My brother Bryan made christmas gifts for the family last year. They were all laser cut or etched and they were pretty awesome. It was impressive how much I enjoyed them considering they were just coasters!
So, now I had a CNC machine and I could buy acrylic. Why couldn’t I make some of the same things? So that was my first project with my CNC.
The Design Phase
This was my first real attempt at making something useful on my CNC. My initial tests were just pen plotting and process refining. Now I had to learn how to take an image, generate vector paths for it, take those paths to a program that could assign G-Code that my CNC could interpret and finally cut the acrylic! Luckily the Shapeoko website and forums are a great lunch time read at work and I was able to learn a lot about these things there. I knew I could use MakerCAM.com to generate G-Code and assign different milling functions to my designs, but I had to make the designs! For makerCAM I needed to upload .SVG files that it could recognize. I had read about .SVG’s because I was thinking about contracting my brother to do some laser cutting for me before I bought my own mill. I was able to find software called InkScape that saves in .SVG natively and is a fairly good vector drawing manipulator.
My Brother did star wars, so no need to re-do that. So I fired up google images and searched for some suitable logo’s or symbols that would look nice on a coaster. I found a bunch from video games that I would like to do, and I am also a fan of the A Song of Ice and Fire books, so why not some Game of Thrones Sigils on coasters too! InkScape has a handy tool that will trace images and give you a vector path that follows the silhouette, perfect! This meant I could get the correct paths and generate the code to cut out my designs!
I spent a night laying out a bunch of designs of various game logos and GoT house sigils that I could cut in some acrylic. I also setup a symbol from Stephen King’s The Dark Tower series that my friend requested. This is the first one I decided to engrave.
The Cutting Phase
I had recently purchased the acrylic to engrave, and a 1/32″ engraving bit to do some very fine work with. This allowed me to produce some very nice lines, but not quite as precise and fine as my brother could achieve on a laser. But I had to work with what I had! So I chucked in my engraving bit, fired up the dremel affixed the acrylic to the wasteboard with double sided tape and started streaming G-Code to my controller. Minutes later I had this:
Great! the pattern cut OK and you its definitely noticeable. Now the bad: It didn’t cut the outline complete because I didn’t level it out correctly, and I couldn’t cut it free because the engraving bit isn’t capable of that! For this one switched out my bit for a 1/8″ ball nose end mill to cut out. But I had lost my zero, and this machine doesn’t have homing switches installed yet. How could I find the correct zero point to cut out the outline? Well the answer is I didn’t. I had not considered this problem. My solution right away was to manually jog my machine and cut it that way. This sort of worked, but required a lot of post-processing to clean up the edges and add the rounds. The finished product looked like this:
Not bad! A little rough around the edges (literally) but it had worked! I knew there had to be a better solution, but the limit switches I had ordered were still in China somewhere and I was impatient to cut something out.
Fixing the problem
So I could engrave and I could cut. But seemingly not both with good results. I devised a plan though, that night while I was laying out some more designs. I would engrave on my first pass, and also engrave a 1/8″ diameter circle at the origin! That way I could line up my 1/8″ end mill and get the outline I expected to get in my design. This worked out great. The next design I cut was the house sigil and words for House Stark from Game of Thrones. I think it came out very good:
The zeroing method worked! I was able to design in the engraving and outline in one file and then export them separately and do a tool change in between. Some of the lettering and features are a little too close to each other for my 1/32″ bit but overall it looks very good. I also learned about milling deep enough on the outer ring to properly part it out. I got a nasty slice on my thumb from a super sharp piece of partially milled acrylic.
I milled a couple other coasters that day, and they all turned out pretty good, but I really liked the House Stark coaster. I think I can get even better results with a finer tipped engraving bit, that will have to wait until I can get one on order though! Below are a couple more that I’ve cut out lately. Got any other ideas of what would look good? Let me know!