Engineering Report Denman Island Chocolate CBWS

Oliver Terry, Mike Viala

9/7/2015

Engineering report for the design, manufacture, and testing of the CBWS Chocolate Bar Wrapper Stamper designed and constructed for Denman Island Chocolate.

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Table of Contents Executive Summary ....................................................................................................................................... 3

Introduction .................................................................................................................................................. 4

Prototyping and Concept Development ....................................................................................................... 5

Design Description ........................................................................................................................................ 6

Overview ................................................................................................................................................... 6

Detailed Description ................................................................................................................................. 7

Motion................................................................................................................................................... 7

Control ................................................................................................................................................ 11

Stamping ............................................................................................................................................. 14

User Interface ..................................................................................................................................... 15

Use ...................................................................................................................................................... 15

Evaluation ................................................................................................................................................... 16

Overview ................................................................................................................................................. 16

Design Issues ........................................................................................................................................... 16

Next Steps ............................................................................................................................................... 16

Conclusion ................................................................................................................................................... 17

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Table of Figures Figure 1: Prototype Wrapper Hopper ........................................................................................................... 5

Figure 2: The CBWS ....................................................................................................................................... 6

Figure 3: Cylinder Valve Manifold ................................................................................................................. 7

Figure 4: Suction Head .................................................................................................................................. 8

Figure 5: Suction Head Suction Cups ............................................................................................................ 8

Figure 6: Hot Stamper Pancake Cylinder ...................................................................................................... 9

Figure 7: Vacuum Generator ......................................................................................................................... 9

Figure 8: Input Hopper Platform ................................................................................................................. 10

Figure 9: Linear Screw and DC Gearmotor .................................................................................................. 10

Figure 10: Pneumatic Reed Cylinder Switches ............................................................................................ 11

Figure 11: Upper Platform Limit Microswitch............................................................................................. 11

Figure 12: Lower Platform Limit Microswitch ............................................................................................. 12

Figure 13: Photoelectric Sensor .................................................................................................................. 12

Figure 14: Photoelectric Reflector .............................................................................................................. 13

Figure 15: Click PLC ..................................................................................................................................... 13

Figure 16: Hot Stamping Machine .............................................................................................................. 14

Figure 17: Hot Stamping Dies ...................................................................................................................... 14

Figure 18: CBWS Control Panel ................................................................................................................... 15

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Executive Summary The Denman Island Chocolate CBWS (Chocolate Bar Wrapper Stamper) is an automated hot-stamping

machine for encoding dates onto the outer paper wrappers of their chocolate bars. Its design status is

that of a late-stage prototype, and can be used as-is in their production line. Several recommendations

have been generated based on the construction and operation of this prototype that will lead to a more

complete design that can be advanced to a commercial product.

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Introduction Denman Island Chocolate is a small chocolate company located on Denman Island, BC. While some of

their production line is automated, most notably with a 1950’s-era machine which wraps the chocolate

bars in foil, as well as an automated foil-cutting machine, many tasks are done by hand.

Due to changing regulations and requirement by vendors, Denman Island Chocolate is now adding best-

before information to their wrappers. Due to the dynamic nature of the best-before date of the

chocolate bars produced, these cannot be added to the wrappers during printing, but must be added on

an ongoing basis during production.

Previous solutions to this problem included using a laser printer, which did not work due to the

minimum paper size requirements of most printers and the tendency of the wrappers to stick together

and their slickness; a roller-based hot stamping machine, which did not function as advertised and had

to be returned; and finally, manual stamping using a TRODAT date stamper.

In order to do away with the tedious and time-consuming process of manually stamping the dates onto

each wrapper, several commercially available options were explored in order to do this task, including

the purchase of a hot roller stamping machine from Dalemark, which did not function as advertised and

was returned.

After further research revealed that no commercially available, non-custom machine was suitable for

this task, we were commissioned to build such a machine. This machine would be fully automatic, low

maintenance, and would be capable of stamping 1000 wrappers per hour.

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Prototyping and Concept Development Our initial step was to identify the main challenges inherent in this design. These were paper

handling/destacking (singly separating) the wrappers, which have a tendency to stick together, and

stamping the dates on the wrappers. We undertook research into commonly used technologies in these

areas in existing packaging systems.

