Sharpening the blade

Second Iteration of experimenting with computer controlled cutting.

My original week resulted in fairly broad experimentation in joinery and left me comfortable enough to prepare a file to cut any design, keeping in mind design and joinery constraints as well as machine tolerances.

What’s left, however, was to, first, extend tools I prepared for the tests as a general tool, and second, properly apply the knowledge.

Laser

Generalize

Regarding the first step, so far I extracted following joints from my script:

• snap joint;
• flex joint.

// As I get free time I try to go through similar process for other joints to simplify their later usage - towards a toolset with things I learned and implemented from the Academy.

This required some clean up and general organization. Moreover, I found useful to apply the script to an actual piece I deigned for press-fit kit so that I can test issues like orientation, proportionality and scale of various curve manipulations I did before to place the joint on a segment. Additionally, I tried to generalize to not depend on specific design: for example, previously I was generating the opening for snaps to go into independently, cause they happened to align with outer edge of the piece, instead the cluster now give opening which according to design can later be processed with overall piece shape.

Application

During the break between cycles I got to apply this skill for three ongoing side-projects:

• Digital postcards (using halftoning);
• Board games:
  • Game series: Custom Backgammon;
  • Game Series: Custom Go.

I found that of all the tools this is one that is simplest and fastest to deign around and can be twisted to fit a very broad range of needs.

Finally a press fit that I generally had already mostly designed but not polished - got polished.

– Press Fit Process –

First test, despite my fair confidence went awry: after material tests (confirming thickness, checking cut and engrave conditions that could ideally suit the material) I happily sent the whole file to print very happy by my efficient use of scrap material in full by rearranging pieces to match available real-estate.

– Press Fit Placement – – Press Fit Process Timing –

– Press Fit Detail –

– TODO: Failed Press-fit kit piece placement – – TODO: Failed Press-fit kit failed joint –

After some pondering I narrowed down the reason of fail to this: the design required to make the joint smaller which I didn’t check would hold as it did in the bigger test - rookie mistake, I know. Solution I had was to match proportions of the joint with reduced piece size. This increased the area occupied by the joint itself, so to compensate for it I increased minimal length and radius of pieces and reduced kurf spacing to add more flexibility to the long elements. Further more, playing with elements at this scale, I noticed that kurf flexibility was reduced since accounting for laser tolerance I offset the outline, but not of the kurf cuts, thus making cuts not go all the way though.

Last adjustment I thought I would make I decided to increase power of cut passes since the bed in the laser machine is not very even, making some areas not able to cut all the way through, which made it even more difficult to remove especially in brittle areas such as joints themselves.

After applying working proportions, varying detail sizes and extending kurf cuts I was ready to try again. I set to print one circular element and one long one to double check my hypothesis.

Additionally I found that the cutting bed is not even so placing elements close to center made cuts not go through at all.

– Cut unevenness –

– Piece Placement –

– Laser cut process –

– Piece details –

Final settings that produced cleanest cut in Epilog Engraver Mini 40W, I used for 3mm MDF boards (3.1mm really) were:

• engrave: 55% speed, 15% power, frequency 500;
• cut: 5% speed, 95% power, frequency 500.

– TODO: settings screenshot –

After successful cut I got these results:

– Press-fit kit pieces –

– Press-fit kit assembled configuration –

– Press-fit kit: details –

Conclusions:

• I found that the way the extraction system working in the lab creates a drag in the chamber pulling fire of the burning material to once side, leaving asymmetric burn trace. One way to negate the effect is to place most cut elements perpendicular to it. A proper solution though should be to rethink machine layout.

– Press Fit Directional Overburn –

• Kurfing setting worked very well and details were very flexible (even more surprising given how rigid the material is on its own). However, the issue, I discovered is that close to the connection it experiences a lot of stress and gets too bridal. A solution I imagine I could apply is to add a gradient to the length of kurfing lines in the beginning to reduce material subtracted in the beginning. – Kurfing weakness –

• No mater how thought out the design of a joint is. It has to be tested with exact material and with exact scale.

• In situations where tolerances matter as much as with joints - before each cut, the thickness of the material should be double-checked since even .2 mm can affect ability of a joint to fit in.

Vynil

While I did get to use vynil-cutter in previous cycle for a touch-pad for my final project (TODO: add link once I write it) - there were few things I screwed up some what in the previous test, so I wanted to apply it again.

First thing I realized I did wrong was not having enough patience to fund depth where the blade wouldn’t cut as deep as it did.

Second issue I had to approach from design point: while it is fluid to do any outline, It works best if final removed or removal piece is one, otherwise process of transferring and separation becomes more hustle than help.

I found in archives a cool experiment in parametric design of growth system - that I could use as a laptop sticker (boring I know, but ), set on one solution and prepared to cut. Applying lessons from previous trials here are the results that I got.

– TODO: Vynil cut: settings tests – – TODO: Final Sticker Design – – TODO: Vynil cut: process – – TODO: Vynil cut: process – – TODO: Vynil cut: transferring – – TODO: Vynil cut: separation –

– TODO: Vynil cut: result – – TODO: Vynil cut: result –

** TODO: Files for mentioned mini-projects: **

1. GH cluster for snap joint;
2. GH cluster for flex joint;
3. Final press fit design GH;
4. Final press fit design baked in Rhino7;
5. Final press fit design PDF;
6. Vynil Cut Design baked in Rhino7;
7. Vynil Cut Design PDF.