developing and has a long way to go before it can be applicable for high volume manufacturing applications. Electric sanders have the promise to reduce electrical consumption by decreasing the use of compressed air, however, they still need to work on and develop features to support all applications within commercial and industrial market segments.
RECOMMENDATIONS Based on these results, it is recommended that this technology be assessed again at a later time when the technology has fully developed and has overcome the shortcomings listed in this report. Although random orbital sanders are widely used in many applications such as wood manufacturing, auto body shops, sheet metal shops, and fiberglass manufacturing etc., this technology was tested at a wood manufacturing plant only. Therefore, it is recommended that this technology be tested and evaluated for its energy efficiency potential for other applications (listed above) as well. It is also recommended that another Emerging Technologies (ET) sub-program Technology Development Support (TDS) engage the customer as well as the manufacturers to understand and possibly address the following electric sander concerns: 1. 2. 3. 4. 5.
Increased weight Reduced Revolutions Per Minute (RPM) Reduced ergonomics Increased heat on the handles Improved torque characteristics at variable loads (if applicable).
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