Another Vertical Lathe Video

[Scott_M]

Opps I posted this in the wrong forum, so if you saw it over in the sprut forum here it is again.

Here is another Vertical lathe video. I am making some quick connect air fittings complete with tapered pipe thread. ( Pretty cool ! ) I used ganged lathe bits and set each one up as a different work offset. ( G54, G55, G56 ) each tool had its own zero so instead of a tool change it just changed offsets. I used Sprut Cam to generate the code but had to tweak it a bit for the work offsets as opposed to tool changes.

http://www.youtube.com/watch?v=iXfj-hI340w]Tormach Vertical Lathe turning and threading - YouTube



Also in HD at YouTube


Scott

[bevinp]

Very nice Scott.
I know you said you installed a 5th axis, but how does the controller know where the start of the thread is? Or put another way, how does the controller know what is the rotational position of the spindle?
Sorry if you have already explained this but if so, I missed it.
Bevin

[philbur]

+1. How did you coordinate the feed rate and the spindle speed in order to cut the thread.

Phil

[Scott_M]

Hi guys
I did cover that in the other posts. When I added the 5th axis I added an additional breakout board, that gave me some additional inputs for Mach so I hardwired in a spindle sensor. The spindle sensor is the key to threading and CSS without spindle feedback it would not be possible. If you listen to the spindle in the video you will notice that the rpm goes up as the diameter gets smaller in order to keep the surface speed the same. This gives a nice even chipload and a great finish. The spindle sensor reports true rpm and position once every revolution. So Mach calculates the feedrate on rpm and thread pitch. It then starts the feed at the same position every pass. I am just guessing that it is when the sensor triggers. Multiple start threads are also possible. My guess here is that it starts one at the trigger and the other halfway to the next trigger. ( For a 2 start thread )
Another benefit of the sensor is having a tach DRO on my screen. There is a setting in Mach for "Closed Loop" spindle control and "Feedback averaging" with these set if you program S1500 the spindle will in fact run at 1500rpm.

Scott

[TXFred]

5th axis? Do tell! I've been thinking a bit about that lately, and would love to know how it worked out for you.

[Scott_M]

Hi Fred

I posted awhile back about the 5th axis you can read about it in this thread. As stated in that thread it was for my 2nd 4th axis. I just havn't had time to build my trunion table yet.

Scott

[dbrija]

Hi guys
I did cover that in the other posts. When I added the 5th axis I added an additional breakout board, that gave me some additional inputs for Mach so I hardwired in a spindle sensor. The spindle sensor is the key to threading and CSS without spindle feedback it would not be possible. If you listen to the spindle in the video you will notice that the rpm goes up as the diameter gets smaller in order to keep the surface speed the same. This gives a nice even chipload and a great finish. The spindle sensor reports true rpm and position once every revolution. So Mach calculates the feedrate on rpm and thread pitch. It then starts the feed at the same position every pass. I am just guessing that it is when the sensor triggers. Multiple start threads are also possible. My guess here is that it starts one at the trigger and the other halfway to the next trigger. ( For a 2 start thread )
Another benefit of the sensor is having a tach DRO on my screen. There is a setting in Mach for "Closed Loop" spindle control and "Feedback averaging" with these set if you program S1500 the spindle will in fact run at 1500rpm.

Scott

I currently have a spindle tach (vistacnc.com) that gives me a spindle DRO. Seems like I should be able to use that to get a closed loop. I think I would have to write a brain for that though. Any thoughts on that? It is a USB device and a Mach plugin. The vista folks thought about the closed loop operation, but didn't implement anything (nor have any plans to do so).

[Scott_M]

I currently have a spindle tach (vistacnc.com) that gives me a spindle DRO. Seems like I should be able to use that to get a closed loop. Any thoughts on that?

I have heard about that product, but have no experience with it. If you have an unlocked version of Mach try turning closed loop and averging on. Run some speed test and you will know if it works.

Scott

[dbrija]

I have heard about that product, but have no experience with it. If you have an unlocked version of Mach try turning closed loop and averging on. Run some speed test and you will know if it works.

Scott

Not sure if anyone else has a vistacnc tach, but I wrote a simple brain to compare the spindle commanded DRO and the TRUE spinde DRO, and if its higher or lower, to Inc or Dec the spindle. It currently hunts around too much for my liking so I have to work that out, but it looks like it will work to within an acceptable RPM of the command with some fine tuning. Closed loop won't work as I don't have an Index pulse (unless I can somehow get it from the tach plugin).