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Messages - RICH

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2181
General Mach Discussion / Re: Special code for threading?
« on: January 22, 2013, 06:54:27 AM »
For lathe threading see the lathe manual for G32 defnition. Also have a look at G94 & G95.
RICH

2182
General Mach Discussion / Re: lathe threading pitch error
« on: January 21, 2013, 07:15:04 PM »
fast89,
- Do scribe test's for reasons I mentioned. The scribe tests that i did were used to measure pitch to 0.0002" and
  you don't get that from comparison to a tap. The tolerances are noted in threading on the lathe manual, page 26.
  So for a 1/4-20 the error allowed for a 2A over .3" is 0.001". Said a different way.....one thread is 0.50", .3"/.050"=6 threads,
  thus 0.001" allowed. If 0.0008" per thread you are over by .0008 x 6= .0048" - .001"=.0038 lets just say 4X.
- Although I have a C3 board for the index never put it into use. I think Russ has used it so he may comment on it.
- How linear and accurate is your Z axis?

RICH

2183
General Mach Discussion / Re: lathe threading pitch error
« on: January 20, 2013, 07:36:29 PM »
I would suggest that you set the rpm manualy. There is a difference of rpm which Mach is seeing and what your vfd is actualy providing. They are slightly out, not much, and may be fighting each other for Mach's adjustment of the feedrate. Don't change the pitch, but rather change the feedrate.The feedrate is set based on the rpm. If you use the wizard  you can put pitch out to a lot of decimal places, the wizard will show the feedrate rounded to some number, but what you input will be used. Mach can read the rpm more accuratey than you can measure it.  

Do scribing tests as that is easier and more accurate than cutting a full thread thus eliminating mechanical / cutting aspects
of threading. Thus there is no spindle slow down, but at 5HP you shouldn't have any anyway.

Do not use any diagnostics, disable them, as Hood noted.

BTW, make sure you use 3 to 5x the pitch to allow for acceleration of the Z axis, even 10x.
RICH




2184
General Mach Discussion / Re: lathe threading pitch error
« on: January 20, 2013, 07:41:53 AM »
What version of Mach are you using?
Are you using a VFD?
What are you using to generate the threading code? ie; threading wizard, G76,?

Suggest you do a scribe test. Is the pitch correct for the scribe test?
RICH

2185
General Mach Discussion / Re: acceleration and velocity
« on: January 19, 2013, 04:34:21 AM »
Let me make a general comment. You should be  interested in realiable motor power. That accurs where torque x speed is max and falls in a rather small range  on the motor curve. You need to decide what is more important ie; velocity, accel or power. They are all interelated.
RICH

2186
General Mach Discussion / Re: acceleration and velocity
« on: January 19, 2013, 04:28:10 AM »
Assuming your using steppers. Set the velocity for say 10 ipm and accel for 2, jog the machine back and forth
over a distance, if no skipping, then keep doubling  the settings until it skips. At that point reduce from the max 1/2 the doubled setting when it skipped ie; 150 -300, then use 225. That should be rather close to max velocity. Test / play around  that setting to confirm.Now start increasing the acceleration until it skips and when it skips reduce that to 1/2 the doubled setting when it skipped. Now you have a rough max velocity and acceleration. Now reduce velocity and acceleration by 30-40% to leave some headroom for machining. You can refine that setting over over time.

You need to try some cutting of different materials using different feedrates and depth of cuts. Then you'll have some experience on actual machining of a piece.

Dosen't take long to do........,
RICH

2187
General Mach Discussion / Re: acceleration and velocity
« on: January 18, 2013, 05:56:30 PM »
Test to find out. You can calculate it but just as easy to test as you will still need to verify even if you calculate.
RICH

2188
General Mach Discussion / Re: Shopmaster Axes velocity settings
« on: January 18, 2013, 05:52:47 PM »
For threading you want to leave 3 to 5x the pitch so the Z has time to accelerated.
If you use the threading wizard it will check that your velocity settings are appropriate for the defined spindle rpm.
Note that you need enough HP / torque to make the thread cuts and one may want to vary the spindle rpm
accordingly. All in the write up!

RICH

2189
General Mach Discussion / Re: Shopmaster Axes velocity settings
« on: January 18, 2013, 06:05:52 AM »
Quote
I was curious what settings others used?
Have a look at Threading On the Lathe write up which can be found in Members Doc's.
Contains a lot of info on threading. Doesn't matter what others use since it varies depending on your system and what
your cutting.

RICH

2190
General Mach Discussion / Re: Cambam to Mach3
« on: January 17, 2013, 04:49:15 PM »
You can do a simulation of how the deisgn is cut from stock using Cutviewer while in Cambam. Cutviewer is separate software
and must be purchased and requires a license.
RICH

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