Laser Training Checklist
The contents of this checklist are addressed during Laser Cutter Training. Once users complete the training, their HUID and GSD username will be given access to the Laser Cutters and affiliated systems. At the discretion of Fabrication Lab staff, users will lose access privileges if they are found to have been operating equipment in a manner not in keeping with the instruction below:
Table of Contents
How Laser Cutting Works
A laser cutting machine works by amplifying light to such a degree as to either melt or burn a material while following a designated path. Vector and/or raster images are sent to the machine in a similar manner as to printing with a conventional paper printer. Colors within the drawing are used to specify the power, speed, and number of pulses of the laser applied to the image at that particular location, allowing lines to be cut with different settings within one drawing. The power of each individual laser cutting machine available at the GSD varies as the technology has developed over the years they have been acquired. Wattages for the individual machines include 120 Watts and 150 Watts. Increased wattage allows thicker materials to be cut more quickly, but does not necessarily affect the speed or quality of the cut achievable in thinner materials.
Appropriate Materials
Cast and extruded acrylic (obtainable from either the Lab Store or Altec Plastics), mat board, thin wood, wood veneer, craft plywood, non-PVC sign vinyl, cork, rubber and natural leather are materials appropriate for cutting and engraving with a laser. Many clear plastics look identical but are chemically very different and should not be cut using a laser. Consult Fabrication Lab staff or Laser TAs before cutting or etching any material not listed above. Laser engraving or cutting materials other than those listed above is a potential hazard and can cause damage to the laser machine, start fires, or be a significant risk to the health and safety of users and others. Out of regard for the health and comfort of others, cutting materials other than paper, mat board, or thin wood veneer is restricted to those lasers in L40 where adequate ventilation is provided.
- Do not engrave or cut Polyvinylchloride (PVC) based materials.
- Do not engrave or cut materials with reflective surfaces such as glass or metal.
- Do not engrave or cut materials containing melamine resins.
- Do not engrave or cut plastics containing nylon.
- Do not engrave or cut High Density Foam or other materials containing polyurethane.
- Do not engrave or cut MDF or Plywood or other materials containing either urea- or phenol-formaldehyde.
- Do not cut foam-core board or other materials containing Polystyrene or Styrene foam.
Potential Hazards
The potential hazards associated with use of a laser cutter require that they be attended at all times while in use and be under constant supervision. Failure to do so will result in revocation/suspension of a user’s access privileges. To adequately monitor an operating machine, only one laser cutting machine should be operated by a user at any time.
Fire:
Cutting materials with a laser frequently causes flaming and/or sparking. Some materials are more prone to causing flaming or sparking than others. Adjust power, speed and frequency/PPI settings to reduce the flame. Never leave the laser unattended, even if for a very short time, and be attentive while operating the machine. Make sure any flame present does not come into contact with any part of the laser system as flame will damage the machine. Small flames can easily lead to larger fires and risk the health, safety and lives of others. Pay attention to any smoke or smoldering present after cutting as off-cut material may be on fire within the down-draft table. Should a fire ignite, shut off the ventilation to the machine by hitting the red button on the wall next to the card swipe to prevent additional oxygen being supplied to the fire. If small enough, extinguish the fire with an extinguisher present at each machine or mounted to a near-by wall. However, keep in mind that when the top door to the machine is opened, additional oxygen may be supplied to the fire, causing the fire to grow. If the fire is too large, exit the room, making sure all doors close behind you, and alert others by activating an alarm or calling emergency response. An Incident Report must be completed by both the user and Lab Staff within 24 hours.
Particulate:
All airborne particulate presents a potential health concern regardless of the nature of the material being cut. The method of cutting materials with heat as employed in laser cutters generates smoke and causes particulate to be dispersed into the air. Ventilation systems meeting equipment manufacturers’ recommendations are connected to each laser cutting machine to remove air, vapor, and particulate from the unit while cutting. Opening the door to the laser cutter to remove material after it has been cut releases some airborne particulate that has not yet been evacuated; a delay in opening the unit may decrease the amount of particulate dispersed. Disposable dust masks are available to users to reduce respiratory exposure to this particulate.
