University of Virginia Basketball Champions 2019!

This is my salute to the Men's basketball team for winning the National Championship.

Shown here is the Sketch book page where I planned out what colors to use and the details of how the various cut-outs from the stencil would either be filled in or left blank.

I used 9 different pens, including two blues and two oranges.

TT = Texas Tech
V = Virginia

and the final score 85-77 in overtime. For the letters and numbers I used standard commercially available stencils. The silver objects are TV Cameras.

Go Hoos!

The nets and ball seams were free-hand drawn.

Basketball Stencil cut 

with 4 inch focal length laser

The laser power is still good but I did need to increase the percentage by 5-15% compared to the football themed stencil cut earlier this summer. There was a bit more haze on the outer cut edges too, however, by using clever placements of blades and backing tape, the usual stuck on white debris was almost non-existent. Unlike previous design cut jobs, I skipped my usual laser alignment and beam quality check.

For the first time, I avoided use of the exacto blade to cut my 10 inch by 12 inch plexiglass template rectangle. I decided to just make an RDWorks g-code file for that rectangle and let the laser cut it for me instead! While I had the file loaded in memory, I went ahead and cut several more until I exhausted my available space on the sheet purchased from Lowe's. This is a big time saver and avoids tedious manual labor.

It took 38 seconds to cut the rectangle. It took 4 minutes and 5 seconds to cut the full basketball design into the rectangle.

I suffered through a bit of confusion regarding how the on-board system differentiates the origin from the framing outline. Normally I set my design origin to be the upper right corner. I was working on a different computer that had the default changed to the design origin being dead center (the prior user likely was using a circularly symmetric design). Therefore, when I tried to use the on-board framing button on the laser, I got a "X Slop Over" error, which means that you are asking the laser head to position itself outside the bed boundaries. All I had to do was go back to RDWorks, reset the design origin to upper right, resave the Ufile and then all worked as normal with the on-board origin and the framing start point as one and the same. See my Blogsite section titled RDWorks for more details on this issue.

As a courtesy I am now deleting my uploaded g-code files from system memory after I finish the cut job. The on-board memory can only hold 99 files.

8.8 inches by 6.2 inches for the largest ellipse.

Usable stencil components

Cut out pieces

Smooth clean small cuts can be achieved with proper laser settings

I purposely tried a cut line close to tangential to the circle to see how tight the cut line would be. The circle held its own.

All the components in concentric positions and backing tape removed.

Basketball theme stencil

 

Today I needed about 3 1/2 hours to start from scratch to complete this Stencil design in VCarve Pro.

First, I created a 3 vertical oriented concentric ellipses template so that I can quickly use to build stencils down the road based on that layout. Remember, by keeping the ellipse sizes the same across designs, I can later mix and match for new patterns, without any new software design work or laser cutting.

The yellow objects are cameras and the light blue objects are uniform tank tops. The olive green objects at top/bottom are hoops with backboard connectors also drawn in. I made good use of the weld and intersect tools for those.

Learned several new tricks for VCarve Pro; see my VCarve Pro section of this blogsite for details. 

 

 

 

 

 

Football Field design complete

Today I finished the drawing of the football themed design. For this project I kept track of the hours involved in each stage of the process.

Software design in VCarve Pro: 4 hours
Laser file preparation in RDWorks: 2 hours
Laser prep, alignment check, test run and design run: 5 hours
Stencil cleaning, tape removal and review: 1 hour
Sketch book color planning; 1 hour
Drawing: 3.5 hours
Blogging at various stages: 2.5 hours
Total: 19 hours

9 pens for the drawing

sketch book

Football Field and Stadium

Football themed Stencil

Before starting, I did a thorough vacuum and wipe cleaning of the 4 inch focal length laser and the supporting components.

Then I ran my standard beam quality and alignment check. The operating condition at the moment is nearly perfect. The beam cross section is nearly circular at 12% power and even the beam halo is uniform. The beam is hitting center in a left to right sense, and slightly high of center in an up to down sense. This is the case for all 4 corners and the center of bed test points. The slightly high of center is actually preferred, as when the beam is reflected down from the 3rd mirror of the head into the focusing lens, it will be more centered (given the beam width).

Excellent laser alignment results

L: left, R: right, F: front, B: back

notice the uniform yellow halo around the burn spot

I ran a small 2 inch test file that represents the range of shape size/ head speed combinations to make sure I get clean cuts, but without using too power. Everything was good except the larger shapes with a 30 mm/sec speed needed a 7% increase in power to get a cut-through.

As a reminder when working with plexiglass, make sure the exhaust fan on the other laser is ON to prevent any odors of burnt plexiglass from seeping into the workspace.

I am extremely pleased with the overall results, especially considering that this was my most challenging design to date. I used a large number of very small circles and closely adjacent ovals to test the laser precision. The football helmet face-guard also has very thin lines criss-crossing that retained their shapes with cracking or splitting.

The major stencil parts

8.8 inches high. 6.3 inches wide.

