Who want to make a touch probe?

[juliodv]

Boa Tarde

me chamo Julio e sou do Brazil, estou acompanhando os topicos e estou interessado em saber mais sobre esse sistema, como que funciona? qual maquina tenho que ter ?


agradeço a atenção

[Cruiser]

I am sure that making one would be interesting. I bought two from Arnie Minear aminear@wyomingwireless.com for $200 both & $7 or so shipping. I figured I couldn't makem for less and his are ready to go. I have one running in the machine digitizing a propeller I want to make. Its been running for bout 9 hrs so far and total time should be close to 26.5 hrs ! Its like watching paint dry out there in the shop.
I got two so I didn't have to switch em between tool probe and part probe. Both are wired up and work great. Precision is not perfect and probably won't till we get comp incorporated into the software, I use mach3 & smooth stepper and don't have any complaints in that dept.
There are several plan sets out there to build the probe components, and they are all very similar in design and function.

[dalescnc]

Thanks for all the files ;-) Got my probe up and running and works like a DREAM. Got enough spares to make 3 probes after all the mistakes i made lol but still cost me less than 1 $ thats the gratifying part

[rvt]

Hey Guys,

this is my version I have been working on.

Sorry for the bad quality of the image, I couldn't figure out how to assign colors in sub-assemblies yet

basic idea behind it:
- If you have a mil, you can mill it using your 3-axis mill
- No need for exclusive components, you can get all parts and even replace parts for other materials.
- auto centering (not well displayed yet)

The idea is two copper plates with one copper plate having some small bolts, and on the other end a simple copper plate with soldered 1.5^2 copper wire. This system will function as the main switch.
Each copper plate has a simple pattern that functions as a switch in series.


As soon as I have my mill up and running I will make this one and show you good examples.

Ries

[arie kabaalstra]

Hi, can you share the CAD models, they look great. Thanks!!


Pablo

No, sorry, i won't share drawings since i sold my design, and now the company i work for makes em..

www.damencnc.com
check under "Components" / "Tools"

Ok, i admit, we're not givin'em away, but, at the moment these probes will outperform anything within that same price-region..

you get very low probe-pressure, so even the softest materials won't get damaged ( it could easilly digitize an egg ), and it has gold-plated contacts..

i've been putting mine through extensive tests:

"http://www.youtube.com/watch?v=5JnDloaC1YQ"]YouTube- USBCNC-Porsche 917K

[rvt]

Arie,

could you do two scans with your software with a object with a steep ramp (>70 degrees).

The first scan would be moving the probe up/down in over the Z-Axis.
The second scan would scan the same object in the Y axis.

Then compare the dimensions of both objects.

The rationale behind this is that because of the inclinations and the probe needs some pressure (even if it's minimum) the objects shape might be slightly different. I would expect a different in the top part of the scanned object.

You could make software that does a rough check if the object. Then the software can decide how to exactly scan it in high resolution, over the X,Y or Z axis.

I should have made a picture to clarify I guess.

If it really matters for us hobbyists is debatable

Ries

[arie kabaalstra]

well , anything that can be described in algoritms can be programmed.

you only would have to do a lot of calculations within the program to see is a certain surface is steep, so it would have to be scanned on a different axis..

mind you, the probe triggers the software as soon as it switches ( within 0.005mm of movement), the CNC then still has to start decellerating, so it looks worse than it actually is..

calculating will cost a lot of programming and processor capacity,

[rvt]

Arie,

what I basically trying to say is that resolution depend on the steepness of the object to be scanned and you could change the scanning strategy on that information.

In your case you switch at 0.005mm movement (in any direction?) this your accuracy would be well within most requirements.

PS: I have seen your probe (here on CNC) it it looks really nice! Well done.

Ries

[MichaelHenry]

Has anybody bought one of the probes that Arie designed and that are now being marketed by DamenCNC?

I'm about to buy one and would like to get some input from users before plunking down my money. What sort of location accuracy are you seeing and does it seem to retain calibration from one use to another?

They get expensive quickly for those of us in the US.

Mike

[dkp_design]

Hey Guys,

this is my version I have been working on.

Sorry for the bad quality of the image, I couldn't figure out how to assign colors in sub-assemblies yet

basic idea behind it:
- If you have a mil, you can mill it using your 3-axis mill
- No need for exclusive components, you can get all parts and even replace parts for other materials.
- auto centering (not well displayed yet)

The idea is two copper plates with one copper plate having some small bolts, and on the other end a simple copper plate with soldered 1.5^2 copper wire. This system will function as the main switch.
Each copper plate has a simple pattern that functions as a switch in series.


As soon as I have my mill up and running I will make this one and show you good examples.

Ries

Any further pictures?? I am really intrigued by all designs. Not sure which way I'll build yet.

[rvt]

Currently I don't have more picture, unless I create a other rendering.

Working hard to get the CNC ready here (almost done.. yuppie!)
THen I will properly come up with some real photo's and know a bit better if this is a good design or not.

Ries

[dmauch]

I have attached link to an article written by B.J Rao describing a unique ultra precision touch probe.
http://www.intricad.com/touchprobe/i...efeelforit.pdf


Dan Mauch

[rvt]

Dan,

nice PDF you have there.
I think this method will work well where high precision is needed, however the electronics will not be simple for the average Joe.

if I recall correctly (my electronics is very rusty in this area) a piezo element will generate a voltage when pressure is applied properly some FET will be needed to change that into something usable (http://en.wikipedia.org/wiki/Piezoelectric_sensor)

One other method could be to put the piezo element within a resonance circuit (rather then applying a frequency to it). When a force is applied, the frequency will change.