Radiation:
Exposure to the laser beam may cause physical burns and can cause severe eye damage. Do not stare at the bright light emitted by the laser or at the red dot pointer. Safety mechanisms are installed on the two doors on each machine to immediately disable the CO2 laser beam when open, however, the red dot pointer is not deactivated by the opening of either door.
Fumes:
Fumes can be released when materials are heated, melted and burned. Cutting certain types of materials with a laser will release toxic fumes. For this reason, a number of materials are not permissible for cutting with a laser. Cut only those materials listed above as appropriate and do not attempt to cut those which are not on the list without first consulting with Fabrication Lab staff or Laser TAs. Fumes released that are not necessarily toxic can still be a nuisance and offensive. For this reason, cutting materials other than paper, mat board, or thin wood veneer is restricted to those lasers in L40 where adequate ventilation is provided.
Parts of the Machine
Because the GSD has 7 laser cutting machines that were acquired over the past 5 years, there are differences between the physical parts of the machines and the interfaces for them, but they all operate in the same manner and have the same basic operating parts to pay attention to. Be aware of the location and functionality of each of the below components.
Laser Cartridge
Contained within the back cabinet of each machine is a sealed CO2 laser cartridge that produces intense visible and invisible laser radiation. This is what produces the beam of light that is used to cut materials. These units do have a life-span that affects the power of the light beam that they are capable of producing.
Mirrors
From the back cabinet of the machine, a series of mirrors bend the laser beam to direct it to the focus carriage as it moves in X and Y above the material to be cut, making their alignment and cleanliness important. A misaligned mirror or missing shroud could direct light from the CO2 laser cartridge to outside of the machine.
Focus Lens
The beam of light from the laser passes through the focus lens and converges at a small point, called the focus point, 2 inches beneath the lens; this lens is located at the bottom of the focus carriage. The operating focal range of the lens is within .05” of the 2” focal length of the lens, so the material surface should be located within this Z (height) range.
Focus Tool
This is a tool used during manual focusing of the laser, and is a stick with a base and a beveled edge at 2” height. It is placed beneath the focus carriage such that its flat face is in contact with the front flat face of the focus carriage. When adjusting the Z-height of the table to focus the laser onto the material surface, the focus length is achieved when the focus tool tips out of plumb due to the carriage pushing down on the beveled edge of the focus tool.
Focus Carriage
The focus carriage moves the Focus Lens and the concentrated point of light in X and Y across the surface of the material, it is driven by the XY motion system.
Y Motion System
The motion system of the machine consists of the mechanically moving parts of the machine that control the X and Y movement of the focus carriage, this system is made up of motors, rails, belts and bearings. The CPU controls the movement of the motors which drive the belts to move the X-rail along the Y-rail, and the focus carriage along the X-rail.
- Y-motor: drives belts along Y-rail that move the X-rail
- Y-rail: on either side of cutting area, guide front-to-back motion
- X-motor: drives belt along X-rail that moves focus carriage along X-rail
- X-rail: spans the cutting area, guides left-to-right motion
- Bearings: facilitate movement along rails, check for obstructions, derailment or damage
- Belts: pulled by pulleys connected to motors, check for obstructions or damage to teeth
Z Motion System
The Z-motion of the machine is controlled by the user when focusing the lens on the surface of the material. Unlike the XY Motion System, the Z-motion is not active while the machine is cutting a file. The controls, either on the control panel on the front of the machine or through the on-screen laser control interface, allow the user to move the engraving table up or down, closer-to or further from the focus point of the lens. One motor drives a belt which turns two lead screws, raising and lowering the table.
