David Heiserrer, of Jiggernaut fame is renovating a sailboat, and part of the renovation involves some new electrical doodads, so he emailed me a file and dropped off the electrical box you see in the picture above, except it had none of those holes in it.
How to mount such a thing on the table for cutting? The four mounting holes on the back with threaded inserts looked like a good bet. It turned out to be a standard polycarbonate enclosure from Hoffman, so a datasheet showing the spacing of the mounting hole spacing was pretty easy to turn up.
It was the perfect opportunity to do something useful with an oil-stained piece of half inch MDF that was sitting around. I quickly programmed and drilled the rather oddly spaced hole pattern and mounted the board to the back of the enclosure using flathead screws, then mounted the board to the machine.
Experience has shown that an unsupported piece of plastic like the door (where I needed to do the cutting) will vibrate like a drumhead, so I also cut another piece of half inch MDF to fit inside the door to back it up and attached it with double sided tape.
David’s original design had round holes for all the components, but he brought samples. A little quick googling turned up datasheets for all of them, so I fine tuned the dimensions and added anti rotation features.
David now has a very high quality electrical box with parts that will remain neatly aligned. It doesn’t matter whether I have to think inside the box, outside the box, or both, my focus is always on creative solutions to my customers problems!
First you start with a couple of big old rough sawn white oak planks:
Then you cut them up with a CNC router:
Then you do some finishing and assembly, and what you wind up with is, Indeed, a welcome sight to Minnesota beer drinkers:
This particular specimen was found in the wild at Uptown eating and drinking establishment Muddy Waters.
Forgot to take pictures of these sign letters while they were being cut, but here they are assembled to the steel backing. The material was 3/4″ Extira, a variety of MDF (medium density fiberboard) with outstanding weather resistance, which is also used for exterior architectural trim and moldings.
The picture above shows the twin of the sign in the first picture in place and mounted to the building. The design, assembly, and mounting were done by the very capable Sean Doyle. He also cut the delicate tree design on the corner of the building, which is visible above his left shoulder by hand with an oxyacetylene torch. The rest of us can only dream of having such well developed fine motor skills.
Interesting little parts made from HDPE. I probably shouldn’t tell what they’re for yet. This started out as a DXF file from an ancient version of Adobe Illustrator which was emailed and imported just fine.
A quick wave of the heat gets rid of a lot of the scuffing and scratching on the original surface of the sheet, much like flame polishing acrylic. The rounded over edges are easily done on the CNC router.
I wound up running these in 12″ by 24″ sheets that yielded 48 parts per sheet.
Prototype foam parts. About 5 inches deep at the lowest point. Coffee cup shows scale. This is a test cut made in cheap one-pound foam from the lumberyard. The yellow lines are where the two-inch sheets were glued up with urethane foam.
Here it is flipped over after cutting the bottom side.
And here is the finished part, cut free from the frame.
If you think this looks like just another useless desk, toy, you are sooo wrong! It’s actually a sample to demonstrate my plastic cutting capabilities. I was perusing Thingiverse looking for inspiration, and found this version, which at number 1082 appears to be a pretty early thing.
I liked the Reuleaux triangle because it incorporates some interesting geometrical concepts. Here’s a diagram to illustrate:
It just so happens that this shape rolls around nicely inside an appropriately sized square, as the following animated gif illustrates:
It’s a principle which has actually been utilized to drill square holes. Click here to see the Wikipedia entry. Reuleaux, in spite of his French-sounding name, was actually a German engineer who did pioneering work in kinematics.
Here’s one last macro shot of my sample, showing the chamfer cut on the recesses where the nuts fit:
The nuts which fit in these recesses are 10-24 thread size, and are 3/8 of an inch across. Those toolmarks on the bottom are from an eighth inch diameter bit.
The plan is to put promotional engraving on these, check back for examples!
Lasers work well for cutting plastics- they’re fast and accurate, and leave a nice shiny edge, which is usually a good thing. There are however some drawbacks. Those nice looking shiny edges can develop cracks when glued, because they have stress “baked in” by the laser.
And you also can’t add 3D features like this nut pocket:
With a router you can also add bevels to the edges of a part like this:
The part in the picture above is made from extruded acrylic. It doesn’t machine quite as nicely as the cast acrylic in the first two pictures, but with good sharp tools and appropriate cutting strategies it can be cut quite well.
If you have parts that were already cut on a laser and need some additional features added to them I can definitely help.