This Instructable will walk your through the steps of creating a scrollable paper platform to use in a laser cutter. This allows you to cut a continuous pattern in a long strip of paper that could not be done given the standard area of a laser cutter. This project will provide a continuously scrolling paper spool that you can make multiple cuts on in a quick amount of time.
While this platform does not provide an automatic way to scroll the paper it is the first step in making a usable, continuously scrolling paper design in a laser cutter.
Designed and built by:
CU Boulder, Things That Think, Spring 2011
Step 1: Parts and Materials
To build some logic and control the behaviours, Arduino Uno was used. The Arduino Uno has built in support for two servos but more can be added if the servo inputs are spliced and placed into the correct pins on the Arduino board. A better description and documentation on the Arduino Uno can be found here http://arduino.cc/en/Main/arduinoBoardUno.
The laser cutter that we used for this project was the VersaLaser 1100 along with the drivers and software that come with the laser cutter. Adobe Illustrator was used to produce the template for the cutting surface. The laser cutter that you use to develop this prototype might differ and will affect the size of the platform, the template that you build to the cutting area, and many other considerations for the project.
Wood (Platform and Supports)
Our platform and supports are built out of wood but acrylic could be used too. The size of the platform is specific to the size of the laser cutter that we used. The supports are also sized according to the receipt paper that we used.
This is a simple receipt paper picked up from any home office supply company. If you want to use a different type of paper for the project make sure the supports for the platform are changed accordingly along with the servo dowel.
A properly sized dowel is required to be placed on the end of the servo to pull in the receipt paper.
This is basically a button that triggers the programmed movements. A touch sensor could also be used in place of a switch.
Resistor (10k Ohm )
Only one resistor is required for this project. This resistor is necessary to control the behaviour of the electric circuit. The exact placement for these resistors will be explained further in the Instructable.
360 Degree Servo
A continuously rotating servo is required in this project to roll up the receipt paper. The servo we used was purchased from Sparkfun and is available here. http://www.sparkfun.com/products/10189
Ladyada Motor Shield
Arduino on its own cannot power itself or the servos without a USB connection or A/C Adapter. To create a more portable automaton we built a Motor Shield as described in http://www.ladyada.net/make/mshield/make.html and we connected it to the Arduino. We then connected an independent power supply and the servos to the Motor Shield.
During the development phase, the power was supplied through a USB cable connected to a computer. In the production phase, we used a pack of 4 AA batteries.
Step 2: Designing the Circuit
In this diagram we can see the battery pack is connected to the Motor Shield by correctly attaching the +/- outputs to the screw-down terminal.
The circuit for the switch requires three separate wires. The first (yellow) wire is connected to a pin on the switch and to the +5V pin slot on the Motor Shield. The second (red) wire is connected to the appropriate input pin (A0 - A5) on the Motor Shield and a pin not associated to the first wire on the switch (remember on switches like this, pins opposite each other are associated). The third (blue) wire requires an in-line 10k Ohm resistor and is connected to a pin on the switch that is associated with the red wire and to the ground (Gnd) on the Motor Shield.
When this switch is in the “off” position the current will run from the +5V on the Motor Shield, through the yellow wire, and back out through the grounded wire. When the button is pushed or switched “on” the current will run from the +5V, through the yellow wire, and choose the path of least resistance through the red wire. This will trigger the action assigned to that particular input (we will cover the code in a later step).
Step 3: Building the Platform
The platform for supporting this project was built around the cutting surface of the VersaLaser laser cutter. The cutting area was 12 inches by 24 inches so we cut out the platform to correspond to this area. An area was then cut in the base of the platform where the laser cutter will be cutting the paper. Our cutting area is 6 inches by 1 and a half inches (the width of the receipt paper). We extended the area cut out of the platform by 2 inches on each side to allow for error.
We then glued two platforms the height of the receipt spool to keep the paper level while it is being pulled across the laser cutter area. There is another small tab of wood glued to the base of the platform that elevates the servo and provides a place to attach the servo to the platform.
