Rich Johnson Garden Railroading & Lasers

Morn Laser Engraver

This machine has a working area of 24 by 36 inches and that is lots of room to make stuff.  I can move the head in all four directions on one level.  This is called the "X and Y" axis.    The X and Y are numerically controlled  by the laser controller from the information provided by my CorelDraw drawing inputs.  The "Z" axis ie; the table height must be set manually before the projects begins.  I can lower and raise the table as needed up to about 12 inches away from the laser head.  But the laser focus distance to any project is about 3/4 inch and is reset each and every time the "Z" height is changed.

The 80 watt laser beam is a infrared light and at its "focal point" it is very hot.  For example when acrylc is "cut", what is really going on, is the beam is so focused and hot it vaporises the acrylic into a gas and it is blown away with the air asist that is in the laser head.  Sometimes acrylic residue can be found on the table and must be cleaned off.  There is an vapor extraction system that will pull (vapor) air out of the working area of the machine and vent it out side.  The blue tube behind the machine in the photo above is part of the venting system.

If the project is wood (as in the photo above) then the beam will burn the wood away.  I can control how much it will burn with the adjustments I can make with the controller interface.  Sometimes it take many trys to get it just right.  If it is to hot it will scorch areas outside of the cut and leave it brown or even black.  That indicates, I need to adjust the power and or the speed of the laser.

Some of the other materials used act much different.  Rocks and Slate will not cut, but by adjusting the power and speed I can do what is called "Scan" or "Etching" and that will mark the surfaces.

 Metals and glass cannot be cut with this machine, but a material called "Cermark" can be sprayed on the surface and then the laser will burn the Cermark onto the surface.  It really does not penitrate the material it just burns on,  much like powdercoating.  A spray can of this stuff is ordered on line and the cost is over $75 each can plus shipping.

Add ons and or improvements

 Laser head 

I am always checking and testing my machine.  I want it to cut streight and with out issues.  After we moved to Los Banos  I found on "you tube" a guy that was explaining things about our china laser machines.  I still watch this guy a lot.  He has made over 150 videos about these machines.  It has been a great resource to learn and enjoy this machine even more.  He has made  many improvements and has shared with us to make our machines perform better.  Focus is a big issues for us.  You need to get it just right for each and every project and material that you are working on. 

One of this years discoveries is the need for a new and better laser head.  The old head can be seen in the machine photo at the top of this page.  After much testing is has been found that the mass of the existing laser head is causing a vibration or "Backlash" issue.  The following photo is a focus test that shows the problem.
This image is dots on paper.  I have lowered the power to 7 and the head speed to 50 mm per second.  What I want to see is dots and lines with out any halos or overlaps.  If you look at this close it is hard to make out dots and the lines.  In the next photo the image is larger for us to see the issues.
 The top row should be different length lines and they should be straight.  They are not!  The next row should be evenly spaced and formed dots.  They are not! The bottom row should be a dot a space the same size as the dot and then another dot and space.  Wrong also.  

I now have an  idea what causes this and or why.  Russ the guy on You Tube has found that our laser head is heavy enough to cause this issue.  This is like a "backlash".  It should be fixed so I can get a better quality cut and or scan.  The fix is replace the head!  Russ has created a new head made from acrylic that we can make.  This project also replaces the head mounting bracket that is much stronger.  The new head I made from the drawings I have down loaded from Russ.
Here is the new head I made.  I added a Mirror assembly I purchased for this project and added a red dot pointer as seen at the bottom left.  The head once adjusted seemed to work great for cutting.  Parts were straight and dropping out once cut.

So I did the focus test stuff and found out I did NOT fix the problem.  Turns out that the added Mirror and aming dot stuff added to much weight also,
I have to go and remake the head and try again, With out the added stuff......  

And so it goes ...        stay tuned to see my progress with this. 
BTW this was 11/13/18
A few weeks later and a couple more tries here is the new head.  The mirror assembly is replaces with an acrylic one from the Russ Design.
I had to make a bunch of changes to get this to fit my machine.  Mostly height changes.  I cut some parts and it seems to work just fine.  I did the scan test and there is much improvement, BUT it is not yet 100%.  I still have to do some more testing and adjusting.
On the left of this image is the old scan test.  Wavy lines etc.

On the right is with the new laser head.  The test shows improvment.

I think there is more testing and adjustments can be made.

This backlash issue fix is so I can make Laser engraved photos much better.  And that will be my next project.  My progress will be placed here when it happens.  Stay tuned.
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