Laser Cutter

JHU Laser Cutter Instruction Manual (version 07/26/07): Page 1

JHU Laser Cutter Instruction Manual The laser cutter is an efficient tool for rapid manufacturing of flat parts. It can cut geometry from a two-dimensional CAD file into sheets of various wood- and thermoplastic-based materials (not metal). It is an ideal tool for cutting intricate shapes with sharp internal corners. It is also excellent for creating quick prototypes and for building things that can be assembled from 2D components. The laser cutter owned by the Johns Hopkins University Department of Mechanical Engineering is an X2660 by Universal Laser Systems, Inc. Its dual 60-watt lasers can cut through materials up to 1/2” thick and it can also score the surface of the material without cutting through, a process that is also known as engraving. The maximum size that the laser cutter can cut is 32” (81.2 cm) by 18” (45.7 cm). The maximum speed at which it can cut is over 200 inches per minute (508 cm/min), but this varies with material and thickness. The laser cutter is connected to a PC that runs AutoCAD; this program can be used to draw parts, or it can load a DXF or DWG file that you have drawn in another program. Once the geometry of your parts has been defined, you use AutoCAD to specify how they should be cut. AutoCAD then translates your two-dimensional drawing into plotting commands for the laser. The materials that you can cut and engrave on the X2660 include fabric, leather, paper, cardboard, plastic (sheet, film, and molded), rubber (natural, synthetic, and foam), and wood. Additionally, you can engrave (mark only) glass, ceramic, metal (coated and bare) and stone (natural and synthetic). Please ask before trying to cut a material that is not on this list - the laser cutter is a valuable tool, and some materials may damage its optics. Users must undergo a training session to learn how to operate the machine before they can use it on their own. This session will take about one hour, and it will familiarize you with the workings of the machine and its safe operation. Once you have completed the training, follow the steps listed below to create a part on the laser cutter. Note that you must obtain a budget code to enter in the log to pay for the time you use the machine. As of this writing, the cost is $15 per hour of actual cutting time.


A. Prepare Drawing The first step to creating a part on the laser cutter is to make a two-dimensional CAD drawing of the geometry you want to cut. If there is no one else waiting to use the machine, you can draw simple parts on the laser cutter computer in AutoCAD. For most projects, you will need to draw your parts ahead of time and then save or export them as DXF or DWG files, the formats that AutoCAD can read. Almost all CAD programs can provide this functionality. When you are making your drawing, keep the following points in mind:

• Your drawing should use inches as the base units, rather than metric units.

• Make sure your parts will fit on the laser cutter bed (32” left-to-right by 18” front-to-back) and on your sheet of material.

• Each operation should be on its own layer; for example, a cut profile should be on a separate layer from an engraved detail. Use your drawing program or AutoCAD to control which layer your geometry appears on. (For advanced users, you can use only the line color, instead of layers, to specify cut settings.)

• The laser cutter will cut entities twice if they appear twice, so be sure to clean up your drawing before exporting.

• If you need dimensionally accurate parts, you must compensate in the drawing for the width of the laser beam and the melt/burn back. This width of material that disappears is called the "kerf ", and it varies by material and thickness. It is usually between .008” and .010”, so offset your part .004” to .005”. If your project requires dimensionally accurate parts, run a test cut in your intended material and measure the kerf for yourself.

In addition to AutoCAD, the laser cutter computer has Pro-Engineer and Visio. Pro-Engineer software is also available in the Kreiger Academic Computing Lab in 160 Kreiger Hall (http://www.jhu.edu/KriegerLab/) and the Mechanical Engineering Senior Design Lab in 113 Latrobe Hall. CAD tutorials can be found online using Google to search for terms such as "AutoCAD tutorial" and "Pro Engineer tutorial". B. Prepare File for Cutting The next step to creating a part on the laser cutter is to process your geometry so that the machine can cut it. This processing requires the use of AutoCAD, which is available on the laser cutter computer.

1. Login to the computer: If not already logged in, enter the username “user” and the password “user” to start Windows XP. If a regedit error appears, ignore it and continue. (This happens because you are not logged in as administrator.)

2. Load file onto the computer: If you draw your geometry ahead of time, you will need to

load it onto the laser cutter computer, which runs Windows XP and is connected to the Internet. A USB flash drive is a good option for this transfer, as is sending your file to


yourself via web-based email. Once you can access it from the laser cutter computer, copy your DXF or DWG file to the laser cutter computer’s hard drive.

