Monday, March 4, 2013

RecycleBot v2.3 Controls by jpearce - Thingiverse

RecycleBot v2.3 Controls by jpearce - Thingiverse


A RecycleBot is a waste plastic extruder that creates 3-D printer filament from waste plastic and natural polymers.
This is a fully automated version of Recyclebot v2.2 with many improved features. For more info see C. Baechler, M. DeVuono, and J. M. Pearce, “Distributed Recycling of Waste Polymer into RepRap Feedstock” Rapid Prototyping Journal, 19(2), pp. 118-125 (2013).


The mechanical design is equivalent to RecycleBot v.2.2 - I strongly recommend reading that first. This design is, of course, far from optimized particularly with respect to cost and DYI, it is primarily being used by the Michigan Tech in Open Sustainability Technology Research Group to make new fucntionalized 3-D printing materials (e.g. electrically conductive) to support a full range of products open-source disributed manufacturing...lots more to come.

Some of the improved features over RecycleBot v2.2 are:
1. Type of plastic can be selected from the keypad interface and the controller automatically updates the extrusion temperature for the plastic.
2. Extrusion temperature can also be feed by the keypad interface for any type of plastic which can be melted and extruded.
3. LCD interface for better process monitoring.
4. No extrusion until the extrusion temperature is achieved - automatically controlled by microcontroller, with (manual option).
5. Low cost power control options using a Triac and MOSFET.

The energy performance of v2.2 can also be significantly improved with insulation.

Heating Zone
As the heater is the most important section it must be designed and fabricated precisely for better results as changes in temperature of few degrees can result in different mechanical properties of the extruded plastic. Another important criteria for the heating section is to create uniform heating environment so that the temperature remains nearly constant throughout the barrel such that the extruded plastic is uniform. To achieve this, high temperature ceramic beads were used to insulate the bare nichrome wire so as to achieve electrical isolation from the iron barrel, and an advantage of using this scheme is high-quality thermal insulation from the ambient environment and heat transfers efficiently to the iron barrel as the bottom side of the ceramic beads rest on the metal tightly and the top surface is insulated to the air, which is then insulated as well.

Steps to make the heater section

1. Clean the barrel and then make the top surface rough with a file.
2. Again clean the surface and remove any residing metal debris and dust.
3. Cut the required length of nichrome wire and straighten that up and hook the ends to a clamp.
4. Carefully insert the ceramic beads onto the nichrome wire one by one till the whole wire is completely covered up with ceramic beads.
5. Take the furnace cement and cover-up the iron barrel throughout the surface, it need to be made sure that whole surface is completely covered up with furnace cement as any exposed bare metal can posses the risk of short circuit with the bare nichrome and hence elevating the chances of electric shock (and destroying your power supply).
6. Gently take the nichrome wire and place it over the barrel and slowly cover up the barrel as if making a coil out of nichrome wire.
7. Fix the two free ends of the nichrome tightly to a clamp and apply furnace cement to cover up the whole surface of ceramic beads and it should look like the picture given in gallery. Again it is stressed that the furnace cement must be applied all over to cover the whole surface of ceramic beads so as to adhere strongly to the underlying metal and it should also make an electrical insulation layer such that bare nichrome shouldn't touch the metal anywhere.
8. Allow it to dry for at least 24 hours.
9. Connect the two free ends with alligator clips to power up the heater.

Safety note use gloves while using furnace cement as its alkaline in nature and can injure you and damage the skin if exposed for a prolonged time, if by chance skin comes in contact with furnace cement, then wash it under running water immediately. It is recommended that you do this in a hood if you have access to one.

Temperature Monitoring and Process Control

Controlling the temperature and other related processes of plastic recycling and extrusion in an efficient manner and simultaneously decreasing the cost is the key challenge for RecycleBot development especially for home applications. In order to promote the RecycleBot for open sustainability, the whole control system is designed to work on Arduino, which is a very popular open source microcontroller based application development platform. Being easy to use and program with excellent user community support, Arduino is a low cost rapid prototyping platform ideal to implement control system for RecycleBot. Arduino Mega was used to design and implement the system, having enough input/ output pins for interfacing LCD, keypad, and other components.

The whole process is divided into two parts: Input mode and Control mode

Input mode

The process starts with user input of either plastic selection or extrusion temperature. With the option of 10 different types of plastic, user can select the desired type of plastic to recycle and the program automatically loads the optimum temperature range for operation/ extrusion for that particular type of plastic. Alternatively, user can also feed the temperature of extrusion for any type of plastic which can be operated below 350C. After the extrusion temperature is set, program ask the user to confirm the temperature and once the temperature is set, the program steps into the control mode.

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