ORCA Laser Build

When I first saw the ACRO laser build, my brain registered it as ORCA. Not sure why, but then my brain started churning up a logo one boring Sunday evening so I opened up the GIMP and this is what I came up with:


Now I needed to build a laser cutter to slap the logo on. I love the Acro design, but I felt I needed to put my own little twist on it in an attempt to maximize the 1500mm x 750mm cutting area and - most importantly - so I could use my new logo I spent way to much time making. To do this, I redesigned the gantry plates to position the laser back further so the beam would be inside the frame when the Y gantry plates were all the way forward (Y 0). Originally, I went to TAP Plastics to get ¼ inch acrylic. I found a bunch of large chunks in the scrap bin at $1/ pound but it was all clear, and I wanted black (or smoked). In the same bin was some black ABS scrap for the same price. I snagged several of the pieces I thought were ¼ inch thick to use for the plates and the control box. However, when I got them home and measured them with my calipers, I discovered they were 6mm thick rather than 6.35mm. I also realized it was not as stiff as the acrylic. I came up with a fix for this by making “stiffener” plates where needed. So, after creating the g-code in Sketchucam for the plates, I went out to my CNC Router to cut them. I used a ⅛ inch (actually 3.17mm) single flute endmill for cutting and drilling. I also found out milling plastics seems harder than wood or aluminum - at least for ABS. I still have not figured out the proper feed and speed for ABS for my set-up.

To ensure I always started in the same spot on my material - since I still have not set up my limit switches yet after 2 years - I screwed down a scrap of 5mm plywood, set my 0,0,0 position physically and in GRBL Panel, and cut out an L-shape to align the ABS material on. I just always jogged to the X 0 and Y 0 position prior to shutting down GRBL Panel and the machine. It worked great and allowed me to use very small scrap pieces of ABS to cut some of the parts. You can see that L- shaped piece in the photo below of the X gantry plates being cut.




I also wanted to give the super glue/masking tape method a try. It is a method which someone posted awhile back where you put a layer of tape on your bed and a layer of tape on your material you will be cutting then glue the part down with super glue spread between the two tape layers. After the part is cut, you pull the parts up and all that is left is the two pieces of tape super glued together, which easily peels up. My modification to the method was to do all drilling first. Then, for extra security, I would put a couple screws in to help hold the part down. Here is a picture of that process which was taken after cutting the inside Y gantry plates. It worked better that I imagined! I like it so much, I ordered the large bottle of Hobby King Superglue and some activator.




Here you can see how my L-bracket and superglue helped me get rid of some scrap by cutting out 6mm spacers to save on aluminum spacers which I was running low on (who needs homing switches).



And here is how they were utilized. They were glued on with acetone. Not only did these work as a substitute for 6 mm aluminum spacers, they added stiffness to the ABS, as well.




All the gantry plates were cut out. I modified the X axis plates slightly as well because I designed my own Z axis linear actuator.



I also redesigned the “legs” from the original Acro. They are similar to Wild Bill’s who provided me with the focal length of 112 mm for the laser both he and I have. Below are the legs and the stiffening plates (which look much bigger than they are in comparison).




And with the ”stiffener plates glued on:




I also needed a bunch of cast aluminum 90 degree brackets with the tabs on one, or both, of the sides ground off. I used my bench grinder to do it. I made sure it was square first.







Then I assembled the gantry plates with stepper motors. On the Y gantry assemblies, I used ¼ inch aluminum spacers on the inside plates and the 6mm ABS spacers (I made) for the outside plates. I also used 1mm precision shims on each side of the eight Y gantry xtreme v wheel kits and four X gantry xtreme v wheel kits. On the X gantry assemblies, I used 6mm ABS spacers I made.




For my Z axis, I wanted to able to control the height with a small, lightweight stepper motor so I desighned a Z assembly around a Nema 14 motor and 9mm rods harvested from a defunct flatbed scanner. I designed it in Fusion 360 and the main part is two pieces printed in PLA I cemented together with Tap Plastic’s acrylic cement. It chemically “welds” PLA like acetone does ABS.



Printed:



Glued



For the part the laser mounts to, My big plan was to print the entire piece out of POM since it is self lubricating. That led me to a whole bunch of experimentation and frustration. POM will not bind to regular build surfaces and I tried so many different ways. Imagine that. A self lubricating plastic not wanting to stick to anything That is ok, there was always plan B to salvage the money spent.

I had heard it will stick to porous materials like cloth so I tried printing on glued down paper. It almost worked, but almost doesn’t count. The paper peeled up.

Finally, I redesigned the part with larger holes and then just printed POM bushings with slits, so they can be tightened down on the shafts. I also made a build plate out of porous plywood that worked great. I found that printing at 250 degrees on a 60 degree plywood build plate with a skirt worked great for adhesion. I was almost tempted to go back a try the larger part again.







For those who want to see the print in action:



To be continued...