Here we go again . . . MK4

[1nbcnc]

Thanks 1nbcnc. Glad the old spreadsheet is still helping people out to get a feel for it all.

The original connector plug that came with the spindle was either GX16 or GX20. Certainly that style anyway. It was many years ago so can't remember if it was 3 or 4 pin. I think it was 4 and only 3 pins were used in the socket on the spindle side (going to the 3 windings in the motor). I added an earth cable from the spare 4th pin on the spindle side to one of the screws behind the end cap and used 4 core CY shielded cable to wire it up to the VFD. Note there is not really any strain relief with the GX16/20 connector.

This all went well for many years until one day there was a large blue flash from the connector and it damaged the VFD beyond repair. After years of use the repeated movement of the cable pulling at the connector plug it had loosened the pin connections and it arced. This is fatal for VFDs as they must not see a spindle disconnect when running.
Adding a strain relief above the connector had been on my to-do list, but you know how it is, just one more job to cut and then maybe I will get around to it. Well, it served me right.


So after that I wired the cable DIRECT to the windings, including an earth, and added a cable relief grommet which passes through the hole in the cap and has a nut on the back. 22mm hole in the end cap rings a bell but I really can't be sure as it was many years ago. This is what you saw in the video, the old strain relief grommet. What you then saw me do in the video was replace this with a longer cable, but it is still DIRECT wired to the spindle with the strain relief to manage the stress. This means it cannot be quickly disconnected.

It is similar to this one, but I think it might be a bit larger. Next time I am out in the workshop (sorry, not this weekend and at least the following weekend) I will see if I can measure anything although the spindle is buried in the Z axis.
https://www.ebay.co.uk/itm/Spiral-Ca...UFt:rk:18:pf:0

Many on this site would recommend fitting a removable connector AND strain relief after it, and I would not argue against it. However, I've had no cause to remove the spindle, and I know with the direct wiring and long strain relief grommet it should run OK for a long time. Hope this helps.

Thank you! That's helpful, I will certainly give your suggestion a try.

On a different note, have you had any challenges with the ball screw lock nut in the past? I noticed on my router that the lock nuts will back out when the gantry is moving in one direction, I know that the lock nut is supposed to preload the inner race of the AC bearings, and the set screw on them are so tiny and I can't really torque them hard or they will strip, to be honest the set screws don't seem to work that well. I've seen people order ball screws with a longer thread for two lock nuts back to back, but it's not an option for me any more. Any suggestions or solutions would be appreciated.

Thank you!

[routercnc]

I have had them come loose occasionally over the years. I've always managed to tighten the nut and carefully tighten the grub screw but yes there is the fear of stripping the thread or more likely rounding out the allen key hole.

Other options to think about:
As you say, longer screws and double lock or jam nuts
Maybe blue loctite on the nut but don't get it near the bearing, or maybe PTFE tape??
Dropping a short length / disc of brass rod in the grub screw hole first, then the grub screw will mold it onto the thread
Making a brand new nut from steel (and then heat treating it) with a larger grub screw?

Anything from anyone else?

The other thing to think about is how to hold the ball screw when tightening the nut (once it is all installed with coupler on etc.). I fold up plenty of shop towels into a narrow strip about 30 mm wide then wrap it around the ball screw. Then apply as much pressure as you dare using a mole grips . . . . . pause while I find the US name for such as tool . . . . vice grips, to hold the ballscrew and tighten the nut using a spanner/wrench.

[1nbcnc]

I have had them come loose occasionally over the years. I've always managed to tighten the nut and carefully tighten the grub screw but yes there is the fear of stripping the thread or more likely rounding out the allen key hole.

Other options to think about:
As you say, longer screws and double lock or jam nuts
Maybe blue loctite on the nut but don't get it near the bearing, or maybe PTFE tape??
Dropping a short length / disc of brass rod in the grub screw hole first, then the grub screw will mold it onto the thread
Making a brand new nut from steel (and then heat treating it) with a larger grub screw?

Anything from anyone else?

The other thing to think about is how to hold the ball screw when tightening the nut (once it is all installed with coupler on etc.). I fold up plenty of shop towels into a narrow strip about 30 mm wide then wrap it around the ball screw. Then apply as much pressure as you dare using a mole grips . . . . . pause while I find the US name for such as tool . . . . vice grips, to hold the ballscrew and tighten the nut using a spanner/wrench.

Thank you for all the suggestions, I will give them a try for sure.

[jkkmobile]

I use oneway bearing wrench to hold the ballscrew when tightening the nuts.

Also, my SYK bearing holders have nuts with setsrews, but the thread hole does not go all the way tru so you don't destroy the ballscrew threads.

This is my wrench:

https://www.amainhobbies.com/align-f...t00005/p213519

[1nbcnc]

I use oneway bearing wrench to hold the ballscrew when tightening the nuts.

Also, my SYK bearing holders have nuts with setsrews, but the thread hole does not go all the way tru so you don't destroy the ballscrew threads.

This is my wrench:

https://www.amainhobbies.com/align-f...t00005/p213519

Thank you for your suggestion, I will give that a try as well.

[silopolis]

Anything from anyone else?

Think that's This Old Tony that uses a hardened steel ball under the screw to create a "single point" of contact and increase the pressure on the shaft.
Could even have a video just about that IIRC



Envoyé de mon ONEPLUS A5010 en utilisant Tapatalk

[routercnc]

Yes, for a plain shaft that is OK but remember this is pressing down onto the thread. A steel ball would damage the thread making it difficult to remove the nut so the brass disc is a better option as it is soft and will mold into place.

[jkkmobile]

SYK nuts have brass inserts:

https://www.syk.tw/en/product/201705040003

You can buy them from resellers like cnc4you:

https://www.cnc4you.co.uk/BK12-12mm-Nut?search=Nut

[Vulcano]

Episode 22 is now ready . . .

Episode 22 is now ready ok hmmm when you planing episode 23 with some mesurment\s ??

[routercnc]

Episode 22 is now ready ok hmmm when you planing episode 23 with some mesurment\s ??

It could be a couple of weeks away based on the little free time I have at the weekends and the long list of things to finish off.
I have been doing a bit here and there and filming short sections. See if you can spot the joins !