Complex Stencil Cutting

The most recent effort with the laser involved several changes to the procedure:

1. Many support blades were removed to decrease the amount of debris that needed cleaning after the cutting. Fewer support blades also mean that the underside of the plexiglass was LESS likely to chip. The trade off is that there may a bit more bounce when doing the auto-focus, though if starting at a corner this is not so big a consideration. There is also the extra time involved with removing and replacing support blades.

2. I am now using 3 standardized cuts: inner, middle and outer circles. This will allow me to interchange sections of one stencil with a different one to multiply the number of design combinations.

3. The whole deal is getting ready for Hollywood! Not really, but I did capture video and post processed to reduce background and added in photos to tell a nice story. I used Audacity to clean up the noise in the audio track and Movie Maker and YTD Downloader to produce slideshow videos and convert movies to AVI.


I did have one element that was too close to the outer circle cut that soon cracked off after handling. Next time I will be more careful to stay farther from the edge and use masking tape on the backside to hold marginal pieces in place. I still have the inner shape intact so the stencil is still quite usable.

Stencil before and after cleaning with rubbing alcohol
click on the links, then click again on the photos to zoom 
or the video thumbnail to play

Photo link: Before cleaning

Photo link: After Cleaning


Video to introduce the laser cutting process


Video: The stencil actually getting cut

Aligning the Laser Beam

Monday, Thursday and a long day on Friday were devoted to aligning the beam on the 4 inch focal length laser on mirror #2 and #3. This is a time consuming and careful process that involves a number of minor, sometimes counteracting, adjustments working in tight spaces. In the end the beam was very well aligned and several lab mates were satisfied with the quality of their jobs after the alignment.

Here are the lessons learned:

1. Don't rely on the red beam.

To save time on frequently closing the side doors and lid for every laser test pulse, as well as being able to see the beam, I decided on Thursday to just try aligning the red beam. This proved to be frustrating as I was stuck with the beam slanting down and to the left. The beam cross section quality was also uneven and diffuse. After a phone call with a Boss technician he convinced me to abandon the idea of practicing/aligning on the red beam and just go back to pulsing the actual laser. Following this advice produced useful results on Friday (described below).

2. Big movements early and small adjustments late

The 3 directional adjustment knobs on the mirror mount are for up/down, left/right, and diagonal from upper left to lower right. There is no lower left to upper right knob. Once the burn spots become within about 1 diameter of each other, pare down the twist amount on the knobs, or else you run the risk of overcompensation, thus backtracking on progress.

3. Take an indirect route

For example, if you see that the downstream beam is high and right of the upstream beam, instead of using the diagonal knob, consider using the up/down and left/right to achieve the same effect. Or use all 3 knobs. The more knobs you use, the more likely you are to achieve a three dimensional adjustment that will get you to the target beam location.

4. More layers, less tape.

Convention calls for 2 layers of masking tape and frequent tape changes. More time efficient and more informative is to make a 3 layer tape and put more spots on it before a change out.

5. Clean before align

If you use a triple layer, this will also help minimize any char residue from the tape after pulsing that would require a re-cleaning of a mirror.

6. Protect the assets.

At the very start when you may have no idea what direction the beam is going. construct a protection board to block stray beams from hitting the microelectronics, wires, cables and the keypad control board components at the front right of the machine. This probably only needs to be in place for the first few pulses and can then can be removed once you are certain that pulses will land on the tape.

7. Side doors

Remember to close the side doors for safety before pulsing the beam, as the interlock is only on the main top lid.

8.  Loosen all the way

The set collars on the adjustment knobs should be loosened all the way back to the knob itself while making adjustments; the collar tends to creep forwards when messing with the knob. When you are aligned, remember to retighten the collar flush to the mount to secure the position. Use your other hand to hold steady and firm on the knob head while spinning the collar back to its lock down position.

Progress of alignment tests going from top to bottom

It is dark inside the nose cone

a useful head mounted flashlight

O-ring out of position and burnt through

Lens Cleaning

1. Throw them a curve

It is difficult to see from a side view which side of the lens is curved. Here is a trick to get it right. Position yourself directly under a long fluorescent light tube on the ceiling. If the reflection of the tube is thin and you can make out the details of the shape, that is the curved side. If the white reflection is broad and covering most of the lens, that is the flat side.

2. Especially for you

We now, under Taylor's guidance, are using a specially formulated lens cleaning liquid in a dispenser bottle that comes with it. Also, we are no longer using the one-time disposal Fluent brand wipes to clean lenses or mirrors, nor are we using any type of rubbing alcohol.

3. It's a drag

Do not swirl the lens tissue or cleaning wipes; this will only recirculate any particles on the lens surface. Drag in one direction instead, that'll remove particles and debris.

4. Blind it by the light

Wear a headband mounted flashlight to work on the nozzle when loosening or tightening the retaining ring. Otherwise it is hard to see inside the recessed column of the nozzle.

