Filament Flow Rate Control

Help with printing with specific plastic filaments.
Post Reply
harshabharadwaj
Posts: 6
Joined: Thu Feb 07, 2019 8:30 pm

Filament Flow Rate Control

Post by harshabharadwaj » Thu May 09, 2019 3:49 pm

Hello,

I am currently using a TAZ 4 printer. But, I am not able to find an option in CURA LE for the flow rate control of the filament. Is it at all possible to change the extrusion rate of the filament or is it preset?

If it is indeed preset, where can I check the preset extrusion rate?

Thanks a lot for the help, in advance.

Best Regards,
Harsha Bharadwaj

b-morgan
Posts: 258
Joined: Fri Aug 11, 2017 8:53 am

Re: Filament Flow Rate Control

Post by b-morgan » Fri May 10, 2019 1:45 pm

You didn't mention which version of CuraLE but in 3.6.3 select Print Setup, Custom and type flow in the search box. If you don't see Flow and Initial Flow Rate under material, then from the menu select Settings, Configure setting visibility..., and check the Check all box. See the screenshot below.
CuraLE_Flow.png

JoeBowler300
Posts: 83
Joined: Thu Apr 28, 2016 12:20 am

Re: Filament Flow Rate Control

Post by JoeBowler300 » Sun May 12, 2019 9:33 am

I have a tough time understanding that “Initial Layer Flow Rate”. Should it be set higher or lower then the “Flow” parameter?

User avatar
mwester
Posts: 92
Joined: Sun Nov 26, 2017 8:02 pm

Re: Filament Flow Rate Control

Post by mwester » Sun May 12, 2019 9:58 am

JoeBowler300 wrote:
Sun May 12, 2019 9:33 am
I have a tough time understanding that “Initial Layer Flow Rate”. Should it be set higher or lower then the “Flow” parameter?
Equal to or higher -- I can think of no practical reason to go lower than the normal flow of 100%.

Conceptually, if your printer's e-steps is set perfectly, and your filament diameter is accurately measured and entered into Cura, then your Flow should be 100%.

Conceptually, if your printer's bed is perfectly level, your X and Y axis have no "flex" in them, and your z-offset is set perfectly, then one can argue that setting the "initial Layer Flow Rate" to the same 100% will be correct -- it will extrude just enough filament to perfectly establish that first layer. So primarily, setting that to larger than 100% is intended to 'squash' more filament onto the first layer, making up for variances from perfection.

(That said, if I understand the initial layer settings correctly, that in the case of "perfection" you may find visible lines on the bottom of the object -- In other words, I think that you may need a bit of over-extrusion in order to get that perfectly-flat bottom with minimally-visible lines that some folks are looking for.)

The way I approach the initial layer setting is to first work on the Flow rate -- I prefer to adjust my esteps myself (I don't use the settings on the label on the extruder), and I measure the filament diameter frequently as the roll is consumed. This may or may not make the non-first-layers look great -- I often tweak the extrusion temp and the fan settings to get proper adherence and such. But, once I'm happy with what the layers look like near the middle and top of the object, I'll then focus on the first and close-to-the-bottom layers. For most of my prints, where there's a lot of contact with the bed relative to the object height, I'll go with 100% for the initial layer flow, and just double-check the z-offset. For small objects, I shift the object close to the corner of the bed (eliminates any trouble with the z-axis drooping near the middle to the x-axis). For objects with little contact relative to height, I may adjust the initial flow to 110 or 120 percent -- if the initial layer isn't critical to the object's appearance, or if the object geometry makes it easy to trim off the excess "squeeze-out" on that first layer. If the first layer is important, I've experimented and tried everything I can think of, and in the end even though it feels like a "kludge", I find a raft is the best way to get a perfect first layer of the object while still getting the appropriate bed adherence in the face of imperfections in bed height and level-ness.

