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Messages - skunkworks

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11
General Mach Discussion / Re: Perfect Lathe threading
« on: August 13, 2015, 01:28:59 PM »
there are really 2 types of controlled tapping.  

rigid tapping -> the z axis is geared to the spindle rotation and follows.
synchronous tapping -> the spindle is in effect a rotary axis and the spindle and z axis do synchronized move (exactly like a z - a move.)

Mach seems to use synchronous tapping.  (having a servo spindle that can position well enough to tap)

Linuxcnc can do both - although most use rigid tapping.  A spindle that can reverse quickly really doesn't over shoot much.  (but you do have to take it into account..)

https://www.youtube.com/watch?v=cGr37Dn6YgM

how about gear hobbing...  :)

https://www.youtube.com/watch?v=ZhICrb0Tbn4

sam


12
General Mach Discussion / Re: Missing program
« on: August 05, 2015, 07:36:41 AM »
Yes - I have heard of this.  (never experienced it though - linuxcnc is rock solid).  The trajectory planner/motion/hal/ladder in linuxcnc are running in realtime.  It takes priority over everything else.

the story is one of the first adopters of linuxcnc (emc at the time) had the screen totally lock up.  emc happily ran the rest of the gcode with no issue.  He rebooted and everything was fine.

13
General Mach Discussion / Re: Missing program
« on: August 04, 2015, 04:04:32 PM »
Can you expand on the display will halt? 

Thanks Craig,

any knowledge is good to have.

Been having a little play with Linuxcnc too. Seems the opposite way around with that system. The display will halt and must wait for the code to run. I especially like that latency test where you abuse the computer to see what it's worst case jitter will be. Can't have your cake and eat it though, it's a pig to learn if you want to get into customising things.

Keith.

14
General Mach Discussion / Re: Maximum processing speed?
« on: February 12, 2015, 08:52:08 PM »
With linuxcnc you have a path tolerance..  Times are as follows..  (btw the linuxcnc has a very poorly implemented run time estimate - doesn't take into account acceleration - says 8.1 minutes. ;) )

Follow path within (using 40in/s^2-600ipm for xy and 50in/s^2-200ipm for z)
.001" = 44min21sec http://electronicsam.com/images/KandT/testing/forum/Screenshot%20from%202015-02-12%2017:27:51.png
.005" = 32min25sec http://electronicsam.com/images/KandT/testing/forum/Screenshot%20from%202015-02-12%2016:15:06.png
.010" = 25min27sec http://electronicsam.com/images/KandT/testing/forum/Screenshot%20from%202015-02-12%2016:41:28.png

Follow path within (using 200in/s^2-600ipm for xy and 200in/s^2-600ipm for z)
.001" = 21min16sec http://electronicsam.com/images/KandT/testing/forum/Screenshot%20from%202015-02-12%2018:12:31.png
.005" = 15min43sec http://electronicsam.com/images/KandT/testing/forum/Screenshot%20from%202015-02-12%2018:32:46.png
.010" = 12min33sec http://electronicsam.com/images/KandT/testing/forum/Screenshot%20from%202015-02-12%2018:58:18.png

Now one with Follow path within (using 300in/s^2-600ipm for xy and 300in/s^2-600ipm for z)
.001" = 17min45sec http://electronicsam.com/images/KandT/testing/forum/Screenshot%20from%202015-02-12%2019:49:09.png

This is using the new 2.7 pre-release version of linuxcnc (2.6.4 is current release).  It has a lot better trajectory planner in it.  (hope to release soon)  But it seems not too far off from what mach was doing.  (although increasing acc does increase cut speed)

sam

15
General Mach Discussion / Re: Maximum processing speed?
« on: February 12, 2015, 07:35:39 AM »
how big?  you can attach files here it looks like if they are less than 6mb..  (additional options drop down in the reply page)

sam

16
General Mach Discussion / Re: Maximum processing speed?
« on: February 11, 2015, 09:16:09 PM »
no chance to see the gcode? 

thanks
sam

17
General Mach Discussion / Re: Maximum processing speed?
« on: February 11, 2015, 10:47:35 AM »
Could you post the gcode?

18
SmoothStepper USB / Re: Dead ... or alive.
« on: March 16, 2014, 09:48:38 AM »
Oh that is ok :) .. - steve has been more than vocal about problems he has with linuxcnc.  the ones I know about are..

1. tapered threads (you have to calculate the pitch along the hypotenuse) -  Not a show stopper as you can cut tapered threads either with a little right angle trig or gcode subroutine.  

2. Jog while paused - work has been done on this maybe in the next release (not been keeping up on it)

3. 1 segment look ahead limitation in the trajectory planner - This is what I have been helping test and am really excited about.  A developer had taken up the challenge and has made a N lookahead trajectory planner that is in the testing stages right now.  we have used steves gcode to test that the new tp.  

It is what it is.  

sam


Well - it isn't really that it does it wrong as it doesn't do it like any other control and no one has made a canned cycle to fix it yet..  (that I know of anyway)

G33 spindle synchronized motion in linuxcnc was made to be very flexible..  You are not limited to z axis moves.  ie - you could cut a scroll if you wanted to.  or a fusee.  That though required that the pitch be calculated along the move.  So if you move x and y the same amount (45deg angle) the pitch is along the hypotenuse.  If you are cutting a taper - you have to specify the pitch along the xz move - not the z move.  (clear as mud?)  People have made some gcode subroutines to do the calculations..  Here is a good thread (no pun intended).

http://www.linuxcnc.org/index.php/english/forum/40-subroutines-and-ngcgui/13006-ntp?limitstart=0

Here is G33 from the manual
http://www.linuxcnc.org/docs/devel/html/gcode/gcode.html#sec:G33-Spindle-Sync

sam


Ha ha Sam, yes I cut fusee and scrolls every day of my life, really handy, who the hell needs pipe threads anyway ;D

Better not ask you about all the other issues Steve Blackmore has mentioned that really pi$$ him off about LinuxCNC as you will have to get your spin doctoring skills turbocharged.

Just having a bit of fun Sam :)

Hood

19
SmoothStepper USB / Re: Dead ... or alive.
« on: March 15, 2014, 10:21:31 PM »
Well - it isn't really that it does it wrong as it doesn't do it like any other control and no one has made a canned cycle to fix it yet..  (that I know of anyway)

G33 spindle synchronized motion in linuxcnc was made to be very flexible..  You are not limited to z axis moves.  ie - you could cut a scroll if you wanted to.  or a fusee.  That though required that the pitch be calculated along the move.  So if you move x and y the same amount (45deg angle) the pitch is along the hypotenuse.  If you are cutting a taper - you have to specify the pitch along the xz move - not the z move.  (clear as mud?)  People have made some gcode subroutines to do the calculations..  Here is a good thread (no pun intended).

http://www.linuxcnc.org/index.php/english/forum/40-subroutines-and-ngcgui/13006-ntp?limitstart=0

Here is G33 from the manual
http://www.linuxcnc.org/docs/devel/html/gcode/gcode.html#sec:G33-Spindle-Sync

sam

Sam,
 does LinuxCNC still do tapered threads wrong or has that been sorted?

Hood
[/quote]

20
SmoothStepper USB / Re: Dead ... or alive.
« on: March 12, 2014, 07:48:49 AM »
Linuxcnc has always done this...

https://www.youtube.com/watch?v=Z_LxyosF2yc

http://www.linuxcnc.org/docs/2.5/html/gcode/gcode.html#sec:G76-Threading-Canned

You can specify an entry or exit taper - this move is synchronized with the spindle.

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