Extrusion multiplier very low!

Hi,

I am just starting to use Slic3r 0.8.4 with macpronterface for printing with my Reprap Mendel.

My machine is all setup correctly and my E steps per mm is correct (extruding 50mm draws 50mm of PLA into the extruder). I use a 0.5mm nozzle. My PLA measures at 2.94mm - I have entered this into Slic3r.

Slicing the 0.5mm thin walled calibration piece calculates that I should get a 0.53mm wall. I printed this and ended up with a 0.7mm wall. Applying the recommended calibration procedure in Slic3rs documentation suggests I should set my extrusion multiplier to 0.57. When I do this I get a 0.53mm wall which is good, but it seems that my multiplier should not be this low.

Since my E steps is definitely correct I don't really understand what is going on. Is this a problem with Slic3r? Is it even a problem I should be worried about? Or should I just accept it and move on?

Thanks

Andy

Hi Andy,

We had the same problem. We don't know why. We reset out steps per unit and then put the extrusion factor back to 1 and have been printing happily since. Again, really don't know why this number wound up being so far off. It is curious that our number was almost exactly 50% off.

I'm getting the same thing too. Setting multiplier to 0.76 gives me accurate wall width and better prints but all parameters have been calibrated well. Using a j-head by the way.

Anyone work out why yet?

I have had problems with 0.8.4 in that the only way to get the actual extruded width to be the same as what slic3r calculates is to reduce the extrusion multiplier. But then, I found, the print quality is not good. There are two issues (confirmed) in 0.8.4: - Perimeters are placed outside of where they should be by 0.1mm and the actual extrusion width is quite a bit larger than what slic3r thinks it should be so it places outside of where it should be. The upshot is that pegs are about one to one and a half extrusion widths too big and large slots are too small by the same amount.

I raised these issues with the developers and they acknowledged and fixed them.

People who's opinion that I respect say that this is a peculiarity of the J Head but I won't go as far as saying that I disagree but I don't understand why this would be. Reducing your extrusion multiplier will not rectify this problem, even if you set it to 0.

I follow the slic3r development on github closely. I tried out the new flow branch before it was merged to the new gui branch and then into the master. I build and use the master branch now and my parts are all correctly sized and the print quality is very good. As far as I can tell, my extrusion width in a thin wall print is now pretty much as slic3r predicts and I have a unity extrusion multiplier.

So, I'm thinking that all your problems will be fixed by 0.8.5 when it comes out. If you can't wait, follow the wiki instructions on github and build your own master branch. A word of warning though. Your old slic3r config files don't work as the new gui uses two files. They have split the printing and filament settings into two files.

---

Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

Quote

People who's opinion that I respect say that this is a peculiarity of the J Head but I won't go as far as saying that I disagree but I don't understand why this would be.

A hot end cannot effect the the flow rate calculation since all the plastic going in come out, regardless of the nozzle size. Slic3r's maths must be wrong for all hot ends.

J-heads actually have a nozzle size less than stated so that effects slice3r calculation of the best width to use from nozzle size. Basing the width on nozzle size is flawed since it doesn't take into account die swell.

These two major flaws led me to abandon it and return to skienforge.

---

[www.hydraraptor.blogspot.com]

MotoBarsteward Wrote:
-------------------------------------------------------
> I have had problems with 0.8.4 in that the only
> way to get the actual extruded width to be the
> same as what slic3r calculates is to reduce the
> extrusion multiplier. But then, I found, the print
> quality is not good. There are two issues
> (confirmed) in 0.8.4: - Perimeters are placed
> outside of where they should be by 0.1mm and the
> actual extrusion width is quite a bit larger than
> what slic3r thinks it should be so it places
> outside of where it should be.

I've been following the whole slic3r perimeter issue as well as the other thread regarding slic3r and J-Heads. I guess i'm going to have to try out the 0.8.5 ahead of it's release to see if I get any improvement.

What I have done is try to reduce the nozzle diameter in slic3r and check the resulting G-code .The overall volume of plastic extruded is pretty much the same (as expected) regardless of nozzle setting but there are some differences between most segment extrution numbers and some aspects of the print improve with a lower nozzle dia setting.

What I can't understand is the maths of it all. If I have e-steps calibrated accuractely as well as x,y,z and filiament diameter then why do I have to reduce my multiplier to get a print to match what is expected in. There must be something fundamentally wrong where certain setups reveal the problem more than others but it is still there nevertheless.

When leave multiplier @ unity I get decent prints but the two biggest negative effects that i get are:
- Larger wall width resulting in a differerance in outer and inner dimentions greater than the 0.1mm caused by aforementioned issue.
- Build up of pressure that results in more oozing and blobbier perimeters at layer changes and travels.

I can tell that too much plastic is being extruded as the head draggs when moving across previous layer and the extra plastic that is forced down during >80% infill can sometime push out the perimeters on certain print further exacerbating the inaccuracy of the outer/inner dimentions.

