Automatic XY skew calibration
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I also fall into the build it properly camp now, but I didn't used to. This is a useful feature at the lower end of the market, but that's not where duet users typically are.
I'd say do it if it's easy to include (which I suspect it's not) or don't use time that could be better spent on more useful features.
Agree 100% with this sentiment!
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I agree that this is a feature that is most useful to new users with specific hardware ( Prussia i3 mk2).
But then again, should we not include support for those who most need it rather than just support the experienced and competent users? It seems that this kind of sense/compensate feature has uses in multi-axis/cnc applications and it would be good to support it - but not perhaps at the top of the list!
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"with specific hardware ( Prussia i3 mk2)."
what about others users with the same bed but not the same printer?
agree that it could be placed somewhat down the list and maybe be expanded to compensate for other than XY skew if possible
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I didn't express my own opinion earlier because I didn't want to bias the discussion. But this thread has been live for a couple of days so I'll express my opinion now.
- The only thing that Prusa is offering that we don't do already is automatic (as opposed to manual) compensation for XY skew.
- From what I can see, Prusa isn't offering any sort of compensation for XZ or YZ skew, whereas RRF does
- If a printer build doesn't have X and Y accurately at right angles to each other, then I suspect it won't have Z accurately at right angles to both X and Y, unless the nature of the design makes it likely that the XY angle will be much less accurate than the XZ and YZ angles. So I don't see much value in automatic XY skew compensation without also having automatic XZ and YZ skew compensation.
- Measuring XZ skew and YZ skew automatically would not be easy, because the mechanism of using a bed with markers placed in it restricts you to probing at a height very close to the bed.
- That type of bed also restricts you to using only as many mesh bed compensation points as there are markers on the bed, which is 9 in the case of the Prusa i3 Mk2 bed. Whereas the Duet WiFi supports up to 441 bed probe points. 9 points is likely to be sufficient for small Cartesian printers, but not for larger printers.
- As far as I know, no firmware other than RRF has supported any form of skew compensation before Prusa added it, and I've never seen anyone raising skew on Cartesian printers as an issue on any of the forums I monitor. So I see no evidence that XY skew is a common issue (or even a rare one).
So my gut feeling is that automatic XY skew compensation is a solution to a non-problem. Most people don't have difficulty getting their X and Y axes perpendicular. For those who do, manual skew compensation is available, and if used as instructed it also provides XZ and YZ skew compensation.
So I'm inclined to put it waaay down on the priority list. But we're customer-driven at RRF, so your votes are what counts.
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I saw a couple printers that would have benefited from this compensation at MRRF due to errors induced in transport - some traveled better than others. Or at least on brief inspection, a few looked a bit off. But that's typical for MRRF, people slap their printers down and hit print, any auto-cal is beneficial because no one's wanting to sit around calibrating when they could be talking to others and enjoying the fest. Now whether the issue should have not occured if they'd been build more solidly is a different question, but I was very glad to have full autocalibration on my delta while there.
That might be a rather unique use case, though, not sure how often people travel with their printers.
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"no firmware other than RRF has supported any form of skew compensation"
Repetier does, but also has to be done manual
Q…. Would the mini IR board be a batter choice here? and how well would it work on that black matt surface with PEI sheet on?
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boelle
There could be a way of using an IR sensor, combined with an accurately manufactured "datum" sheet to do the same form of compensation. A pattern (similar to a bar code) can be printed at various points on the datum sheet which the IR sensor, if scanned at the right height, can detect. The sheet would need to be manufactured with cutouts or very varied reflectivity
This would be a lot of work to implement and (unlike other forms of auto calibration like delta auto calibration) is not as common an issue.
Further more neither of these methods works with a touch probing system like the peizo sensor.
My view is it is a low priority in comparison to most other things.
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I'm thinking of signing up to the indiegogo campaign, but have a quick question as I use a Mini height sensor board…
Will the Mini height sensor board be be compatible, based on the height sensor instructions:
"PEI: this is highly transparent to IR. Paint the underside matt black (see below) before using adhesive sheet to attach it to the bed plate."
I assume that as the MK42 heated bed is black and the PEI is applied directly to this, this step wouldn't be required?
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you are right
the mk42's are matt black and the PEI is put on top
i too will end up with the mini ir, i assume that the duet will make use of the analog output
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My heated bed from the indiegogo campaign has arrived
Does anyone know if the Mini height sensor will be able to cope with the matt black PCB and thin PEI or would i be better off getting a sheet of Buildtak instead?
Willing to experiment, but if the PEI is a lost cause I'd rather not put it on to only have to peel it off 30mins later… -
PEI placed on top of a matt black surface with no intervening adhesive should be OK, but if there is an intervening adhesive sheet then reflections from the light-coloured adhesive are likely to cause problems.
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PEI placed on top of a matt black surface with no intervening adhesive should be OK, but if there is an intervening adhesive sheet then reflections from the light-coloured adhesive are likely to cause problems.
Thanks for the reply the PEI does have a thin adhesive layer. I might play safe to start with and get in a bigger buildtak sheet as I know that works well with the sensor.
I like the idea of the piezo sensors but I will need to think about how to mount it on a i3 with a Titan Aero…
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We have a titan bracket system now not many in use currently but it works. Will work with titan and titan aero. See the site below or search DjDemonD on thingiverse. It's based on the official bracket from e3d.
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We have a titan bracket system now not many in use currently but it works. Will work with titan and titan aero. See the site below or search DjDemonD on thingiverse. It's based on the official bracket from e3d.
Thanks, I had a look at that I'll need to redesign it to fit my setup, I see that your bracket has some flex built in the base I'll need to come up with a way to add this to my carriage or make a two part carriage to incorporate your bracket
I've just made this for the IR sensor which is working quite well. (https://www.thingiverse.com/thing:2441400) So I'll stick with this and buildtak in the short term and keep an eye out for Cartesian Piezo carriages/brackets and switch if i need to move over to PEI
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No worries, these things are quite versatile. The tuning window (the usable range if you prefer) will be narrow but they can work just bonded to the side of any part that flexes on nozzle contact.
