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Thread cutting

Posted: Tue 16 Jul , 2019 10:39 am
by Chay
I've been getting things up and running with the NovaTurn even though all I have is a very old version of the Denford programming software. Problem I have is when I write a program for screw thread cutting it seems to run only a section of the process at a time, if I hit stop and play then it continues but it's messed the thread up by then. It sometimes does the stop start with other programs but not as consistently as with thread cutting.
Does anyone have any ideas on how to get this going? I have some 16mm and 25mm aluminium so if anyone has a thread cutting g code for me to compare and try that would be great!

Re: Thread cutting

Posted: Tue 10 Sep , 2019 20:20 pm
by MadeForThat
what do you mean by "section" and "stop?" Something you may want to keep in mind is the delay for the spindle to settle into the correct speed for machining. It shouldn't be that much time, but if you are stopping it-maybe. The spindle controller will give it full power to get to speed, then depending on the tune of the controller, will overshoot, let off, drop below, turn on, overshoot etc... until it is very close to the required speed. The cycling it does before it settles in can take up to a quarter second for my machine, (i can hear it oscillate) so if i was threading and stopping each pass, it would definitely need to be accounted for. Just my thought, could be completely wrong ;)

Re: Thread cutting

Posted: Tue 10 Sep , 2019 21:08 pm
by TDIPower
Post up your G code file. Are you doing the design on LatheCAM designer? Which version of machine control are you using?

I've done threading using Lathcam as the design package but my control is DOS based. (now have both Quick turn and VR turning but need to convert my control card over, car restoration has got in the way of that project)

From memory, one the bar is to dia. my ATC would select the threading tool, spindle would slow to the required speed, the tool would approach the end of the bar, traverse in quite rapidly (move from right to left towards the chuck), withdraw, traverse out (travel from left to right to the tail stock). Move to the start of the bar, pause until it was in sync with the thread and repeat the cycle until the thread was cut to the correct depth.