Heavy Metal

Ok, its just aluminum.

Yesterday evening i've been in the FabLab again. But not to turture the 3D Printers. I wanted to use the mill. Grinding material instead of melding and fusing.

As told in the last entry, we don't feel confident with the screwed plastic motor couplings for the z axis. So i went to the next ahrdware store to buy some aluminum, round 20 x 500 mm.

The source...

In the end i will get some couplings, as seen on the last picture down in this entry. The only thing missing there are the 3mm threads to fix the axis.

the plan...

While the 8 mm drilling hole on the right side should be enough to fit the threaded rod (there are smaller, even if called M8), the drilling on the left side for the motor axis is tight. Torsten and i thought about shrinking these couplings onto the motor, like it is done with a marine propeller. The couplings will be put in the oven, expanding in the heat. While still hot we will press them onto the motor. Wen cold (and shrinked) they will be really tight fit and fixed. For some additinal security we will still use a small screw to fix it there.

The aluminum was sawed into 30mm high cylinders with a handsaw.

Than they got into the mill to get the saw smoothed. With some help from others in the FabLab (was the first time i was using a mill) it was a nice work. It's a pitty that i was so happy while working that i didn't take any photo.

The heights of all cylinders where a little bit different - no wonder, if i'm working with a saw :)
I measured the smallest one and than milled all the others to this length. 29 mm were remaining. 

In the end - after some calculations and using the digital calipers on the mill i got six nice cylinders which differ by no more than 1/10th mm - that's enough for me.

Next the mill will be used as a drilling machine. After setting it to a clear reference in the middle of the cylinders, we drilled an 5 mm hole thru them. The next was the 8mm drill, which we used down to the middle of the cylinders. Voilà, a nearly ready coupling.

We need a M3 thread for the grub screws, so i used a 2.5mm drill to get the needed holes. 2.5mm is the core-diameter to cut a thread into it. We made a simple leading edge to get all the holes into the right places (one for the motor side, three on the threaded rod side to center it).

This is what we got:

the result ... 

Now some threads must be cut, but thats another story....