Piezo20 probe and piezo kit now available
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Hi DJ,
Er yeah - bit confused TBH. With a probe such as DC's, the trigger point is some way above the point where the nozzle touches the bed. That is to say if Z=0 is the point where the nozzle touches the bed but the probe triggers say 2mm before that, then I need a 2mm positive trigger height in my G31. So I'm thinking that with your Piezo sensor and my moving mount, the trigger point will be after the nozzle touches the bed so the trigger height would need to be negative. In your case it's only 0.1 or less but in my case, it's likely to be nearer 1mm. So, I guess my question really should be does G31 accept a negative offset value to "tell" the machine that Z=0 is below the point where the probe triggers? Or, should I use M208 to define the Z axis minimum as being something other than zero?
Is my mud any clearer than yours?
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Yes G31 accepts negative values, which is what you need to use for any sort of nozzle-contact probe.
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Yes G31 accepts negative values, which is what you need to use for any sort of nozzle-contact probe.
Thank you.
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Yes you can have a negative offset, but I am curious to find out if you will actually need one. If I set -0.1mm as my offset I'd be milling a line in my print bed.
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Yes you can have a negative offset, but I am curious to find out if you will actually need one. If I set -0.1mm as my offset I'd be milling a line in my print bed.
No actually you won't. It works kind of back to front to what one might expect. When it's positive, a larger value moves the nozzle closer to the bed because what you are telling the machine is that the distance from the trigger point to the nozzle tip is greater and to get from the trigger point to Z=0 it must move further. In your case, if you set a positive offset, you are telling the machine that it must move the nozzle closer to the bed after it sees the trigger point but in your case, the trigger point happens after the nozzle touches the bed so Z=0 is in the opposite direction.
Edit. Having re-read that, it seems clear as mud - just try it and see.
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Well I am trying it Ian. I've been printing with a positive offset and a piezo probe hotend for a few weeks now. I've just fitted Lykle's latest effector/probe combo, so all bets are off until I've had a bit of chance to test this version.
I know you're putting forth sound theory but my experience has been I need to use a positive offset (which I apply in my slic3r rather than in Duetwifi config).
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Sorry DJ, no offence meant. It sounds arse about face to have to do that but if it works for you, then fine. Maybe slic3r works the opposite way to Duet config? Dunno…...
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Well I am trying it Ian. I've been printing with a positive offset and a piezo probe hotend for a few weeks now. I've just fitted Lykle's latest effector/probe combo, so all bets are off until I've had a bit of chance to test this version.
I know you're putting forth sound theory but my experience has been I need to use a positive offset (which I apply in my slic3r rather than in Duetwifi config).
If you have to add a positive Z offset in your slicer, this indicates that you need a lower (I.e. more negative) trigger height in your G31 command.
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I think that is probably the Difference
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Sorry DJ, no offence meant. It sounds arse about face to have to do that but if it works for you, then fine. Maybe slic3r works the opposite way to Duet config? Dunno…...
None taken its clear the way the offset is presented differs from the firmware to the slic3r, I wasn't aware of that, but given cognitive biases I am likely to see it everywhere from now on.
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The value in the G31 Z parameter is the probe trigger height, not an offset.
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A little update for the delta brigade, Lykle's latest effector design with less flexible piezo works and seems fairly reliable, we are just tweaking the design to make assembly more straightforward. But I think we are getting closer to having a solid system.
Next steps:
-try a 20mm piezo to see if we can make a smaller overall unit.
-Make a version for i3 style printers (since they are the most popular design) I don't have one anymore so I will need some help with that.
-I have got a piezo sensor working now on Duet/RRF, Marlin/Ramps and now Re-Arm/Smoothie (in fact it works really well on Smoothie as setting < zprobe.debounce_ms 1> for z probe means I can probe at full speed). Is there anything like this on RRF David? This practically eliminates false triggers - I don't know how this works but it seems to work very well with this probe.
-See if there is a way to reduce the chance of wire-breaks on the piezo unit itself, the leads are very thin and desolder easily. -
You can adjust the debounce time by adjusting the threshold in the G31 P parameter. Lower values give lower debounce times.
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New boards have arrived and are made up, I'm currently testing them and they should be ready to post early next week.
Of the the first batch of 12 I've sent out 10 and donated I think £55 to the charity. Unfortunately I'm not in a position to keep doing that, I had to buy more parts to make the new batch and the boards are larger and more expensive so now I'm going to be selling them. If you've already been told that the money is going to the charity then that is where it will go but in the interests of transparency, from this point on, the money is going in my pocket.
I will be writing up documentation (hopefully this weekend) and I will publish that free for anyone to use.
I didn't foresee the demand for these boards so I only ordered six this time, I think three or four are already spoken for. I'll be ordering more asap.
I've previously discussed a piezo endstop handling board, they are also made up and being tested and will be ready to post next week to beta testers.
Idris
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Idris. That's great news. I think it might be a good idea to possibly start a wiki page on reprap for this system as it is coming together nicely, and all the relevant information such as how to use the board and how to assemble the units would be well placed.
David - I will experiment with this. I have been setting the P parameter dependant on the analogue value but it might be worth revisiting the digital setup as it does seem to work extremely well on smoothie as a digital sensor with 1ms debounce.
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Okay so this is the current incarnation of the sensor mounted in Lykle's latest effector system (which will be able to have a Nimble extruder bolted straight on - or just used with your current Bowden/flying extruder):
Nozzle wobbly practically non-existent and calibrating to a 0.02 precision over a 330mm bed.
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I have the stl's for this effector now on my thingiverse. Lykle will publish it also (with step files) if anyone needs to edit it to suit their setup. Please feedback to us on how you are getting on with it, any additions and improvement you make as well.
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DJ did you get his larger one I sent you you will need that to go with the Alloy carriages that I am getting cut it has a hole to take the Bardair cooling tube integrated into it (Reminder to self to order a bardAir system)
Doug
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Thanks Doug, I did get it yet. I will reprint and upgrade the effector when the carriages are in. I am looking forward to that.
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This seems to be a nice way to use the probe for automatic perfect first layers:
https://www.duet3d.com/forum/thread.php?id=940
