Posted by Jim Earman ● Tue, Feb 21, 2017 @ 08:00 AM
Basic Langolier Fiber Laser Troubleshooting Guide
I believe that anything that is made can and will fail one day. I’m dismayed when I see advertising for fiber laser marking systems stating that everything in the system will be failure free for 100,000 hours. I’m not sure where that 100,000-hour number came from, but I believe that it is the estimated life of the pump diodes used in fiber lasers. That number has been misconstrued to suggest that everything will be perfect and failure free in a fiber laser marking system for 100,000 hours. A standard 40 hour work week is 2080 hours per year. If you think that any laser system is going to provide 48 years of failure free operation then I think you are being overly optimistic. So, having said that, let me address what kind of things can go wrong and try and provide a straightforward troubleshooting approach to our Langolier Fiber Laser Marking Systems.
The major components in a fiber laser marking system are:
- A fiber laser module
- A controller for the fiber laser module containing control wiring and power supplies
- An optical system containing the fiber laser output device (Isolator) and a scanhead and focusing lens
- A computer with a control board which allows the marking software to communicate with the laser and scanhead
- A laser marking software package (Prolase)
If any one of these things aren’t behaving properly then the system will not mark properly. There are a few things that we can eliminate pretty quickly. Let’s start our fiber laser troubleshooting with the marking software.
Why the Software is the Last Thing to Troubleshoot
Probably the last thing to look at if problems occur is the marking software. Whether you are using Prolase XP, 7 or 10, Prolase is pretty solid. There are a few known bugs in Prolase XP, but those bugs generally manifest themselves in mark job setup rather than the actual marking. If a problem has occurred within the software it is probably because the Prolase configuration file has been accidentally modified. The configuration file in Prolase defines the type of laser, the type of control board, and the properties of the scanhead and lens. With a quick phone call to Jimani, we can determine whether or not the configuration file is correct for the components being used.
Troubleshooting the Jimani Laser Controller
The Jimani Laser Controller is very robust. This is the chassis with the 3 toggle switches on the front. Wiring doesn’t go bad and the active components inside of that chassis are the laser module, a time delay relay, and a power supply. The power supply provides the following voltages:
- +/- 15VDC for the scanhead reference voltages and + 15VDC for the mechanical shutter in the optical unit
- +5 VDC for logic signals
- +24 VDC for the fiber laser pump diodes
If a problem occurs within the laser controller it is most likely in the power supply or the laser module. We’ll discuss laser module problems later so let’s talk about the power supply.
In order for the control chassis to be turned on, the keyswitch must be turned to the right and the Emergency Off button must not be depressed. Ten seconds after turn on, the front panel ammeter should display a current reading. That ammeter is in series with the +24 VDC line and if it displays any current at all then the 24VDC power is probably OK. If the toggle switches light up when toggled on then the 5VDC line is probably OK. If the mechanical shutter opens and closes when the Shutter toggle switch is cycled then the 15VDC line is probably OK. If there are no front panel lights and no current displayed in the front panel ammeter then either the unit is not turned on, has no AC input power, or the power supply has failed.
The scanhead and portions of the RTC control board can be tested simply by making a mark with the guide laser turned on and then watching to see of the red guide laser moves in the correct pattern. That simple test won’t guarantee that the scanhead and control board are working properly but, in all likelihood, it is a good indicator that those components are doing their job.
The most common problem I have had to address is that the laser either isn’t marking or that the marking is incorrect. In order to make marks, the laser must output laser light and that light must get through the optics and be focused at the workpiece and then, the galvos have to steer that light from the laser over the part in the appropriate manner. By observing the motion of the red laser described in the previous paragraph, we can deduce that there is a clear path from the laser to the work. If there was no red guide laser light then either the guide laser has failed or the path to the work is blocked. If the cover on the optical unit is removed and the guide laser toggle switch turned on, there should be a red laser beam coming out of the laser output device (the isolator) that enters the optical unit from the rear plate. If there is no red laser light coming out then there has been a failure somewhere in the laser module or isolator.
The marking laser is disabled when the red laser is turned on. If the red laser is turned off, the laser safety shutter switched open and the lens placed at its focal distance to the work, the system should make a mark on the part when commanded to do so. If it doesn’t then things to check are:
- Is the guide laser toggle switch turned on? If so, turn it off
- If the system has an enclosure, is the door open? If so, close it
- Is the safety shutter really open? You should be able to hear an audible sound from the shutter solenoid as the shutter toggle switch is toggled on and off. Please note that if the cover is removed from the optical unit, the 2 white safety switches are disengaged and the shutter will not open. Replacing the cover will re-engage those switches or they can simply be pulled up and locked into an engaged position.