Ellipses in VCarve Pro

Be careful when creating ellipses in VCarve Pro and then exporting as dxf, ai or eps. VCarve Pro will make two identically sized ellipses superimposed exactly on top of each other. This creates havoc when you import into RDWorks and run a simulation, as the apparent priority layer order set by you may not be respected because of the double ellipses. Black is set as the default priority 1st color for layers, and the hidden layers will be colored black. Since you could not see them to color them anything else, the simulation will then do all the visually hidden ellipses as priority 1 ... and then go to your priority 2.

I even tried exporting out of VCarve Pro as a PDF which Inkscape can read, then exporting as dxf out of Inkscape. The problem of double ellipses still holds, but now the redundant ellipse has jagged edges and is merged with the true intended ellipse.

The work around without going back to VCarve Pro is to set the layer property for the ellipse to "hide yes" by double clicking on it in the Work Tabsheet. This will reveal the hidden ellipse as colored black; delete it. Then unhide (set "Hide = no") on the actual ellipse that is colored and you want to keep. Remember to File -> Save the changes before running a simulation.

You can see the issues with the images below. If the outlines in the image are dim on your view screen, just click on it to enlargen and darken.

There is an ellipse underneath the red inner ellipse.

The hidden ellipse is revealed.

See the hidden ellipse now has jagged edges after using Inkscape as an intermediate DXF creator.

Football theme stencil design using VCarve Pro and RDWorks

I made heavy use of the Mirror copy, Weld, Interactive trim and boundary based Trim tools in VCarve Pro in putting together the design.

I'm trying smaller circles than any of my previous designs at 0.15 inches diameter.

Always remember to zoom in on intersection points in VCarve Pro that have been manually connected using the Validity tool and look for the square with + icon at the intersection points as verification.

Important: If you are experiencing incorrect geometries from imports of DXF files into RDWorks, make sure you go to Main Menu: Config -> File Para Setting and fill in the check boxes for "Import DXF text info" and "Import dxf point". Otherwise, you may get a variety of issues; in this case independent arcs getting connected into closed shapes and a large scaling down occurred. You may also try exporting out of VCarve Pro as an .ai file, which RDWorks can import dependably.


RDWorks: Config -> File Para Setting: check both DXF boxes

Here is what my stylized football object is supposed to look like

and here is a markup of what RDWorks does if the DXF options for  import are not set. The highlighted area shows where RDWorks (upon import) adds a connecting segment between the three shapes at the four "edges".

This was a problem on the Build RVA computer's installation of RDWorks that I was NOT able to reproduce at home on my laptop running Windows 10 and RDWorks V8.01.28. Next week when I am at Build I'm update this post with the RDWorks version installed there.

Baseball

Here I show the early design, an intermediate stage and the final drawing of my latest stencil of SymArt.

I attempted to raise the complexity of the design (my first oval stencil) and introduce an even larger assortment of colors and pen tip sizes into the final drawing.

This was my first attempt using 130 lb cardstock, to help reduce any buckling or stretching of the paper from the very wet inks, especially the metallic inks. The backside of the paper is very dry and even/smooth. I will likely use 130 lb cardstock going forward, as it also had firmer and smoother feel while drawing than 65 lb cardstock.

This drawing was the most time consuming I tried to date with my stencils, as I added blocks manually outside of the stencil using a ruler - semi-freehanded if you will.

Sketch book - note the numerous details and color trials

Early Outlines

intermediate stage

Variety of pens 

Baseball final artwork

Baseball 

With MLB Spring training getting started and the opening day for the 2019 season only about 6 weeks away, I thought that a baseball themed design was in order.

I loaded the baseball theme design into the Boss laser LS2436 with the 4-inch focal length optics.

Here are some Lessons Learned:

To set up my standard 10 in by 12 in rectangular piece of plexiglass it's best to only remove the center eight blades.

I had to rerun the outermost oval (30 mm per second) for 15% power because at that speed my first try at 10% power did not cut all the way through. On the second run, the trick is to either set layers at 1% power, either on-board or in RDworks software, so that fall through layers do not get recut. Something very low say 1% power so the laser won't fire. Then only assign the higher power or the lower speed (or both) to the layer to be recut. In the future I'll avoid this problem and make sure my Concentric Circle test samples all of the head speeds that will actually be in the design run.

Note that we are no longer adjusting the compressor pressure away from the default set by the manager.

I am now deleting my files after I'm done. The on-board memory max's out at 99 files regardless of size.

The photos show that all the cuts are very clean. I report that there are essentially no cracks or divots on the back side, nor were there any burn or char marks (either on the backside tape or on the plexiglass). This is proof that the laser is well-aligned and has a good beam cross section. Additionally, there was very little rubbing alcohol & terry cloth cleaning that I needed to do on the surface of the plexiglass stencil parts; debris was kept to a minimum.

Design size is 8.8 inches by 6.3 inches

Outer oval and baseball, bat, field and scoreboard

middle and inner ovals

partial sampling of the small pieces

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.