I really would like to get to the bottom of this. Hopefully 0.8.5 performs better

Edited 2 time(s). Last edit at 08/03/2012 02:20AM by HaniC.

This is me trying to understand what you are saying, Nophead.

By die swell, are you saying that the plastic density just before the plastic exits the nozzle is higher than just after it exits?

If it's not this then the only other way I can see is that the plastic velocity in the nozzle is higher than just after it exits. I can understand this as there will be friction with the trailing edge of the nozzle as it is stationary with respect to the plastic. However, I would have expected the pulling effect of the bed moving with respect to the nozzle to over come this especially as the rate of pull should be exactly the same as the extrusion rate of the plastic.

Your comment about nozzle diameter being used in calculations is no longer true for 0.8.5dev as Sound says that the only thing nozzle diameter is used for is in controlling bridging. They re-wrote the width calculation and flow rate stuff in the new flow branch before it was merged back to the master with the new GUI stuff.

The proof, for me, is in the parts. Stuff I print is now the correct size, taking into account shrinkage, which I've not got on top of yet, and parts fit together. This all happens with unity extrusion multipllier and saying that the nozzle diameter is what it is.

nophead Wrote:
-------------------------------------------------------
> People who's opinion that I respect say that this
> is a peculiarity of the J Head but I won't go as
> far as saying that I disagree but I don't
> understand why this would be.
>
> A hot end cannot effect the the flow rate
> calculation since all the plastic going in come
> out, regardless of the nozzle size. Slic3r's maths
> must be wrong for all hot ends.
>
> J-heads actually have a nozzle size less than
> stated so that effects slice3r calculation of the
> best width to use from nozzle size. Basing the
> width on nozzle size is flawed since it doesn't
> take into account die swell.
>
> These two major flaws led me to abandon it and
> return to skienforge.

---

Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

MotoBarsteward Wrote:
-------------------------------------------------------
> This is me trying to understand what you are
> saying, Nophead.
>
> By die swell, are you saying that the plastic
> density just before the plastic exits the nozzle
> is higher than just after it exits?

No it simply comes out wider than the nozzle aperture so when deciding what range of extrusion widths you can use it is important. It has no effect on the volumetric calculation but it does affect how much the plastic is stretched.

---

[www.hydraraptor.blogspot.com]

I guess that it has a lot of dependent factors: extrusion speed, hot-end geometry (nozzle length), temperature, ABS quality...

how can we deal with all these parameters? Do we have to make calibration for every case? According to you, what are the mandatory parameter(s) to adjust to calibrate the printing? Skeinforge seems to use width over thickness ratio and extrusion multiplier. Why has the air extrusion diameter been removed?

The more I read stuff about die swell and all related stuffs, the more I'm puzzle... As I have a lot of difficulties to get twice the same results, I think all parameters have to be very precisely tuned, and minor variations can have great effects (

---

Frédéric

With SF you specify the width and layer height so you need to do that with the knowledge of the nozzle diameter and free air extrusion size. The slicer doesn't need to know anything about the extruder as plastic out always equals plastic in.

Slice3r tries to work out the best width from the nozzle size so it would need to know the free air extrusion size.

---

[www.hydraraptor.blogspot.com]

From a theorical point of view, is it possible to have the extrusion width vary a little bit, all other parameters remaining the same (by pushing more or less plastic, at the same feed rate)? How do we determine the limits?

---

Frédéric

Yes, extrusion width is not a function of the nozzle size. The filament is stretched as it leaves the nozzle, the width is a function of the layer height, movement speed and the volume of input filament.
What Slic3r does with the Nozzle diameter is try to determine the "optimal" width for a given layer height. IME it tends to produce very high W/H ratios ( >2.0 )
You can enter the W/H ratio explicitly in Slic3r, but as of 0.7..x (the last version I used) it's still clamped based on the nozzle size.

Ok, I see. Thanks.

---

Frédéric

I am having a similar problem explained more here, but I have to set the extrusion multiplier to .1. I am using a high-torque extruder so I had to set my E-steps to 6400. I wonder if the higher E-steps value is exaggerating the problems others on this thread are experiencing.

stabbs Wrote:
-------------------------------------------------------
> I am having a similar problem explained more here,
> but I have to set the extrusion multiplier to .1.
> I am using a high-torque extruder so I had to set
> my E-steps to 6400. I wonder if the higher
> E-steps value is exaggerating the problems others
> on this thread are experiencing.


Are you using microstepping on your extruder? If so, dialing it down or disabling microstepping completely would reduce the e-step multiplier to something a bit more reasonable, and effectively let you run the extruder faster.


-Rob A>

putting down the steps per mm on the w, makes lees plastic come out, extruder go slower::_?? I am running skeinforge 50 and can´t get the right amount of plastics out always a lot, and to calibrate there is not such thing as extrdue 50 mm on replicator G 040, it justs says amount of seconds to extrude.