- Is the lens really at the focal point on the workpiece? This is the most common problem. The beam is simply out of focus.
- Are the laser settings in the software such that the material of the workpiece will mark?
If all of the things mentioned above have been checked then we have reason to be suspicious of the laser module. The first thing to look at is the small status light on the front panel of the laser control chassis. When the control chassis is turned on then the status light should be green after 10 seconds of applying power and should remain green. If it is off (we treat off as one of the failure modes) or red or orange then we have a failure in the laser module. Try cycling the laser controller power off and then on again to see if that might reset a fail condition. The status light colors mean:
- Green- normal operation
- Red- Back reflection failure (cycling power off and on again should reset this condition)
- Orange- MO failure. This is bad news and generally means that the laser module must go back to the manufacturer for repair.
- White- Over Temp. - This generally means insufficient cooling air flow. It could be a failure of the controller cooling fans, a blocked filter or failure or blockage of the fans on the laser module itself. There are 3 cooling fans on the front of the laser module inside of the laser controller chassis. Over time, dirt and debris can build up inside of those fans and block air flow. The fans are inside of the laser module and a buildup of dirt or dust is not obvious without a closer inspection. If this is the problem then the symptom is generally that the laser operates for a few minutes then stops emitting laser light and the status light turns white. After things cool down, the status light turns green again as things cool down. Clean the fans in the laser module! Things are plugged up.
If the status light on the controller chassis is green and the system will still not produce a mark then take a look at the front panel ammeter. When the software initiates a mark, it sends a laser power command to the RTC control board and the RTC board sends the actual power signals to the laser. When the laser is trying to produce power, it draws more current from the 24VDC line. Since the front panel ammeter is in series with the 24VDC supply, the reading in that meter will increase as the laser pump diodes draw more current in order to produce laser power. If the reading in the front panel ammeter does not increase in value during a marking operation, then it is most likely either a failure in the RTC control board or a disconnected cable between the computer and the laser controller chassis.
Troubleshooting Incorrect Marks
The most difficult problems to diagnose are those associated with marks that just don’t look correct because the marked vector lines are not in the right location. That problem is generally an indication that something has gone wrong in the scanhead itself or the RTC board. If the marking is a graphical object then replace that object with a True Type font text object to eliminate possibility of a poorly designed graphical image. Time delay settings in the Prolase configuration file could also be the cause of improperly marked vectors but, in order for that to be the cause, someone would have needed to make changes to the configuration file.
It is also possible for the marked vectors to be in the right location but the mark doesn’t seem to have burned correctly because there wasn’t enough laser power. Assuming that focus and laser settings are correct, there just might not be much laser power reaching the workpiece. This can be caused by a dirty or damaged lens or galvo mirror or by a failure in the laser module itself. The lens assembly can simply be unscrewed from the bottom of the scanhead. Turn off the power to the laser controller, remove the lens, hold it up to the light and look through it. If it looks dirty then it is dirty. The bottom piece of glass in the lens assembly is a coated piece of protective glass, not an actual lens element. If smoke and fumes are generated during the marking process, unless they are removed or blown away, they will waft up and collect on the lens protective glass. It can be cleaned by just spraying Windex on a SOFT cloth and wiping it. While the lens is removed, using a flashlight, look into the bottom of the scanhead and inspect the mirror that is on each of the galvos. If either of those mirrors are burned, then laser light will not reflect off of it and cannot reach the workpiece. If a galvo mirror is burned then the scanhead must be returned to the manufacturer for mirror replacement. Burned galvo mirrors are almost always caused by light reflecting back into the lens because of a dirty protective glass at the bottom of the lens. The reflected light bounces back through the lens and then can refocus on the scanhead mirror. It is important to keep the protective glass at the bottom of the lens in a clean, clear condition.
Note: Turn off power to the laser before looking inside of the scanhead!!
Assuming the there are no dirty or damaged optics then the low power problem might simply be caused by a failure in the laser module. Without a laser power meter, there isn’t much way to know what is going on inside of the laser. In a situation like this, we would be forced to deduce the condition of the laser output power by a process of eliminating all other possible causes of a poor mark.
The things that have been described in this guide are not the only things that can go wrong but they are the most likely. If you need help with the system, give us a call. We are always happy to support our equipment!
You may want to check out these posts on fiber lasers:
- Color Marking with Fiber Lasers
- Custom Engraving With Fiber Laser Systems
- Getting Started Using a Fiber Laser