CO2 Laser Beam Alignment on Chinese Laser Engravers/Cutters While Seeing (yes You See It) the CO2 Beam

BEST GUIDE FOR THE FASTEST LASER ENGRAVER BEAM ALIGNMENT

CO2 Laser Beam Alignment for

A CO2 laser engraver/cutter with a focus lens

Using the Mahoney beam visualization tool for an expedited process

Welcome to the best guide for your fastest laser beam alignment for top performance of your laser engraver/cutter machine. Good beam alignment reduces the overall cost of fabricated parts. This guide features the speedy method using the visualization tool from Mahoney, so that you keep the laser on and see its beam while performing adjustments. In this manner, you quickly and precisely center the view-able CO2 laser beam on the crosshairs, saving the tasks of iterative laser on/off with potentially harmful soot leading to damaged mirrors that comes with traditional masking tape or paper alignment methods. So, get on the new program for speedy alignment and use your CO2 laser beam visualization tool from Mahoney.

Though the majority of laser beam alignments do not involve a skewed laser tube or skewed gantry to its linear guideways, there remain a significant number of, mostly Chinese laser machines, that do need adjustment. After performing the standard alignment procedure below, and failing to get an acceptable laser beam alignment then you can see the problem then adjust the tube or fix the gantry’s linear guideways. Following this step, then repeat the beam alignment procedure. The visualization tool reduces your time required to perform these steps in order to get an accurate beam alignment to improve your overall CO2 laser cutter job quality.

The guide shows images representative for a Chinese laser engraver, though the Mahoney visualization tool has adapters for most popular laser engravers and laser cutters on the market, including legacy systems.

Guide Objective: To maintain a non-moving and centered laser beam into the final beam bender (mirror/reflector).

Advantage: A non-moving and centered laser beam into the final mirror will maintain a central focus spot that does not deviate over the entire laser table. And, the co-axial flow of nozzle air will evenly distribute the air pressure while cutting or engraving. Further, laser power is the same over the entire table.

Benefit: Laser cut shapes will have connected corners as specified in the software. Laser cut width (kerf and Heat Affected Zone—HAZ) are consistent over the entire laser cut job. Laser cuts are straight. Engraving shows no fading or variation at any angle.

Typical Causes for Performing a Laser Machine Beam Alignment

· Bad parts, inconsistent parts quality, irregular cuts, slower cutting speed, parts not dropping out of a nest of parts.

· Loss of power in a portion or sections of the laser machine work table

· Power is fading or different and not consistent over the entire work surface

· Engraving shows variations across the material

· When running a job, corner lines leave gaps and do not connect

· Angled cuts appear on thicker materials when laser cut

· The laser tube was replaced

· The mirrors were replaced

· Seasons changed and the change in temperature caused misalignment

· The laser machine was moved and the change in level caused misalignment

Supplies

1. Mahoney laser beam visualization tool, computer (if optional camera accessory purchased with tool) for mirrors alignment

2. Masking tape for nozzle/focus lens alignment

3. Safety glasses

Step 1: Beam Alignment Spot Check Procedure:

Spot Check Objective:

To determine if the laser beam is not moving and centered laser beam into the final beam bender (mirror/reflector).

1. Put on your safety glasses, and follow all instructions per the government requirements. On the internet, go to the recognized authority for laser safety—Laser Institute of America, https://www.lia.org/store for further information to purchase laser safety standards or the necessary safety gear, etc. The LIA members advise the government (government agencies) and quasi-governmental agencies (membership organizations like ANSI) regarding best safety practices for lasers. Note that maintenance like a beam alignment poses greater safety risks and hazards. Put on your safety glasses with side-shields now (and they should be rated for the CO2 laser).

2. Power on the laser machine and let it complete the homing startup process. Insert the Mahoney beam visualization tool into the final beam bender. Turn on the CO2 laser and adjust the laser power so that the laser beam is visible and not too bright, on the side viewport. If you have the camera option then look at the target on your computer.

3. Note the position in the cross-hairs. In other words, check to see that the laser beam is located approximately in the center of the cross-hairs, and note down its position (e.g., upper right, center high by a small amount, perfect center).

4. Jog the focus head to each side of the laser work table and note whether the laser beam has changed positions substantially in the cross-hairs.

5. Move the laser machine gantry to the front of the laser machine and then repeat the step of jogging the focus head to each side of the laser table then noting the position of the laser beam in the cross-hairs. Repeat for the back of the laser work table.