So in summery - I'd encourage one to adjust e-steps and measure the filament to get that 100% Flow rate, and then if the first layer can be trimmed, set the initial layer flow a bit higher than normal -- and if that first layer cannot, well, set to 100% if you can and use a raft if the object has trouble staying stuck on the bed.

There's a lot of room for personal preferences here - the above is just my strategy for this! :-)

JoeBowler300
Posts: 83
Joined: Thu Apr 28, 2016 12:20 am

Re: Filament Flow Rate Control

Post by JoeBowler300 » Sun May 12, 2019 1:47 pm

Thank you for your response and theory however from what little research I've done I see quite the opposite is true and it should be set lower than the Flow parameter. The information bubble when you hover over the parameter says that this setting is used to compensate for filament "die swell". A quick Google search says die swell is something along the lines of (paraphrasing here) more filament being extruded due to having to overcome some resistive forces, once overcome more filament is extruded as a result; given everything else being equal. So to counter balance the die swell phenomenon I would think you'd want to go slightly lower.

To obtain better first layer adhesion you could set the "Initial Layer Height" to something more than the "Layer Height", or use a brim or even a raft as you suggested. There's always more than one way to do something though and Increasing the "Initial Layer Flow Rate" would be synonymous to increasing the "Initial Layer Height" IMO.

What you say makes sense if everything were dialed in 100% such as your e-steps and filament diameter then there'd be no need to adjust the flow beyond 100%, well except for that die swell thing. Setting it higher than 100% would compensate for under extrusion if your e-steps were short and would cause over extrusion if your e-steps were too high you would then be pushing more filament.

Given this information it seems difficult to conclude whether to set it higher or lower but is rather a tweak setting to compensate the natural forces of science and get things closer to their intended purpose. From what I read different materials will have different die swell values; that makes sense. So this value should be adjusted on a materials based case and your results of whether you need to adjust upward or downward.

I asked cause my prints (even small ones) seem to have an ever so slight elephant's foot and I saw this setting in Cura. I print mostly PLA & ABS with my print bed not overly hot, 55C for PLA and about 110 for ABS. From print tests and measurements I've concluded that 90% flow is the best value for dimensional accuracy. As for "Initial Layer Flow Rate", adjusting downward seemed to help.

harshabharadwaj
Posts: 6
Joined: Thu Feb 07, 2019 8:30 pm

Re: Filament Flow Rate Control

Post by harshabharadwaj » Fri May 17, 2019 9:31 am

b-morgan wrote:
Fri May 10, 2019 1:45 pm
You didn't mention which version of CuraLE but in 3.6.3 select Print Setup, Custom and type flow in the search box. If you don't see Flow and Initial Flow Rate under material, then from the menu select Settings, Configure setting visibility..., and check the Check all box. See the screenshot below.

CuraLE_Flow.png
Hello thanks a lot for the reply. I can set it in terms of percentage and I can actually go upto 150% without getting an error. But I am not sure if its going to work or not.

But, when I set it to 100% what does it mean in mm/s or whichever appropriate units. Can I get an excat value corresponding to that 100 % ?

I am having problems of solidification in a custom designed nozzle. So, I assumed with a higher flow rate which increases pressure I can reduce the solidification a bit.

Brent.I
Aleph Objects | LulzBot
Posts: 497
Joined: Mon Jan 20, 2014 8:21 am

Re: Filament Flow Rate Control

Post by Brent.I » Fri May 17, 2019 9:45 am

harshabharadwaj wrote:
Fri May 17, 2019 9:31 am
But, when I set it to 100% what does it mean in mm/s or whichever appropriate units. Can I get an excat value corresponding to that 100 % ?
The flow rate percentage will have an affect your set esteps/mm in the firmware. 100% will use the exact number while changing this percentage will use that percentage of the set value.

If you have changed a nozzle, you will want to double check that your Esteps have not been affected by following this guide: https://ohai.lulzbot.com/project/fine-t ... libration/

Post Reply