Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: fisherjim on November 14, 2008, 03:15:58 PM
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Hi,
I'm using the latest version of Mach 3, V3.042.18 and I have a lathe threading problem.
On the first pass of the tool I get a different feed to the one programmed in the G76 canned cycle, the same when using G32.
For example if I set a pitch of 1.411mm (18tpi) the first pass of the tool shows a feed of 1.8mm,as shown by the DRO, then all the rest of the passes are correct at 1.411.
I know it's me but I can't see what I'm doing wrong.
Jim.
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you say the feed shows 1.8mm, is it actually doing 1.8mm or just showing? I have never paid atention to what the DRO is saying so just wondering.
Hood
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Hi Hood,
No it's actually doing 1.8mm on the first cut , then it does the programmed thread of 1.411, which leaves the thread crest torn up. Suppose I could try a cut above the thread dia. on the first pass then do the actual thread in subsequent passes, using G32 it would be possible. Be a pain in the A.. if I have to do it on all threads though.
Are you using V3.o42.18?, are your threads OK?.
Jim
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Nope, not upgraded since 015 as I have not used the lathe much in the last week as its been all milling and welding this week. Threads were fine in 015 but then again I use the smoothstepper so my testing of the 018 version wouldnt help you out :(
Hood
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Ok, thanks for the reply.
jim.
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Just wish I could test for you but afraid I dont have a parallel port on that computer in the lathe :( Hopefully someone else will do a test and let you know.
Hood
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I tell a lie, first pass of the thread runs at 2mm pitch, second pass runs at 0.95 pitch, it's not until the third pass does the thread pitch revert to the programmed pitch of 1.411mm.
Have checked all my settings, spindle index led works on the Diags page so Mach should pick this up, also turned off spindle speed averaging.
Anyhow, I've added two lines of code to my G32 thread, two air cuts then do the thread. This seems to work on G32 but I think G76 will be a no no.
I'm starting to look kindly at SmoothStepper, pity the exchange rate is bad.
jim.
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Have a look at the plugins and enable the one for threading and send your data to Art with a description, he has been doing fixes on threading for the PP and although most people seem to be sorted with the latest versions he is still trying to track down a few errors that people are seeing.
Hood
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Oh on the SS yes the exchange rate is not in our favour at the moment but there is a place in the UK that has them (not sure where you are) they were more expensive than actually buying direct from Greg but that may have changed now due to the $/£ exchange rate.
Hood
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Hi Hood
Well I ran the plugin and lo and behold the first two passes have no Index pulse, after that it finds the Index pulse and runs as normal.
I've emailed support so we shall see if its my setup or Mach.
Do you know where I can get the smoothstepper in the UK? If so it might be a good idea to get one.
I'm in the Isle of Wight by the way otherwise I could drop in for a chat hi.
jim.
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Jim that is good news, well bad but good ;) Hopefully Art will be able to determine where your problem lies.
I believe www.routoutcnc.com have the SmoothSteppers, they dont seem to advertise it, possibly because they do their own similar device. I know one member here emailed them and got a price but he was actually around £20 better off getting direct from Greg even when customs grabbed some money from him. Exchange rate has changed so possibly it would be cheaper to get from them now, one way to find out I suppose :)
Bit far to go for a chat :D
Hood
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Problem sorted. I needed a 3 second delay before threading to give the machine time to reduce RPM from 2000 on turning to 400 for threading.
Thanks to Hood for the advise and to Brian for the solution. Much appreciated.
Jim
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Excellent news, yo would still like the SS though LOL
Hood
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Hood,
Does backlash compensation work with the G32 when using the PP & V.018?
RICH
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Sorry Rich, Dont have a clue, I have never used backlash comp on any of my machines.
Hood
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Well i quess it's time to find out.
Will post here after i install the latest version on the turtle but solid laptop with a PP.
Never used the G32 for threading but can generate the turning code reguired.
Another case of ADD CNC in the shop! ;D
RICH
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:)
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Hi All,
MACH V 3.042.18 using PP / NEC LAPTOP with PP.
Just DRY ran a number of thread cut tests and don't seem to have any problems.
The backlash compensation works during threading, no index problems.
Feedrate changes on the rapids to what it should be, feedrate and rpm DRO change accordingly to slow down of and speed up of the spindle ( speed up only after a spindle slowdown ) ( response seems to be rather quick ), G94 & G95 change correctly.
I like the new diagnostics.
So looks good on my end. BTW my spindle rpm is set manualy. I quess the only bummer is if you don't have a program
which generates the G32 threading code.
Will try some actual cutting tomorrow and see what happens.
RICH
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You can generate the code in the wizard by altering your macro I think. If you change Test=False to Test=True I am sure it puts out the G32 code.
Hood
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Hood,
Which file needs to be modified. Is it M1076.m1s located in MACH DIRECTORY as shown or one of the files located
in Mach3\macros\Mach3Turn
Macros are uncharted territory for me. I may be lost in the ocean!
RICH
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Yes its the one in the Mach3 folder and NOT the one in the macros folder.
Hood
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Thanks Hood,
Will modify and see what happens.
Threading works in the latest version of Mach and also SS plug in. To get good threads there should be no backlash in your
lathe. ( i know, i know.....get off my duff and fix the punny lathe already!) That is not going to be the case for a lot of users and they will need to have backlash compensation anad we know that may not give the desired result . The SS still dosn't provide for it as of today. So about only chance for the user to get a thread will be using G32 and having the Gcode produced will be desired. That leaves one with with few options:
1.Write the code
2.Have a program which generates it
3.Modify Brian's Wizard ( generates G76) output by changing "test=false" to test=true in m1076.m1s as shown in previous post
using the vscript editor.
4.Use papabears Quick Threading ( don't remember the code output, but, will refresh my memory)
5.Change the macro ( see 3 above )
May be others but that's what comes to mind.
RICH
MODIFIED: ADDED TO 3. ABOVE