Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: PerEklof on November 03, 2013, 11:05:45 AM
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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
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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
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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
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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
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Hood,
I do not have any VFD. I will try another version tomorrow.
I will post my progress in this.
Regards
Per
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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.
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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
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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
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Are you using the pokeys as the motion controller?
Hood
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Yes. Is this a problem
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It may be, as I said earlier threading has to be done in the device, so check with Boris or Matevž to see if the Pokeys does support threading.
Hood
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Ok I'll do that. I have a milling machine that used the standard breakout board and computer with a parallel port. I was thinking I could hook my lathe up to that and see if anything happens. If it does turn out to be the pokeys that does not support threading then would I be as well getting a separate motion controller and using the pokey for basically turning stuff on and off.
Thanks for your help so far. I' v looked on the forum quite often over the last few years and you have quite a few posts. You seem like you know your stuff.
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If using the parallel port then you will almost certainly have to input the index via the parallel port so that you get an accurate Index for threading.
Hood
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Oh also if deciding to go for another controller then make sure it supports lathe threading, not all do and in fact likely most of the lower end ones dont.
Hood
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How much are we talking for a good motion controller and are they connected via USB. Do you know where I would find one in England.
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Depends what you mean by good ;)
And also good depends on what you expect ::)
For me I want analogue commands, 24v I/O etc.
Likely if you are using steppers and 5v I/O already the best option would be an Ethernet SmoothStepper, there is also the USB version but the Ethernet one is better.
Dont think you can get in the UK but Greg would be able to advise.
One thing however is make sure that the Pokeys can not do threading, as no point in wasting money if you are satisfied otherwise with the Pokeys.
Hood
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I' v contacted polabs about the pokey so I' m just waiting for a reply.
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please let us know the outcome.
Hood
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Pokesys doesn' t support threading. The control must be from the pokeys it's self and not from mach. If that makes sense. If I wired the spindle sensor to a spare output on the breakout board on my mill is it likely that that I will see an rpm. Bearing in mind the mill is running on an older version of mach
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The issue is whatever is creating the actual motion (i.e. the actual pulses), be that the computer via it's PP or an external controller, has to be able to see the spindle pulses real time inorder to sync movement to the spindle pulse(s). Whenever you introduce things like USB or Ethernet into the mix, you introduce indeterminate delays (i.e. the delay varies depending on various factors which lead to random time delays), so you can't have for example the spindle pulses being inputed to the PP and expect an external motion controller to be able to sync to them as the delay would cause unreliable syncing.
For external motion controllers there are a few options. SS/ESS are probably the most popular at the cheaper end of the market, but you've got buy from the US or Aus (PMDX do them, and if you're needing a new BOB, PMDX are some of the best).
In the UK, Zapp Automation sells the russian controller which I've completely forgotten the name of (control logic???), and CSLabs stuff. Best to drop them an email to see what they've got in stock as website stock levels aren't always accurate.
Other UK option is Eaziform/ConquerorDesign, but none of their stuff is Mach compatible.
Everything else I can think of are all US based.
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Hi!
I tried to install a later version of Mach3 but it did not work so I decided to remove all Mach3 files on the computer (I dit remember to backup my .xml files and licensefiles :)).
I installed the newest version (the one I had from start) and now it works perfect again. I have not installed some plugins that I need yet but I will do that soon and see if the problem returns, hopefully not...
Thank you all for your help :).
Regards
Per
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I'll have a look at that. Although I have tried the sensor through the mills breakout board and the speed can be read in the DRO so we are half way there. I got the lathe rigged up to run through a board that my father in law made and everything worked. I tried doing a threading cycle but it just stops. the X position goes to the first cut depth and the Z axis is supposed to start at o.1 which it does. It moves to about 50 thou in and then stops. Is this likely to be because of what you are saying or could it be something in the G76 line or something in the mach software. Sorry if I seem a bit slow with this but I'm not up on electronics. My father in law is doing all this sort of stuff.
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Jason, what is actually creating the pulses to control the lathe?
To display the speed on a DRO, the input can be taken from pretty much anywhere, but as I said in my last post, inorder to sync motion to the spindle (i.e. when cutting threads), whatever is generating the pulses must be capable of the required syncing, and have the spindle pulses directly fed to it.
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I forget the name but it is an LED that shines on to the indexing disc that has a reflective strip., This creates the pulse and is wired straight into the break out board.
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What I meant by pulses, are the steps for the stepper drivers.
Are you still using the Pokeys to control the steppers?
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No the steppers were wired through the breakout board as well.
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That's fine.
Are you using a licensed version of Mach?
Threading is not enabled if you don't have a valid license.
I've never used the PP for threading so the only other thing I can think of is do you have the index input (Ports and Pins -> Input Signals) set to the pin you have the spindle sensor connected to?
The fact the tool moves into position then stops, sounds like mach isn't receiving the spindle signal. When you command a thread cycle, the tool moves into position ready to start, then pauses briefly while it waits for a spindle pulse.
The other problem could be your acceleration/speed isn't fast enough for the thread you're trying to cut, although I'm not sure what Mach does if that is the case. However a quick way to test for this, would be to slow the spindle down and cut some air to see if the threading is going to work.
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When Ii tried threading through the breakout board that my father in law made we I used another laptop because it had the parrallel port on but didn.t have a license. So this could be the problem as you saide.
The index pulse is configured to the correct pin. I would have thought that if it was not then I would not see a an RPM
I am cutting air anyway just to try it and slowed the speed down to 100 RPM.
I shall try the breakout out board again with a licensed copy of mach and see what happens.
If I get no joy then I guess I' m going to have to bite the bullet and do as you said before and invest in a separate motion controller.
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Just to let you know I' v got the index working and I just run a couple of threading programmes in thin air. This is through the parrellel port and seems to be fine. The real test will be when I actually cut material. I'll let you know how that goes.
Thanks for all your advice.
Regards. Jason.