Engraving Table
The solid flat area on which materials are placed for cutting is 18” x 32” on all of the laser cutting machines available. Materials can be taped to this surface if they are being engraved only (and not cut through). If cutting acrylic and there is no downdraft table available, users should raise the acrylic off of the surface of this table to prevent the material from bonding to it. Users must thoroughly clean this surface with isopropyl alcohol and paper towels after each use.
Downdraft Table
All the laser cutting machines have a downdraft table is installed. The open honeycomb structure of the surface of this table allows air to be pulled through it, removing smoke and debris from the underside of the material. This table is recommended when cutting acrylic as it also prevents the acrylic from bonding to the table surface. Small off-cut material will fall into the table, requiring it be emptied on a daily basis to reduce risk of fire.
Exhaust Plenum
At the back of each laser cutting machine is a vertical plenum which draws smoke and air out of the cutting area and directs it into the external exhaust system. Excess build-up and off-cut material within the plenum can decrease the circulation of air through the machine, preventing the evacuation of smoke, particulate and vapors created during engraving or cutting and increasing risk to the health and safety of users and others.
Air Assist Cone
On those lasers located in L40 and L40E, an air assist cone is installed to help extend the life of the lens by preventing the buildup of debris on the lens. Compressed air is supplied to the cone to help keep the space in front of the lens free of smoke and particulate. Improper use and settings can contribute to build-up of residue on the interior of the cone, preventing the focused light from passing freely, decreasing quality of cut and increasing potential damage to the Focus Lens. Compressed air must be flowing through the cone in order for it to offer protection to the Focus Lens.
Interlocks
A number of sensors are installed to either side of each door and detect when the door is not sufficiently closed. Because the hinges of the doors are prone to breakage, it is possible that sensors are not lined-up properly. Consult a TA if this seems to be the case. Be aware that there may be more than one door with interlocks. The Universal lasers have three doors, one in the front, one on the top and one in the back. The doors and hinges are relatively fragile, do not slam doors shut if they are not closing easily as this will promote door and interlock failure.
Sensors
To establish the home position in X and Y and establish limits to Z motion, a number of sensors are located along the axes of travel. There is one senor in both the X and Y directions, activated when the carriage is in the top right position. There are two sensors for the Z direction, at the top and bottom of its travel. Obstructions or damage to any of these sensors will cause malfunction within the motion systems and can cause files to be cut incorrectly.
Creating a Cutting File
Both raster images (pixel-based) and vector drawings (zero-weight lines) can be used to create cutting files. Either type can be sent from AutoCAD, Rhino, or Adobe Illustrator. Files can be prepared in other software and exported as a DWG to be cut from AutoCAD, Rhino, or Illustrator in the lab. It is possible to cut from other software as well, but the GSD Fabrication Lab staff will not support nor troubleshoot issues encountered when using other software.
Measure
Oftentimes actual material thickness differs from its advertised thickness. If fitting and accurate dimensioned parts are important to your model, you should measure your material thickness before making the final cutting file. Also be aware that the laser beam does have a “kerf” and a small amount of material will be removed between the cut piece and the surrounding material. After focusing the laser, cut a part with the desired settings and measure its cut size as compared to its drawn size. Most likely, the cut part is slightly smaller than as it was drawn as the center of the laser will follow along the curve, removing material on both sides of the zero-dimension curve. Offset your geometry accordingly, if necessary. Variation of laser kerf may occur between machines and with different settings or materials.
Line weight
For drawn geometry to be recognized as a vector, line weights must be scaled such that they are less than 0.001 units in AutoCAD, Hairline in Rhino, or 0.072 pt. in Illustrator. Lines that are heavier than this will either not print (if “vector” is selected as the type in the laser configuration setup) or will print as a raster dot pattern (if “raster/vector” or “raster” is selected as the type in the laser configuration setup).
