Laser Cutter

Latest revision as of 14:35, 11 September 2012

Laser Cutter (Edit)
Make	G. Weike
Model	LG900N
Date Manufactured	2011
Discipline	Woodworking
Hackable	No
Ownership	Kwartzlab

Hardware

This be our excellent water cooled, 60W CO2 laser etching machine with 36" x 48" work area.

Who Can Use the Laser Cutter

Members can use the laser cutter, after receiving training.

If you are doing production work and selling the results, then Kwartzlab would like a cut. Talk to a board member.

Non-members cannot use the laser cutter. However, they can make a deal with a member, and get the member to do some work for them, for a price, with a cut for Kwartzlab. Suggested pricing is $1 per minute (to be donated to Kwartzlab), plus whatever the member wants to charge for their time (eg, $50 per hour). In these cases, it should be pointed out to the non-member that it might be cheaper to join.

Software

Software that came with the machine is LaserCut 5.3 for USB. There is a hardware key that is required to operate the software.

Inkscape

Inkscape is a Free and Open Source vector graphics program. It does have the ability to save to dxf files, but you need special knowledge in order to get usable results.

• Before starting Inkscape, run "sudo apt-get install pstoedit" from the shell. This will install the recommended DXF export filter.
• There are two DXF export filters, both with their own features and bugs.
  • One is "AutoCAD DXF R12" (installed with the pstoedit package). This is the one I recommend. It works by using Postscript as an intermediate format, but you don't have to set any parameters in the postscript dialog, just click through. This filter has the best support for preserving your content. It preserves colours, which turn into layers in LaserCut -- very nice if you have mixed cutting and engraving. Unfortunately, it screws up position and scaling information. You need to move the object back onto the cutting area, and scale it to back the desired height and width.
  • The other is "Desktop Cutting Plotter (R13)". This one works for some models, but is unusable for others. It preserves scale and measurement. It doesn't preserve colours. Sometimes, it deletes content and there's nothing you can do about it. If you group several objects, then duplicate or copy/paste the group, then the copy will have the "transform" attribute set in the SVG file, and it will not be exported to DXF. That's a deal breaker for one of my projects.
• Inkscape's dxf exporter only exports paths. In Inkscape, most things (like squares and circles and text, etc.) are not paths by default.
  • If you highlight the things you want to export and click "Path -> Object to Path" from the top menu it will convert the selected items into paths.
• Lines in Inkscape may be given a thickness, but this will not be reflected in the output dxf.
  • The resultant document will just cut from point A to point B.
  • If you highlight a line and click "Path -> Stroke to Path" it will turn a thick line into 4 points, representing a shape that is the dimensions the line used to be
    • This should also take care of any other line attributes you used, like rounding corners or line cap styles
• Use of Inkscape's path operations can be very helpful
  • In my example I had a black square with a series of white objects on top of it to make a shape. This made a lot of path noise in the output.
  • Instead, I highlighted everything (once I'd converted all of the objects to paths and performed "Stroke to Path" on all the lines) and used "Path -> Union"
    • This joins all of the paths that overlap into one path that traces the outline (Don't use this for inner surfaces like holes)
  • For inner surfaces, like holes, one can use "Path -> Difference" to use one path to cut a hole out of another shape.
    • This is what I eventually did with my square with shapes over it. I unioned them all together, then used that result to cut the shape out of my square, leaving me with one square with a man-shaped hole in it.
• One last thing to remember, I don't know if this is typical or not, but while Inkscape shows you the border of your "page" surface, it doesn't output a rectangle there.
  • If you want to cut out around whatever it is you've made, you'll need to add the border directly

After figuring this stuff out, I had pretty good results moving from Inkscape into the laser cutting software.

Using Inkscape to clean up PDFs (Trevyn Watson)

If you're like me, you get a lot of your files for lasering from sources other than drawing them in Inkscape - I've used programs to generate PDFs of boxes, and I've downloaded random drawings from the internet. Usually I end up with objects made of a bunch of little line segments instead of continuous paths. This results in non-optimal toolpathing when interpreted to gcode.

In the past, I have solved this by manually tracing the lines with a continuous path. Very tedious, not very practical, basically impossible for objects that have curved lines. However! I've just discovered that Inkscape can make it all happen automatically. It's very easy: just combine your objects into one compound path (select them, Path->Combine) (this also converts things like polylines to paths), select the path edit tool (pointer with blue nodes), click+drag to select all the nodes, and click "Join selected nodes". It seems to join each end node with the closest end node it finds. You'll know it worked if the number of nodes indicated in the status bar at the bottom suddenly gets a lot smaller. It also works for objects with small gaps - in that case, choose "Join selected endnodes with a new segment" so that the nodes don't move around.

