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Messages - SteinarN

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You could set A axis to linear. then set the number of steps for one revolution to one inch. then a command
G01 A36 X1
should give 36 threads per inch. 

I have been thinking the same. The problem is it is probably necessary to stop the spindle two times each pass as the Y changes direction.

I see now that my crappy G-code does nothing but crashing the tool in absolute mode...... Would be an even more time consuming task to write the G-code in absolute mode by hand.

One thing I forgot to consider is the max speed of the encoder pulses. For any degree of accuracy it is necessary with a high count encoder, possibly via a gear system to achieve the required resolution, say 3600 pulses per turn. 2000 rpm gives 120,000 pulses per second. I suppose this is way beyond the capabilities to Mach3 and the parallel port?

If there is an additional index slot (one slot per revolution) on the spindle it should be possible to make a macro doing the "homing" to Rotational position mode automatically. It should be possible to make a macro shifting to Continuous rotation mode also.

In this way it should be possible to do some milling with Rotational position control, call a macro in the G-code shifting to Continuous rotation mode for turning and calling a new macro in the G-codes shifting automatically back to Rotational position mode for more milling without loosing the exact rotational position.

I see my previous post probably was an answer to a question nobody have asked......

Back to the continuous run question.

I don't know how fast an indexing board type axis can spin, probably not that fast due to the gear ratio. If so, not well suited to turning small diameter pieces.

But here is what I'm thinking on. Maybe a complicated system.....

A turn spindle with a 3-phase motor and an encoder connected to a board receiving position signal from Mach3 and controlling the VFD with say a Hz signal. A Hz signal is probably the most accurate type of signal due to its precisely controlled frequency. Another encoder connected to Mach3 for visual control of the rotational position with high accuracy.

When requiring continuous rotation for turning, make a button in Mach3 sending a 5V signal via a BOB to the VFD. This VFD input is configured in the VFD to place it in "Continuous rotation mode" regulating the spindle speed from a spindle speed signal from Mach3. That should be easy to configure Mach3 to do.

Shifting back to "Rotational position control" is done by manually by hand or by manually driving the VFD to a position where the encoder in Mach3 is ending at 20, 40, 60 or 80.0000 degrees. A mark on the spindle indicates which of these rotational position is the original "zero" position. When this position is accurately achieved then zero the A position and switch off the button sending the "Continuous rotation mode" signal to the VFD. These two operations should be done by one single button with a VB script.

It is also necessary to reset the encoder board controlling the VFD when shifting from Continous rotation to Rotational position control. Or possibly better remove the power from the board when shifting to Continous rotating mode and reconect the power when entering Rotational position mode.

In this way it is possible to run in "Rotational position control", shifting to "Continuous rotation mode" and back to "Rotational position control" without missing steps or position.
Say first milling some keyways, then do some turning and then do some more milling while retaining the exact same rotational position as when milling the first keyways.

The only thing is I don't know if it exists a board with an encoder input and a Hz or PWM output.

General Mach Discussion / Re: Help with Mach3 config.
« on: April 26, 2009, 01:05:47 PM »
I think you shift between metric and imperial on the setting page.

In the lower right corner you have a button "Units Alt-U". Hit it and the metric/imperial led turn on-off. See what you have there.

I'm a totally newbie to practical machining with cnc machines and G-codes but I nevertheless give a try on a solution

I have a couple suggestion to how to accomplish "continuous" rotation of the A-axis to do some specific machining operation.

First example: Milling a radial slot 360 degrees in 4 pass with gradual plunge of the tool. One final rotation of the work piece with the tool not plunging further.
The last example have only 120 degree final cut due to the plunge taking place in the first 60 degree move

(Tool in place Z0)

The same operation making a zigzag slot:

(tool in place Z0Y0)

Edited the G-code. Some lines were duplicated.

General Mach Discussion / Re: Making a DRO read-only?
« on: April 25, 2009, 01:06:57 AM »
Sorry for this stupid question.

What is GUI?

General Mach Discussion / Re: Motor tuning calculations
« on: April 25, 2009, 01:01:57 AM »

I have also written lengthy replays several times and lost them when posting on various forums. Now I always copy what I have written just before I post it. Has saved me from rewriting a long reply many times :-)

Works in progress / Re: Refurbished standard screen
« on: April 24, 2009, 04:01:09 PM »
I placed the CV Distance and the CV Speed buttons on the main screen. These settings have a great influence on speed versus accuracy on some jobs like high feedrate wood router jobs.

Set file and slightly modified main background image attached.

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