3. Launch AutoCAD: Launch the AutoCAD program by double-clicking clicking on the

“AutoCAD” icon on the desktop.

4. Open file in AutoCAD: Open your DXF or DWG file in AutoCAD by clicking on “Open” and navigating to your file on the computer’s hard drive. The program will then show your geometry in the main window.

5. Assign layers: If you want to make more than one type of cut, you will need to place

your geometry on separate layers. Use AutoCAD’s layer functionality to do this if you did not assign your geometry to layers in your original CAD program. AutoCAD will display the geometry on each layer in a different color. If you have dimensions on your drawing, you should put them on a separate layer unless you want to cut them in your material.

6. Set plot parameters for cutting: The next step in creating a laser cutter part is to specify

the operation, material, and thickness for each layer of your drawing.

Begin by selecting the Plot command from the File menu. A window will appear with two tabs: Plot Device and Plot Settings. You will need to configure both of these in order to cut your part correctly. The Plot Device tab is where you specify how your geometry is going to be cut. It should appear with the settings below.


Click “Properties” next to the X2-660 device, and plotter configuration window, shown below, will appear.

Click the "Custom Properties" button. The X2-660 Properties window will appear, as shown below. This window allows you to configure the type of operation you want performed on each layer of your drawing.


If you have only one layer in your drawing, it is most likely the black layer, which is displayed on the screen as white lines on the black background. Note that, even if you do not have a black layer, the laser cutter will not cut the other layers unless the black layer is set to cut.

Layers marked with pen mode “SKIP” will not be cut. You should set layers with profile lines to be cut in the “VECT” (for vector) mode. Engravings made from images that are pixel-based should be cut in the “RAST” (raster) mode. For each layer that you want to cut, you should set the following important items:

• The “Power” option adjusts the strength of the laser from 0% to 100%. • The “Speed” option changes the rate at which the machine will traverse your

geometry, ranging from 0% to 100% of its maximum speed. • The “Set” button locks in your settings for the selected layer. If you do not push

“Set,” your changes will be lost and the system will use the previously configured operations to cut your file.

Check the X2660’s manual for the cutting power and speed suggested for your material. You should always perform test cuts with a material that you have not personally cut before to ensure the correct settings. Some notes about materials: We hope to update this manual to include suggested materials, including vendors and laser cutter settings. The most popular material used with the laser cutter is Acrylic (also called Plexiglas). Quarter-inch acrylic cuts very well. Here are some hints for cutting acrylic (may apply to some other materials as well): • Keep the paper on the bottom side of acrylic stock, but remove it from the top side.

The paper on the bottom protects the finish from possible burn marks. It also provides good confirmation that you have cut all the way through the material, as the burning paper emits a bright light.

• Flames will form on top of the part, possibly burning it, when you cut close to the edge of your stock. There are always flames underneath your part, and they leap to the top of the part when there is only a small distance between the laser and the edge.

• Cutting thin pieces of acrylic (1/8") often produces warped parts, as they absorb a great deal of heat and are not very stiff. It can help to put a thermally insulating layer underneath your stock, such as foam core or cardboard, so that the flames do not heat up the plastic as much.

• Sometimes it can be useful to use double-sided tape to attach thin stock to the insulating layer so that cut parts do not move during cutting.

• The cut surface is not perpendicular to the plane of the material - it has a slant. Some postmachining on a mill or postdrilling on a drill press may be necessary to make straight-sided edges and holes.

Once the layers are all configured correctly, click “OK” to return to the plot window. If it asks, let it make a temporary PCS file for this cutting operation. The Plot Settings tab, shown below, is where you specify the layout of your geometry.


The important items to set are the following:

• Select a scaling factor for your drawing from the Scale drop-down menu. If you want your part to be the size you drew it, select “1:1”. Otherwise, choose your desired scale factor.

• At the left-hand side of the window you can choose to plot the “Limits,” “Extents,” or “Display” of your geometry. Choosing “Extents” will plot everything you have drawn, while “Display” will plot only the items presently visible in your window. For most applications, “Extents” is the best choice.