A warning: manipulating a lot of objects or nodes can be very slow - be patient and let Inkscape do its thing. You'll especially see delays after selecting or joining a lot of nodes. Also if your paths appear to get filled in, make sure the fill is set to off.

Hmm, looks like the first thing you should do before combing anything is to turn off any fill on the objects and turn on a stroke for the lines so that you can see exactly where the objects are. This makes pre-combining fiddling much easier. In the file I'm working on now, some of the corners have little squares around them that need deleting and they weren't visible until I applied a stroke rather than a fill.

Operating Procedure

1. Prepare Artwork

Prepare a file using your favourite software. Export it to one of the supported file types. Transfer the file to a USB storage device (or use WIFI on the control computer).

• DXF (AutoCAD) -- you can export from Inkscape (for best results, refer to above guidelines), Corel Draw, SolidWorks
  • From Adobe Illustator: Under AutoCAD Version, select R13/LT95 or R14/LT98/LT97; Layers are flattened.
• AI (Adobe Illustrator)
  • Save as pre-CS; no compression; no extra features.
  • Layers are flattened.
• PLT- HPGL Plotter file
• DST – Tajima
• NC – G-code
• BMP/JPG/GIF
  • Must be 1-bit B/W
  • Will not be to scale, but can be resized with LaserCut (TODO: determine DPI)

2. Clear Cutting Bed

Open the front lid on the laser cutter and clear any material from the cutting bed before turning it on. This is important because the laser head will return to the home position when powered on.

Remove alligator clip if Mark left it there. TODO: more explanation

3. Power On Laser, Chiller, Air

Turn on the laser cutter by rotating the stop button to the right.

The laser should power up and beep; the chiller should turn on and hum; the air compressor should turn on and buzz.

4. Start Software

• Start up the LaserCut software. If it was already running, it will need to be restarted to re-establish communication.
  • If communication fails, replug the blue USB cable.

5. Set Up Job

Import the file that you want to cut.

Set Laser Speed and Power: You can cut or engrave different parts of your drawing using different speed and power settings. Here's how. In the upper right corner, there is a table of one or more "layers": each table entry has a colour, a mode, a speed, and a power. Initially, the entire drawing is black, and there is one layer, black. You can create additional layers by selecting subsets of your drawing, and clicking on a colour icon in the bottom row, which assigns a colour to the selection. Double click on a layer to set the laser speed and power for that layer (which controls the speed at which the laser cutter will move and the amount of power that the laser will output). You should also specify a mode (engrave or cut). The laser power setting for engraving will be much smaller than the value that would be used for cutting. The settings will also depend on the type of material that you are cutting. Be prepared to use some scrap material to run test cuts until you have the settings correct.

6. Set Up Material

Carefully place the material that you want to cut onto the cutting bed. WARNING: the honeycomb bedding is fragile: you can damage it by hefting a heavy slab of material onto it at an angle.

If the material is too thick for the laser head to pass over, use the Z- button to lower the table. DO NOT PRESS Z Datum!

Use the X-, X+, Y- and Y+ buttons in the LaserCut window to position the laser over the middle of the material. Hold a button down for continuous movement.

Focus the laser. If the material is hard and flat then you can use the autofocus function. If the material is soft or thin then you must focus manually.

NOTE: The autofocus feature is currently disabled. You must focus manually.

Automatic focus

With the laser positioned over the middle of the material, press the Z Datum button from the control software. The Z-axis will rise until the sensor is triggered. The sensor is the cylindrical brass finger beside the optics. Once this is done you should manually check the focus with the focusing tool. WARNING: Do not press the Z Datum button when the laser is in home position, or the table will crash into the head. If this happens, the head will need to be readjusted. DO NOT CONTINUE IF THIS HAPPENS!

Manual focus

Lower the Z-axis, so you can place the material underneath the lower tip of the laser head with about 3 mm of space. Slowly adjust the Z-axis while using the Focus Measuring Tool to check the height of the laser head. The "Tool" is a 15mm x 58mm clear acrylic rectangle with the word TOOL engraved on it, with an overhang to mark the height of 55 mm, which is the distance from the top of the laser head to the material. The overhang on the tool is placed on the top of the laser head, and will extend down past the laser head and just sit on the material when adjusted correctly.
WARNING: Do not lower the Z axis all the way to the bottom. There is no limit switch. If this happens, the table will need to be realigned. DO NOT CONTINUE IF THIS HAPPENS!

