A new tessellation project enters…

Been quite busy lately – my son got married in the Dominican Republic so that pulled me away from doing any more computer or woodworking activities.

I thought to get back into it though I’d try something extending what I learned from tackling the reptile project. The new effort requires a bit more precision than the last one. Since I live near the coast a sea based design may be appropriate. This one is also Escher inspired and is a tessellation based on seahorses.

Since this design needs to lock into each other more than the last, I thought using design parametric and constraints would be a great way to start. Fusion 360 lets you define relationships between lines (e.g., they must be the same length, they must per perpendicular).

The equal signs in the illustration above show when a line has a length equality relationship with another line, in this closeup of the seahorse gills. This ability to define the relationship is useful since the gill elements will need to fit inside each other.

To create the g-code to manufacture the seahorse, I used the trace (for the eyes) and contour capabilities to define the commands to cut out the outline. These were defined to be cut using a 1.5 mm bit.

It took 4 iterations before I was able to reliably produce the seahorse. In the final design, I had to turn off the constraints on some design elements (up by the mouth of the seahorse) to interlace the design elements effectively.

I am going to use walnut and maple in an alternating design to produce the final result. So far, I’ve just been creating the walnut designs and they seem to be produced reliably.

I’ll put out another post when I put them all together and epoxy the design. It will be at least a week though.

The finished version of my CNC’d holiday sign

I originally thought I’d mount this on a walnut base but changed my mind when a piece of Purpleheart fell into my lap. I ran a saw blade dado cut down the middle of the board and cut it to length.

I have some refinements to do on the design, but I think it turned out OK for a first attempt. I ended up painting the stars gold with the rest of the design taped over. I then pulled off that tape and taped over the stars. I then painted everything black. I could then remove all the tape. Next, I then ran it through the sander until the black paint was removed, leaving the paint in the letters. Finally, I polyurethane the whole thing, just to keep the humidity out.

A two bit project

I am back home after being gone for a week and a pile of projects awaits.

  1. The Railroad group wanted a HO gage 3D print of an A10 for the airbase on the layout. It is printing right now. I had to do it in 2 parts, since it was larger than my little 3D printer could handle.
  2. My wife’s sister wanted a couple end-grain cutting boards (Texas sized 19” x 16” x 1.5”) to give as gifts. I am trying a four-wood design (Maple, Cherry, Sapele, Walnut) using a couple different designs. Hopefully, they will come out as I envision them. Boards like this can easily cost >$200 retail.
  3. I still have a few gifts of my own to finish as well.

While working on that I thought I’d attempt a CNC design using 2 different bits. A 1.5mm bit for the course work and a 1.0mm bit for cleaning out the contours of the letters.

Here is the design I am trying to produce:

The first pass with the 1.5 mm bit will take out the bulk of the material for the letters, using a 2D pocket milling operation:

2D pocket

Since this design is small (150 mm x 150 mm), it leaves quite a bit of the letter details uncut. So, another pass is required. This one will only focus on the 2D contour of the letters.

2D contour

This gets into every nook and cranny that a 1mm bit can reach.

You can see in the Fusion browser there are a few G-code passthrough operations defined to: stop the spindle and raise the bit…, so I can make the bit change between the two cutting operations.

Once this is milled, the plan is to paint the letters in the appropriate colors (e.g., stars yellow, letters black) and then sand off the top millimeter or so. This will allow for the letters to be painted (including the sides) and yet have the wood surface show unpainted.

I’ll have to do another post when it is all done and show the finished result.

3D printing a vacuum system for my CNC machine

I mentioned in an earlier post that I was going to look into creating a vacuum system for my CNC. I decided to go the inexpensive route of taking a small consumer shop vac and using its nozzle attachment as the basis for the vacuum.

Here is what the model looks like that I created in Microsoft 3D Builder.

This model is positioned with the side that snaps on the spindle point toward you. The narrow nozzle of the vacuum fits into the fixture on the right side of the illustration.

Here is what it looks like mounted on the CNC machine, trying to collect some dust from a Christmas ornament being cut out of Cherry with a 2D contour cut and a 1.5mm bit.

Next, I need to get back to understanding how to focus the laser on the mount I built previously.

Injecting G code in the Fusion 360 post processor

One of the issues I encountered was that at the end of a job my CNC machine would keep its spindle running. For some reason the UGS software did not have a way to automatically add some G code at the beginning or end of a job. I had to figure out a way around this, since all my 3D printing software supported it — and its quite useful.

Fortunately, Fusion 360 can easily get around this with a minor modification to the post processor code as described in this post.

https://knowledge.autodesk.com/support/fusion-360/learn-explore/caas/sfdcarticles/sfdcarticles/How-to-use-Manual-NC-options-to-manually-add-code-with-Fusion-360-HSM-CAM.html

The following screen shot shows the step I needed to add in the setup process to manually perform a pass through of G-code. The dialog on the right shows the actual pass through entry with the M5 (stop spindle) command.

The manual NC commands in Fusion can be used for a range of things like manually asking for a tool change… as well. This is a whole new area I need to look into, since it could significantly improve processes and reduce bit breakage.

The picture of the object being designed is a Christmas ornament based on the South Carolina flag, by the way. I plan to cut it out with a 1mm bit.

Escher inspired reptile pad nearing completion

I finally got all the reptiles cut out and assembled and decided to epoxy them together. I’ve never really worked with two-part epoxy, so this was a learning process.

Waiting for epoxy to dry

The first thing I did was place painters tape around the sides, to form a container for the epoxy. Then I mixed the epoxy and poured it in. Next time, I’ll try electrical tape or something that is a bit more water/epoxy proof than the painters tape. It tended to run out the side and generally seep through more than I expected.

Another unexpected issue was the number of bubbles that came out of the material into the epoxy. I used a torch lightly on the top of the epoxy for over an hour (since they popped almost instantly) and still ended up with one small bubble solidified into the design and I still have a bit of cleanup where the tape/paper towel stuck to the bottom where it leaked out.

A near finished design sitting on our counter top

Adding a LASER to my CNC

This week I had someone ask me if I could put a picture on a piece of wood for them. I’ve been doing laser scribing with 1” wooden medallions for a while, but not on anything larger, so I took this as a challenge. My CNC machine came with a 2.5W laser sufficient to burn wood, but I’d not even taken it out of the box yet.

When I unboxed the laser, I noticed there really wasn’t any place to mount it on the machine. Too bad, since it wouldn’t have been that difficult for the manufacturer to do.

Spindle

The only real mounting option provided was to pull the spindle motor out and replace it with the laser whenever I wanted to make the switch, but that just didn’t sound right. Instead, I thought I’d ‘side mount’ the laser on the spindle. It wouldn’t be a problem for the software that drives the machine, since it is all relative movement from the starting point. The biggest concern would be collision between the moving parts, and anything being worked on.

After taking some precise measurements, I made a model of the spindle and its housing. It was then just a matter of subtracting that design from a laser mount design to come up with the following mount:

Side-mount design

This design snaps onto the spindle motor mount and should allow for enough support for the laser to do its thing, without too much vibration. Here is a picture of the whole assembly in place:

Finished initial design

Since I have the basic snap-on solution figured out, I’ll also try a front mount version to see if it is more usable. I’ll also try adding a bolt and wingnut clamping system, to make it more stable.

Next, I’ll tackle a vacuum system for the CNC machine, to help control the dust level. But first I need to figure out this whole lasing process, since focusing the laser is critical to the amount of detail I can burn.

Note: Lasers are dangerous and can easily cause eye damage, so be sure to use effective eye protection.