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Thursday, December 16, 2021

MoBeam: Configurable bed

 Bed Design

The bed in the MoBeam is unique in that it allows for:
  • Objects to be placed below the focal plane
  • An adjustable focal frame that can be adjusted up/down from the focal plane. This focal frame is mounted to the base frame
The adjustable focal frame can have these inserts:
  • Nothing
  • Solid surface
  • Angle inserts that can be placed anywhere in the frame

Below the Focal Point

In this scenario, the entire base frame is adjusted up/down with bolts in the corner of the base frame.


Adjustable Frame @Focal Plane

In this scenario the adjustable focal frame can have:

Solid bed

 
Open bed with angled slats to facilitate cutting and airflow

 
Enjoy and please comment,
Don

MoBeam: Laser Head Mounting

 The Laser Head

I have a habit of overcomplicating my first prototypes and the laser head in the MoBeam is no exception. This is all part of the learning process and the willingness to "iterate".

The original design included a plastic cage to allow the laser head to slide up and down fastened with thumbscrews. https://donsthings.blogspot.com/2021/09/l7x-vertical-adjustment-slide.html

As I climbed up the learning curve I found these things that helped me get to a simpler solution
  • You can purchase a Laser Diode head mounting bracket 
  • A refrigeration capillary tube is a good choice for routing air assist 
  • The head and the air assist must be adjustable for both G8 and G2 Lenses
    • The FL for the G8 is 30mm.
    • The FL for the G2 lens is 10mm

A Simpler Head Mounting Design

This design replaces my original vertical adjustment approach 

New
Old


 Air Assist

An air assist nozzle was implemented using a piece of capillary tube that I salvaged from my HVAC replacement last summer. You can get tubing here: https://amzn.to/3q55qMa

The tubing is held to the laser module with two magnets that hold it to a piece of sheet metal when in operation. The sheet metal is screwed to the face of the laser module. This setup allows the nozzle to be adjusted up/down when moving the laser module for different lenses.

Existing mounting plates

These plates came with the unit. The black plate is used to cover the belt and carriage wheel access holes giving a flat surface for the new adapter plate to mount.

New Adapter Plate

The height adjustment plate is mounted to the face of this Lexan plate from the back. This plate is mounted to the carriage via 15 mm cap head screws & the supplied thumbscrews. These fastners sandwich the existing and new mounting plates together and to the carriage. 

Height Adjustment Plate

This Laser Module Mount Holder Spring Clamp assembly was purchased from NEJE. This assembly holds the edges of the laser module with a spring-loaded clamp. The laser module can be adjusted vertically by loosening the cap screw sliding the module up/down and then re-tightening the screw.
My process to adjust for FL is to place a precision block under the lens, loosen the clamp, slide the head until it interposes the block, and then tighten the clamp. This approach is simple and accurate. I plan to use two lenses, a G8 and G2 dictating that the head be able to be adjusted a delta of 20mm.


Optical Sheild

The optical shield design originally included a disk that also served as a means to rotate the lens for focus. https://donsthings.blogspot.com/2021/10/mobeam-focus-with-safety.html
Testing revealed that the lens can be adjusted one time for fine focus and then the entire head moved to achieve final focus. This is especially true of the 30mm (F8) lens. 
After measuring and calculating the size of the shield I decided to attach it below the laser module with two magnets. This way the head can be adjusted down inside the shield for the short FL lense leaving the optical shield in one place.

It is important to note that MoBeam is designed so that the target material is always below the focal plane. Therefore the head only needs to be moved for lens changes. 





Watch it in action!!!



Enjoy and please comment,
Don

MoBeam: Baseframe build update #1


Build Notes #1

MoBeam is intended to be a shop tool like a router or jigsaw. To that end, I focused on its mobility with the ability to engrave on finished woodworks of various types and sizes including vessels turned on my wood lathe. I traded off automation for simplicity and at the expense of more manual adjustments.

A fundamental concept was to leave the laser diode module at a fixed focus and instead move the entire assembly and/or a focal plane insert up-down as needed to get the target in focus. Sound crazy?