A box is then built as far away from the laser as possible that will house the electronics and protect them from the laser. The box has a hinge on it to change the batteries. It also has a spot on the top with holes cut in it for the wires to connect to the spooling button.
The Platform is going to be custom to the laser cutter that you are using and the receipt paper. Please make sure you take this into consideration when you are building your platform.
Step 4: The Servo and Spool Assembly
The servo is attached to a small tab of wood that is glued to the platform. If the servo was purchased from Sparkfun as described in the materials section then screws will be provided to attach the servo to the wooden tab. We used the four arm servo mount on the servo (the Sparkfun package comes with a few different mounts). A wooden dowel is then attached to the servo. Again if you purchased the servo from Sparkfun it comes with screws to connect objects to the servo mount. The dowel is 2 and a half inches long to adjust for errors during spooling. An attachment is then made by taping poster board in a cylinder with a circle of poster board glued to the end. This allows for the spooled paper to be easily removed from the end of the servo while keeping the spooling paper inline with the other spool.
The other end that holds the paper is a simple metal L-bracket with another dowel screwed to the upright end of the L-bracket. The dowel is small enough that the receipt paper roll can spin freely without much friction. An endpiece is then screwed on to the end of the dowel with a hand tightened eye screw to keep it on.
When paper is loaded onto the dowel it should be able to spin freely. Pull a length of paper off of the paper spool and feed it across the cutting area and onto the poster board on the other end. At this point you can either tape the paper down to the poster board or cut a slit in the poster board. If the poster board cylinder was made to fit snugly on the dowel then friction alone will be enough to hold the paper onto the cylinder.
Step 5: The Code
The code we wrote for this project is fairly straight forward. We feel that the best way to demonstrate the code is by viewing it. The code is written in C and reads an input from the AO input on the motor controller board. The output pin is the servo pin 9. The code can be edited for your specific servo and dowel size. We used two different numbers to get the correct spooling. The first number, called rotations , is used to determine the number of milliseconds required to make a full rotation of the dowel. The second number, which can be found down in the run loop, determines the number of milliseconds that needs to be run to provide six inches of rotation given the first number.
The code is fully commented and can be adjusted according to your specific needs.
Step 6: Bringing It All Together
So now we have a completed circuit board, 2 paper spools, and a wooden platform. It’s time to put all of this together. The first step is to insert the full spool at the right edge of the wooden platform.
The 360° servo is then glued to the left side of the wooden platform. An empty spool can be easily added (or taken-off) when a new task is beginning (or ending). The servo is responsible for rotating both of the spools to move the receipt paper forward.
Place the completed electronics in your protective box (if you felt like building one) and attach the servo wire to the Motor Controller Board.
Place the platform inside the laser cutter. Follow your laser cutters instructions for leveling the cutting surface (the paper) to the laser. With the laser levelled and your template loaded, run a single cut of the template. Once the laser has completed its cut and is back in it’s default position, press the button to scroll one length of paper. Perform another cut. Scroll, cut, repeat.
This is where some tweaking may be required. We found that because of the servo that we chose for this project the amount of paper spooled in was inconsistent. We placed a mark on the platform where the template cut stopped and we needed to provide a small adjustment of the paper by hand to place the paper at the right location to make a consistent cut. Your servo, spool, paper size, and laser cutter will require you to modify all of these things manually and find the best combination of spooling distance and rate for you laser cutter.
Step 7: Future Modifications
The steps that we have provided in this instructable will allow you to build a working prototype of a scrollable laser cutter. However there are some issues that need to be resolved for this project to work better.
A consistent method of scrolling the paper needs to be implemented. If the Servo was higher quality or the degree of rotation could be controlled (a continuously rotating servo isn’t controlled by degrees rotated but by the time of rotation) then a mathematical calculation could be performed to adjust to the diameter of the servo as paper is spooled up. This will reduce the need for the manual adjustment that is required to get a good continuous cut in the current model.
Another modification would be to remove the buffer around the cutting area and have the laser cutter cut from one end of the cutting area to the other. The buffer was in the original design because of the lack of precision in the scrolling of the paper. If that can be resolved then the buffer would no longer be necessary allowing for a longer cut.