• At the bottom of the window, you can choose to center or offset your geometry on the bed of the laser cutter. If you chose “Extents” in the previous step, a good option here is to check the box marked “Center Plot.” This choice will put your parts in the middle of the bed of the laser cutter. Adjust the offset if you choose.

• The “Preview” button at the bottom will show you what the laser cutter is presently configured to cut. Verify that your part is the correct size and that it appears on the correct part of the machine’s workspace. If not, adjust the above settings and preview again.

C. Prepare the Machine Now that you have finished processing your file, you are ready to set up the laser cutter. Leave the program open on the computer, ready to plot your file, and approach the machine.

1. Clean the lens and mirror: ME staff members check the laser cutter regularly during the workweek. If it is not a normal workday (Saturdays, Sundays, and Holidays), the laser


lens and mirror may have gathered significant residue from previous cuts. This residue can burn and crack the lens and mirror, necessitating expensive replacement parts and machine downtime. Thus, you should clean the lens before using the laser cutter. • Use your hand to remove the two screws that hold the lens/mirror assembly in place.

(There is space for three screws, but one was lost at the time of this writing. Be sure to set aside the screws in a safe place.)

• Grasp the lens/mirror assembly and slide out of the housing.

• Get the optical cleaning fluid and a cotton swab from the upper right drawer of the laser cutter computer desk. Put a small drop of fluid onto the swab.

• Clean the mirror and both sides of the lens, using a motion that spirals the swab from the center of the mirror/lens to the edge. For each new surface you clean, add a drop of fluid and use a different area of the swab. Be very careful not to drop the mirror/lens assembly as you clean it.

• Replace the lens assembly and the screws. If you drop a screw (or anything else) into the porous bed of the laser cutter, you can open the laser cutter bed drawer, remove the bed, and look inside for the item as shown below. Push the bed all the way back into the laser cutter when you are finished.


2. Turn the laser cutter on: If the laser cutter is off, turn it on by toggling its orange power

switch. The switch is low down on its right side, next to the computer desk.

When the laser cutter first turns on, it goes through an initialization sequence and warms up its various components. Wait until the initialization completes (check status on the four-line LCD screen on the upper surface) and it says "ready" before you start working with the machine.

3. Set the laser’s focal length: The laser needs to be manually focused for the thickness of material that you are cutting. This setting is independent of material type. Improper focus can prevent your part from being cut all the way through and can leave a poor surface finish. Drastically improper focus (e.g. forgetting to lower the bed for 0.5” material) can also cause the laser to crash laterally into your part.


Once the machine has completed its initialization, open the hood, and press "SELECT" to enter the file display. Then press the “Z” key at the far right of the control panel. Press “SELECT” on the first line of the menu to begin manually setting the table height.

Place your material on the bed of the laser cutter in the location where you plan to cut. If the bed of the laser cutter does not look straight, push it back against its guides. Use the down-arrow button to lower the bed of the laser cutter if your material is thick. The head of the machine should be at least half a centimeter above your material before you adjust its location on the bed. When the cursor is highlighting the tenths place in the vertical offset field, each press of the button jogs the table down about 0.100.” Press “SELECT” again to advance to the hundredths position for more precise control. Once the bed has been lowered sufficiently, use the “X” and “Y” jog buttons to move the head of the laser cutter over your material. The machine will move slowly when you first push the button and then speed up. To avoid injury, do not place your hands inside the machine while it is moving. Obtain the focusing tool from its storage spot at the left-hand side of the laser cutter, under the hood.

Set the focusing tool on top of your material with its top vertical surface against the red front-plate of the laser head. The laser head should be flush with the notch on the focus tool, not the top of the tool. Use the coarse and fine adjustments of the table height (up and down arrow buttons) to locate the lower corner of the head at the top interior corner of the focusing tool. The images below show the correct positioning of the laser head.


When you are done setting the vertical offset, put the focusing tool back in its storage place and press "ESCAPE" twice. The laser head should return to the zero position. Remember to do this focusing step, and do it properly. You must refocus the cutter every time you use a material with a different thickness.

4. Check laser head setting: Press "ESCAPE" once more to return to the main menu. Highlight "Preference" then "Options". Make sure that "Dual Head" is set to "Off". Then press "ESCAPE" until you return to the main menu.