6. If the laser beam is not approximately in the center of the cross-hairs or has moved substantially (more than the diameter of the visible beam or more than 2mm), then perform a standard beam alignment.

7. Note: if an inline red dot pointer is installed on the laser machine, then repeat the above steps to determine if the red dot pointer is aligned coaxial (centered) to the CO2 laser beam.

Step 2: STANDARD BEAM ALIGNMENT PROCEDURE

Objective: To maintain a non-moving and centered laser beam into the final beam bender (mirror/reflector).

1. Power off the laser machine. Put on your safety gear. Put on your safety glasses with side-shields now (and they should be rated for the CO2 laser). See Spot Check step number 1 for additional safety requirements.

2. Remove the beam expander/collimator if installed on the laser engraver.

3. Power on the laser machine and let it complete the homing startup process. Insert the Mahoney beam visualization tool into the first beam bender. Turn on the CO2 laser and adjust the laser power so that the laser beam is visible and not too bright, on the side viewport. If you have the camera option then look at the target on your computer.

4. Examine the location of the raw CO2 laser beam in relation to the cross-hairs. It should be approximately in the center. If it is not in the exact center, that may be acceptable for your machine and it does not need to be moved, because the objective is for the laser beam not to move in the final beam bender, and so the current position of the first mirror may be just fine. Therefore, adjust the mirror mount for left/right/up/down, and if absolutely necessary, then the laser tube—but this is typically only determined when working upon the final beam bender. Be sure to tighten the locking rings on the mirror mount adjustment screws upon completion.

5. After completing the first mirror check, and adjustment if necessary then turn off the laser beam. Insert the Mahoney beam visualization tool into the second beam bender. Turn on the CO2 laser and adjust the laser power so that the laser beam is visible and not too bright, on the side viewport. If you have the camera option then look at the target on your computer.

6. Move the laser machine gantry to the front of the laser machine and then note the position of the laser beam in the cross-hairs. Repeat for the back of the laser work table. If the laser beam moves, then adjust the first beam bender so that it corrects so that the beam is not moving in relation to the cross-hairs (again, same as the first mirror/beam bender, the location is somewhat important but not paramount, as the objective is to maintain a centered and not-moving beam in the final beam bender. If adjustment is required, the 1nd mirror mount may be adjusted as needed to move it left or right or higher or lower. Be sure to tighten the locking rings on the mirror mount adjustment screws upon completion.

7. After completing the second mirror check, and adjustment if necessary then turn off the laser beam. Insert the Mahoney beam visualization tool into the final beam bender. Turn on the CO2 laser and adjust the laser power so that the laser beam is visible and not too bright, on the side viewport. If you have the camera option then look at the target on your computer.

8. Jog the focus head to each side of the laser work table and note whether the laser beam has changed positions substantially in the cross-hairs.

9. Move the laser machine gantry to the front of the laser machine and then repeat the step of jogging the focus head to each side of the laser table then noting the position of the laser beam in the cross-hairs. Repeat for the back of the laser work table.

10. If the laser beam is not approximately in the center of the cross-hairs or has moved substantially (more than the diameter of the visible beam or more than 2mm), then continue with the standard beam alignment.

11. Adjust the second beam bender mirror as needed to center and maintain center over the entire laser table. If this is not possible, then adjust the laser tube as needed to ensure that the beam vertical angle and/or horizontal angle matches the final beam bender motion across the laser table. Be sure to tighten the locking rings on the mirror mount adjustment screws upon completion.

12. Repeat the steps above for the inline red dot pointer, adjusting the red dot pointer within its mount for all adjustments.

13. Install the beam expander/collimator then spot check the final beam bender. If not in alignment, then adjust only the expander/collimator to gain proper beam alignment.

14. Finally, align the final beam bender to the focus lens by adjusting its alignment screws until the laser beam comes out of the center of the nozzle. Use masking tape to cover the nozzle then pulse the laser and adjust until centered. Be sure to tighten the locking rings on the mirror mount adjustment screws upon completion.

Step 3: Additional Information (optional Reading)

The laser beam alignment procedure is used when initially

installing a laser machine, and also periodically due to seasonal drift or other factors such as power fading, discontinuous line segments, angled cuts, or variations in engraving shading or other appearance factors, and also when a mirror has been replaced (recommended annually or when a power drop is noticed that is not caused by the laser source).

