"Krembo" Wrapping Machine
The "Krembo" Wrapping Machine is an automatic machine designed to wrap the delicate chocolate covered marshmallow treats- "Krembo", a task done by hand in every company in Israel.
The project was initiated March 2014 and completed January 2015 by undergraduate student Yoav Golan.
A short video demonstrates the wrapping machine in action:
This project deals with the design and manufacturing of a prototype machine that would wrap the chocolate covered marshmallow treat “Krembo” in aluminum foil. This type of machine does not exist in Israel, and the wrapping is done by hand in all of the factories that manufacture similar products.
The machine must be able to wrap such a product fully in a wrapper similar to the one used today, and without damaging the integrity of the delicate product. The machine is meant for Israeli production lines; however the design process will be conducted independently.
The main issues to face in achieving our goal are grasping a fragile product, dealing with inconsistent products (each one is of a slightly different shape than the last), using a relatively delicate wrapper and fully enveloping the product without much wrapping material.
Our machine incorporates two main stages- the first stage places a wrapper on the top side of a product, and flattens the remaining foil around it. The second stage receives the semi-wrapped product from the first, grasps it with a pair of gripping claws, lifts it, pushes the surrounding foil down with an air blast, closes the remaining wrapper on the bottom portion of the product and sets the wrapped product down.
These two stages have gone through the preliminary design stage (PDR), critical design stage (CDR), manufacturing, assembly and testing. The original design for the second stage proved to be problematic, and did not provide the desired result, therefore a new design went through all the aforementioned design stages to produce our final prototype. This work shows the original design briefly, and the final design in detail.
During the first stage, a contraption holds a new wrapper with suction, descends onto a waiting product, thus placing it on the product with minimal force, but enough to reshape the foil- flattening the surrounding area. When the contraption completes its descend, the suction is switched off and replaced with a short burst of air, to release and part of the foil that may have stuck to the contraption, which then rises back up to its original position.
The second stage relies on grasping claws padded with a soft sponge, the claws can rise or descend in their entirety, and close or open independently via air cylinder. The claws close to a point where the force acted on the grasped product is exerted only by the sponge. In this way relatively little force is applied to the product. An air blast (or jet) may be passed through nozzles in the gripping claws, these nozzles direct pressurized air downwards, reshaping the foil that surrounds the product and preparing it for closure. Two wrapping closing mechanisms act to fold the reshaped foil onto the bottom part of the product. These mechanisms are air cylinder actuated “V” shaped plastic pieces that “gather” the foil and flatten it upon the raised bottom surface of the product. This type of mechanism is used in the food manufacturing industry.
Our machine is based on pneumatic actuators, controlled electrically by a programmable logic controller (PLC) of the type “SPC-200” (by FESTO), programmed to run the system automatically. The power sources are a 24V DC supply, an air compressor (6 atmosphere working pressure) and a home vacuum cleaner.
The prototype can wrap the “Krembo” fully and without damaging it. Still, the wrapping is not sufficiently aesthetically pleasing, and the machine’s reliability to fully wrap the product is low (the reliability in not damaging the product is, however, very high). The machine works slowly, but this is mostly due to a deliberate slowing of the processes for human control. In order to incorporate a similar machine in an industrial manufacturing line a redesign should be made, oriented to this purpose and based on the prototype, while implementing improvements where needed.