Melzi 2 Esteps calibration - no existing figure to recalculate from??

Hi all, am after a little help if possible with extruder estep settings on a prusa Mendel i2 that I'm rebuilding for a friend if possible.

I have it mostly functioning except for two issues:

1 - Main issue - the extruder pushes out 50% more filament length than it should (so 150mm when you tell it 100mm). Now I know of course how to calculate a new ratio for this normally, but here's the problem - the existing settings in the eeprom are zero for everything (see pic) so I have no start point and don't know how to therefore calculate even remotely what number it needs. How can it be working like this?

Worth noting that I have changed the extruder drive and while it's still direct drive (not geared) I think the drive pinion is now possibly wider diameter which might explain the wrong extruded length, but I don't get how to recalculate for this when the figures are all zero. Does this mean it's set in firmware and I'll have to try another firmware version that I've customised or something?!

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Prusa Mendel i2 - Melzi V2

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Prusa Mendel i2 - Melzi V2

Not sure what happened here sorry as the image I added and half of the post disappeared but the main important bit is there at least!

Thanks all

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Prusa Mendel i2 - Melzi V2

Anyone able to assist with this Estep conundrum at all please? Really grateful if someone can point me in the right direction, thanks.

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Prusa Mendel i2 - Melzi V2

Never tried this?

from [reprap.org]

"RepRapFirmware will report the current steps/mm if you send M92 without any parameters."

Ahh, I never spotted that before. Brilliant thank you so much!

Will try this tonight once I'm home.

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Prusa Mendel i2 - Melzi V2

Hmmm, well I fired up the printer and connected it etc, but when I just send M92 alone to it the log varies what is shown. For instance one time it will show N39 M92 *2, then another was N66 M92 *8, then N87 M92 *7 etc etc, so I'm sure this can't be right for the Esteps since it's varying each time I send the M92 command by itself with no parameters.

I'm pretty sure this must be me doing something wrong but I don't know what....

So I found then that M500 code apparently saves the current settings to the Eeprom and I thought this would be perfect if it does since I can then open those settings in repetier and see what they all are and adjust where required. But when I send the M500 code then open the Eeprom settings they are all still blank.

One thing I noticed was that yesterday it was allowing me to extrude filament (it's not going into the hot end/extruder and the filament is just going into the air for testing/measuring, and allowed me to do this without heating the extruder but when I try this today, it gives an error for cold extrusion prevention.
I understand why of course, and have dealt with this before, ages ago on my own printer, but I'm not sure how it allowed me to use the extrude button yesterday and now won't....

Is it worth me just getting a version of Marlin and loading it in since if I know what it is then at least I will know the firmware settings to begin with? My only concern is losing the current version which I know has worked well for my friend, with very nice acceleration setup etc on the way it moves compared to a previous board/firmware he used. The settings for the printer settings state a URL of Mendel-parts.com, and that it's Marlin Protocol 1.0, but that website doesn't seem to exist from what I can see, so I'm worried if I try another firmware version I won't be able to get it back easily how it was.

But more importantly I'm not sure why the M92 code isn't showing me the steps figure (unless I should be looking elsewhere to the log at the bottom of the screen?), nor why the M500 code does not put the settings its using into the EEprom settings screen.

Apologies if I'm completely misunderstanding this stuff. I had to learn a ton when I built my own Mendel a few years back but I've not had to look at things like firmware and step settings since then so am rusty on it all.

Anyway, I note that M302 will temporarily disable the cold extrusion prevention so I can try this then see what happens when I meddle with step settings to try things out since I can't see the current setting.
I also just read this quote about the eprom settings screen: "If you can open but do not see any values your firmware wa scompiled without eeprom support.", so I think that explains a lot!

Thanks
Jim

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Prusa Mendel i2 - Melzi V2

Right - I don't need to worry about the above tooooo much now thankfully.

I don't know why I can't get any settings returned but it must be (maybe) to do with the firmware option not having eprom support perhaps.
Anyway, with the cold extrude issue sorted, I was able to happily muck about with the e-steps and got it settled around 87s/mm as being pretty accurate. I've only tested that over 150mm of filament but it must be very close to being spot on I think.

The next issue was that the moment I tried to extrude any plastic it jammed.
I figured this was from an earlier attempt to extrude when the fan wasn't turned on, and I think the PTFE tube may not have been fully seated so a bulge happened in the filament inside the extruder, which caused a blockage and I think then caused the stuff in the nozzle to burn in situ.

After stripping it all down and cleaning the short tube section above the nozzle itself (a removable threaded section) with some carburettor jet cleaning 'files', I got the filament to go through quite nicely. Once it was reassembled and heated, it extrudes fairly well between 195 and 205c (1.75mm PLA) with the tiny built in fan working all the time to prevent heat creep. Played around with it like this for a while, just extruding lots of PLA and pausing, then continuing and repeating, and while I'm certain it won't be anywhere near perfect settings, it seems it is now feeding and flowing pretty well, and with barely any weight on the carriage (remote mounted extruder stepper) I'm expecting it to perform fairly nicely once properly dialled in.

So lots of progress made - thanks for the assistance!

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Prusa Mendel i2 - Melzi V2