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Author Topic: Z axis laser focusing control  (Read 4305 times)

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Offline da21

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Z axis laser focusing control
« on: April 17, 2008, 03:11:14 AM »
Hi , has anyone added or could give further info on interfacing a Linear displacement transducer ( LVDT ) , we have a laser we are retrofitting to Mach3
which has a Foot fitted with an LVDT , to track the Z axis height over a distance of 2.5mm , used for keeping the lens focused etc , how can we incorporate this function , or will it need a plugin etc ,

Any help appriciated

Dave
Re: Z axis laser focusing control
« Reply #1 on: September 09, 2020, 01:30:37 AM »
Hi Dave, Did you manage the LVDT working on your laser? We have the same setup that we want to use LVDT
Re: Z axis laser focusing control
« Reply #2 on: September 09, 2020, 04:41:50 AM »
Hi,
Mach3 is not a feedback controller, the communication delays and particularly the motion buffer delay, preclude any useful closed loop performance.

If you wish to use the LVDT as a feedback device and use it in manner not dissimilar to Torch Height Control, familiar to plasma table
enthusiasts, then you will need an external motion controller that can close the loop. Mach3 can supervise the but cannot close the loop
itself.

The two best known feedback capable controllers are the Hicon Integra or the CSMIO/A at $1200 (with the required activations) and 600 Euro
respectively.

If your feedback requirement is very low bandwidth, say of the order of seconds, then using a Mach3 Brain would work.

Mach4 has a similar feature called PMC but is nearly two orders of magnitude faster and so might be used to make a feedback loop
of 10Hz or so. Indeed NFS has released a THC feature that uses this technique, while not the high bandwidth you would expect from
a realtime controller, its still adequate for THC with modest dynamic requirements.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'
Re: Z axis laser focusing control
« Reply #3 on: September 09, 2020, 08:32:26 AM »
Hi Craig,

Thank you very much for your quick reply. I am using a Hicon Integra controller. and the setup is the same as what dave have indicated.

which has a Foot fitted with an LVDT , to track the Z axis height over a distance of 2.5mm , used for keeping the lens focused etc , how can we incorporate this function , or will it need a plugin etc

Would this be possible and do you have the Mach 3 brains or a plugin? Thank you for the support
Renato
Re: Z axis laser focusing control
« Reply #4 on: October 05, 2020, 07:07:37 AM »
Hi,
do you have the closed loop activations for the Hicon?

The Hicon can close a control loop so it will be a matter of using what Vital Systems  publish about their controller.

If you wish to go the Mach3 Brain way.....don't....too slow......too clunky.

Get Mach4 and try PMC to see what a real Brain can do. Note that you can program in Ladder logic (PMC) or you
can code in Lua (PLC), both are an order of magnitude faster than the similar Mach3 versions of the same thing,
and way WAY more flexible, capable and robust.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'