Michael Chao, Ian King, Esther Lee, Shengnan Xiang (Duke University)
Figure 1. EasyShrink machine
ABSTRACT
This project creates a safe and efficient approach for employees with disabilities at OE Enterprises to shrink wrap nutritional supplement bottles. Application of such seals maintains product purity and prevents tampering. The device physically isolates the heat gun from its users within a wooden insulating box. Pushing a single button activates the heat gun and motorized turntable for a preset time interval. Because the EasyShrink offers a protective and simple solution, many employees can now perform the shrink wrapping task without fear of burn injuries, and they generate consistently high quality results in the process.
BACKGROUND
OE Enterprises is a community rehabilitation organization that provides occupational opportunities to individuals with disabilities. An offered service entails applying shrink wrap to nutritional supplement bottles sourced from another company. This process normally involves directing hot air at PVC seals using a heat gun held in one’s bare hands. Commercial heat guns have uncovered metal nozzles that reach high operational temperatures and generally lack user protection equipment. Many employees have suffered serious burns from heat gun-related accidents and are thereby unwilling to engage in shrink wrapping. Consequently, the few staff members possessing proficient manual dexterity exclusively undertake such roles, which hinders output expansion and limits their time supervising other tasks.
PROBLEM STATEMENT
This project aims to provide individuals with disabilities a device for safe and efficient application of shrink wrap onto nutritional supplement bottles.
DESIGN
In considering device design, safety always remains the top priority. Physically isolating device components greatly improved user protection. The heat gun was held stationary to avoid unnecessary movement and oriented at a specific position relative to the bottle for optimal shrink wrapping results. To enhance client accessibility, emphasis was placed on accommodating different bottle sizes with minimal adjustment and also incorporating an automated interface. The EasyShrink is depicted in Fig.1, and its various components are detailed below.
Heat Gun
The Master Appliance heat gun (Fig. 2) operates at 120V and 14A over a temperature range of 500 to 750ºF, emitting a powerful source of hot air to shrink wrap bottles. As the most dangerous device component, it is carefully contained within an insulating box. For convenient insertion or removal, the heat gun is positioned upside down, with its handle protruding from a slit opening on the insulating box’s lid.
Figure 2. Interior of insulating box with heat gun and aluminum sleeve
The wooden insulating box prevents accidental contact with the hot components. Its lid connects to the body of the box with a hinge and can be opened. A slit cut into the lid allows the heat gun wiring to exit the box and room temperature air to enter as the heat gun blows out hot air. A small wooden block (Fig. 2) attached to the bottom of the box enables the heat gun to rest at a proper height, so its nozzle aligns with a circular opening. This aperture in the side of the box (Fig. 3) projects the hot air towards a motorized turntable. Handles are attached to the box for ease of transport.
The aluminum sleeve fits securely into the insulating box’s circular opening (Fig. 2). It stabilizes the heat gun and orients the nozzle to disperse air flow in a horizontal, outward direction.
Figure 3. Turntable setup
Motorized Turntable Platform
The turntable consists of a main platform that rotates on a single axis attached to the motor shaft. The air flow can thereby hit one side of the bottle at any given time and yield uniform heat application on the bottle’s top and sides.
The bottle rests upside-down on a puck-shaped platform centered on the turntable (Fig. 3). The puck-shaped platform has a specific height and a diameter smaller than that of the bottle to allow the shrink wrap to rise above and envelope the bottle lid when properly positioned during heat application. This set-up eliminates the need for height adjustments to accommodate the different bottle sizes relative to the insulating box. In the upside-down position, all bottle lids are held at the same height. The puck is removable and held in place by two polarizing pins.
Figure 4. Motor box
The motor (Figs. 4) controls the turntable, thereby eliminating the need to turn the bottle manually. Keeping one’s hands free during the shrink wrapping process decreases the likelihood of contact with hot air flow. The turntable rotates at a constant speed of 12.5 RPM. The right angle motor operates on 5V (DC) and 90 mA, which is supplied by the interval timer kit.
Wooden rods serve as stabilizers (Fig. 3) by resolving the inherent difficulty of balancing the upside-down positioning of the bottles. The rods also function as guides for the centering of the bottles on the platform. These supports slide smoothly into designated holes drilled at three equidistant positions around the turntable.
To further increase stability when accommodating large bottles, a circular wooden collar (Fig. 3) can be attached to the top of the wooden rods. The bottle placed within the collar does not tip during device operation.
The metal control box (Fig. 5) houses the electrical components of the timer and relay system.
Figure 5. Control box
A Velleman adjustable interval timer kit controls the motor and heat gun. By pressing the start button located on the control box, the timer activates the motor and heat gun for a predetermined time, and then automatically switches both off once the specified period elapses. The time interval can be adjusted with a knob on the control box (up to 35 seconds). The timer activates the heat gun by switching on an Omron AC relay within the control box.