After extensive testing of the wrappers, we determined that this tendency seemed to stem from the

cutting process used during the printing of the wrappers, and was therefore beyond our control. A

roller-based destacking system, such as that used in the unsuitable Dalemark machine, and in laser

printers, did not seem able to overcome the tendency of the wrappers to stick together. We explored

various other forms of paper separation, including those used in bank note counting, and finally settled

on a method using suction cups to separate one wrapper at a time from a stack, which overcame the

problem of the slickness of the wrappers. Preliminary testing of this idea using drinking straws and the

vacuum produced by the human lung yielded favourable results.

For stamping the dates, we settled on a hot stamping system, similar to other machines on the market,

including the unsuitable Dalemark machine. Other methods of stamping dates, including laser printers,

generally used water-soluble or other slow-drying ink. The ink used in these methods tended to smear,

rendering imprints from this method illegible. Hot stamping machines melt a layer of ink on a ribbon

using a heated die. After removal of this ribbon and die from the surface, the ink quickly dries and

becomes permanent. Tests undertaken using an inexpensive hot stamping machine verified these

results.

In order to avoid both mechanical and heat damage to the bars, we chose to stamp the wrappers before

their application the chocolate bars. This also simplified the task due to the more uniform dimensions of

the stacked wrappers as opposed to the wrapped bars.

We also prototyped a method of restacking the wrappers, as the

wrappers would have to be in a relatively neat pile in order to be

useful in the packaging line at Denman Island Chocolate. After

exploring various options involving chutes and ramps, we found that

a rectangular vertical hopper provided good stacking, as the air

escaping around the sides of a falling wrapper naturally caused the

wrappers to fall in a neat stack. A picture of the prototype hopper is

show below in Figure 1.

Overall, preliminary tests were favourable, and showed that

construction of a machine to fulfil the design requirements of

automation, low maintenance, and sufficient speed was possible,

while overcoming the problems particular to the wrappers. Figure 1: Prototype Wrapper Hopper

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Design Description

Overview The Denman Island Chocolate CBWS (Chocolate Bar Wrapper Stamper) is a fully automated date coding

machine, using pneumatics and a ball screw linear guide for machine movement, a PLC and various

sensors for control, and a hot stamping machine to physically stamp the wrappers.

It features simple and intuitive controls, and is self-resetting at the end of each stamping run. The input

and output hoppers can accommodate approximately 2000 wrappers.

Figure 2: The CBWS

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Detailed Description

Motion

The CBWS uses pneumatic cylinders to control its motion; these are powered by a Makita MAC-700 air

compressor and controlled by valves attached to a manifold, as shown in Figure 3 below.

Figure 3: Cylinder Valve Manifold

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The motion of the suction head is provided by a dual-rod guided pneumatic cylinder, as show in Figure

4; the vertical motion of the suction cups on the suction head is provided by two pancake pneumatic

cylinders, as shown in Figure 5. One more pancake pneumatic cylinder controls the actuation of the hot

stamper, as show in Figure 6. All of these cylinders are supplied with air from the compressor, limited to

60 psi with an external regulator, and feature meter-in fittings to allow fine-tuning of the cylinder speed.

Figure 4: Suction Head

Figure 5: Suction Head Suction Cups

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Figure 6: Hot Stamper Pancake Cylinder

The vacuum cups on the suction head are powered by a vacuum generator, which is shown in Figure 7.

This vacuum generator is supplied with air at the pressure of the compressor.

Figure 7: Vacuum Generator

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The motion of the input hopper platform, shown in Figure 8, is achieved using a ball screw linear

actuator powered by a 24VDC gear motor, both shown in Figure 9.

Figure 8: Input Hopper Platform

Figure 9: Linear Screw and DC Gearmotor

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Control

Motion control of the pneumatic components of the CBWS

is achieved by on-cylinder reed switches actuated by the

magnetic pistons of each cylinder. An example of these,

shown on one of the suction cup cylinders, can be seen in

Figure 10 below.

The input hopper platform advances automatically, with a

roller lever microswitch sensing the level of the paper, as

shown in Figure 11. A second microswitch controls the

maximum lower position of the platform, to prevent

overloading the motor and burning out the windings, as

there is no current protection elsewhere in the circuit; this

switch is shown in Figure 12. All switches are configured in

such a way as to disable their outputs in the case of a fault

in the system, which prevents mechanical component

overload and breakdown.

