Flatbed Plotter Based Laser Cutter

With the use of a flatbed plotter to control position, this concept has many advantages to any other DIY laser cutter idea. While simply intercepting the pen down/pen up commands, the whole operation can be completed without much additional work.

If a laser is mounted in the position of the pen, the whole device can rapidly be physically complete. However some additional programming may be required to control it effectively.

Lasing

While a nice big gas laser would be great, they have a couple drawbacks of which probably the largest is their cost! A red diode laser however, can be used to create a low power cut capable of going through dark coloured paper. Additional lasing capability could be obtained through the use of other power/colours of laser beam, however a very easy and cheap source of suitable red laser diodes is readily available.

Inside a DVD burner!

Acquiring a Diode

Any DVD burner will contain a possible candidate for this use, but the faster the burner, the stronger the diode. After selecting a donor drive, I had to remove the diodes from it. This proved to be more difficult than expected as the diode was soldered completely inside its heat sink.

Instead I selected another drive, and using a YouTube tutorial I successfully removed the diodes!

Assembling the Diode Module

Although the laser diode produces enough lasing power to cut paper, it requires the beam itself to be focused, this would require some form of lens to do so. After some initial research I had found a good solution to this, that would also give me a simple method of mounting the whole laser module onto the plotter - a Focusing Laser Housing.

I had also researched that some form of constant current driver would be required in order to keep the diode in good working order for long periods, and although I had found some circuit designs for this, a cheap driver board was also available from the same supplier. As this board would fit inside the housing, this would allow everything to be neatly hidden away.

After these items had arrived I checked that the diode would fit inside the housing properly, which required some careful work with a small grinding disc to remove some excess solder left from when it was removed from the original heat sink. The diode could then be push-fitted into position.

First, however, it would need to be soldered onto the driver board. This I did, plus some wires onto the other end. The laser was essentially complete!

Next I needed some sort of power supply, and after checking what voltages and currents were required I got a phone charger with the required output.

Finally I inserted the laser diode and driver board into the housing and after a quick check, found that it successfully produces a laser beam. Additional time will be needed to produce a focused beam capable of giving a good cut. This would be best done with the whole thing mounted on the plotter, and could possibly be accidentally changed before the whole thing is complete, so there would be no need to do this just yet - it is also a little bit safer if it can't cut just yet!!

Mounting on Plotter

Getting Power Across the Plotter

Although the laser now works, when the plotter is creating the designs, it will be moving quite a large distance, and as such some form of cabling will be needed to keep the laser powered as it is moves around.

As it would probably be better if replacing either the laser module or the power supply could be done without the need for de-soldering anything, some form of removable cabling would be ideal and as such a design that has sockets would be best. This I accomplished with the use of some modem cabling and the phone line sockets from 2 old modems. Attaching one socket to the laser module and the other to a power/control board gave the exact cabling design I intended.

Securing the Laser Module to Pen Holder

After checking the diameter of the laser module to the pen holder, and comparing the design of a couple of the original plotter pens, I realised that although the module would fit directly into the plotters' pen holder, it would require some way to stop it slipping downwards during use. As such I carefully removed the ring from an empty pen that was used to perform that very function! I then needed to attach this to the laser module, this would be done carefully using a glue gun.

Control

After discussing options for doing this, we came up with a few possible solutions

  • Full software-based control. Making a program to take the HPGL code and outputting the commands to the plotter for movement, using a simple arduino to turn the laser on and off.
  • Full arduino control. Using an arduino to complete the above - separating the pen down/up commands out to the laser, while slowing down all the commands to allow cutting time.
  • Simple mechanical laser control. By mounting a micro switch next to the pen movement, it may be possible to capture its movement and as such to turn the laser on and off, while letting the original HPGL commands to the plotter do everything else.

Of these possibilities, the mechanical laser control is the least viable, as it will have relatively slow response times. It is also the only option that cannot compensate if the laser has a slow cutting speed, which is quite likely to be the case. The full software method would be simplest to produce of the 2 solutions that can offer this, as the programming required would be easier to complete.

Updated

After some additional thinking, Martyn and I realised that the pure software-based methods would not work as intended - the PC does not know exactly when the plotter arm reaches the postion that the laser would need to start cutting, so would be unable to start the laser at the correct time.

As such, we decided to try another method of controlling the laser.

This would either be to use the mechanical method we had initially thought of, or to gain access to the control wires of the solenoid proving the pen up/down movement.

Access to these wires was easily found, however they were contained within ribbon cables for practically the whole distance. The end contained within the base of the plotter was attached to the main control board, and due to the heatsinks attached to some of the components on it, we decided to try at the other end. At the solenoid end, the ribbon was split off into 2 wires on a PCB, and would be relatively easy to access. However attaching the control here would mean that removal of the laser module would be slightly more difficult, as it would be necessary to disconnet 2 connectors, instead of the one we had originally intended.

We decided this would however be a much more sensible idea, and so next we needed to check the voltage that the solenoid line was running on, as to switch the laser on we will require at least 2.5V.

As such I used some veroboard to create a simple connection board, which would be used in the final project to take the connector from the power supply, as well as the new connector from the solenoid control. The wires from the laser module would then be soldered onto this board.

To do List

  • Mount laser module on plotter
  • mount power module on plotter
  • run cabling such that it stays out the way during operation
  • focus laser
  • get controller program made (Martyn)
  • get arduino + program done (Martyn assist) no longer needed
  • test!
  • design/make box for safety
  • decide upon method for viewing cutter operation inside box
 
laser/flat_bed_plotter_based_cutter.txt · Last modified: 2011/06/14 11:16 by andrewt
 
Except where otherwise noted, content on this wiki is licensed under the following license:CC Attribution-Share Alike 3.0 Unported
Recent changes RSS feed Donate Powered by PHP Valid XHTML 1.0 Valid CSS Driven by DokuWiki