The AC/DC adapter converts the 120V, 60Hz AC current to a 15V DC current that powers the timer/relay/motor system.
The heat gun, motor, and timer system all connect to a surge protector and are controlled by a single on/off switch. Turning the switch “on” activates these components. When the device is not in operation or during emergency situations, switching off the surge protector deactivates the entire system.
DEVELOPMENT
In a preliminary prototype, the user was still isolated from the heat gun and any hot components by a wooden insulation box. The heat gun was also immobilized, and directed heated air downward to the bottle and shrink wrap instead of from the side. The main issue posed by vertical heating was the bias of hot air to the top of the shrink wrap compared to its side, which resulted in inconsistent sealing. Heating the shrink wrap from the side proved successful but did not prevent it from rising off the top. To bypass this issue, an upside-down configuration was implemented. This new approach in combination with a standardized motor and heating system produced the current EasyShrink model.
EVALUATION
The EasyShrink was primarily designed for user safety. As such, OE Enterprises has utilized this device over the course of three-and-a-half months without any accidents or injuries. Additionally the device endures daily use shrink wrapping bottles for six hours with minimal maintenance, demonstrating its durability.
Figure 6. OE's daily bottle production without and with EasyShrink
It was also important for the device to create a sense of security for the operator. The employees must be willing to use the EasyShrink confidently and without fear of injury. After its debut, the employees have been eager to use the device and several have been performed the shrink wrapping task with excellent results. “Nobody is afraid of using [the EasyShrink]. Actually, everybody wants to use this,” said James Hurst, an OE staff member who oversees the shrink wrapping task. “This is the best thing. It’s helped us out a lot, and we want another one.” Regardless of size, the device can shrink wrap each bottle within 20 seconds. Since its induction, the EasyShrink has increased total bottle output from 250 a day to 700 a day, nearly tripling the production rate as shown in Fig. 6. In addition, multiple employees can perform the task with ease, and a few veterans may now work independently without supervision.
Shrink wrapping quality was assessed based on smoothness and tightness on the bottle’s top and sides, its positioning on the bottle relative to the lid, and uniformity of orientation. The shrink wrap must have little or no wrinkles on the top or sides, be flush as possible with the bottle surface, cover the lid top and gap between the lid and bottle body, and be aligned straight with the bottle. Operating the heat gun by hand generates significant variations in quality between bottles. The EasyShrink successfully overcomes this lack of consistency, producing high quality results.
DISCUSSION, COSTS, AND CONCLUSIONS
The EasyShrink enables employees at OE Enterprises to perform the shrink wrapping task safely and effectively, thus increasing their workplace opportunities. Also, staff workers previously occupied by this responsibility can now allocate their time and efforts elsewhere, if needed.
Operation has been whittled down to the following actions: positioning the shrink wrap on the bottle, placing/removing the bottle from the turntable, and pushing a button for device activation. This allows the user to shrink wrap hands-free and reduces the likelihood of accidental contact with hot components. Simplicity in setup and utilization method enables a wide range of users to complete the task, while simultaneously increasing throughput efficiency.
The upside-down orientation of the bottles eliminates any height adjustment to accommodate different sizes. Shrink wrap does not need to be meticulously arranged on the bottle; once the bottle is put in place, the seal is forced into a level and even position. Also, the materials used to build the device are all relatively cheap and easily attainable. The design itself is fairly reproducible with access to a machine shop and someone with knowledge of basic circuits. On the downside, the insulating box’s circular opening exposes the metal sleeve, which can heat up during device operation.
The most expensive component of the EasyShrink was the heat gun, costing $114.07. Electronic components – relay, AC/DC adapter, surge protector, motor, and timer – totalled $66.43. Insulating box materials – wood, screws, handles and hinge – required $50. This puts the replacement cost of one device at $230.50 ($116.43 sans heat gun).
In conclusion, the EasyShrink has empowered OE Enterprises employees with disabilities to perform a task they previously were unable to do. Fear of injury has also been alleviated. Employees and supervisors at OE Enterprises have warmly received the device and given positive feedback, commenting that the Easyshrink allows more people to do their job and has tremendously increased productivity and product quality.
ACKNOWLEDGEMENTS
Special thanks to Dr. Laurence Bohs and Veronica Rotemberg for advising us throughout the design process, Steve Earp for assistance in machining device components, and our clients at OE Enterprises for their helpful input. This work is supported by the National Science Foundation under Grant No. CBET-09672221 and a NISH/DEED grant for Assistive Technology Development.
PRIMARY AUTHOR: Ian King; 3751 Bethlehem Rd. Springfield, TN 37172