5. Mom says so: trim those nails

to avoid scratching mirrors and lens, even if you have gloves on!

6. A gentle push

The black O-ring between the retaining ring and lens easily moves out of position. Try to coax it, often multiple times, back into position while turning the retaining ring. Do this by taking a Fluent brand wipe, rolling one corner to make a thin cone shape, and use the tip of the cone to move the black O-ring around.

7. Spin the cone

This may better than turning the ring tool when loosening/tightening the retaining ring.

8. No Trespassing

Unless absolutely necessary, do not touch the Zoom ring right above the silver exterior spring. Moving this will cause auto-focus to be off.

9. No head banging

When spinning the nose cone back on the air flow tube, stay clear of the mount head attached to the gantry. That head is very sensitive to alignment to even the gentlest force/bang/knock.
 

New Version of RDWorks software

It is version v28. It basically is the same as v18 but they have added a few new import formats and some more submenu choices under Edit, Draw and Handle. I have been using it and it seems stable. THE PREVIOUS VERSION OF RDWORKS WILL BE REPLACED BY THE NEWLY INSTALLED V28.

Remember to go to Config -> File Para Setting and check both of the boxes in the DXF control area.

get it here

Flaking of etched glass

When I was doing a slow shallow etch of the waxwing bird on a cylindrical glass, I was having lots of flaking. I asked Boss Laser Tech Support what to do to improve the process and they recommended the following. 

"We have seen a lot of people have success by placing masking tape over the glass on the area that they are wanting to engrave over. This typically helps them a lot with the flaking on the glass. Also the air flow seems to be too high for that material it would probably be better to be around 20PSI.

Lastly, some lasers have a hard time firing at 14% power or below, I definitely recommend trying to up the power to at least 15 each and every job so we can ensure the laser is consistently firing for you."

I'm not sure I agree that this will help:

1. The masking tape will be hit many times in a small area and may cause lots of debris issues near the laser head.
2.We prefer pressures more like 60  psi for a reason, again, to get the debris out of there.
3. We have good experience with dependable firing at as low as 10%.

 I will consult with Seth to see if any of the suggestions from Boss Laser make sense.

Summary of training and meeting notes with 

Boss Laser in Sanford, Florida on April 24, 2018

Boss Laser visit photo album

Kevin Lucas and Ken Trenholm were my hosts. I spent most of my time with Ken, who is the Senior Lead Technician at Boss with 27 years of laser experience.

1.  We should look at exhaust boxes

 https://www.bosslaser.com/expand-filtrabox-fume-extractor.html  

(see photo) Even though they are high cost and  high maintenance they include filtration, are relatively easy to move (small cabinet sized) on wheels and they'll be very quieter compared to our current exhaust fan.

2. Another way to reduce the noise of the work area is have compressors that are stored outside.  A brand mentioned was Ingersoll Rand.  You should put a roof or some type of cover over the top of the compressor  outdoors to help keep it robust from inclement weather and to keep the sun off of it.

https://www.aircompressorsdirect.com/tools/ingersoll-rand-air-compressors.html?utm_source=bing&utm_medium=cpc&utm_term=ingersoll%20rand&utm_campaign=brand+-+ingersoll+rand&msclkid=368887d5025e11e18d70dd3a5fbda7bf&utm_content=Ingersoll%20Rand

3.  Each laser with their own filter box would be especially useful for absorbing fumes from acrylic, leather and wood or when working in high power mode and generating a lot of smoke.

4.  Ken also said the only reason we should really be using the 4 inch laser for cutting is for doing foam, otherwise the 2 inch focal length is fine for all cutting and engraving. Either the lasers can be converted into a different focal length; we are not bound to the way they were installed.  We probably just wanted it that way when we first received them, as we figured we should have one of each type, but we don't have to stay with it that way.  In order to convert between two different focal length we need to find the official Boss Laser toolboxes (see photo).  They are black and red and they're going to have accessories that we need not only for conversion but for service going forward.  If we need remote technical support on hardware, they will also want to be asking for components in that support box with the Boss Laser technician on the line.

5.  In regards to using the rotary tool, there is an additional Y axis controller port on the right back side of the laser.  This will be easier to access and is better amenable to lighting for connecting and disconnecting the rotary roller tool than the rear Y-axis port. People with shorter arms or are uneasy reaching around the gantry system may find the side port to be preferable. It is your choice.

6.  The direction that you put in the bed support blades is really of no operational consequence.  In fact, you can run without any of the blades in there at all because if our compressor and exhaust system are working properly; you'll get good air flow with or without them.  The blades are mainly there to support your material and  media.  The reason why there are so many of them is because Boss Laser understands that there is a variety of shapes and sizes for people's Materials/Media/Substrates; this allows you to customize the support and drop down openings on a job by job basis.

