I have made multiple attempts at colored inlay with 3D printing and CnC milling in the past. My best results have been with epoxy resin and dye. It is hard to work with. Either you slop it on or pipe it in with a syringe. Slopping it on runs the risk of voids and has a lot of surface cleanup. Using a syringe has better control, but the stuff kicks off quickly when placed in a container like that. I had experimented with Acrylic paints in the past with only modest success. I tried again on my 3D prints and had a bit of a breakthrough.
I picked up some craft acrylic paint for general purpose use. It comes in a bottle and is the consistency of ranch dressing. The previous stuff I worked with was in a tube and was very thick I poured some black into a 3cc syringe and piped it into a cavity of my 3D print.
I started with a 25 gauge straight needle, but the paint flowed too freely and I ran over on one of the parts. I dropped down to a 30 gauge needle and had a lot more success. The paint flows in, sticks well to everything, and doesn’t appear to run. You can use the needle to guide it up to a wall if it didn’t quite reach everywhere.
These prints are my corner radius templates for the router table. The text is face up and have 3 perimeters. Not sure if it will bleed through 2 perimeters or not. I suspect if you had inset text on the side of a print it would seep out and run along the Z-layers. I haven’t tried it yet though. If you do happen to run over, the paint wicks down into the top layer and never comes fully out. Sealing it with a spray lacquer, before you paint, might fill the gaps and buy margin for error. I was just really careful and used a small needle after the first screw-up.
Once I got the hang of it I didn’t make any more mistakes and was able to fill them out in a minute or two each part. Maybe some day I will get a multi-color capable printer, but until then, this is a really easy effective method of adding color to inlaid text on 3D prints.
I think I finally finished my inlay journey. See previous attempts here, here and here. I made two different wooden projects with inlay, and aside from leaving out one important step, they turned out well. The projects are my the “Cube Sweet Cube” signs that I have attempted to make over and over again, and a baseball bat trophy thing for my little cousin. He is into tee ball, and has some game winning balls to display.
I milled out a deeper pocket (0.05″) and instead of filling it completely with paint, which didn’t go well, just tried to coat the inside surfaces with paint. Thinning the acrylic with a little water helped it coat evenly.
The results were pretty good, the color was consistent, there wasn’t a voiding issue, and the surface planed clean really quickly and easily. This was due to the very thin layer of paint on top. The only thing that went wrong was a little bleeding into the grain. It is worse on the red than the black. The oak didn’t do this as bad as the pine did. I was lazy and didn’t do any sealing, so I only have myself to blame. No we know that is important!
Mill text pocket with either flat or round bottom mill to at least 0.05″ deep.
Spray area with a sealer such as spray lacquer. It is cheap and dries quickly.
Mix desired acrylic paint color with a small bit of water to make it spread easily.
Let dry overnight and either sand or plane off excess paint on top.
I used the shapeoko to mill out the somewhat complex area around the handle. I could have cut this with drill bit and band saw, but this was quick and came out really well. I don’t have enough travel to do the whole thing, so I finished the rest of it with my bandsaw. A forstner bit made pockets for holding the balls, and a quick trip around the router made a nice round over.
Inlay is going to turn into a saga If this keeps up! I had previously tried doing my own alternative to inlace’s resin infill material. It was kind of a disaster. The dye I added had a very adverse effect on the two part epoxy and resin. A few weeks later I looked at the casting dye and noticed that it had completely separated. There are no instructions on the bottle to mix before use, so it isn’t 100% my fault. I remember last time that I had to add a lot of the stuff to color the resin, and It still wasn’t very opaque. That could have been my issue all along.
I created another test structure and went to work. I don’t need to revisit inlace, I know it is good. For the acrylic paint, I tried to slop it on really thick so when it shrinks the pockets will still be filled. The two part and polyester resin were done with a minimum amount of dye added. This time they looked proper dark. The results were unfortunately bad. The polyester resin didn’t adhere well, and the two part epoxy had kind of a rubbery feel to it.
Well acrylic it is then! I went a little deep with the sanding and buzzed off part of the R, but other than that It looks good. Without further thought I ran off to make the “Cube Sweet Cube” sings I wanted to make weeks ago. The results were not issue free.
The acrylic paint shrinks considerably when it dries. The shrinkage is difficult to predict and often includes bubbles. I was trying to go thin on the pocket milling so I didn’t have to use as much paint. In trying to plane everything flat I shaved the paint right off in sections. The neat byproduct of that is some really cool looking shavings.
I have one last test up my sleeve. The acrylic paint coats well, but does not build up consistently. I will try taking a rounded bit and make deep pockets. These will get a good but thin coating of paint. I can shave or sand plenty off the top with out worrying about going too deep. Assuming the surface finish of the paint is ok, this should be a good solution. More results to follow!