The laser focus is set at 30mm [G8 lens] up from the bottom surface of the base frame. The entire assy or alternately just the focal frame is then adjusted up/down based on the thickness of the target. In a way setting up MoBeam is similar to setting the bit depth on a wood router.


The laser module gantry assembly is mounted on a piece of 3/4" plywood into which an opening is cut. This opening is left open or alternately accommodates a honeycomb bed [the one I bought for my K40 and never used]. The entire assemblies surface is adjustable with 4 1/4-20 bolts

Very thick or odd shaped targets:

When left open the target is placed on the bench under MObeam and the entire assy is adjusted up/down with 4 legs until the target is parallel to the bottom of the base plate.


Small Flat Targets That Fit on the Cutting Bed [in the focal frame]

When the focal frame is used it is mounted in the opening and 4 screws allow it to be adjusted until the target’s [laying on the bed] surface is the correct distance from the laser's lens. The assy is mounted into the base plate with 4 thumbscrews. Focus adjustments are made with a gauge block.



Large Flat Work
If a larger flat material needs to be engraved [front of a chest] the gantry assy can be dismounted from the base frame by removing 4 [thumb] screws from the side plates.

The gantry assy is placed flat on top of the target and no additional adjustment is needed.



Laser Module Adjustments
The only time the laser module needs adjusting is if the lens is changed and then it is simply located to the surface with a gauge block.



Cheap n Dirty Build Highlights
Views showing the adjustments for the base frame and focal frame insert.


Detailed views of the focal plane adjustment mechanism.
Yes I know, I cringed when I started this design …
However this assy worked better than I expected. Then again I took a lot of care to ensure the holding bracket and the bed mounts were perfectly aligned. The adjustments [one screw at a time] were not as clunky and painstaking as I thought and it did not bind until I adjusted only one screw a ridiculous amount relative to the others.


Known problems:

The nutserts in the lift bracket don’t like the thin AL angle and tend to come loose, a PEM nut would be better.
The honeycomb bed is not really flat [never realized that] a thin perforated metal plate would be better.

Known Improvements/Adds & Before You Ask

  • Tilt and lift interlocks on laser power
  • Air evacuation. I am working on a plenum that slides under the baseframe.
  • Filter: considering a canister filter design that uses the evac fan salvaged from my HVAC replacement
  • Completed: Thumbscrews and cap head on adjustment screws to prevent striping and the need for hand tools.
  • Protective cover and handle for storage.
  • The use of metal vs wood for the base plate would help with fastening and dimensional predictability but beam reflections would need to be considered.
  • Taller Acrylic side plates for better stability.


Enjoy and please comment,
Don


Tuesday, November 2, 2021

Laser Diode Engraving and Cutting Information

Useful Laser Diode Information

This post is a collection of important information that pertains to Laser Diode machines

Homepages

The homepages for sites whose contents are highlighted below

Software

Laser Types and Response

Laser Focus

Material Absorption

Laser Cutting & Engraving


A-very-cheap-and-simple-diy-enclosure-for-an-engraving-frame-ortur-lm2/

Controller Wiring

Grbl

G-codes


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Laser Diode Lens Specifications

 

There are 4 common types of diode laser lenses:

  • 3 element
  • G2 (short focal) (cutting)
  • G7 (similar to 3 element lens)
  • G8 (Used in VG-L7x)

The G8 has these specs:

  • Optimal focal range: 30-100 mm
  • EFL: 8mm
  • NA: .2
  • Best focal range 70-75 mm
  • Smallest laser beam spot: 77 x 130 microns (0.0030315 x 0.00511811")



Briefly about a 3 element laser lens

A 3 element collimating lens w/ AR coating for 405nm – 465nm. It has M9/P0.5 threads that will work with a lot of standard diode housings available. This lens is good for correcting laser beams for long ranges.

Briefly about a G2 laser lens

This lens is the best choice for short ranges, as in an engraving machine. For long ranges please consider 2 or 3 element lenses.

