ArmyrHex

Todays task was to complete the driveshafts, ensuring they are completely stiff as well as adapt the axeljoints to fit on the motors. This turned out to be more interesting than planned.

The first step was to test the bearings I made last time and ensure the were properly shimmed and were completely gap free. One of the shafts needed one additional 0.1mm shim. Now they are all three rock solid. The flex in the construction is smaller than the flex in the 10mm thick steel plate that they are attached to.

The second step was to open up the holes in the axel joints to fit on the motor axels. With a bit of careful mounting, that was a piece of cake.

But these motors need to have keyed holes. So I saw this video a while back about the “broach” technique for making non-round holes. Skip to 9:56.

So suddenly I am doing a whole handful of firsts:

• Grinding a piece of HSS metal into my very first custom tool.
• Mounting said square tool in a chuck.
• Actually successfully broaching a key slot in each of the three axel joints.

The result wasn’t particularly pretty because I didn’t grind as much on the tool as I chould have, but for a first ever I am really pleased. I feel that once you have broached a hole with a custome tool, then noone can even call you a newbie again.

Finally all the pieces for a complete driveshaft for an axel. And below we have the Z-axel completely mounted. 😀

Seems to be my new main project for the forseeable future. Building a CNC machine is not done in a day, even if all of the parts mostly exist… Also, I have done my first 3d-print but I will need to colect it tomorrow as it did not quite complete before I had to go home.

So today I started with the rebuild proper. A run-though by Eric Cederberg about which parts belonged where, and I got working.

Above you see the fastening collars that will attach the ball screws to the bearings. These carry all of the force of the movements, so getting them to exactly the right size for a snug fit in the bearing houses is critical.

To make sure the collars do not start slipping after a few years, we decided the drill through the collar and ball screw and fixate them with a spring steel pin. This was really scary as the ball screws are custom made in Asia meaning they are expensive and delivery times are long. Obviously, we had no spares.

Either way, the goal was to get the entire assembly to be about 27mm wide, and I find that the tolerance achieved is perfectly OK. 😀

So below we see the status right now. Three ball screws securely fastened in their bearing houses and the most critical part of the build is completed. Note that the Z-axis bearing house is not actually assembled as the other part of the bearing house is stillf astened to the machine.

So that was a good first day. Next steps are:

1. Drill out the motor holes from the axel joints so they fit our motor axels.
2. Fasten the axel joints onto the ball screws. This requires disassembling the bearing houses above. When doing that, the shims should be rechecked. I believe that one of the bearing houses perhaps should have 0.1mm less shims and the other 0.1mm more shims to be perfect.
3. Open up the gap in the Z-axis mount plate on the Terco a bit more as these ball screws seem to be a bit wider than the originals so the Z-axis cannot actually be mounted as it is today.
4. Start assembly of the Terco.

So the Terco was not going to do any more work until it got some love and some spare parts. The spare parts are still on their way, but the love was availible here and now.

The insides of the Terco are jam packed with cables and electronics. Three power converters, a complete computer, three drivers, and an inverter to drive the spindle. Not every single cable connecting all these parts together had been done in cleanest of ways. I even found one original cable from the 70s. The rubber was fascinatingly different from what we use today, and was cracking completely.

For one, the power converter for the display was stored inside the case, with its power cable sticking out through a gap in the case. Not particularly elegant. So I decided to cut that cord and connect it to the 240V power we allready had inside the case. And there I was reminded why you should never have multiple power sources connected to the same machine. Cutting off a live 240V cable doesn’t only blow a main fuse. It also converts your side-clipper into a wirepeeling clipper in a puff of smoke. But now the screen gets power from the main power cable that drives the entire machine.

So today, I opened it up completely and resoldered, shrinkwrapped, trimmed and gathered the worst of the cables. Now all cables have the proper length and there are no unnecessary sugar cubes or temporary extensions. Also, the motor driver fan only turns when the drivers are actually powerd, unlike before when it started as soon as the main power switch was turned on.

Looking at the image below, you may wonder if this is what “tidy” looks like, and all I can say is that this is very much better than it was before.

Finally, the Terco got a proper vaccum cleaning and a proper alcohol wiping of all internal compartments. Now it is ready to get brand new motors and hopefully become aven better than before. 😀

So today, the plan was to start mass-producing frame parts. I need a total of 4 side frames and two front/back frames. The plan was to make half of these just to see that it all fits together.

Unfortunately, this is what the CNC machine looks like now. One of the motors has given up and needs to be replaced. New motors are ordered and the machine will be rebuilt, but it will be about 2 weeks.

So I spent a few minutes in the wood-shop and made a frame to mount the motor testbed in and went to work on the regulator. So this is what that looks like now:

So all of the previous posts were written in one go. So why did I decide to document my process just now?

Well, because I just saw this clip by Bernadett Banner, a costume historian whose video blog I found recently and which very much suits my personality. Yes, historical dressmaking and programming machines to cut metal into pieces that will become a semi-autonomous robot. This is 2019, and I don’t need to limit myself.

Anyways, back to the video I saw. Here it is:

I mean, just listen to Cathy Hay’s voice. Did you ever hear a voice so steeped in passion? And it ends with the wonderful quote “Oh, and go do something impossible today”. Yes Bernadette. I will.

Or rather, even if I now realize that this robot project of mine is way harder than I had planned and is going to take a year or two (Or more if I decide to add cameras and teach it to hunt in the night), it is nothing compared to that dress. But impossible was never more than a shade of gray.