Re: Hight sensor

On 9 Oct 2000 07:10:07 -0000, you wrote:

I work on laser cutters and these have two types of sensors.
The older ones use a hinged loop around the cutting nozzle attached to a
spring loaded LVDT [ hope I've got the letters right] The output from the
LVDT goes to a board which turns the output into an analogue signal for the
Z servo board to read.
The newer ones work purely by capacitance <sp> There is an insulated copper
disc just above the nozzle that is connected to a small board that I
presume does the same.
Sorry if these descriptions are a bit vague but I'm not an EE.
The first version is adjusted by bending the hinge on the LVDT to adjust
hight and the second is adjusted by a pot on the board.
The EE responsible for looking after these machines has a newer board that
he's fitted to one of the older machines and it works. I could try to ask
him for a description but it's a bit hard work as he's of Turkish
extraction and hard to understand. Would a photo of the board from both
sides help?

As regards dual motors on a plasma gantry the newer lasers have this due to
their size, they can handle 3 metre sheets [ 10' ]
They have two largish pancake type double ended servo's at either end
joined by a jack shaft.The output end of each motor has a precision pinion
on it and this drives a rack directly.The speed these travel at is amazing.
They can rapid from one end of the bed to the other in about one second.

> From: ptengin@...
>Subject: Re: Re: dual motors on Plazma Gantry
>
>In a message dated 10/08/2000 7:00:48 AM Hawaiian Standard Time,
>tom@... writes:
>
><< I shouldn't be too difficult
> to build a closed loop circuit that would keep the torch at a
> constant height above the work, but is that all that is required?
> I know that a lot of the guys are just interested in making
>chips (so am I) but I am also trying to figure out a way to "retire"
>from working for someone else >>
>
>
>Tom,
>
> If you can come up with a good torch height system, I know you could
>retire. Proximity sensors will give different readings over different metals,
>the response will vary if caked with slag or clean. I think a lot of outfits
>have tried this and other schemes with only limited success. If your sensor
>goes over the edge of the palte, will it drop down and cause the nozzle to
>hit the plate? If your plazma blast turns around and hits the sensor, will it
>be toast? These are some of the obstacles that must be overcome to retire
>early on this one ;)
>
>Peter
>THRD, Inc.
>
>Some of the newer hypertherms have an air cooled drag nozzle which allows the
>torch to be simply dragged on the surface. The thing still has the problem of
>hanging up on stuff on its journey.
>
>
>________________________________________________________________________
>________________________________________________________________________
>
>

--

Regards,
John Stevenson
Nottingham, England