Briefly about a G7 laser lens

The G7 is a second-best high pass single lens but it won’t increase the beam divergence as the G2 does. The G7 has a long focal length just like a 3-elements lens. It’s a well-balanced lens that has the advantage of 3 element lens (very good divergence) and G2 (in terms of power).

Briefly about a G8 glass collimation lens.

Broadband AR Coating 400nm-700nm
This lens is a long focal length single-element glass lens with a broadband AR coating. It has a 90% pass efficiency which is amazing for a longer focal length lens. It does an amazing job of cleaning up stray light around the projected spot with many common diodes caused by the small amounts of uncollimated light escaping the lasing cavity reflecting off things like the edge of the emitter, walls of the module or inner walls of the lens barrel. Like the G2 lens or countless other similar lenses being sold as G-2’s, it creates a reduced spot size while maintaining a 90% pass efficiency compared to the 96% pass efficiency of a G2 lens.

Comparison of Lens Performance

3-element lens (cleanest beam profile, best for low power lasers)

The 3-element lens has a long focal length, low divergence, and clean beam profile but it has a significant output loss.
Advantage Tight laser beam with the cleanest beam profile
Downsides 84% efficiency (1W diode = 700mw using this lens)

G2 lens (best for power)

The G2 is a single lens enabling the maximum true power of the laser diode for rapid close-range burning and engraving.
Advantage 94% efficiency, reduces the beam aperture
Downsides Increase the beam divergence (thickness) and the beam profile

G7 lens(Balanced Multi-Purpose Perfection)

This lens is a cross between the divergence and the power lens. With the G7, the beam divergence won’t increase as it does with the G2 and you will still get very close power of the laser diode.
Advantage 91% efficiency, long focal length and increases beam aperture.

Monday, November 1, 2021

USB Microscope Review

Unboxing 

Every once in a while the beams align while making and a surprise outcome is realized!

I set out to buy a USB microscope and follow the lead of some others to use this for focussing my laser diode engraver.

After some research, I chose this unit; https://amzn.to/3lnjjEq

It worked right out of the box (connects like a webcam) including my Windows PC and Android phone.

It came with a nice zipper case, holder, software disk, USB adapter, and graticule.

I was happy with the image it created and even if it does not end up being the best way to measure focus I will use it for electronics projects and measuring images.

Android

 PC

What a Deal

Then an interesting thing happened. I got an email from the seller offering me a deal. Write a 5star review and they would send me a free metal microscope stage.

I had been here many times before. Write a review and then the promised thing never arrives.
This was different. I was ok writing a 5 review because I was very happy with the unit. I let the seller know by sending a screenshot of the review and then to my shock and awe … the thing arrived.

It really was made of metal. In fact, it was well made not the plastic junk you usually get for free!

Enter, a New Tool

Then here is where the beams aligned.
I had been sketching up a design for a tool to help properly insert heat-set plastic fasteners. My manual soldering iron approach had gotten painstaking and never resulted in a straight insert.
Then it hit me that I could use this microscope stage to install heat inserts using a woodburning iron I already had mounted into this new stage.

After making a PVC adapter for the iron and turning threaded heads that fit all sizes of my inserts I had a new tool.





Enjoy,

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Don

Sunday, October 31, 2021

MoBeam: Grbl Startup

Grbl Newbie Stash 

Being new to Grbl this is a stash of information that I will reference for converting my stock controller to the MiniGrbl.

Grbl 1.1 Laser Mode


Enjoy,

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Don

Saturday, October 30, 2021

MoBeam: VigoWorks Setup & Operation

VigoWorks

Documentation

The documentation describes the functions but not in enough detail to understand how they impact engraving and cutting quality.

Software_manual

Notes:

  • Many modes of the software are single-threaded. Ensure that windows are closed and you exit active modes before trying to make settings changes. Sometimes the interface does not intuitively tell you to change modes.
  • I do not see any way to engrave and cut at the same time. There is no way to mark image features as cut lines.
  • There is a way to design text string but there is no image or vector editing. 
  • You supposedly can upload Gcode and Images.
  • I have experienced intermittent crashes and the controller needed to be power cycled.
  • No way to add stuff to the gallery?

The Effects of Settings on Imaging 

I plan to update this until which time I change to LightBurn.