D. Test and Cut

1. Delete any old files in the laser cutter memory: To make sure that your file is the one

that will be cut, you should delete any previously uploaded files from the laser cutter. Hit the "ESCAPE" button multiple times until you reach the main menu, shown below left. Then use the up and down arrow buttons to scroll to "Memory control" and press "SELECT". You will see the screen shown below middle. Scroll to "Delete all files" and press " SELECT ". Then confirm your desire to clear the memory, as shown below right.

2. Send your file to the laser cutter: Next you need to send your file to the laser cutter machine. First ensure that the switch box on top of the computer is set to communicate


with the laser cutter, not the printer. Back at the computer, click on the “Plot” button in the window you configured in step B above. The file will take a few seconds to transfer over.

Once your file arrives, the laser cutter screen will enter file display mode and show you information about the presently selected file. On the example screen below, it indicates that it will cut the file named "Example" at 100% power and 2.4% speed.

Occasionally when the file is sent to the laser cutter, an error occurs and the power, speed, and PPI settings are not sent to the laser cutter. When this happens, the display shows the power, speed, and PPI settings all 0. A solution that has worked in the past is to go back to the Plot Device tab. Under “Plotter Configuration”, change the NAME from X2-660 to X2-660.pc3, complete the plotter configurations, and send the new settings to the laser cutter. The display should now correctly read the power, speed, and PPI settings that you sent.

3. Double-check settings: Check the display on the top of the laser cutter. Make sure the

proper file name, layer, material, and thickness are listed. Then double-check the laser focus to make sure it is set correctly.

4. Consider safety measures before you cut: Before you actually cut your file, it is

important to know what you should do if something was to go wrong while the laser cutter was running. The biggest hazard when laser cutting is that the material inside the laser cutter can catch fire if the settings are incorrect. Such a fire can do serious damage to the machine and could endanger you as well.

• The first thing you can do to prevent such a scenario is to make sure you

understand how the laser cutter works, check to make sure your settings are all correct, only cut approved materials, and ask someone else if you have any questions or concerns.

• The second thing you can do is to pay full attention to the machine while it is cutting. Once you do turn it on, you should always be within arm’s reach of the machine, and you should be watching it continuously to make sure nothing is going wrong.

• The third thing you can do is to act quickly if you see a fire starting. Press the “PAUSE” button as soon as possible. Pressing this button will stop the laser cutter once it has completed its current vector cut and return it to its home position, away from the fire. Turning the power off with the switch is not as good of a solution, as it


leaves the laser right above the fire, which is very bad for its optics and electronics. After you press the “PAUSE” button, do not open the hood. If the fire does not go out immediately, turn OFF laser cutter, turn OFF the air supply on the wall behind the laser cutter by rotating the red handle 90 degrees clockwise, and leave the blower (green unit on the floor) ON. This will allow the blower to suck all the air out of the laser cutter, depriving the fire of the oxygen it needs to sustain itself. If the fire does not go out immediately after that or if there is smoke in the room, leave the room and notify the guard at the entrance to the Wyman Park Building to call the fire department. Dial 9-911 from any phone if there is no guard at the desk.

• Some materials will exhibit a flame very briefly during cuts at the point where the

laser hits the material. Your material is not "on fire" unless the flames are sustained in a single location. If you do everything correctly, the material should not catch fire.

5. Test run with the visible laser: Now that you know what to do if something goes

wrong, you’re ready to test run your part. Keeping the hood of the laser cutter open, check to make sure the red light on the console is flashing. This means that the machine detects the open hood and will not use its cutting laser. Press the Green Start Button to run your file. The laser cutter will sit still for a few seconds and then go through the motions of the cut (but it will not actually cut your part). The visible red laser allows you to see where it would cut the material if the cutting laser were on. It will cut the geometry in a somewhat random order. Watch it throughout the cut time and make sure everything is going correctly. If things are not scaled or positioned to your liking, delete this file (following Step D.1), edit the plot settings on the computer, and send it again. Make sure every cut will be contained by your material so that the high-power laser beam will not hit the metal grating alone. If the material is not positioned correctly, you can either move your material on the bed of the laser cutter or adjust the Print Offset setting in AutoCAD (as described in Step B.6). If you want to pause the machine in the middle of the work, you can press the Pause button and cutting will stop at the end of the current command. Do not put your hands or anything else inside the bed of the laser cutter while it is moving.

