Super hard nozzles - Test pilots

Discussions concerning the Ultimaker 2 / Ultimaker 2+ series of printers, including the Ultimaker 2 Go
Anders Olsson
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Re: Super hard nozzles - Test pilots

Post by Anders Olsson » February 20th, 2016, 5:03 pm

Thanks a lot of that very comprehensive report Neotko! :)

It wasn't until recently that I also got a feeling for this e-steps related underextrusion that becomes very visible with the ruby.
That explains why printed things always ends up quite much lighter than they were supposed to be, which actually has been a big question mark for us when we try write scientific articles on 3D-printing.
When you for example print neutron shielding and your objects always ends up 10% lighter than the theoretical weight, people start asking questions.. :-?

I am considering to order the next batch of rubies with slightly larger shoulder to make them more forgiving, but at the same time I hesitate to trade overhang quality for better top layers, as the problems with the top layers are not really caused by the ruby, but by lack of precision/calibration in the Ultimaker feeding.

Here is an example of what an UM2 can do with 1.75 mm filament, the direct feeder and a ruby nozzle (printing slow of course and with PID-bed temp control):
2015-09-28-6263.jpg
My main issue is if I want to aim the ruby nozzles towards the Ultimaker machines with their lack of feeding precision, or towards printers with higher precision direct feeders and 1.75 mm filament. (Or sell them together with a 1.75 mm Olsson block kit and a direct feeder kit maybe :) )

Regarding the E3D hardened nozzle, I did some comparisons and thought I had photos, but I can not find them right now.
Anyway, the performance on overhangs was worse with the hardened E3D nozzle than with normal brass nozzles in the tests I did.

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Neotko
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Re: Super hard nozzles - Test pilots

Post by Neotko » February 20th, 2016, 5:49 pm

Thanks :D btw that print looks gorgeous :O

The other factor that worries me it's that if the printed object has more than 12 movements per second then the um board (marlin & old chip atmega) stop to continue. That was something that I saw when printing complex curves (s3d allows you to adjust the level of simplification of the stl) so when doing long oval areas, to make them really look smooth, I did had troubles because the speed fluctuated. Ofc in the end I just found the middle point where the curves looks good enough but since the software (any atm) can't tell you how many movements it does per second (or better put gcode instructions) then there's no way to control that. And why would you want to control that, print quality. Why? Because then the processor stops to read the next 12 steps and set them in memory, if the speed it's high, it causes feeder speed changes, blops, underextrusion (because preassure through bowden want to find an exit) then when the instruction it's processed the cpu doesn't compensate for the time lost). And the sollution it's quite hard and easy, other printing cpu with more power like Smoothieboard or replicape but the problem it's that there's no other board (atm) that allows to use pt100 without having programming or electrical knowhow...

Anyway back to the topic. :D

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Izzy
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Re: Super hard nozzles - Test pilots

Post by Izzy » February 20th, 2016, 5:53 pm

Cheers Neotko, I run a UM2 and like your photos I was not satisfied with some of my top layers with what looked like under extrusion, I spent a little time printing a flat sheet and just playing with the extrusion percentage, and came to the conclusion that increasing it to approx 115% gave me good coverage with good connection between passes and at the end of each pass.
I was thinking that I had poor bed levelling, or a slightly warped plate, or slightly blocked nozzle...
I now print my first level at 120%, and reduce it to 112%-115% on the second level checking it to see how it's looking. This e-steps probably explaines it, I was wondering if anybody was done an idiots guide to working it out and if it can be corrected EASILY into the settings or do we just up the extrusion rate percentage.
Nice prints by the way guys, I like the UM robot as a test piece it has some nice features for testing, and looks great when you have an army of them in different colours and materials. When I get round to testing the 0.8 or 1.0mm nozzle I'm going to print one to the UM2 height limits and try it as a garden gnome, I've tried the 0.25mm at 1/2 scale of the origional (17mm high) and when I have time I want to try my 0.15mm nozzle and print one at 8mm high, at least that one could use Laberns drill :lol:
Izzy.

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Neotko
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Re: Super hard nozzles - Test pilots

Post by Neotko » February 20th, 2016, 7:20 pm

Well izzy, on that week that I did expend doing the esteps of mineI found out a couple of thinks.

a) There's no perfect calibration system.
b) Bowden adds a very hard factor to control.
c) There are almost 5 different aystems to calibrate and noone really has a perfect 'recipe'.

I did some google to check academic info about how to calculate the preassure inside the extrusion area + bowden, length, etc. I did find some info related to plastic industry and heavy metals but the math it's quite complex. Specially when the amount of preassure changes with heat and kind of material.

Many guides say that you must do the estep math and then adjust accordingly. I did that and now I have 2 machines that print almost almost the same. Ofc there's a point where it's 'ok' but what's really 'ok' for one print won't work for other kinds of prints.

Anders I think that, since probably ruby nozzle won't be cheap (its a ruby!) I personally think that precision it's more important than a blurred print. Specially when with software adjustments these are factors that can be controlled.

