As usual, click any photo to bring up a larger version.  

Making a CNC carving from a Pin

 

This is a small metal pin, about 1-1/4 inches or 3cm in diameter. The goal of my project is to take this image, the figure on the pin, and turn it into a much larger carving, about 11 inches or 23cm in diameter. All I have is the pin; I do not have a digital source file. So, I had to figure something else out.

First here is a very truncated background story, and you can skip this part, if you are not interested. I listen to the No Dumb Questions podcast. This is a discussion podcast between Destin Sandlin and Matt Whitman. In the fall of 2019, they sent out these pins as rewards to people who supported them on Patreon. The figure is that of a Winged Hussar, which were Polish Calvary in the 16th-18th century. The Winged Hussar became a "thing" on their podcast starting at Episode 34

TL;DR -- blah, blah. It has to do with some nerdy podcast. Get on with the build!

I've done something similar in a previous project, but at that time I had a digital SVG (vector graphics) file that I could load directly into my CNC software.

ALSO, please note I am not a CNC expert, I'm just telling my story. Please look elsewhere if you are seeking detailed instruction on how to use a CNC system.

I thought about taking a careful photo of the pin, but I was pretty sure that it would be finicky, or even downright difficult, for me to get a clean non-distorted image. Instead, I put the pin on my document scanner. By putting it on the scanner, it is dead flat on the glass, so there is no angle or distortion. Also, it has a flat white background, and the light of the scan ensures that it is brightly and evenly lit.

I set my scanner to the highest possible resolution, which is unfortunately only 600dpi on my inexpensive scanner. I want as big an image as possible, hence the high DPI. I also set the scanning software to "Black and White" -- which actually gives a greyscale image. Finally, I set the image format to TIFF, as I wanted a high quality image and I know that JPEG has some compression that can affect that.

I took the resulting image and loaded it into Gimp. Gimp is the photo editing software that I use. It is free, and has been under development for years, so it is quite full featured.

I needed a purely black-and-white image, in order to be able to import it into my CNC software, which would convert the black to lines to be carved on the CNC. A quick googling and I found that Gimp has the "Posterize" option under the "Color" menu, which will reduce the number of colours in the image.

(Next two photos) I accepted the defaults which changed my image to a grey + black + white. I then used the fill tool to change all the greay to pure white. And continued, filling all the areas inside the helmet and feathers area, until all the grey was gone. I now had a pure black and white image.

There were still a few problem areas where there were breaks in the image. I scaled up the view to 400-percent, so I could zoom in on the image, and then used the drawing tool to draw over the gaps. In this photo, the red arrows indicate several areas at the bottom of the horse's foot where I filled gaps.

You don't need to worry about drawing "perfectly". Since we are zoomed in so much, I could just do my best, and when we zoom back out, any "irregularities" will not be noticed.

I also completely replaced the outer circle. It was easier to just erase the mediocre scanned image and draw a perfect circle with Gimp. I also had to slightly rotate the entire image, in order to end up with the feet of the horse appearing to be level and flat. The end results are shown here. I could then export this image and take it to the CNC software.

In this photo I have signed onto the easel.inventables.com website. On the left side there is an "import" menu (The arrow entering the box icon) and if I open that, there is an "Image Trace" option, which is what I want.

This pops open a window, and from there I upload the file that I am going to be importing, and I can adjust the "Threshold" and "Smoothing" values to suit the file being imported. The smoothing value will help get rid of jagged lines, and the threshold has to do with edge detection. Please see the Easel website for more details.

The software then imports my image, and I can resize it to the 11-inch size that I want. I then can proceed with setting the cutting depth, bit size, the material type and so on.

If you're lucky, you are now ready to start carving.

My image still had a few spots where the lines were too thin for the cutting bit that I was using (1/8" straight bit). This would result in gaps in the image. I had to use the CNC software to add lines to the image. In this photo I have hidden the imported image, so you can see all the places I touched up the image. I did not need all of these, but in several places it was just easier to draw one long line, rather than several small line segments.

This was easier than it sounds, since I could just trace over the image. The red arrow shows where I am adding a line over the image. I just click in several areas and the software connects the dots. I can come back later and move the dots if needed.

NOW I was read to carve my image.

I then went to my shop, hooked my laptop up to the CNC, and started carving. I have a small Xcarve CNC from Inventables. It's small, and I have an old version with a rather underpowerd spindle cutter motor. But, it is big enough for this job. I don't use it that often, and never did get around to building a Dust Collection hookup for it, so my job at this point is to watch and use the shopvac to vacuum up shavings as needed.

And the carving went great, right up until the end...

At the end, for some reason, the CNC wandered off a bit as it was cutting the circle - visible in the lower-right area of this photo. Unfortunately there is not much you can do in that situation except start again, which I did. Just on the top edge of the photo you can see a fragment of another circle. I repositioned the work piece and three times tried to have the system carve the circle -- just the circle. Each time it wandered off the path as it was moving the cutter head. I tried making a few hardware adjustments but eventually gave up. There is something misconfigured or I don't know what.

I decided that since the original was a pin/medallion, that I could save this project by also turning it into a round medallion. So I took it to the bandsaw and trimmed it off around the circle cut. I then sanded it a bit, and used a carving knife (Next photo) to clean up the edge and remove any lingering small black bits.

The project was now ready to frame. I am not going into details on the frame on this web page. I have another project page where I go into detail (and provide a video) of one method I like to use when making picture frames.

I made a small frame out of cherry, and used some surplus 1/8" cherry plywood for a backing. I finished the frame with a few coats of spray lacquer. And I attached the carving to the frame with a few small screws screwed in from the back. I could then add it to the wall of shop art that I have been acquiring in my shop.

(And yes that is the mighty Nail and Gear behind me. TL;DR another nerd podcast thing, move along...)

Some of the Tools/Supplies Used In This Project: (Affiliate Links)

 

Thanks for reading!

See Also:


Designing Picture Frames


Picture Frames Build


Hello Internet Nail and Gear Plaque