LinuxCNC Support Forum :: Topic: esab ultrarex retro fit plasma / flame cutter (2/13)

PCW OFFLINE Moderator Posts: 1645 Thank you received: 86 Karma: 116	Not an encoder recommendation but I would be sure to get a encoder with differential outputs (line driver or RS-422 type) as the encoder is in a electrically noisy location
	The administrator has disabled public write access.

Re:esab ultrarex retro fit plasma / flame cutter 12 Jan 2012 15:31 #16697

BigJohnT NOW ONLINE Administrator Posts: 4947 Thank you received: 85 Karma: 134	I've used Automation Direct in the past for encoders and they can be either open collector or line driver for the most part and Peter might know what open collector ranslates to www.automationdirect.com/static/specs/encoderselect.pdf John
	Last Edit: 12 Jan 2012 15:41 by BigJohnT. The administrator has disabled public write access.

Re:esab ultrarex retro fit plasma / flame cutter 13 Jan 2012 03:36 #16714

andypugh OFFLINE Moderator Posts: 4106 Thank you received: 139 Karma: 129	jd896 wrote: the machine currently has a capacitance sensed hight control and is driven with a servo but it has no feedback ie encoder or such Ah, but, it does have feedback, it has the torch voltage... In theory you can close the servo loop on arc voltage, no need for an encoder.
	The administrator has disabled public write access.

Re:esab ultrarex retro fit plasma / flame cutter 13 Jan 2012 04:06 #16715

BigJohnT
NOW ONLINE
Administrator
Posts: 4947
Thank you received: 85
Karma: 134

andypugh wrote:

jd896 wrote:

the machine currently has a capacitance sensed hight control and is driven with a servo but it has no feedback ie encoder or such

Ah, but, it does have feedback, it has the torch voltage...
In theory you can close the servo loop on arc voltage, no need for an encoder.

If you all ready have capacitance sensed height control would it not be better to use that knowing that the voltage will vary with speed (like slowing down for corners) providing it is accurate enough. I guess the problem still is how do you Z up to clearance height with a servo drive with no feedback. Seems odd that a servo does not have some sort of feed back to the THC unit now...

John

The administrator has disabled public write access.

Re:esab ultrarex retro fit plasma / flame cutter 13 Jan 2012 04:10 #16716

andypugh OFFLINE Moderator Posts: 4106 Thank you received: 139 Karma: 129	BigJohnT wrote: If you all ready have capacitance sensed height control would it not be better to use that knowing that the voltage will vary with speed (like slowing down for corners) Does it? Do you know why? I thought it depended only on arc length?
	The administrator has disabled public write access.

Re:esab ultrarex retro fit plasma / flame cutter 13 Jan 2012 04:20 #16717

BigJohnT
NOW ONLINE
Administrator
Posts: 4947
Thank you received: 85
Karma: 134

He demonstrated that it worked in the video by using his hand to make the torch move up and down... I know that flame cutting capacitance sensed height control is all they have. I don't know if it is better/equal/worse than voltage sensing for plasma. Just thinking out loud that it would be an easier refit if you could just tie into the current THC system and provide it with what it wants for signals if it is possible.

John

The administrator has disabled public write access.