Messages

41

General Mach Discussion / Re: Height Following

« on: October 28, 2008, 01:53:27 PM »

fer_mayrl

Any progress on your end here?  You stated "I have been looking into linear pots and LVDTs, and plan to have mach red the analog voltage and control the position of the z axis".

That's the correct solution - or so it seems to me.

For our part, we are planning to use one of the PoKeys input units for the analogue in (they will handle up to 4 analogues).  That gives us a nice expansion of useable I/O, and allows the analogue inputs and ability to use encoders (for mapping as an example).

42

General Mach Discussion / Smooth Stepper

« on: October 28, 2008, 01:42:50 PM »

I see that lots of you have managed to buy a Smooth Stepper.  I've logged in and have been accepted as an "approved" whatever.

Now what?

There is no address, no phone number, no fax number, no buy page, and no link to go to anywhere you can buy the things.  How do you manage to purchase one?

I've emailed them twice, but I can't even get a response there!

So, what's the secret?

43

General Mach Discussion / Re: Height Following

« on: June 14, 2008, 03:16:43 PM »

For almost anything I do that would work great.  I think the toughest application would be laser where height is critical and cutting speeds can be fairly high.

44

General Mach Discussion / Re: Height Following

« on: June 14, 2008, 12:20:31 PM »

As far as I'm concerned, an ultrasonic device would be perfect.  It outputs a signal that varies from 0-10 vdc.

Now, if there was a way to read in this analog signal to the Mach interface that would plunge until the feedback was 5vdc, and then maintain that 5vdc by moving the z-axis up/down as the voltage varies - you're there.

Hopefully, something like that is possible.

45

General Mach Discussion / Re: Height Following

« on: June 12, 2008, 06:03:06 PM »

Wow - lots of interest here.  As Hood said "Good for Mach" - and us too!!

A good solution should work through Mach so that current position is always known - or "closed loop to Mach" .  I think that's the goal everybody is talking about.

Should work well on anything - plasma, laser, waterjet, etc.

Once the basics are worked out, I'm expecting that several entries will pop up for consumer sales.  The trick will be making one that is low priced for the masses.

46

General Mach Discussion / Re: Height Following

« on: June 12, 2008, 03:14:41 PM »

We've only just started thinking about this.  If we can buy a package that works (is the one in the picture a production thing or custom made?), we will use what's available.

Otherwise, we'll use a linear encoder and make something similar to your picture.  We don't care if it's +/- 10 vdc or 0-20 vdc, or whatever.  However, 0 vdc to 24 vdc is REALLY easy since every system we've ever done has this already.

Currently, we use two LPT ports for Mach3.  We'll use the Smooth Stepper when it's ready.  For this device, we'll use whatever you recommend that works.

Sure would be nice to be able to set the high, center, and bottom voltages in Mach.  That would eliminate the need for a manual adjustment to get the height right.  Actually, just the middle might work - with a choice of polarity for what raises or lowers the z-axis.  That is, depending on the resistor and wiring, an increasing voltage might mean you are either too close or too far away.  A simple check box could be used to set polarity.

Another possibility would be a variable for response speed if this is to be truly dynamic, or alternately a response distance.  For example, if the sensor reads "too high", the plunge is 1/20" and recheck.  That could prove easier by eliminating the possibility of "hunting" like a badly tuned servo.


BTW - forgot to ask if this could be used for twin heads - nothing's ever simple!!

47

General Mach Discussion / Re: Height Following

« on: June 12, 2008, 01:24:56 PM »

That's great news!

I really don't care what voltages you pick - we'll work with whatever.  However, we prefer to work with or inside of a 0-24 vdc range.  The sensor we are planning to use is 10 vdc to 24 vdc.

What are you planning on using for the laser?

48

General Mach Discussion / Re: Height Following

« on: June 12, 2008, 09:40:07 AM »

#2 is the correct answer, almost.  We wouldn't be cutting a groove.  Think plasma torch, laser, or in our case waterjet.  This would be especially nice when cutting underwater where you couldn't see the material or the cutting tip (also done with plasma torches).

In general, plasma set-ups do exactly what you suggested.  They plunge to a set voltage and then maintain that voltage.  With plasma, this can be read in the torch itself as the voltage increases as the cutting tip gets farther from the material.

What we'd like to do is use a linear resistor that passes voltage from 0-10 vdc.  The setting for height would be at 5 vdc.  This could be attenuated using a potentiometer to adjust the perceived voltage and to set the start point (that is, plunge to position and let the basic setup pick a height - then turn the knob to adjust up/down slightly to a proper height).

So, the z-axis would plunge to a start point - the point where the feedback voltage is 5 vdc.  The height could be altered manually with a potentiometer, if required.  From there, the control would move the z-axis up/down to maintain the voltage at 5 vdc.

49

General Mach Discussion / Height Following

« on: June 10, 2008, 05:17:29 PM »

Has anybody out there found a good way to do height following?  That is, to have the z-axis plunge, have a sensor read the material surface and set the height, then maintain that same height above the material as the part is being cut?

50

General Mach Discussion / Re: Shortest rotary

« on: June 07, 2008, 02:02:39 PM »

Many thanks.  I changed my code as follows:

Note that I used NEGATIVE numbers for CW moves and this works in both the absolute arc center and radius offset examples.

Also, to get the speeds to work better, I set "Use Diameter for Feedrate" on the Toolpath Configuration screen, and set the Rotation Diameter to 0.1" on the Settings Page.


NOTE - The DXF I used is plsted below.



N5 (Posted with Water Only.pst)

N35 G0  X2.0000  Y0.0000 F600
G0 A180
N40 M3 (Water On)
N45 G1  X0.0000 F600
G0 A90                   (This works because I have “shortest rotary for G0” turned on)
N50 G1 Y3.5000 F600
N55 G2  X0.5000  Y4.0000  R0.5 A-0.0001 (Note – A-0.0 turns the wrong way)
N60 G1  X3.5000
N65 G2  X4.0000  Y3.5000  R0.5 A-270
N70 G1  Y0.0000
G0 A180                   (This works because I have “shortest rotary for G0” turned on)
N75 G1 X2.0000
N80 M5 (Water Off)
N85 G0 Z0.0000
N90 M30

 

AND

N5 (Posted with Water Only.pst)
N35 G0  X2.0000  Y0.0000 F600
G0 A180
N40 M3 (Water On)
N45 G1  X4.0000 F600
G0 A90
N50 G1 Y3.5000 F600
N55 G3  X3.5000  Y4.0000    R0.5 A180
N60 G1  X0.5000
N65 G3  X0.0000  Y3.5000    R0.5 A270
N70 G1  Y0.0000
G0 A0
N75 G1 X2.0000
N80 M5 (Water Off)
N85 G0 Z0.0000
N90 M30

 

AND

 

N5 (Posted with Water Only.pst)
N10 G0  X3.0000  Y2.0000 A270
N15 M3 (Water On)
N20 G2  I2.0000  J2.0000 F500.00
N25 M5 (Water Off)
N30 G0  X4.0000  Y3.5000
N35 M3 (Water On)
N40 G1  Y0.0000
G0 A180
N45 G1 X0.0000
G0 A90
N50 G1 Y3.5000
N55 G2  X0.5000  Y4.0000  I0.5000  J3.5000 A-0.0001
N60 G1  X3.5000
N65 G2  X4.0000  Y3.5000  I3.5000  J3.5000 A-270
N70 M5 (Water Off)
N75 G0 Z0.0000
N80 M30