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mark-hale

14.07 Purge of material at start

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Hi

Have just updated my UM2 to the latest firmware version 14.07. Noticed when I started a print, the print head moved to the front left and purged a whole load of pla out before starting.

Its in the middle of a print now and all seems well so don't yet know if this was a one off thing. Is this a new feature?

Edit - just started another print and again right at the start, before the print moves to the print location, it purges the filament,more so than on the previous firmware. Don't have a problem with this tbh, and thinking about it, I have had the odd occasion when the initial priming of the filament wasn't quite enough

Just curious to know if this is intentional

Cheers

Mark

 

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This is actually a very usefull feature in my opinion. It makes sure your hot end is actually full of molten filament before starting to print. It has happened to me multiple times that it started printing without plastic coming out because I just changed the fillament and it hadn't reached the hot end yet. The purge helps you to make sure there is material coming out :)

 

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Yes, it's a deliberate feature that I added recently - or at least fine tuned to where it works a bit better. (It actually used to try and purge as much or more, but did it so fast that most printers couldn't keep up - and that lead to stripping of the filament on some printers.)

It purges 50mm³ - a little over half of the contents of the print head - at a fast normal printing speed. The idea is to ensure the head is full of plastic, make up for any filament that might have leaked during heat up, and flush through most of the plastic that may have sat hot in the print head for a while.

I'm still open to ideas on how to make this work better. I think it should probably do it a bit closer to the bed, so the ejected plastic is more likely to stick to the bed (and/or the front left glass clip). And then maybe do a quick left to right pass on the front of the bed, almost touching, to try and wipe off the head before the print proper starts...

Any ideas or requests?

 

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I would highly recommend to stay with the present procedure. If the purge is done closer to the bed you would not have any chance to grab the extruded filament with pincers if necessary.

Any attempt to wipe the nozzle may lead in covering the outside of the nozzle with filament which has almost always a negativ impact onto print quality.

 

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On my UM1, I put a small ridge of tape (wiper) on the bed near the home position. I typically purge the nozzle by hand before initiating a print. My start Gcode purges a bit more, and then drags the nozzle across the ridge of tape and then across the bed to the start point. This shears off the small sprue that gets purged by the start code and the nozzle is fully primed to start printing.

I'm not sure of the UM2 start sequence function, so please excuse that.

So on an UM1, the start code first does an auto-home, then lowers the bed 15mm, then extrudes a few mm of filament. Normally, that's the last motion before cutting diagonally on three axes to the start point (drizzling all the way). Before that happens, I give a move code to 10,10,0 (nozzle a bit to the right and behind the drool that accumulates at 0,0,0). Then the sliced Gcode takes over and the nozzle traverses the print bed crossing the tape ridge (at a 45 deg angle at about 20,20,0) to get to the start point. The nozzle is primed and clean at the start of the object. Yes, it takes up a bit of print bed space, but for most prints, I am rarely cramped for X,Y space.

A small hole in the bed under 0,0 could be used the same way, but I haven't gone there. It would also prevent any stalagmites starting there.

 

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Yes, it's a deliberate feature that I added recently - I think it should probably do it a bit closer to the bed, so the ejected plastic is more likely to stick to the bed (and/or the front left glass clip). And then maybe do a quick left to right pass on the front of the bed, almost touching, to try and wipe off the head before the print proper starts...

Any ideas or requests?

 

Having now done several prints with this I like the fact that it stays well to the edge of the Bed and remains high, it does mean I can easily remove it if I happen to miss the purge as most of the time the excess has fallen off the bed which rules out the risk of it being dragged onto the print which has happened on previous versions when I didn't quite get there in time. Plus the height does mean its less likely that I will burn my fingers which is always a plus :)

Cheers

 

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I also like the new 14.07 action and agree that the bed should have a good distance to the head when purging. I often get the first bits in a loop so I just quickly yank it down with my fingers before the purge ends. Not sure why the "loop" happens but I have learned to live with it.

 

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what would be good is for a menu option to heat up the head and initiate a purge, rather than have to do this on a print.

do you think this is possible?

 

Do you mean in addition?

Replacing the procedure at the print start with a separate option would have the negative effect of emptying the nozzle due to oozing between purge and print.

 

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yes I mean having this in the menu system on the printer. Last night I had a major clog of the print head so needed to run a print job at high temp for quite a while, just thought it would be good to have the head static and be able to run a purge direct from the printer menu

 

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I saw an UM1 with a square chipped out on the 0,0, so the purge would fall into the frame, in an container, next moving it to the right Z height, wiping of the nozzle towards the startpoint, and drawing a nice line. Very cool design!

 

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I also like the way it is done in 14.07.

But this week I added an Octopi and now (probably because I cannot use UltiGcode anymore) I lost this feature.

Now it gives a blob somewhere on the bed and most of the time the first line is missing because the nozzle is not fully primed.

Is there a way to get this action back by editing the start code?

If so, what do I have to change?

 

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