Figure 11: Upper Platform Limit Microswitch

Figure 10: Pneumatic Reed Cylinder Switches

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Figure 12: Lower Platform Limit Microswitch

When the input wrapper supply is exhausted, a photoelectric sensor, shown in Figure 13, detects a

reflective disc fixed to the platform, shown in Figure 14. This causes the platform to reset to its initial

position.

Figure 13: Photoelectric Sensor

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Figure 14: Photoelectric Reflector

The machine is controlled by a Koyo Click PLC, which runs off 24VDC; the PLC, along with the system wiring, can be seen in Figure 15.

Figure 15: Click PLC

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Stamping

The stamping of the wrappers is achieved using a hot stamping machine purchased as a unit. This

machine feeds a hot stamping foil ribbon over a heated die, which can be seen in Figure 17. When the

die is pressed against the wrappers, it sandwiches the ribbon between the two. The ink melts, adhering

to the paper, and remains when the die is removed from the wrapper. The hot stamping machine as

modified for use with the rest of the machine can be seen in Figure 16.

Figure 16: Hot Stamping Machine

Figure 17: Hot Stamping Dies

As the ink must be melted onto the wrappers, the dies must heat up before the machine can be used.

This takes some time and must happen before system readiness can be achieved.

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User Interface

The CBWS has three user inputs, and two outputs. The inputs are a power on/off switch, an emergency

stop switch, and a button which starts the program. The outputs are a red and green light, used to show

machine readiness and unreadiness/malfunction respectively.

Figure 18: CBWS Control Panel

Use

In order to use the CBWS, one must first power up the machine, and load wrappers into the input

hopper. Once the green light starts flashing, indicating machine readiness, the machine button is

depressed. This will prompt the machine to advance the input hopper platform to bring the paper stack

into the correct position for the stamping cycle, with the paper flush with the top edge of the input

hopper. Once this has happened, the machine button is depressed again to begin the stamping cycle.

The stamping cycle will complete and repeat automatically, until the stack of wrappers is depleted.

When this occurs, the stamping cycle will stop, and the input hopper platform will return to the starting

position.

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Evaluation

Overview Overall, the Denman Island Chocolate CBWS stamping machine exceeds the requirement of being able

to stamp 1000 wrappers per hour with minimal outside intervention, in fact being able to stamp 1200

wrappers per hour.

As this machine is essentially a late-stage prototype, some design issues remain. In order for it to be

manufactured as a marketable product, the information learned in prototyping, testing, and running this

machine will have to be incorporated into future design revisions.

Design Issues A few of the components chosen for this prototype machine would not be wholly suitable for

production use or would require a design revision for improved function or compatibility:

The hot stamping machine uses rigid dies which require a flexible medium which they are

stamping. In terms of machine performance, this translates to a decreased amount of wrappers

that can be loaded into the input hopper; rather than loading 2000 all at once, they must be

loaded in stacks of 500.

The ribbon used by the hot stamping machine may become misaligned, resulting in an

incomplete stamp or premature filling of the output spool.

The air compressor used, while inexpensive and quiet, has a low capacity and flow rate; the

machine requires a higher flow rate than anticipated, resulting in continuous operation of the

compressor and a high rate of water condensation within the tank and input air line.

Next Steps A few recommendations detail the pathway to take the CBWS from a prototype to a piece of

commercially available production equipment:

Replace the hot stamping machine with a superior, custom hot stamping assembly, and feed the

paper wrappers in singly; this could be done as part of an integrated packaging line which also

puts the wrappers onto the chocolate bars.

Replace the hot stamping machine with a rubber stamp type date stamper, which would allow

large stacks of wrappers to be stamped with no outside intervention. This solution might require

further engineering and research to ensure stamper ink suitability and integration with existing

machine infrastructure.

Accurately measure the air consumption of the CBWS, and select a suitable compressor based

on this data. This data could also be used to correctly integrate future machines with existing

production lines.

Refine the COTS (components off the shelf) bought, to improve suitability for final CBWS design.

Improve the cosmetic appearance of the CBWS, to guard against misuse, injury, or damage

against the machine, and to improve perception of the CBWS as a technically mature product.

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Conclusion The Denman Island Chocolate CBWS is a successful late stage prototype, can be used in Denman Island

Chocolate’s existing packaging line, and is the first step in the road towards commercialization of similar

products. Information gained in constructing this machine has proved invaluable in generating

recommendations to increase the success of future designs and to more fully address design

requirements.