Color
When assigning color to geometry, be sure that the values in the color profile match those defined in the laser configuration setup. It is advisable to select only basic RGB and CMYK colors. The order in which the colors appear in the laser configuration setup will control the order in which each color is cut. For some of the lasers, the order of these colors in the configuration setup can be changed by the user, but for the older Universal lasers, this is not the case, the color (and cut) order is fixed. Some of the laser cutter drivers allow users to specify the order in which colors will cut, others may not. Within each color, the some of the laser cutting machines are capable of optimizing the cut order for speed. Depending on the software program, white and gray scale colors may or may not print with the black configuration settings. Through color, control the cut order such that etching occurs first, then any interior cuts (windows), and finally the exterior perimeter cuts. Cut parts may move while the laser is cutting subsequent parts, making it advantageous to cut interior shapes before exterior ones.
Scale
Many students find it helpful to scale their drawings so that they print at a 1:1 scale, drawing a bounding box that matches the dimension of the cutting area of the machine and then using it to define the print window or Art Board. The upper left-hand corner of the print window or layout corresponds to the upper left-hand corner of the engraving table and should be used as the point of reference in both the file and the physical setup of the machine. It is recommended that the bounding box be drawn on a non-print/ non-plot layer (or with a non-print line weight in Rhino).
Location
Offset geometry at least 1/4” away from the extents of the cutting area to ensure the geometry will be contained within the cutting area and material sheet. A quick and easy way to precisely locate cut geometry on a piece of material is to first cut a sacrificial piece of material as a reference frame into which you then place the material to be engraved. This method is suggested as a way to accurately place laser-cut geometry onto a part that has been pre-cut to size.
AutoCAD
Organize your vector work into layers such that the color of the geometric entities will control the settings applied to the geometry and the cutting order. (All lines to be etched should be a different color from those to be cut.) Make sure all geometry is on “plottable” layers, is planar, and is located at Z=0 (accessible through the properties menu). Vector entities should have their line weight scaled to 0.001 units or less (also accessible through the properties menu). Setting color or line weight “by layer” is oftentimes not effective, instead, select the geometry and set these values explicitly through the properties drop-down menus.
Rhino
Either an entity’s Print Color or Display Color can be selected as the output color and therefore used when assigning engraving settings to the entity through the Rhino Print Setup. However, for the sake of consistency, it is recommended that all users organize geometry using layers that have Display Colors corresponding to the basic RGB and CMYK colors and Print Colors that either match or are assigned by layer. Print Widths must be set to Hairline in order to be recognized as vector entities. White entities will not print.
Illustrator
Through the file menu, set document color mode to “RGB Color”. Colors of the lines themselves, rather than of the layers, determine the engraving settings that will be applied to the geometry and graphics. It is helpful to scale the art board to match the material dimension. Line weights must be scaled to 0.072 pt. in order to be printed as vector entities.
Settings
Power and speed work together to control the depth of the cut. Higher power and slower speed produce deeper results. Lower power and higher speed produce shallower results. The combination of settings for power and speed, as well as PPI will depend on the material you are cutting, the machine you are using, and the desired results. Consult posted charts for starting guidelines and always do a small test in the material you will be using before cutting your final geometry.
PPI
The laser beam is never “on” continuously, rather, it pulses. The PPI setting indicates the number of pulses per linear inch that will be emitted. These pulses will fire equally spaced regardless of changes in the speed of the carriage. Using less than 150 PPI will result in pulses being spread so far apart that they may not touch one another, producing a dashed appearance. Higher PPI settings will cause more of a melting or burning effect on the edges, necessary for acrylic but not appropriate for chip board or wood.
Power
Settings are available from 0 to 100%. This setting directly relates to the depth of the engraving. The higher the setting, the deeper it will cut. Low values are appropriate for etching, higher values are necessary to cut through thicker materials.
Speed
Settings are available from 0 to 100%. This setting determines the maximum rate of travel of the XY motion system. The actual speed may slow when cutting curves versus straight lines or when turning corners.
Mode
There are four options to choose from in determining how the settings are mapped to the colors.
- RAST/VECT: This setting treats fills and lines thicker than 0.001” as raster entities, cutting them as a dot pattern, similar to a conventional ink jet printer, and treats those that are smaller-than or equal to 0.001” as vector entities, cutting them by following the curve directly, much like an old pen plotter.
