Technological Design Engineering Thijs Platteau

Stands specifications

The four stands under the machine are M10 headless bolts. Made from the steel type 9SMnPb28K. With a length of about 100mm.
They have a strength class of 5.8. This means the ultimate tensile strength is 500N/mm² and a yield point of 400N/mm². (500 x 0.8)

The amount of pressure the stands deliver to the ground. One stand has a diameter of 50mm. The machine weighs 400kg.

surface area: 25².pi = 1963,5 mm²
weigth force : 400 . 9,81 = 3924N -> divided over the 4 stands = 981 N / stand

One stand gives 0,5 N/mm² pressure to the ground or 499619,2 Pa.

Technical Improvement

Rivets specifications

In these tables we can see that the rivets are made in steel type QSt 32 -3. This material has an ultimate tensile strength of 390N/mm².

These rivets are 3 mm wide and have head width of 5.2mm (see second table) and will have a length of approximately 10mm ( 2 x 3mm (sheet metal) + 1.5 x 3mm (extra length needed)).

Overview

R factor PU foam

The PU foam used for insulation of the machine has an R factor of R7 - R8 per inch.

link:
http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11600

Printboard

This is the heart of the machine.

- It makes sure the temperature is constant.

- When a coin is accepted and a choise is made, it powers the right coil.

- All the data transport goes through here.

Drawer blocking system

This simple system makes sure you cannot reach the products inside the machine.
When you push the lid the other lid also rotates so that acces to the machine is impossible.

The red part here is a two force member.

Slideshare

link:

http://www.slideshare.net/PlatteauThijs/how-a-vending-machine-works-short

Production techniques

materials and junctions

- casing: sheet metal

The choise for this type of material is pretty obvious. It's easy to form and it has a sufficient strength. The metal is durable. Most of the time the casing has a paint coating for extra protection against rust.
It also easy to mount with techniques like spot welding or rivetting.

- PU insulation foam

PU foam is a common insulation material. It's easy to handle which cannot always be said about its glass fibre antithesis. The fibres can cause troubles within the machine, because we sell snacks and because there's a cooling system with a fan that produces air circulation.

- dispensing coils: stainless steel

The steel ensures that the coils cannot break in any circumstances. The have a certain flexibility. They also can be dip coated with PET or another polymer. ( see Bekaert examples )

- finish: inox

This material has only one use and that's quality. The more inox, the more your machine will look like a quality product. A vending machine stands in all sorts of places. When it stands in a train station it will have a small plate of stainless steel or non at all. But when it stands in an office of the head staff of a company it will have more inox elements and so a less cheaper look.

- layered glass: glass + PVB

The layered glass is for safety purposes. It's very hard to break through this type of glass, although it's not impossible. The PVB layer will keep most of the broken pieces of glass together as it sticks to the glass.
They could of course have made the front in sheet metal too, but it's all about seduicing the people to buy. So when the products are visible, the client knows what he's getting for his money.

- bolts

The bolts underneath the machine make sure the machine can be leveled out. When the surface is not flat, the stands can be finetuned so that the machine is.

- rivets

This is an easy and quick method to mount sheets of metal to each other. They can be replaced as well.

Dispensing coils

- different types: lead, diameter
- almost no friction (steel - plastic): negligible capacity of motors
- 360° turn -> 1 lead forward

MEI EC 6000

- H: 371mm W:138mm D: 80mm
- MDB interface: multidrop bus, serial bus, standard since 1995: simple protocol, add different features is easy (smartcard, coin exchanger, bill acceptor, card reader; only 1 per feature)
- easy accesible path: maintenance; (dust -> wrong screening)
- non optical
- 4 high capacity exchange tubes: 20 x 5cent, 10 cent, 20cent en 50cent. 1 en 2 euro directly fall into cash register.
- always return possible: at first the tubes are filled as the machine receives coins. When filled, the rest falls into the register.
Imagine everyone pays with 1 and 2 euro coins and the tubes get a lack of coins to exchange. Then the machine will first ask to pay with a fit amount. ( Research: this message causes 50% less buyers). Worst case scenario: the machine cannot return.