Offline Imaging

Default file on SD card

  • Name: sd_default.nc
  • One file is allowed and must be named with .nc extension
  • Verify: Uploaded and overwritten from VigoWorks?

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Don



MoBeam: Positional Accuracy

Movement Scale

I found that the X & Y movement was 1/2 of what it should be. In other words when I told it to move 50mm it moved 25. I found this using the arrow keys in VigoWorks.

I changed the steps/mm from 80 to 160.
The preset value when this model is selected is 80.
Yet the manual says 160 in a picture of the settings.
I set the steps to 160 and it now scales correctly.
I am concluding the presets are wrong!

Settings in manual 

Settings when L7X model is selected

Settings I changed

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Enjoy,

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Don

MoBeam: Software/Firmware Updates

Software Update

VigoWorks 3.25_2110203

When I opened VigoWorks it asked if I wanted to update to which I said yes.
It simply took me to a download site, it did not directly update the code. I assume this is because VigoWorks is a .exe, not an installed program. After download and extraction, the .exe ran without error. now I have two versions on my desktop. 

  • New version: VigoWorks_v3.25.exe

Firmware Update

The extracted file from the download site also contained a firmware file and tools.
  • New Firmware: Firmware_for_328p_v3.12_20211023
On the Settings tab and under Model there is a checkbox to upgrade firmware.
Checking this box opens a file dialog and allows the selection of a .hex file.
Select the .hex file that was downloaded
There is a ribbon at the top of this dialog that shows upload progress.
Unfortunately for me, this FAILS and I have no idea why??

OTA Update?

I tried updating the firmware via WIFI and IT WORKED. I say that because it no longer asks me if I want it updated and I think I saw some LEDs blinking strangely. BTW it seemed to just update automagically without asking me to select a file. Where did it get the file from? Does VigoWorks only update OTA and do you have to use the flash tools if you are serially connected?

Upload Tools

There is also an upload tool under "Driver_And_FwUploadTools" but I am confident how to use it and do not want to brick my controller.

Using the Upload Tools

Trials of a Poorly Supported Controller

I do not know if I need to upgrade the firmware nor what the new version does. [I wonder if they fixed the Grbl problem and I can now use Lightburn].

I cannot find any support help nor documented release change information regarding the firmware update ..... just an upload site and good luck with that.

This is what happens when your controller is not properly supported and has incomplete documentation

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Enjoy,

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Don

MoBeam: Laser Focus

Laser Module in MOBeam

Is this module actually a NEJE module

If so which one?
  • 30820
  • 30610

Focus

Mistake in the manual???? Yes my focal point is 30mm.

If you assume the VG-L7X manual had the wrong units for focus, i.e CM vs MM.

Then I have a G8 lens in my unit? Is this a coincidence?

The smallest beam spot also explains why the dot looks rectangular (laser diodes do not operate in TEM00).

However, at the focal point, the intense area of the beam is round.

https://laserpointerforums.com/threads/there-is-something-wrong-with-my-beam-spot.59400/

Finding The Focal Point

Focusing Techniques


4% is low power setting used for focus

The Empirically Derived MoBeam Focal Distance

Focus Using a USB Microscope

There are multiple videos on the use of a USB microscope to safely look at the output of the diode and adjust the focus. I decided that I would start finding my focal point by using this method.

Test Setup

I used a USB microscope purchased* from Amazon. 
* I am very happy with this unit's price and performance. https://donsthings.blogspot.com/2021/10/usb-microscope-review.html
  • Make a target by painting a substrate with flat black paint. I used a round steel medallion. A black surface makes it easier to see the most intense part of the beam. 
  • Put on your laser safety glasses
  • In Vigoworks turn on the "weak beam"
  • Place the microscope on its stand in front of the laser module focussed on the beam.

Adjustment

Watching the beam on the microscope:
  1. Adjust the entire module up/down to get the smallest round spot.
  2. With the module fixed in position adjust the lens until the smallest round spot is achieved. 
When you adjust either the module or the lens you will note that the beam changes from a round spot to a rectangular one as it goes in and out of focus.