- RAST: This setting will treat all lines and graphics as raster entities regardless of line weight and cut them as a dot pattern much like a conventional ink jet printer.
- VECT: This setting will only cut appropriately scaled lines (0.001 units or less) as vector entities, following the curves directly, it will skip all thicker lines and graphics.
- SKIP: This setting will ignore all geometry assigned the associated color.
Once users have found settings that produce desirable results for a particular material on a particular
machine, it is recommended that they then save the laser settings for future use. Files are saved to a .las file
and can be loaded into the printer configuration rather than assigning settings to colors for each and every
job sent to the laser cutter
Sending a Cutting File
There is essentially one type of laser cutting machines at the GSD. The user interface on
each machine is nearly identical, but there are small hardware differences that also manifest in the printer software.
General Steps
The process of sending a file to cut is the same on all of the machines, but the particular
steps for doing so vary due to differences in the user interfaces and hardware.
- START Button: The laser cutting machine and affiliated compressed air and ventilation will not turn
on until you have done so. Each laser cutter has an associated green “Start” button, a yellow light
will be activated when the “Start” button has been pushed. - Focus: With material placed on downdraft table or engraving table, raise the bed to the appropriate
height under the focus carriage using either the focus stick (all Universal lasers). It may be necessary
to move the focus carriage first, so that it is over the material. - Plot/Print File: From software program of choice, print the desired geometry. Select the affiliated
laser cutting machine from the drop-down menu and be sure to set the laser settings in the printer
configuration dialog (accessed through printer properties or setup in the print/plot interface). - Close Door and Confirm Ventilation: Make sure all doors to the machine are closed and the
ventilation is pulling through the unit. Confirm there are no obstructions within the cutting area, it
may be necessary to tape your material down. - Start Cut: Confirm the correct file is displayed in the UCP or the filename on screen on the unit.
Using either the on-screen button or start button on the unit, begin cutting. - Observe: Watch the machine as it cuts or engraves to make sure it is the correct file and it is located
correctly within the cutting area. Double-check that you’ve correctly set the laser speed, power and
PPI settings by confirming that there is no excessive flaming and your material is being cut through
as desired. If you need to leave the area, for even a short duration, pause the machine, it can be
resumed upon your return. Users may not operate more than one machine at a time. - STOP Button: When done cutting and leaving the laser, press the red “Stop” button; located beneath
the “Start” button used to turn it on. This will shut-off the machine as well as the compressed air and
ventilation. - Clean: After removing your parts and off-cuts, thoroughly clean the machine. Remove any chips
with a vacuum and wipe the engraving table with spray cleaner if you’ve removed the downdraft
table. Leave the adjacent table and computer area clean as well.
Universal PLS Lasers
The lasers located in L40 and L40E have displays on the units themselves in addition to the UCP. Functions such as moving the focus carriage or engraving table can be accomplished through these physical buttons in addition to starting or stopping cutting of the file name displayed. Files sent to the machine can be browsed and printed multiple times without re-sending them. Advanced users can also adjust the power and speed settings while the file is cutting through these controls.
Exhaust System
All Laser Cutters at the GSD are connected to a ventilation system that exhausts to the roof. This system is automatically turned on when the green “Start” button is pressed. Hitting the red “Stop” button after you are done using the laser cutting machine will allow the fan for that unit to turn off, saving power and reducing noise.
Make sure the fan is pulling air through the laser cutting machine before beginning to cut. Any indication
that sufficient ventilation is not being provided to the cutting area of the machine must be responded to
promptly. An accumulation of smoke is a good indication that the exhaust system is not functioning normally. Stop cutting and notify Fabrication Lab staff or a Laser TA immediately. Notify other users of the issue by placing an “Out of Order” sign on the machine. Failure to do so could result in unsafe conditions or damage to the laser cutting machine as the fume extractor is not able to extract potentially harmful particulate or fumes