Once you are satisfied with the visible-laser test, you are ready to cut your geometry in your final material.

6. Turn on the air supply: A high-pressure air line runs vertically along the wall behind

the laser cutter. This air is used to cool the laser head and protect the optics from smoke damage. To turn it on, rotate the red handle a quarter-turn clockwise so that it points down (parallel to the line), thereby opening the valve and allowing air to flow. This air line, along with the following ventilation systems, creates a lot of noise, so it is generally left off when the machine is not cutting material. The image below shows the air supply in the "on" position.


7. Turn on the blower: The green blower on the floor to the left of the laser cutter is used

to suck smoky air out of the machine. Turn it on by lifting up on its red paddle switch.

8. Turn on the fan for the room’s ventilation system: Turn on the switch on the wall to

the left of the blower to prevent fumes and smoke from accumulating in the laser cutter room.

9. Cut your part: Now you’re ready to cut your part. Lower the hood of the laser cutter and press the Green Start Button to run your file. The laser cutter will sit still for a few seconds and then go cut your part. It will cut the geometry in a somewhat random order. Watch it throughout the cut time and make sure everything is going correctly.


Press the “PAUSE” button if anything goes wrong, and turn off the laser cutter if there are persistent flames. Follow the safety instructions described in Step D.4 if necessary.

10. Inspect your part: When the machine finishes cutting your geometry, it will make a

dinging sound. Raise the hood and look at your part. Try to gauge whether the cuts went all the way through the material. If they did not, you can re-run your program. Make note of the settings and increase the power or decrease the speed next time. Before sending another job to the laser cutter, you'll want to clear the memory first, following Step D.1.

11. Shut down: When you are happy with your parts, turn off the ventilation system, blower,

and air line. If no one else is waiting for the machine, turn it off as well and log off the computer.

12. Log your time: Enter your name, the budget code for your project, and the start and end

times for your use of the machine. E. Clean Up When your part is done, go through the following steps to clean up the area and prepare the machine for the next user:

• Remove your part and all scraps from the bed of the laser cutter.

• If you have excess material that you don’t want, please donate it to the lab’s laser cutter scrap pile. Someone else will be very happy to use it. If your scraps are very small, make sure you throw them out.

• Delete your files or move them to an inconspicuous place on the hard drive of the computer. Note that these files may be deleted at any time. Please do not leave them on the desktop.

• Straighten up the surrounding area and make sure you have all of your personal belongings.

Revision History rev 0.0-0.5, 1995-2001 Stanford PRM LaserCamm Manual: John Wadsworth, Bryan Cooperrider, Katherine

Kuchenbecker rev 1 9/06 Katherine Kuchenbecker adaptation of Stanford PRL manual to JHU equipment rev 2 10/06 Allison Okamura thorough revision and added images rev 3 10/06 Allison Okamura made corrections suggested by expert users rev 4 7/07 Allison Okamura added problem-solving tip (courtesy of Netta Gurari) to section D.2 Suggestions for future versions: - Add a section on 2-1/2 D design and prototyping - Table on materials (purchasing information and laser cutter settings) - Add links to CAD tutorials


JHU Laser Cutter Instruction Summary

A. Prepare Drawing B. Prepare File for Cutting 1. Login to the computer 2. Load file onto the computer 3. Launch AutoCAD

4. Open file in AutoCAD 5. Assign layers 6. Set plot parameters for cutting

- Plot device tab → Properties → Custom Properties → configure the pen mode, power, and speed for layers → Set

- Plot settings tab → select desired Plot scale, Plot area, and Plot offset

C. Prepare the Machine 1. Clean lens and mirror 2. Turn the laser cutter on 3. Set the laser’s focal length 4. Check laser head setting D. Test and Cut 1. Delete any old files in the laser cutter memory 2. Send your file to the laser cutter 3. Double-check settings 4. Consider safety measures before you cut 5. Test run with the visible laser 6. Turn on the air supply

7. Turn on the blower 8. Turn on the fan for the room’s ventilation system 9. Cut your part 10. Inspect your part 11. Shut down 12. Log your time

E. Clean Up

Laser Cutter

Documents

plot device tab

green start button

set plot parameters

laser cutter settings

laser cutter computer

cad tutorials

laser cutter

focusing tool