7.  Because we can move all the bars if we want to, this allows us to use the 4 inch focal length laser for the rotary tool.  That's because the rotary roller tool has been designed in conjunction with the bed to be supported by the bladeless bottom of the bed in a flat manner.  In fact, there should have been an option for us upon purchase of the laser to have two low support bars put in to the bottom of the bed (see photo) expressly for this purpose of holding a rotary roller tool with all the blades removed so that the length of the cone of the 4 inch focal length head does not preclude us from using such tool.  I have taken a picture of what these bars look like. If you don't want to remove and replace bars, you may be able to get away with simply inverting the L-shaped bracket holding the wheels to be upside down to make more vertical space for the nose cone.

8.  When working with wine glasses on the rotary roller tool, the two main problems that we've experienced are (a) that flat base of the glass falls off the support wheels and (b) designs are large in the vertical direction not been fully etched as the laser goes out of focus after large curvatures at the bottom of the cup.  A suggestion for keeping the glass from falling off the wheels is to spread the two rubber band of rings just a little bit and wedge that in that part of the base in between they'll rings so that it doesn't slip off.  With regards to being out of auto-focus, instead of auto-focusing on the highest point of the curvature of the cup, choose a point that would be in the midway section of your design. Yes, this is a compromise of some precision, but we still get the whole design down and depending on the curvature, it may still look very nice.

9.  We want to make sure that we're always doing auto-focus so that the tip of the head is pointing down nearly perpendicular to the surface of the substrate.  We want to avoid having to make contact with the substrate at an angle with the cone because that can torque or bang or take out of alignment the optics and mirrors on the laser head.  This is something one also keeps in mind when regarding the wine glasses; actually do your auto-focus at the crest or highest point of the curvature of the cup, and then use the X direction control to purposely move it a little bit off the auto-focus towards the bottom of the design.

10. As regards to the computer communicating directly with the laser, a Boss Laser thumb drive was given to us when we purchased the machines; it should have all the drivers we need for the USB Port.  I did inform Ken that we did find the third party drivers with an Internet search, but in the absence of that, one can install from the thumb drive to make sure we did we have a base system that is complete.

11.  Lubrication: white lithium grease squirted anywhere you can see metal on the rail of the gantry, and also a few spots on the belt, help to keep everything running smoothly.  It's also fine to squirt some of the white lithium grease on the tooth side of the belt.  After doing so make sure you traverse in the X and Y  directions using the on-board controls to make sure the grease is evenly distributed.

12.  Our original idea of retrofitting permanently the 4 inch laser to become a metal cutting laser with an oxygen source is not practically feasible according to the Boss Laser technical in-house team.  I've taken some pictures to show the specialized parts and blades that are used in their HP line of machines which are specifically engineered for metal cutting and metal cutting only.  The claim from Boss is that the optics and mirrors, as well as the head size and shape, while in principle could be made to work with an oxygen source at the right focus distance for cutting metal,  that the quality of the work will be degraded and that we will have frequent breakdowns and be spending lots of money on replacement optics and accessories.  Additionally if we do buy an HP machine Ken essentially insisted that we bring in Mr. Mike Stone from Boss lasers for in house training as there are enough significant differences between operating a metal cutting machine vs. our current lasers that we would need proper instruction to get started.

13.  We should use double layers of tape when testing the beam spots on the mirrors for doing a beam alignment. After every adjustment, take the gantry all the way forward, test a pulse, and then all the way backwards, and test a pulse. After alignment, use the alcohol treated towel wipes to remove tape residue. It is best to use your pinky finger and make sure the fingernail is trim. Too much force can put the beam back out of alignment, and a finger nail can scratch a mirror.

14. Feel the laser head and nose cone to make sure it is cool to the touch. If the beam is out of alignment, the head and cone will be at least very warm.

15. Use cast acrylic rectangular blocks, elevated on a roll of tape, to pulse the laser after alignment to help make sure that the beam is straight down. I brought a few back with me from Boss and will give one to Seth. Beam alignment is even more critical on the HP class of lasers that do metal cutting, as the opening in the nose cone is even smaller.

16. Never alter the autofocus ring on the nose cone. If it is accidently adjusted, you will have to manually check the focus distance by changing the Z position incrementally, pulsing the laser, and checking for beam quality.

17. Ken claims that for an ordinary day of usage, the lens should be cleaned twice.

18. The honeycomb support beds can be cleaned by soaking them in hot water with Dawn dish washing soap.

19. The lasers are cw (continuous wave) lasers. As such, even though the RDWorks allows you to set a laser frequency in the layer parameters advanced settings dialog, it in fact has no effect. The default value of 20 kHz is set by Boss Laser simply as a placeholder value; no matter what number we type in there, the net result is the laser runs cw all the same. The field is there to populate in the dialog box because Boss outsources the development of RDWorks to a third party that reuses software components for different laser manufacturers, some of which do actually have lasers with rep rates.