Blidgeport Z axis finally assembled!

Bridgeport Z Axis - Final Assembly!
Hell's bells. I can't think of anything more I can fanny about with instead of finally putting all these parts together that I've been working on (and off) for the last god nose how long.

The bearing retainer plate fits nicely, the bearing fits its bore, the ballscrew machining is completed, the "MkII" housing / motor mount / belt housing / ballnut mount is finished and I have all the little bits and bobs required to slap it all together. What are you waiting for, fatty? 

Here's what I've got, finally. Look at how the motor fixings are bang in the middle of the adjustment slots. It could almost have been deliberate - not bad for something entirely designed in CAD.

This Chinesium 10t pulley needed a bit of its length removing. I could have drilled and tapped alternative holes for the grubs but instead I turned it as far back as I could before the grubs complained. You couldn't go much further than this. Job's a good 'un. 

The whole motor / housing / ballscrew assembly simply slides up through the hole formerly used by the feed trip rod and is held in place by two M6 screws (the only modifications required to the machine). That's the simplicity of this concept - and also why it's relatively rugged compared to the "normal" approach, where the ballnut is cantilevered out the front. 

But before getting too carried away, the ballnut yoke needs to be bolted to the quill. Obviously this will be a little more challenging once the ballnut is in place, as the access hole will be blocked.

You also need some way to swap the ballnut keeper for the actual ballscrew. For this, I've drilled and tapped the end of the ballscrew with an M8 male thread. Then I can screw on a short length of 14mm brass rod and simply slide the ballnut across.

Until then, I've been keeping my balls where they need to be using a sort of butt plug, also made from 14mm rod with M8 screws and washers:

Here we go...

I used the wrong transfer piece here (should have had a male thread on it) but it went OK anyway.

The white plastic wiper tried to make a break for it. so I had to release it and refit it later. It screws down the ballscrew, then is prevented from coming out by means of a couple of tiny, pointed grubscrews.

Finally, all is well.

Next, get the ballnut fastened to the yoke. Once this has been connected up, you need to turn the ballscrew so that the ballnut is positioned right at the bottom, next to the mounting face. Then you can tighten up the two M6 screws, knowing that the bearing is correctly aligned. I've designed the bores for the fixings to have enough movement to accommodate a sensible amount of adjustment (about +/-0.5mm). 

I may well refit the DRO scale once it's all up and running. This is what it will look like.

But for now, I'll focus on getting the limit switches set up. Drill and tap a couple of M4 holes, so I can fit a metallic target for the proximity switches to see:

Does it work, fatty?
It's been so long since I messed with the Newker controller that I've forgotten how to home the machine. For reference, the homing is done by pressing the "Return" button (bottom right panel) and telling it which axis / axes to home. It then moves up, looking for the home switch signal before backing off and setting the G53 coordinate to zero. If it doesn't find that, it will see the hard (limit) switch and stop - unless you have the speeds and accels set to stooopid values of course.

Here it is finally:

Well??
Must say, it's a lot smoother now that the ballscrew is better aligned. You might naively think that a bit of misalignment wouldn't matter so much if you have a ball thrust bearing and ballscrew setup - but you'd be wrong. I'd also forgotten how quiet the whole machine is. Not complaining, mind.

Next Steps:
Now to figure out how to set the axis scaling and speeds / accels for the Z axis. It was set up before but The Stupid Fat Bloke decided it was a good idea to change the pulley ratio to reduce the size of the assembly and increase the reduction ratio (now 1.8:1, was about 1.2:1). If you change the ratio, the axis scaling will change and your soft limits will be in the wrong place. The accels and speeds will also be all to cock, so it's best to sit down and calculate the new values. You also need to ensure the stepper driver itself has the correct steps per rev selected. In my case, I should expect that the Stupid Fat Bloke has been fiddling with the DIP switch settings on the side of the Leadshine Easyservo stepper motor.