This project was the focus of my undergraduate thesis and is large part of my Masters thesis. In this project I aim to create a reliable actuation system for a massive array of tiny pins for use as a reconfigurable forming tool.
Scroll down for more info! My S.B. thesis which goes into more depth of the design process can also be found immediately below.
Scroll down for more info! My S.B. thesis which goes into more depth of the design process can also be found immediately below.
| peters-sb-me-2011.pdf |
Digitally Reconfigurable Surface
A 11,000 pin array! That's as many as 1,100 tens.
The digitally reconfigurable surface is a pin bed mechanism for directly forming physical three dimensional contoured surfaces from a computer aided design (CAD) file. Using a novel clutching mechanism (detailed below), a dense 2D array of pins is actuated in parallel to the desired geometry. As is typical with these kinds of tools, a smoothing, interpolation layer (usually a piece of rubber) can then be vacuumed onto the tops of the pins to smooth the surface and make it non-porous.
Full description (more images/video below)
Normally, molds for casting or forming are made by hand carving or by using conventional machining processes (milling, turning, 3-d printing). Mold fabrication can not only be expensive and time consuming, but each mold usually only has the capability to make one part. An electronically controlled reconfigurable pin mold is a long sought after device that could have the potential to make many moldable surfaces, directly from a digital file. In an ideal embodiment a reconfigurable array could also make molds more quickly and cheaper (in the long run) than most other conventional processes, saving money, time and wasted material.
In the current design, two arrayed clutch plates are used, (more may be used for faster or stronger actuation): an electronically controlled fusible alloy clutch and a moving friction clutch (perforated rubber membrane).
To begin an actuation cycle, the heater array (surface mount resistors) in the electronic clutch is powered on, heating the pins that are soldered (with low melting temp alloy) in the electronic clutch plate. Each pin in the array is now free to move up or down, as the metal alloy soldering each pin in place has become liquid. Next, a perforated rubber membrane that surrounds the lower part of each of the pins is moved away or towards the heated clutch array. This rubber membrane provides a frictional force on all the pins, but is able to slip along the length of the pins if pins are locked in place by the electronic clutch. As this membrane is lowered, resistors are switched off when their corresponding pins have reached their desired final height—known by the current height of the rubber friction plate. Turning off a resistor heater causes the low melt alloy to solidify around the resistor’s corresponding pin. The solidification of the alloy locks the pin in place while the rubber friction plate continues to pull the still-melted pins unimpeded. When the friction plate reaches the end of its stroke, all pins will be in their proper positions to create the surface pattern that was uploaded into the device. Lastly, the rubber interpolation layer is vacuumed down to the tops of the pins, if desired, to provide smoothing of the discrete pins.
Full description (more images/video below)
Normally, molds for casting or forming are made by hand carving or by using conventional machining processes (milling, turning, 3-d printing). Mold fabrication can not only be expensive and time consuming, but each mold usually only has the capability to make one part. An electronically controlled reconfigurable pin mold is a long sought after device that could have the potential to make many moldable surfaces, directly from a digital file. In an ideal embodiment a reconfigurable array could also make molds more quickly and cheaper (in the long run) than most other conventional processes, saving money, time and wasted material.
In the current design, two arrayed clutch plates are used, (more may be used for faster or stronger actuation): an electronically controlled fusible alloy clutch and a moving friction clutch (perforated rubber membrane).
To begin an actuation cycle, the heater array (surface mount resistors) in the electronic clutch is powered on, heating the pins that are soldered (with low melting temp alloy) in the electronic clutch plate. Each pin in the array is now free to move up or down, as the metal alloy soldering each pin in place has become liquid. Next, a perforated rubber membrane that surrounds the lower part of each of the pins is moved away or towards the heated clutch array. This rubber membrane provides a frictional force on all the pins, but is able to slip along the length of the pins if pins are locked in place by the electronic clutch. As this membrane is lowered, resistors are switched off when their corresponding pins have reached their desired final height—known by the current height of the rubber friction plate. Turning off a resistor heater causes the low melt alloy to solidify around the resistor’s corresponding pin. The solidification of the alloy locks the pin in place while the rubber friction plate continues to pull the still-melted pins unimpeded. When the friction plate reaches the end of its stroke, all pins will be in their proper positions to create the surface pattern that was uploaded into the device. Lastly, the rubber interpolation layer is vacuumed down to the tops of the pins, if desired, to provide smoothing of the discrete pins.
Cross section of compliant material friction plate actuation.
Pins can stay fixed, move up or move down simultaneously in this configuration. An 'X' over a joint assumes that it is clutched. Array could still be actuated with friction plate removed.
An advantage of the actuation technique is that in the “off” state of the machine, the pins are locked in place, so no power is consumed while the device is being used for molding. Also, the solidified low melt alloy creates a very strong bond, meaning the surface can withstand considerable pressure before yielding (1,000's of psi).
The mold may be used dynamically to change its shape while molding (for example, to apply residual stresses to the molded material) or for a dynamic 3d display.
The primary intended use for this device is a forming surface. A surface would be designed in a computer and uploaded into the machine; after the surface was configured into the pins, the physical surface (or multiple surfaces put together as a mold) could be used for casting, vacuum forming, injection molding and many other forming processes.
This device has potential for integration all conventional molding machines, allowing rapid customizability for short production runs and rapid prototyping.
NEW video of handheld demo array for ML crit day (red portion is silicone friction clutch). Slides from crit day below.
The mold may be used dynamically to change its shape while molding (for example, to apply residual stresses to the molded material) or for a dynamic 3d display.
The primary intended use for this device is a forming surface. A surface would be designed in a computer and uploaded into the machine; after the surface was configured into the pins, the physical surface (or multiple surfaces put together as a mold) could be used for casting, vacuum forming, injection molding and many other forming processes.
This device has potential for integration all conventional molding machines, allowing rapid customizability for short production runs and rapid prototyping.
NEW video of handheld demo array for ML crit day (red portion is silicone friction clutch). Slides from crit day below.
| crit_day.pptx |
Videos from last sponsor week.
Thermal Imaging
A neat video showing how the fusible alloy micro-clutch array (0603 resistor network) can heat up specific areas. Anyone want to make an alphanumeric thermal display?
Fall, Sponsor Week 2011 Poster
