Inside the MarkOne fiber support

Like I was saying in my previous post, my MarkOne failed during a print and the fiber was jammed up in the feed mechanism.  I had a support call in to Markforg3d, but I decided to be daring and take apart this mechanism to see how it worked.

Thankfully, it was a very simple process.  The feeder is basically two thin metal tubes fixed on either side of a pair of opposing-spinning rubber(ish) wheels.  The fiber is simply forced through by the wheels, just like a baseball pitching machine or battery-powered Nerf gun.

Just after the exit tube is a small gap before the next tube.  This gap is where the razor blade passes to cut the fiber.  They use a standard RC servo to do the cutting, which is a great way to do it.  Closed loop, high torque, small package.  The problem is the noise.  I suspected they were using a servo for the cutter because of the characteristic chirping, and disassembly confirmed this.

So the problem my machine was having was that the fiber got jammed up inside the wheels.  All I had to do was to provide light tension on the fiber by pulling it, while I manually rotated one of the wheels.  I ended up pulling a huge strand out of there!

After the repair, I was able to print two versions of the quadcopter, one with concentric fibers, and the other with isotopic fibers.

Concentric fibers just make outline passes around the perimeter of your object, as well as around any adjacent holes.

Isotopic fibers will do passes like it would for filled layers, but it doesn't do an entire layer of fiber.  Instead, the layer is partially printed with fiber, while the rest is completely filled with nylon.  The next layer is oriented at a different angle, as are all subsequent layers.  You get to control the layup angles through Eiger, if you like.

And the results?  Well, the parts are a little stiffer.  Not a lot, but I think I need to play with infill.  Concentric @ 25% was slightly stiffer than without fiber @ 25%.  Isotopic was a little stiffer than concentric, but that could be because it is basically going to print at 100% fill.

Unfortunately, my long follow up build (to complete all of the quadcopter parts) overnight failed, but this shows off another really nice feature of their system -- I just submitted a problem ticket, and they told me they will go into my machine's logs remotely and try to determine what went wrong!  So my MarkOne is out of commission for a few days, but hopefully this will help them fix a bug or two in the process.