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Increasing feedrate when threading
« on: November 03, 2013, 11:05:45 AM »
Hi!

I am having a problem when I am cutting threads on my lathe.

I have been using the lathe threading wizard and it has worked perfectly.
I build myself a new cnc-case with new Gecko drivers and all the electronics etc. and now I am running into a big problem.

I am cutting an 1 mm thread and the first pass goes smoothly at 1 mm / revolution. The machine goes to the start again but the second, third...  pass is at 2.11 mm / revolution?

Could it be an index problem? I have steady readings from the sensor to Mach.

Regards
  Per
« Last Edit: November 03, 2013, 11:11:58 AM by PerEklof »

Offline RICH

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Re: Increasing feedrate when threading
« Reply #1 on: November 03, 2013, 12:43:05 PM »
There is wirte up called Threading on The Lathe - Mach3  which you can find in Members Docs that covers all aspects of threading.

What version of Mach are you using?
When you use the wizard do you click the button to calculate the number of passes to ensure that you are not exceeding available  feedrate rate?

The rpm DRO should be steady at the set rpm, maybe a flicker within 1 rpm occasionaly.
If there is a slow down of the spindle during threading mach will adjust the next pass to try to correct for it. It cannot correct for a spindle
increase in rpm.

Post the gcode that was generated by the wizard and also you xml file.

RICH
Re: Increasing feedrate when threading
« Reply #2 on: November 03, 2013, 01:43:57 PM »
Rich,

I have read your Threading on The Lathe pdf.file, very good Reading, thank you!
I am using version R3.043.066.

Yes I click on the calculate button and the feedrate is within range.

The rpm DRO is steady on 227 rpm all the time.

The thing is that everything was working perfectly for a couple of months ago, this is a bit frustrating.

I attached the files.

Per
« Last Edit: November 03, 2013, 01:47:04 PM by PerEklof »

Offline Hood

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Re: Increasing feedrate when threading
« Reply #3 on: November 03, 2013, 01:53:24 PM »
I would suggest you try a different version of Mach and see how it goes, 066 is screwed up in a lot of ways, especially for Turn.
Also are you using a VFD? If so does it have a feature to try and maintains speed? If it does see if you can turn that off as it may be fighting against Mach.
Hood
Re: Increasing feedrate when threading
« Reply #4 on: November 03, 2013, 03:15:16 PM »
Hood,

I do not have any VFD. I will try another version tomorrow.
I will post my progress in this.

Regards
  Per
Re: Increasing feedrate when threading
« Reply #5 on: November 03, 2013, 04:18:51 PM »
Hi everyone. This is the first time I've posted on the forum and it's mainly because I'm having trouble with threading. or the lack of it. The spindle is set up to be switched on and off through mach  but notto control the speed. I have an index sensor set up on the spindle and mach is seeing the pulse. Note I am using a pokey55U but this is seeing the signal as well
If I put a speed in MDI or run a programme the DRO will display the speed and the true speed but if I just switch the spindle on using the potentiometer mach doesn't read the spindle rpm as I believe it should with the index sensor.

I have run in synke mode enabled  and speed averaging enabled as suggested by Scott at ArtSoft but has had no affect Does the index sensor have to work in conjunction with spindle speed control which I don't have yet.

I'm getting really frustrated with this as I' v been on with this for a while.

If any one can help I'd be grateful.

Cheers Jason.

Offline Hood

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Re: Increasing feedrate when threading
« Reply #6 on: November 03, 2013, 04:40:17 PM »
I presume you are using the PoKeys as your controller?

With external devices it is the device that has to support threading, does the PoKeys support threading?

Hood
Re: Increasing feedrate when threading
« Reply #7 on: November 04, 2013, 07:54:12 AM »
The index sensor is wired to pin 3 on the pokeys and in the I/O column you can set the type of I/O such as index which I have done. I know is not the signal because it's been tested with an oscilloscope and Scott AT Artsoft thinks everything is set up correctly.  Could it be anything to do with the fact that I'm using the latest version of Mach on windows XP on a laptop. or should this not matter.
I can only manually change the outside of mach but I would think the index sensor would give me an rpm so screw cutting would be possible.

Jason

Offline Hood

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Re: Increasing feedrate when threading
« Reply #8 on: November 04, 2013, 08:16:58 AM »
Are you using the pokeys as the motion controller?
Hood
Re: Increasing feedrate when threading
« Reply #9 on: November 04, 2013, 01:14:44 PM »
Yes. Is this a problem