Also for example the bondtech feeder, with its masive torque could be somethings that could help, since if the feeder can stabilize the preassure needed with brute force it might not affect that much (could be nice if you find someone with that feeder). Um2+ gear feedersure has enough torque also, but I don't think that it can be better than a proper planetary geared nema with double gear gripping the filament without 'deforming' it. Directfeeder with 1.75 I think could be a really amazing combo for users that actually want precision (and flexible material retraction, and be able to use that extra 60cm of filament :D ). But for 3mm I think that a geared feeder or a bondtech one, it's (for general purposes) a must have. I also want to add a geared feeder for my 1.75 um2 motor, just because I want to have enough torque so it remains as constant as posible, and my plan it's to use a double mk7, like if it where a cheap bondtech feeder.

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ivan.akapulko
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Re: Super hard nozzles - Test pilots

Post by ivan.akapulko » February 21st, 2016, 3:37 am

It looks almost perfect!! excellent quality of connection lines, which I have not seen before! Its amazing work, Anders! And Neotko too, of course! ;-)

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Amedee
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Re: Super hard nozzles - Test pilots

Post by Amedee » February 21st, 2016, 3:48 am

@neotko I just read you post, and I brought another theory to my mind...

When you print a big flat surface (so continuous print velocity, no retraction, ...) the Bowden does not play a role.
I do agree that there is some play in the tube, but when you push at a continuous pace, once the play has been 'absobed' then what you push in gets out at the same pace. Bowden has a role of buffer, but once it is full it is like direct extrusion.

So if you push 100% in the tube, you get 100% out ;)

So where are we loosing 10% then?
My take is that the 10% accounts for average slippage on the bolt due to the pressure.
When you extrude 'on the test bench' without Bowden: there is no pressure and 100% rotation translated in 100% displacement.
When you extrude through the Bowden and the hot-end the pressure induce some minimal slippage and 100% rotation in translated in 90-95% displacement.

For 1.75mm you need less pressure so there is less slippage so you need less compensation.

Just my thoughts on this...
Phil.

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Neotko
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Re: Super hard nozzles - Test pilots

Post by Neotko » February 21st, 2016, 3:56 am

The 10%, read the link, it's about the source of the esteps vs the math to calculate them. Umo\umo+ firmware uses 760 * 1.1 on the firmware (math * 10%). If you check the 8mm knurted bolt, add the gears, check the nema, etc and pop the math number you get 760ish, to that ultimaker adds a 'magic 10%'. Also on um2 8mm bolt, if you check the math you get that they add a 10% to the actual math calculations.

What I mean that I was getting cracks it's that I actually had my estep wrong at the time of the first test, but also e3d blurs that and hides it, ruby shows it all. After I found out the missing factor to my estep calibration the prints went back to perfect with ruby.

Also with flat layers are higher speeds than yerk, there a change of speed on the flow so it doesytemain constant unless you could use yerk at the same print speed.

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Neotko
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Re: Super hard nozzles - Test pilots

Post by Neotko » February 21st, 2016, 3:58 am

Also that reminds me that if you set aceleration too low, small infills fail, but you get less vibrations, at high speed aceleration small top layers look better because there's less changes in print flow.

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Neotko
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Re: Super hard nozzles - Test pilots

Post by Neotko » February 21st, 2016, 4:00 am

Oh and yes I agree! The preassure/slippery and room for the filament to expand it's less, but if you do measure the filament moved at a x speed and change the heat, then you get different filament moved. So it's quite a mess to calibrate.

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Amedee
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Re: Super hard nozzles - Test pilots

Post by Amedee » February 21st, 2016, 4:32 am

Yes, that just go along with my theory on slippage on the bolt: Higher speed, more pressure, more slippage, Higher temp, less pressure, less slippage.

Bowden induces another problem which is the buffering of the pressure -- everybody knows now that if you don't manually prime your UMO before start you wont get adherence because you will massively under extrude at start (this is particularly visible on blue tape, heated bed tend to correct that). So indeed, any change in print flow is delayed by the Bowden system...
Phil.

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Re: Super hard nozzles - Test pilots

Post by Meduza » February 21st, 2016, 6:44 am

I have been thinking about adding a encoder on top of the feeder and graph commanded position vs feeded position, to see how much slippage the higher pressures really add.

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Neotko
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Re: Super hard nozzles - Test pilots

Post by Neotko » February 21st, 2016, 7:30 am

With that it could be posible to run calibration according to each temp/speed and generate profiles for the esteps on each case. I would love an encoder actually controlling the real amount of filament move.

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Re: Super hard nozzles - Test pilots

Post by Meduza » February 21st, 2016, 8:16 am

I belive that could make a large difference, even if it only is one part of the whole process to get control of, the next step is to add a second encoder after the bowden tube to map the impact the bowden tube has, and after that it is time to start calculating pressures in the nozzle and making it pressure controlled rather than distance controlled extrusion.

johan
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Re: Super hard nozzles - Test pilots

Post by johan » February 21st, 2016, 12:22 pm

This discussion has gone of topic. Regardless of the setup there is only one way of actually feeding the right amount of filament and that is called feedback. I suggest any further discussions on esteps/extrusion multiplier should move to a separate topic :).

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LePaul
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Re: Super hard nozzles - Test pilots

Post by LePaul » February 21st, 2016, 12:29 pm

We do sort of wander around, don't we? Feel free to kick off such a topic!

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