The next part was to figure out how to mount the pen to the machine.

I have converted my machine to use the common E3D V6 extruder as the stock extruder packed in and was out of stock for around 7 months, so I was already made quite familiar with the available mounting points on the extruder axis.

I focused on using these two screws which fix the extruder assembly onto the force sensor included on my printer’s extruder carriage.

Some important points that I considered (and in fact, influenced the entire design) was how much force that was going to be applied to the pen tip. The mount needed some vertical movement so that the pen tip isn’t just crushed by the force of the bed pressing into it.

As well as how much wiggle room the pen had in its mount. If the pen has a small amount of wobble either angularly or in X or Y axis, then the drawn lines would be less accurate as the design is plotted, limiting the ultimate precision of the tool.

I have managed to solve both of these problems with a miniature linear rail.

I will be honest, I didn’t buy this thing. I managed to get it by discussing my design with some of my engineer friends when one of them pulled this out of a drawer and donated it to me. I don’t even know how much it would cost if someone wanted to buy one.

This linear rail is precisely machined to the point where I can’t detect any wobble of the rail and is smooth enough that the weight of the pen mount will pull it down under its own weight.

There are always alternatives though, a quick search for “Miniature linear rail” on banggood brought this to surface. It’s a bit long but nothing a Dremel can’t sort out. Other than that the dimensions of the rail seem like a reasonable candidate for the design. Cheap too.

Miniature rail (Banggood)

https://www.banggood.com/9MN-Miniature-Guide-Linea...

I then designed the pen mount to hold onto the pen with a snug fit when pressed in, with suitable screw holes in order to mount it to the linear rail and then subsequently to the mounting bracket.

I also quickly mocked up a little bracket to hold the unused extruder assembly. I didn’t want to unplug it as it caused the machine the shut down with sensor errors. Besides, one of the best ways to shorten the life of your electrical connectors is to make and break connections over and over.