Standard Tests

Starting with my upcoming baseball themed Stencil run, I am now performing a standardized 20 second concentric 3 circle test to see what minimum power is need to cut through the 1/12th inch extruded plexiglass.

I tried 15%/20%25% power and all cut through evenly cleanly. Previously, powers as high as 30% were required in mid to late 2018. However, now that the laser is so well aligned and the beam cross section is nearly circular, I'm able to use half the power to achieve full cutting. You are all encouraged to run similar quick tests to find the minimum power needs; running at lower powers will length the tube life and minimize debris in the chamber.

Notice from the photos below how smooth and crisp the cut edges appear.

Well Aligned Laser

From now on, I will be running an alignment and beam quality check before all stencil cut jobs. This will give me some correlation between cut quality and laser status. If I see that the alignment and or beam quality is too low, then I will do a laser tune up before running a cut job.

The check will consist of a beam pulse on triple layered painter's tape on the gantry mirror opening. The positions will be each corner, the center and then again a second pass of left/right-back and left/right front. Those last two will keep the same tape target for two pulses to check beam spot overlap (the more overlap the better).

As you can see from the photos, the laser is in a very good status. Indeed, in the 15 months I've been using the 4 inch focal length laser, I've never seen such highly symmetric beam cross sections and so well aligned on each other (and relative to the center point of the mirror.)

Before running the laser status check test, I thoroughly vacuumed and wiped down the inside and outside surfaces of the laser system, including the surrounding floor, chiller, the accordian exhaust vent tubes and the compressor (the blades were not cleaned by me this time).

Here is what a clean laser system looks like:

Simulations in RDWorks out of order

In order to make sure that the priorities of your layers are correctly simulated, and therefore will be correctly saved to the laser readable g-code Ufile, go to the Main Menu -> Handle -> Cut Optimize menu dialog and set up the parameters as shown in the photo below. Otherwise, shapes will be cut simulated in a random order.

Also, go my VCarve Pro and RDWorks pages, accessible from this Blog's main mnee, to see useful practical ideas for saving time on layer management in RDWorks and a possible artifact upon creating some shapes on DXF export from VCarve Pro.

First VCarve Pro design

Last night I finished drawing my newest SymArt after cutting the stencil with the 4 inch focal length laser earlier in the week. VCarve Pro is proving to be a faster and more versatile tool for creating artistic geometries compared to Inkscape. Additionally, the Makerspace license is free to install as long as we do all exporting on one of the Build RVA Makerspace desktops (as enforced by the Vectric license). Finally, VCarve Pro is a more reliable exporter of DXF formats for the RDWorks laser preprocessing software.

Notice the blue Painter's masking tape remaining on the stylized tree cutouts. The Painter's tape prevents charring and cracking of the plexiglass at the laser cut edges (especially around the supporting bed blades).

VCarve Pro

Upon a strong recommendation by Seth in early July, I decided to transition away from Inkscape and towards a more advanced and powerful software package called VCarve Pro. VCarve Pro is an all -purpose CNC Routing 2D and 3D job creation package that can also export as DXF, which is perfect for RDWorks. Moreover, Seth is claiming that the DXF export/import process has higher fidelity with VCarve Pro then with Inkscape.

So today I finished reading and practicing through all of the reference manual chapters on 2D job creation and general main menu and right click menu usage.

Seth is correct; the complexity of the stencil designs I can create in a relatively convenient fashion far exceeds what can be easily accomplished in Inkscape.

I am now creating a new main menu tab on this blogsite named VCarve Pro that will contain tips, workarounds and alerts to any usage issues with VCarve Pro.

Save time on color assignments: If you are planning to export your design as DXF for importing into RDWorks, use the layer drop down menu in VCarve Pro to set customized colors for each layer. Put each object (or grouping of similar objects) into a layer by itself. The DXF format will respect that, and so will RDworks when you open the DXF of your design there. Conveniently, all of your color designations and layers will automatically populate into the Work Tab. Then all you have to do is set layer properties of speed/rep rate/power/priority. You are saved the time of assigning colors.

Warning: Sometimes, without any notice, VCarve Pro will save redundant and exactly superimposed shapes upon DXF export.  This has happened to me with VCarve ellipses in particular. This will make color assignments, as mentioned above, not be respected visually on the RDWorks Canvas. Typically, all such shapes will appear as black. If you suspect this is happening, just go to the Layers Work Tab, set the Hide property to "yes" and see if any other exact shape/object is underneath with the color expected. Then just delete the redundant shape/object.

F9 will center a selected object to the material space. You can also use the Align transform tool for this. Don't F9 a group, unless the group is already centered or in the orientation you want. For Groups, F9 will center the central point of the group - not the same thing.

Weld and Intersect: You can't do it to members of a group against each other; VCarve Pro considers the group to be one object. First ungroup, apply the transform with left click selects, then regroup.

Pushing the Limits on Plexiglass Cutting

Once again I used Inkscape to design a symmetric stencil, this time using spirals and mirror reflecting the copy of the spiral while superimposing it. I then used a line tool to connect the very short (< 0.03 in.) disconnects as the spirals are very hard to exactly superimpose. This is a big test for the laser, as it will have to precisely cross over cuts already made to get the interior objects of the spiral to fall out. How cleanly can it leave very thin and sharp corners and will the shapes fall cleanly out?

I used painter's tape on the back of the plexiglass to reduce cleaning time for debris, cracks and char marks.

The photos show that the crescent shapes are intact even at the thin tips. All interior spiral shapes fell through cleanly except for one which pivoted upwards. The laser had to be stopped or else it could collide with the protruding plastic. The laser does have some issues picking up smoothly after a pause command to the gantry, leaving some rough edges. Next time I will not use any center support bars and this should fix the problem.

The laser power is so strong after a full cleaning of mirrors and lenses that next time I will be looking to drop the power down from 30%. The full run time for the job is less than 6 minutes.

The original Inkscape design

The painter's tape protects the edges of stencil cutouts 

and the outer circle.

All of the cutouts, in good condition.
Click to enlargen.

Change of supplies

After a discussion with Taylor, there has been a change in lens and mirror cleaning supplies. Those of you read my item number 2. in my May 19th post should note that the language has been replaced by:

"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."