In this video, you can see how I went about finding the focal point.

These tests show that the focal point is indeed 30mm.

Depth of Focus Measurement

TBD

Focusing For Cutting vs Engraving


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MoBeam: Text Engraving

Engraving Text

Aluminum Techniques

Engraving Painted Aluminum Vigotec VG-L7 20W Laser Engraver

  • Speed: 750 - 1250 mm/min
  • Power: 90-95%
  • 13 dots/mm
  • Pause: 45ms
Post clean with alcohol & cotton ball

From YouTube Video

From the Manual

In the right parameter control area of the software,
  • Select Binary-Line engraving mode.
  • Adjust the size of the engraving picture.
  • Adjust the line engraving speed value to 3000,
  • Laser power value to 90%,
  • Line or point density DPM value to 6

1st Lettering Experiment #1

The first attempt at engraving letters was somewhat successful.
Wood engraved easily and at very low power.
Painted Plastic and Steel are also etched at an expected higher power but there are visible horizontal scan patterns for which I do not know the source. I suspect the dots/inch setting has something to do with this pattern in that the scans are not adequately overlapped.

Wood


No horizontal patterns

  • Speed: ?? mm/min
  • Power: 4%
  • 5 dots/mm
  • Pause: 50 ms

Painted Plastic


Horizontal patterns, scan or settings error?

Painted Steel



Horizontal patterns, scan or settings error?


  • Speed: ??? mm/min
  • Power: 80%
  • 5 dots/mm
  • Pause: 50ms

Test #2

I decided to try this same test [on the blackened steel] using the same settings the YouTube video above used. The results were dramatically better. There is a lot more that needs to be understood about how these engraving settings work. 
Note both the settings and USB image overlayed in the screenshot below.



Calculate the resolution @ 5dots/mm:

5 dots/mm x 25.4 mm/inch = 127 dots/inch [very low resolution]
Line spacing = 1/127 = .007 inches

Calculate the resolution @ 13dots/mm:

13 dots/mm x 25.4 mm/inch = 330 dots/inch [more like a laser printers resolution]
Line spacing = 1/330 = .003.

The combination of higher resolution and power resulted in the ablated areas being more "clean". That is, there is more overlap of the beam from scan to scan.

If I guessed the optics characteristics correctly the laser beam is at its smallest 0.0030315 x 0.00511811. This suggests that at the lower resolution 127 dots/in the beam scans do not overlap by .002-.004" which would clearly be visible.

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Don

Sunday, October 17, 2021

MoBeam: Focus on Safety

 Safety

Clearly, the MoBeam needs to have safety considerations included in the design. 
The core design goal is for this machine to be portable able to lay on top of various size targets for the purpose of engraving on them. 

Safety considerations include:
  • Protection from the beam in normal operation
  • Protection from the beam if the machine is lifted off the surface
  • Interlocks on any covers that open horizontally placed relative to the laser.

Head-Sheild

My current approach is to use a light shield under the diode head made of filter material. The body of the machine may be made from clear acrylic. I do not think the body needs to use filtered materials when combined with the head-shield.

Caution: I have not tested this concept. It seems logical that the placement of the shield [close to the surface] would make a dangerous reflection unlikely. Also, this approach
is being used by others that I judge to know what they are doing.

JTech 

JTech is one of the best sources I have found on Laser Diode safety, engraving, cutting, and technique.

Sheild Material

I plan to replace the prototype shield [disk under head] in the picture with this material as soon as I get the specifications for focus discovered. 
These are:
  • Practical FL
  • Practical DOF

250nm to 520nm Laser Shielding – 12″ x 12″

The shield may also serve as the focal adjuster.

PXL_20210916_121149841

PXL_20210916_121027926

Lift Interlocks

To further make this safe I also plan to have the means to turn off the laser if the machine is lifted off the surface. You could also accomplish this with a full enclosure but I am trying to make MoBeam capable of laying on top of various thicknesses of materials, mostly wood. Therefore the bottom of mine will be open.



