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Author Topic: Finial switching over to Mach4 amd Ihave a few question.  (Read 585 times)

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Re: Finial switching over to Mach4 amd Ihave a few question.
« Reply #10 on: March 26, 2019, 02:25:09 PM »
Hi,

You have these tunings:
X axis 160 steps per and 3200 mm/min
Y axis 160 steps per and 3200 mm/min
Z axis 320 steps per and 1600 mm/min
A axis 160 per degree and 3200 degree/min

Note the A axis seems pretty slow, 3200 degrees per minute, or 8.888 revs/min or only 53.33 degrees/sec

Thus if you had a move in X and Y of 200 mm each combined with a rotation of 10 turns:

G0 X200 Y200 A3600

If we ignore the acceleration phase the move would take 3600/3200= 1.125 min to run. The linear axes appear to run slow
but it is because they have to slow down to stay in sync with the A axis.

It gets worse if you do a G1 move:

G1 X200 Y200 A3600 F300

Now, again ignoring the acceleration phase, would take 3600/300=12 minutes to run! This is because the machine
moves at the rate determined by the slowest axis, in this case A axis. The linear axes appear to move only 16.66mm/min.

This effect is exacerbated when you use inch units but it all stems from the fact that the rotary axis is slow and therefore
the linear axes must go very slow to stay in coordination with it.

Craig
My wife left with my best friend...
     and I miss him!
Re: Finial switching over to Mach4 amd Ihave a few question.
« Reply #11 on: March 26, 2019, 06:55:36 PM »
Not sure I understand!  My X axis is motor 0, my Y axis is motor 1 & motor 3 (slave) and my A axis is the rotary axis - motor 4. When using the rotary CNC setup the Vcarve file sends the "Y" axis code to the "A" axis, as the "Y" axis stays at 0.000. My setting for the "A" axis is 26.7 counts per degree @ velocity of 4994 which rotates 1 rev for 360ยบ. ( A axis is a belt driven 1:6 ratio)
« Last Edit: March 26, 2019, 07:00:53 PM by harlindg »
Re: Finial switching over to Mach4 amd Ihave a few question.
« Reply #12 on: March 26, 2019, 07:48:21 PM »
Hi,
OK I misinterpreted the motor tuning pages. Please disregard my previous post.

Motor0 X axis =160 at 3200 mm/min
Motor1 and Motor3 Y axis (and  slave)=160 at 3200 mm/min
Motor4 Z =26.7 at 4994 degrees/min

I assume you must use 8 microstep/full step to arrive at the figure 26.7 steps/degree?

Lets work on the same move I posted earlier:
G0 X200 Y200 A3600
If X (or Y) were the speed limiting axis then the move (excluding acceleration phases) would be 200/3200=0.0625
minutes or 3.75 sec. If the A axis is the speed limiting axis then the move would be 3600/4994=0.7208 minutes or 43.25 seconds.
Clearly the rotary axis is  the speed limiting axis, the linear axes slow down from their theoretical max to match the A axis.

Lets try the same machining move as before:
G1 X200 Y200 A3600 F300
Now the limiting axis is still the A axis rotating at 300 degrees per minute so the 10 revolutions of the A axis will take
12 minutes. The F word (300) applies a  maximum to ALL axes involved in the coordinated move, it this case the A axis
is moving therefore it is limited to 300 units/min or 300 degrees /min and the ten revolutions would require 12min to execute.

If the move were:
G1 X200 Y200 F300
Then the linear axes would be limited to 300mm/min and the move would execute in 200/300 =0.6666 min or 40secs

Lets now convert to inches per minute to see if anything changes.

Motor0 X axis =160x25.5=4064 steps per inch at 3200/25.4=126 inch/min
Motor1 and Motor3 Y axis= 4064 steps per at inch 126 inch/min
Motor4 A axis =26.7 steps per degree at 4994 degrees/min

G0 X8 Y8 A3600
Time to complete = 3600/4994=0.72 min or 43.25 sec, ie the same time. The linear axes have slowed from their theoretical best
of 126 inch/min to 8 inches in 43.25 seconds to maintain synchronization with the rotary axis.

Thus given that the rotary axis is slow it will determine the rate the linear axes travel.....not the linear axis maximums at all.

Craig
My wife left with my best friend...
     and I miss him!