Most CO2 laser machines have a flying optic design, or design where the mirrors and focus lens are moved at varying distances from the stationary laser tube. These instructions assume a design of a stationary laser the reflects off a first stationary mirror, then a second mirror/beam bender located on a gantry (arm that holds the laser focus assembly with final beam bender above), and final beam bender above the focus lens.

Typically, laser engravers and laser cutters are aligned and tested by the manufacturer prior to shipment. As a result, the first and second mirrors beam location is usually positioned well enough so that their adjustment is not needed, however, the second mirror may need adjustment for the final beam bender to dial in a very good beam alignment (and the factory may not have gone through a sufficient effort to dial in a top level of accuracy required by the new owner).

Nowadays, an inline diode laser pointer, or red dot pointer, is often installed on laser engravers and cutters. The purpose for the diode pointer is to assist in beam alignment, though it is a separate laser and may be not aligned with the CO2 laser so it needs alignment. Also, the red dot pointer is widely used to laser job processing prior to CO2 laser cutting or engraving, in order to position the material properly for the job.

An optic combination called a beam expander/collimator is designed into almost all Western made laser engravers, and not commonly designed into Chinese designed laser machines. The purpose of the collimator is to reduce the diverging beam, or straighten it, so that the beam size going into the final beam bender is roughly the same over the entire bed, or table, on the laser machine. It is important to maintain the same size in order to maintain the same cutting or engraving quality. Though divergence specifications have similar values for the RF metal tubes designed into Western made laser engravers, as do the glass tube CO2 lasers installed into Chinese made laser engravers/cutters, it is worth noting that Western engravers have traditionally been designed and sold with smaller table sizes than Chinese machines—thus exasperating the issue of divergence affecting laser processing job quality.

The beam benders or mirror mounts that are utilized on Chinese laser machines implement a design whereby two spring loaded bolts hold the mirror’s mount onto its base, and three hand screws with a very fine pitch thread are turned for adjustment. The design is such that the mirror can absorb heat yet maintain alignment. The heavy aluminum base absorbs and dissipates heat as needed. Silicon mirrors with gold coatings can provide 99.7% reflectivity, and solid metal such as molybdenum can provide 97% reflectivity—though many sellers boost the specification to 99.7% and buyers do not question it.

The focus lens is typically a 2 inch focal length lens on standard sized laser engravers, and raises up to 2.5” on large bed machines to compensate for height variation in the material resting upon the table. It is important to keep the table level, and try not to move it too often as the ACME screws are rather low in their tolerance. The focus lens material is ZnSe, gallium arsenide, and germanium for lower powers, and cleaning these optics and mirrors should be done based upon usage. For example, wood and rubber burning create sticky fumes that must be cleaned off optics or their heating upon the optic results in premature failure. Some shops cut these materials frequently and others not so often. A good exhaust system affects this need as well.

Finally, my tale of laser power fluctuation. In my factory shop, everyone in our commercial strip of fabrication shops—mostly machine shops, goes to lunch at the same time. The impact of lunch upon laser output power is significant. For example, I was running my RECI Z8, 150 watt laser at 150 watts, but after lunch, it dropped about 12 watts to something like 138 watts as all the guys came back and powered on their metal working machines. As I was in the midst of calibrating Mahoney laser power probes prior to the first mirror, the experience was baffling. However, after breaking out the multimeter and testing the AC voltage over lunch and afterwards, it was noted that the electrical service to my facility had an AC voltage change of something like 5-9 volts. After checking the Chinese laser power supply manual from RECI, it warned that variations of input AC voltage affects laser output power. In summary, beam alignment is vital in flying optic laser engravers and cutters, but also know the other factors that can affect laser processing job quality. Do you ever run high resolution laser engraving jobs in large formats, over the lunch break, or past quitting time? In my career, I started with Synrad lasers (RF metal tube lasers) that utilized “regulated” DC voltage power sources, so these devices do not experience power fluctuations caused by variations in AC input power. However, their price is very high and thus the trade-off for low cost brings quality considerations.

The Mahoney beam visualization tool is a great device to speed up the process of beam alignment and enable laser operators to perform it more often (as is really needed) in order to keep the machines running in top shape. Too often laser owners/operators do not want to fiddle with beam alignment and put up with lower quality or operate the their engraver in a confined segment of their laser table. My goal is for the Mahoney visualization tool to overcome the beam alignment obstacles and have laser owners perform spot checks and fix beam alignment issues when they occur, thus having full capability of their laser machine and top quality results.