My mayor worry will be though, that because the element is so sensitive it might result in false positives, specially when the CNC machine is moving to it's next position (stepper motor resonance) thus the software need to be told to only start measuring within the condition that measure is happening and not during movement of the probe, this in return will make clash detections of the needle a bit harder.

Anyways, good food for thought!

Ries

[dmauch]

1.The major advantage of this type of probe is that it is virtually
"insensitive" to rapid movement. No false positives.

2."put the piezo element within a resonance circuit (rather then applying
a frequency to it)." ???

Dan,

nice PDF you have there.
I think this method will work well where high precision is needed, however the electronics will not be simple for the average Joe.

if I recall correctly (my electronics is very rusty in this area) a piezo element will generate a voltage when pressure is applied properly some FET will be needed to change that into something usable (http://en.wikipedia.org/wiki/Piezoelectric_sensor)

One other method could be to put the piezo element within a resonance circuit (rather then applying a frequency to it). When a force is applied, the frequency will change.

My mayor worry will be though, that because the element is so sensitive it might result in false positives, specially when the CNC machine is moving to it's next position (stepper motor resonance) thus the software need to be told to only start measuring within the condition that measure is happening and not during movement of the probe, this in return will make clash detections of the needle a bit harder.

Anyways, good food for thought!

Ries

[rvt]

1) Because it so super sensitive, it would usually be more prone to false positives. THis could specially happen when the frame/steppers get into resonance and things start to vibrate. This could lead to vibration at the needle point and thus create a false positive.

2) It's just a other way of connecting the piezo element...

Still,
this way of creating a probe is harder to make for the average builder because you need to create some sensitive electronics, not easy to build.

The idea is good still, but needs some clever working out of the electronics and testing. The probe using a switch is much simpler to build, no complicated electronics and can usually be connected to a BoB straight from the switch. THis will be good enough for most hobbyists.

Ries

[TOTALLYRC]

Has anybody bought one of the probes that Arie designed and that are now being marketed by DamenCNC?

I'm about to buy one and would like to get some input from users before plunking down my money. What sort of location accuracy are you seeing and does it seem to retain calibration from one use to another?

They get expensive quickly for those of us in the US.

Mike

Hi Mike,
I just recieved Arnie's probe and got it from wildhorse innovations.
Today I was able to put the receptical for the quick disconnect into the back of my control panel. I have the probe itself in a collet holder and stuck in the spindle. I have centered it by eye but will be using an indicator to make sure it is properly centered.

I am also testing the firmware that makes this work with my DSPMC controller and it all seems to be coming together.

I will be doing some real testing over the holidays since I get 4 days in a row off.
I would be happy to report back but if I forget, pm or post and I will be reminded.

Initial feeling are it is pretty well made but for$100 it was well worth the money. It now comes with a tool length tip and seal to keep the coolant out when using it in a tool length application.

Mike

[dkp_design]

You have to center them? is that a tedious job, like trammeling my mill? Thought it was a put in and use kinda deal, just like an endmill?

[TOTALLYRC]

You have to center them? is that a tedious job, like trammeling my mill? Thought it was a put in and use kinda deal, just like an endmill?

Centering the probe involves using on indicator and slowly turning the spindle by hand. You have three adjustment screws to get it as close as possible to zero. If it is off of center your location will not be where you think it is.

Once it is centered, I don't think you would have to recenter it very often unless you crash it like I did.

I was able to do a probing routine using the digitize wizard included in Mach3.
It worked flawlessly. Arnie's probe is also tough. I was testing a specialized function and drove the probe into my vise at 30 ipm. Good thing my hand was on the e-stop. I bent the end of the probe but nothing broke. I will have to whip up a spare tip or 2. So far so good on Arnie's probe.

As far as accuracy, a quick and dirty test using the DRO on Mach3 and approaching the vise from the same direction to take backlash out of the equation, it repeats to within a few tenths IIRC, definitely well under a thou.

Mike

[dkp_design]

Centering the probe involves using on indicator and slowly turning the spindle by hand. You have three adjustment screws to get it as close as possible to zero. If it is off of center your location will not be where you think it is.

Once it is centered, I don't think you would have to recenter it very often unless you crash it like I did.

I was able to do a probing routine using the digitize wizard included in Mach3.
It worked flawlessly. Arnie's probe is also tough. I was testing a specialized function and drove the probe into my vise at 30 ipm. Good thing my hand was on the e-stop. I bent the end of the probe but nothing broke. I will have to whip up a spare tip or 2. So far so good on Arnie's probe.

As far as accuracy, a quick and dirty test using the DRO on Mach3 and approaching the vise from the same direction to take backlash out of the equation, it repeats to within a few tenths IIRC, definitely well under a thou.

Mike

Thx, are these adjustment screws, do they move the body on the mounting shaft, or do they move the stylus?
I found some nice priced Ruby Tipped stylus's on eBay, bought one, now tryng to decide if I am going to make one, or just purchase??

[TOTALLYRC]

The adjustment screws actually tilt the circuit board inside the probe body. This has the effect of moving the stylus.

Mike