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Monday, September 13, 2021

MoBeam: Vertical Adjustment Slide

 Adjustment Slide

Not yet knowing what's the best way to adjust focus for my L7X I decided to build a slide that would enable simple adjustment of the diode modules vertical position. 

UPDATE: this design has been deprecated and replaced by: https://donsthings.blogspot.com/2021/12/mobeam-laser-head-mounting.html

Available Designs:

Some lasers come with a slide... that would have been nice! Laser module w slide
I also found a few on: 
This is a simple design and concept. Replace the stock carriage interface plate with one that has a sliding channel for the diode module. The up/down motion is achieved by loosening a binding screw, sliding the laser module, and then retightening the screw. 
This may be too simple for long-term use but I needed to make a fast prototype that would allow a large yet simple range of adjustment. Using this proto I will identify how much range & precision the vertical adjustment needs to have.

Once the adjustment needs are identified I may change the approach to a screw slide.

Stock Interface Plate

This plate is removed from the unit, the slide replaces its function. I used the stock interface plate as a template to get the holes of the new plate in the right place.
Tape this plate to the blank you are using for the new slide and drill through it to get the fastening holes in the right place.

Slide Design

The slide consists of 3 parts. backplate, side guide, front cover. This is a simple design to help me understand what the final design will need in regard to adjustability. If the head does not need much vertical adjustment and accuracy is not a factor, this may be a good approach. Otherwise, a screw-driven approach may be better. 

Backplate:

This plate mounts directly to the carriage using the stock top thumbscrews. For this plate to mount flush on the carriage it must have features drilled to accommodate the belt and tire mounting bolts.
Note: you will notice many holes in the photos of the slide. I reused some old plastic that was previously drilled. Therefore ignore the holes in the picture and reference the drawings.
Note the heads of the tire mounting bolts and belt retainer

Side Guides:

These two parts create the walls that the laser head slides within. There are two 8-32 nylon adjustment thumbscrews that hold the head in position in the slide. 
These parts also have two #4-40 inserts pressed (with heat) into their edge. These inserts are used to mount the front cover. I used SAE fastners but any type small fastener that will fit edgewise into the guide will work. I got my inserts from McMaster
The thumbscrews came from my fastener collection but most any 8-32 fastener can work. I think I got them at Lowes, Ace is another place to check. I used nylon to prevent galling the side of the laser module.

Right side view

Left side view
Front Cover:

The front cover is made from .080 acrylic but thickness is not critical. This cover exists mainly to keep the side guides from deflecting when the adjustment screws are tightened against the laser module. In a future design, this cover may be replaced as part of a safety cover once I verify what the focal point dimensions are. 

Update: modifications

I had to cut the assy off just below the screws. At the proper focal distance, the slide was in the way of the microscope and blocked me from adjusting the lens. The focal point was set at 30mm below the lens's surface.
*USB microscope used to set the focus.

Modified Slide

Picture

Slide Fab

Attached are 1:1 traced drawings (not CAD) in case you want to fab a slide. These drawings are traced from the actual part and some nominal dimensions taken from the actual parts are added.
 
I made this from 1/4"  & .08" clear plastic (Lowes), cut it on the table saw and drilled with metric twist drills. The larger holes were drilled with Forstner and step bits.
 
I clamped the stock adapter plate to the new slides backplate as a template to get the mounting features in exactly the stock positions. I drilled through the stock plate and into the new backplate.

The laser head was mounted in holes B (see drawing). Make sure the head is at 90 degrees to the back plate. Then acrylic glue was applied to the side of the guides which were then clamped to the laser. This insured an accurate fit to the laser module.  

Drawings

A simpler Slide?

Trace Method of Prototyping

When I am modifying an existing machine I like to build proto's by what I call the trace method. I remove the original parts that I want to modify or replace and use them as a template for drilling & cutting the features that I want to keep. I also sketch a 1:1 drawing for reference and sharing. I attach the template using double-back tape or simply copying the 1:1 drawing and gluing it to the surface with stick glue
If I plan to make a more precise or easily replicated part I create a CAD/CAM version, otherwise, I am done. If you need a CAD/CAM version let me know in the comments.

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Don