This system is modern, so electronic driven. This is less interessting, so here I described a older system that is more based on mechanics.

- coin recognition: 2 coils, there is a current running through the first one, creating a magnetic field. The second coils catches this fields whereby a current is initiated into the second coil. When a coin passes through these coils the magnetic field is changed by its alloy. The current in the second coil changes and is so a measure for the alloy of the coin. When the current matches with the system that is preprogrammed, the coin goes to the next stage. By its weight the coin activates a button that leads up to an electromagnet. The elctromagnet closes the coin entrance for a little while so the coins cannot follow each other too fast. The coin now rolls onto a set of weighers, ordered by diameter. The coin gets stuck at its right diameter, it's weighed with a contraweight. If the contraweight is lifted the weigher will turn so that the coin can proceed its path to the right tube or the register. So the diameter has to match with the weight. It important for this process that the machine stands level.

Older system

Vandalism

- 3 point lock + lever: no acces
- Layered glass: glass - PVB (polyvinyl butyral) - glass (window shields)

PVB: UV reduction + high frequency sound filter

- high centre of gravity (drinks): many deads by being crushed

Stability: 4 legs : M16 bolts

- No acces through delivery drawer

Cooling system

Brand:

http://www.danfoss.com/Belgium_Dutch/BusinessAreas/Refrigeration+and+Air+Conditioning/

How the cooling works:

The compressor compresses cool Freon gas, causing it to become hot, high-pressure Freon gas (red in the diagram below).
This hot gas runs through a set of coils so it can dissipate its heat, and it condenses into a liquid.
The Freon liquid runs through an expansion valve, and in the process it evaporates to become cold, low-pressure Freon gas (light blue in the diagram below).
This cold gas runs through a set of coils that allow the gas to absorb heat and cool down the air inside the building.

Expansion valve

Filled with an similar gas. If it becomes too hot inside de condensing coils, the gas also expands inside the valve. The pressure pushes against a lid, causing the valve to close. The opposite happens when the evaporation coils get too cold. The gas inside the valve shrinks causing the valve to open.

Simple cooling system

Expansion valve

Air circulation causes a constant temperature of 15°C. This is necessary because several snacks contain chocolate. Too cold ain't an option neither because chocolate will get a white color and snacks aren't that appetizing when too cold. The casing is insulated as well.

Visit Drink o mat

Sielaff SÜ 2020

MEI EC 6000

Coin tubes

Printboard

Dispensing coils

Motors for making the coils turn

Layered glass (vandalism)

3 point lock

Lever lock

Rivets

inside door

Anti static wires

Cooling unit (Danfoss)

Fan for air circulation

Cooling outlet

Stand (x 4)

Delivery drawer

Blocking system

Basic operation

How does a vendig machine work basically:

http://www.ehow.com/how-does_4928211_vending-machine-operate.html

Focus

I've decided to focus on a vendig machine that sells snacks. The mechanism used in the machine works with a spiral that turns around to release the snack. The snack falls down and is available for the customer. The same type of vending machine is used here at Howest.

History and types

The most unthinkable products are being vended in vending machines. This has a lot to do with the different cultures. For example: in Holland you can buy prepared food from a vending machine, in Belgium this is not so popular.

http://en.wikipedia.org/wiki/Vending_machine

http://www.automatencenter.be/producten.html

Coin recognition

A very important and interesting part of a vending machine is the part where you insert money into the machine. How does the machine recognize real money. Certain machines accept credit cards, bills and coins. But most of them only accept coins. Now let's take a look how this problem is solved by several mechanisms.

http://blogs.howstuffworks.com/2010/03/31/32069/

http://web.mit.edu/2.972/www/reports/coin_tester/coin_tester.htm

http://www.ehow.com/how-does_4572360_vending-machines-read-money.html