Z height instability January 06, 2014 05:47AM |
Registered: 10 years ago Posts: 14,672 |
Re: Z height instability January 06, 2014 06:02AM |
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Re: Z height instability January 06, 2014 06:04AM |
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Re: Z height instability January 06, 2014 06:11AM |
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markbee
I'm not using the IR/ proximity option, because in my opinion it doesn't work satisfactory yet. [...]
Markus
Re: Z height instability January 06, 2014 06:12AM |
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kwikius
Could try reinforcing it with carbon tube or strip. I think this Carbon square tube on ebay would fit in the insulation layer in atriangle between each screw, glue with cyanoacrylate, and you could add a further one ( may need to be e.g 10 mm strip, but that might fit) under the mdf part along the y axis in front of the extrusion..
Re: Z height instability January 06, 2014 06:20AM |
Registered: 10 years ago Posts: 191 |
Re: Z height instability January 06, 2014 06:22AM |
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kwikius
Would a capacitive sensor be more accurate. You sure have a big aluminium plate as one plate?
Re: Z height instability January 06, 2014 06:25AM |
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Re: Z height instability January 06, 2014 06:34AM |
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Re: Z height instability January 06, 2014 06:41AM |
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Re: Z height instability January 06, 2014 06:46AM |
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Re: Z height instability January 06, 2014 06:48AM |
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Re: Z height instability January 06, 2014 06:53AM |
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Re: Z height instability January 06, 2014 06:56AM |
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Re: Z height instability January 06, 2014 06:58AM |
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Re: Z height instability January 06, 2014 06:59AM |
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dc42
How about making the bed from carbon fibre sheet like this? Does anyone know how rigid, temperature-stable, and heavy this is? Sadly the A4 sheets are slightly too small.
Re: Z height instability January 06, 2014 07:11AM |
Registered: 10 years ago Posts: 256 |
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iamburny
I'd much favor a dedicated Z homing location and some sort of resistive pressure sensor like this, it would require a perfectly clean nozzle to be accurate, but should be fairly simple to rig up and wouldn't require adding more complicated electronic to the moving hot end.
Matt
Re: Z height instability January 06, 2014 07:40AM |
Registered: 10 years ago Posts: 265 |
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kwikius
Quote
iamburny
I'd much favor a dedicated Z homing location and some sort of resistive pressure sensor like this, it would require a perfectly clean nozzle to be accurate, but should be fairly simple to rig up and wouldn't require adding more complicated electronic to the moving hot end.
Matt
So This would be attached somewhere on the bed and the nozzle move down on to it? I like it
regards
Andy
Re: Z height instability January 06, 2014 08:05AM |
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Re: Z height instability January 06, 2014 08:14AM |
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Quote
dc42
You could have one force-sensitive resistor on each corner of the bed, then you could still do automatic bed compensation. Unlike the IR sensor, it wouldn't require any calibration because the software would only need to look for a change in resistance, not an absolute value.
Re: Z height instability January 06, 2014 08:26AM |
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Re: Z height instability January 06, 2014 08:28AM |
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Re: Z height instability January 06, 2014 08:45AM |
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Re: Z height instability January 06, 2014 09:31AM |
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Re: Z height instability January 06, 2014 10:53AM |
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Re: Z height instability January 06, 2014 11:30AM |
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Re: Z height instability January 06, 2014 11:44AM |
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Re: Z height instability January 06, 2014 12:09PM |
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Quote
iamburny
Great, I will start re-designing the x-runner bearing mount to be adjustable and to also include a ~4mm space/slot for a FSR400 force sensor you linked earlier, so a relaxation of force e.g. greater electrical resistance will indicate the head touching the bed.
FSR 400 Datasheet
also for sale on ebay here
Matt
Re: Z height instability January 06, 2014 04:21PM |
Registered: 10 years ago Posts: 578 |
I find that there's play in the Z gearing, and occasional binding (especially after a long run in one direction), maybe this contributes to your needing to reset after a print? I jiggle mine up and down by 0.1mm a few times while manually homing to make sure there isn't a bind. I haven't looked at the compensation code (but should do) - I presume that it's doing a matrix transformation to map the coordinates it's told to the ones that they should be, in which case once set, it'll map any new co-ordinates to that space. Do you cancel the previous compensation (M561) in setbed.g ? (maybe the instructions should suggest that setbed.g starts with this gcode...)Quote
dc42
I'm finding the Z-height unstable, to the extent that getting the Z=0 nozzle height good enough to lay down the first layer needs manual adjustment each time. For example, when a print has completed, if I set run setbed.g (which homes all the axes, as well as doing bed compensation) and start another print, typically the head is too low and the extruder stutters because the head is dragging on the bed.
I thought about a few proximity sensor options when you pointed out the halogen sensitivity of the IR detector a while ago (capacitive, direct force-sensing and laser), but they all have complicating factors: capacitive would be prone to stray signals and variable coupling in the looms, as well as (probably) relative humidity, direct force sensing would require that the position of the sensor would be as low as the tip of the nozzle, laser interferometry is well beyond me. I'd thought of indirect force sensing - perhaps a strain-gauge coupled to the nozzle, and that has probably got legs - and it looks like the FSR monitoring the X-bearing load may be more elegant, but also requires some redesign of the firmware and hardware and may have variable reponse requiring a "window" comparison. Have you considered a switch (either a roller microswitch in parallel with the bearing that breaks when the bearing is unloaded, or conductivity between the bearing and a strip of foil tape running along the rib again breaking when the bearing is unloaded, along with a simple debounce circuit).Quote
DC42
Alternatively, how about a single sensor that monitors the force applied to the x-runner bearing? That would be usable all over the bed, and could also serve as a head crash warning.
Re: Z height instability January 06, 2014 05:13PM |
Registered: 12 years ago Posts: 1,611 |