Pentaflake Tabletop

Sanded and Varnished

I’m still working on the video, but I wanted to get something up on HipNerd.com about finishing this project, since I already posted to social media about it.

I had more trouble with the Maslow, but finally got a good cut.

Pentaflake pattern being cut into plywood by Maslow CNC.

Pentaflake pattern being cut into plywood by Maslow CNC.

The bit was dull from the tests I ran previously, so I changed bits halfway through, then re-ran the program to clean up the hairy stuff from the dull bit. Finally, something worked in my favor, and it cleaned up well.

Before and after changing bits.

Before and after changing bits.

I sanded the insides of the cutouts by cutting up a sanding sponge, folding it over and zip-tying it to a dowel, then putting the dowel in my drill.

I cut the tabletop into a circle using a router on a jig.

Cutting the circle using a router on a jig.

Cutting the circle using a router on a jig.

I painted a coat of clear epoxy resin into the cutouts to seal, then poured the the colored epoxy using condiment dispensers.

Tabletop with Seal Coat and Colored Epoxy

Tabletop with Seal Coat and Colored Epoxy

I sanded off the excess epoxy with 80 grit sandpaper, working in sections.

Sanding in progress

Sanding in progress

I sanded everything smooth, working my way to a final 400 grit hand sanding. I put some edge banding on to hide the plywood edge. Then, I put on three coats of varnish.

Sanded and Varnished

Sanded and Varnished

I’m really happy with the way this came out, and looking forward to some more projects with my Maslow.

Maslow CNC First Project: Pentaflake Tabletop, Test #5 (I Think?)

For test #5 (there’s been so many tests, I think this was #5) of the Pentaflake Tabletop, I modified the clip on the router with a big bushing with plenty of surface area for epoxying, and used some epoxy putty made for gluing metal to metal (JB Weld SteelStik). End result: a really solid bushing, which keeps the clip perpendicular to the z-axis screw.

Router Modification: Added a bushing to the clip on the router's z-axis control to eliminate slop.

Added a bushing to the clip on the router’s z-axis control to eliminate slop.

I modified the g-code (see Hand Editing G-Code for Better Machining), and I added a bungee over the top of the router to keep constant sideways pressure on it.

The test was a success.

Pentaflake Tabletop Test #5

Pentaflake Tabletop Test #5

The cuts are clean, no burning. And, the depth is exactly the same across the whole piece.

Hand Editing G-code for Better Machining

One of the issues I’m having with with my cutting the pentaflake pattern for my Backyard Tabletop project is that the router bit stops in one of the corners of each pentagon shape before moving up. This causes the bit to rub against the side of the cut as it raises, burning the wood, heating and dulling the bit. The problem gets worse as the job progresses, as you can see in this picture:

Side view of the pentaflake pattern showing burn marks getting worse across the piece.

Side view of the pentaflake pattern showing burn marks getting worse across the piece.

What I found out on the Maslow forums is that this is a common machining problem for which there is a common machining solution: something called ‘lead-out’, where the bit moves away from the edge of the cut before performing the z-axis move. Unfortunately, the software I’m using, Easel easel.inventables.com, does not support that function. The other common software used in the Maslow community, MakerCAM MakerCAM, doesn’t even seem to be working, it’s an online tool (as is Easel) and I can’t connect to the site. I looked at some videos on how to use Fusion360, which I have some experience with for 3D printing, but it seemed quite complicated in comparison to Easel or MakerCAM.

I decided to try Fusion360 anyway, first bringing in the .svg file I made in Inkscape, but that bogged down my computer, and brought out the pinwheel of death. I then tried generating the pattern in Fusion, but after the pattern got over 30 elements or so, it bogged down my computer again. Don’t know if it’s Fusion or my computer (an older MacBook Pro), but I gave up on it at that point.

I’ve modified g-code files before for 3D printing. G-code is human readable, and actually pretty easy to understand. I knew that the best way to modify the file would be to use regex, though I hadn’t used regular expressions in a while. Fortunately, there are a lot of online resources for learning regex, and the RegexOne interactive tutorial got me up and running pretty quickly.

I brought the .nc file into the Atom editor, https://atom.io, and wrote a regex to find the entry point for each pentagon shape in the g-code. I added a g-code command to move to that point before each z-axis up move, essentially creating a lead-out.

Editing G-code in Atom using regex.

Editing G-code in Atom using regex.

I loaded the .nc file into Ground Control (the software for controlling the Maslow), and it looks good, but I won’t know for sure until I run it. I reattached the bushing (see previous post) using 2 part epoxy, and I’m waiting for it to cure overnight before testing again.

Maslow CNC Pt. 1

I built a Maslow CNC. This video is part one of the build process—the electronics and assembling the frame. The Maslow is a relatively inexpensive, open source CNC kit. The kit comes with the electronics and specialty hardware, and you provide the lumber, router, and a computer (and a dust control system is a good idea, too). It’s a hanging router, much like a hanging plotter, and is capable of cutting an entire sheet of 4X8 plywood (with some margins). It can also cut thin aluminum, pretty much any material that the router you equip it with is able to cut. I’m very excited about the creative possibilities that this machine will open up for me.

Möbius Roller Update

Part One Here


Finally realized that trying to cut or zip the channels open is just overly complicated, and that (although it seems a little less magical) I should just print in two pieces and glue together. There are multiple benefits:

  1. It looks better. Being able to control the edges of channel where it intersects the outside of the of the cube gives a very clean look, probably better than I’ll ever get trying to open it with mechanical means.
  2. Channel walls come out very smooth. This is mostly the result of the way the slicer processes the model when it’s when it’s a monolithic piece.
  3. Easier to model. There are a lot more considerations when trying to make internal structures in an enclosed piece.
  4. Easier to paint, especially on the inside curves. Although, I do have to take a different approach than primer/sand/spray, which was giving some really nice results.

It’s not done yet, though. As you can see in the picture of it being printed, I did not use supports, and that caused the channels on the top of the arcs to be distorted just enough that the bearings fall out. Reprinting with supports now, and that should add dimensional stability (along with my emotional stability). 🙂

Seeking the Perfect Möbius Roller

I’ve been trying to perfect the process of making these things that I call “Möbius Rollers”.

Issue #1—Painting:

On the top one I used multiple coats of filler primer, sanded it with 100 then 220 grit sandpaper, painted it blue, taped it, painted it green and removed the tape. The paint job came out looking great.

The second one, I used wood filler on the rough areas, which saved me a couple of coats of filler primer. Painted it green, then taped it. But, the tape strips were too small, and didn’t stick well in some areas, so some of the blue paint got under.

Issue #2—Cutting:

There is a channel with ball bearings that ride around inside. In order to get this to print, I have to make the channel just below the surface. Then, I just cut the top of the channel open, so you can see the balls roll around inside.

On the top one I tried different bits on my rotary tool, and when I tried the router bit, I thought it was working at first, but then it skipped all over, and tore the whole thing up.

The second one I tried a grinding wheel bit on a slow speed, and I got a cleaner cut, but it took a long time. Then, after it was open, I tried sanding the channel so the balls would roll smoothly, but I discovered that the channel is pinched in one area, and even a lot of sanding would not open it up. And, even still, I did not like the way the cut came out.

Issue #3—Model:

On my old printer the channels came out wide enough, I don’t know if it’s the slicer, or the printer, but I need to either figure out different print settings, or maybe modify the the model to make the channels bigger. Also, I want to find a way to make the plastic thin enough along the outside of the channel, so that I can pull it open like a zipper.