7. "DownLoad" to Laser

Click on the DownLoad button to send the file to the laser cutter.

Click on the Del all button in the Stand-alone file manager box.

Click on the Download Current button and the file will start transferring to the laser. Close the dialog box when the transfer is complete.

Note: If you change any of the job settings, such as power and speed, you will need to repeat this procedure.

8. Verify Positioning

Click on the Run Box button while watching the cutting bed. The laser head will move in a box shape to indicate the cutting area. Verify that the material is underneath the box. If it is not, reposition the material and press the ‘Run Box’ button again. Do this until you are certain that the box is over the material.

Note that this shows you the bounding box of the last job to be downloaded to the laser cutter. If you've changed your job, make sure to download it again before using the Run Box command.

9. Run Job

Turn on the fume extractor using the power switch on the power bar.

Close the lid and press the Start button. The laser will start cutting the material and will beep when the cutting cycle is complete.

WARNING: Do not walk away while the job is running. Monitor the job, and be prepared to hit the red button and use the fire extinguisher if it catches fire. Tiny flames are okay, but a general conflagration may damage the laser cutter.

10. Remove Material

Open the lid. Use the Datum button in LaserCut (in the X/Y axis cluster) to move to laser out of the way, back to the home position. Remove the material.

11. Power Down

Turn off laser by hitting the big red button. Turn off the fan at the power bar on the floor.

DOs & DO NOTs

A member shall not damage the laser cutter, or by inaction, allow the laser cutter to be harmed.

DO

• DO watch the laser while it is cutting at ALL TIMES. DO NOT walk away. DO NOT go to the bathroom.
  • It takes less than a minute for a fire to start and damage the laser.
• DO load material carefully onto cutting bed.
  • Try not to smash the honeycomb with the corner of your material.
• DO use common sense when experimenting
  • Think ahead and be aware of any potential hazards

DO NOT

• DO NOT bottom out the table (Z-axis).
  • There are no limit switches at the bottom and the table will become uneven, requiring realignment. If you bottom it out, do not bring it back up without verifying the table is level.
• DO NOT press Z-datum (autofocus) while the head is in the home position.
  • The autofocus switch is not over the table in the home position. The table will crash into the head, pushing it up, and it will need to be realigned.
• DO NOT autofocus on soft material (cardboard, cloth, soft wood).
  • The autofocus sensor will squish the material. The table will hit the head. The focus point will be incorrect.
  • Instead, use a hard piece of material (acrylic, wood) of the same thickness to autofocus; or manually set the focus point.
• DO NOT lean on the cutting bed. The honeycomb is fragile.
• DO NOT cut inappropriate or dangerous material.
  • You can't cut metal. (You can engrave anodized aluminum, or etch paint off of metal.)
  • DO NOT put magnesium in the cutter. It may catch fire, the fire burns hot, and cannot be extinguished by normal means.
  • DO NOT use plastics containing chlorine. They will release a gas that corrodes the laser cutter.
  • Lexan/polycarbonate cuts poorly, and the gas gums up the optics.

DO NOT USE THESE MATERIALS EVER

• Lexan/Polycarbonate
• Vinyl/PVC
• Particle board & Plywood (or any other wood containing glue)
• Human flesh (really!)
• Polystyrene or Polypropylene foam (FIRE!)
• Anything else that gives off chlorine gas when burned

Maintenance

Maintenance for the Laser Cutter now has it's own wiki page:

Laser Cutter Maintenance

TODO

• Move laser to shop, build laser room
• Buy or make autofocus assist plates of various thicknesses, for autofocusing soft material
  • Aluminum/plastic plates of 0.5mm, 1mm, 2mm, 4mm etc..
• RFID Access Control
• Water flow sensor for cooling unit

Speeds & Feeds

Raster Engrave

Vector Engrave

Vector Cut

Reference

Manuals

• Kwartzlab Laser Cutter Procedure with pictures
• Hardware Manual (PDF) - Not specifically for our machine, but close enough.
• LaserCut 5.1 Software Manual (PDF)
• Software Addendum for Rotary Attachment (PDF)
• Rabbit Laser Manuals & Tutorials - Manuals & Tutorials for similar machines
• Rabbit Laser FAQ - Useful information

Other

• Chinese Laser Support Forum
• NYC Resistor: Laser Power
• How to determine if a material contains chlorine
• Polymer Identification (PDF)

Other Hackerspace Lasers

• Site 3 G.Weike 18x24
• Think Haus
• i3 Detroit
• Noisebridge - Full Spectrum 12x16 40W
• DIYode has a G. Weike LG900N (same as us)