Ok, watching extruded plastic harden is rather like watching paint dry. Yet, somehow it is downright hypnotic.... I also needed to find a way for 20+ students to see what was printing when I gave a demo at a local middle school.

I'm certainly not the first to get the idea of pointing a camera at the head of a 3D printer -- and I will not be the last. Unfortunately, our generally rather impressive MakerGear M2 does not have an obvious place to position a camera. I tried moving an old USB webcam and a Fire-i400 firewire camera around the printer and, honestly, some viewpoints worked pretty well. Unfortunately, the viewpoints that worked well had the camera awkwardly far away from the printer rather than mounted on the printer. The little insight in this Instructable is that with a particular smaller-than-average USB webcam, you can easily print a part to inobtrusively mount the camera so that a close-up view of the head is provided.

Total cost is about $6 with a build time under 40 minutes... assuming you already have the M2. ;-)

Step 1: Things You'll Need

Mostly you'll need the M2, which is around $1,750 assembled from http://www.makergear.com. Of course, if you don't have an M2 (or similar 3D printer), you also don't need a camera mount for it, do you?

The other parts:

One of the USB webcams like the one shown. They come in a variety of colors and are sold mostly from China via eBay for about $6 to $8. The advertising generally claims that they are something like "8.0 Mega USB Web Cam" -- but basically they deliver either a 320x240 or 640x480 video stream that can be scaled in software to be bigger and correspondingly blurrier. The image quality is lousy on the 320x240 version, but the higher resolution one is actually pretty good, and in either case the form factor and lens view angle are excellent for this use.
A little piece of 2-sided (carpet) tape or a hot glue gun.

Step 2: The 3D Design

As you can see, the webcam mount is a very simple part. I spent only about an hour designing it and creating the part model using freecad.

This is actually the second version -- my first version placed the camera a bit lower and used way more material than was needed to ensure that the camera is held firmly. I had considered making a version with a simple clip on it to hold the USB cable from the camera, but that didn't seem to be necessary as the fact that I routed the USB cable under the printer naturally kept it close to the printer body anyway

I have posted this "thing" over on Thingiverse as an STL file suitable for printing:
http://www.thingiverse.com/thing:62443

Step 3: Print It

This part is only 60mm x 40mm x 20mm, so it prints quickly.

The shape of the part makes it quite rigid, and the webcam isn't a heavy load, so you can use a very light fill on this -- anywhere from 10-20% is plenty. Depending on how you slice the part, it should take 30-40 minutes to print.

Step 4: Some Disassembly Required

If your webcam came in pieces, don't assemble the stand!

If it came fully assembled, you have some very minor disassembly to perform -- because we don't want to use the stand it came with. The clear plastic clip/stand comes apart by simply pulling the steel springs off. You might need a pair of pliers to get a better grip on the springs. Once that's done, the rounded caps on the ends of the camera come off easily. Those caps simply make it easier to smoothly rotate the camera in the stand, and we don't want the camera rotating (slipping) in our mount.

Step 5: All Together Now

Mounting the webcam is now very simple:

The end of the webcam (the end away from the LEDs) should fit firmly into the angle hole in the bracket. If it's too tight to go in, lightly scrape the inside of the hole with the edge of a screwdriver or a file.
The bracket sits on the front left corner of the M2's frame, next to the spinning cap on the Z axis. The little ledge in the bracket fits over the left corner of the frame. Simply place a little piece of two-sided tape over that corner, or squeeze a little hot glue there, and stick the mount on.
Rotate the webcam so that the field of view covers up to the right side edge of the print head's travel. If the hole in the bracket is loose, lock the camera in position with a dab of hot glue or a tiny bit of two-sided tape. The hole in our part was tight enough to hold the camera firmly without any such help.
Plug the camera into a computer and watch the live view. With the print head of the M2 centered, turn the focus ring around the lens to focus on the print head.

Step 6: Done!

With a separately-mounted camera pointing at the printer, we saw a lot of camera shake artifacts due to the printer's motion shaking the table. Although the camera is literally mounted on a frame with moving parts (right next to the Z axis), the MakerGear M2 frame is exceptionally rigid, so we find that the camera vibrates with the frame as a unit, and camera shake simply isn't an issue.

That said, image quality is pretty poor:

Resolution is a mere 320x240 (or 640x480) pixels.
The LED lights on the camera (turned on by a switch on the back of the camera) by themselves do not provide enough light to capture good video.
You do get motion blur from the head/platform moving during the relatively long exposure times the camera uses in ordinary room lighting.

On the other hand, it's pretty effective:

The camera is very inobtrusive in this mount; if it wasn't red, you'd barely notice it.
The camera has no problem at all with close focus and gives a good view angle.
The low-res video is small enough to stream wherever you want it and time lag (video delay in real time) is smaller than for many webcams.
The camera doesn't seem to have a problem with being on for extended periods (some do).
Did I mention the camera cost $6 to $8?

Overall, I can pretty strongly recommend this... which is why I threw this Instructable together.... ;-)