ABS + HIPS dual extrusion layer height problem

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sunraise
Posts: 7
Joined: Mon Aug 14, 2017 8:01 am

ABS + HIPS dual extrusion layer height problem

Postby sunraise » Mon Aug 14, 2017 9:41 am

Hi guys,

I bought my N2 Plus couple of weeks ago, but I am still having issues with dual printing.

After two weeks of calibrating of the plate and the two heads, I found out, that the problem is in the diameter of the extruded filament.

Diameter of the ABS thats printed from the left nozzle is roughly 0.5mm
However, the HIPS printed form the right nozzle is around 0.66
(idle head hovering over platform, extruding into the air)

When i take the ABS and stuff it into the right extruder, I am getting the same 0.5mm as from the left extruder.

My prints are coming out really nasty, as the first layers, where raft and support meet the abs, are grinded together beacuse of their incompatible heights, and the higher this happens, the bigger problem it causes, taking 4-5 layers before the print looks any good.

I am wondering what is the correct extrusion diameter, and how to reach it, as the only way I was able to extrude in the same width is to use the "Tune" section on the display and set the right nozzle flow rate to 20%. However, I cannot simply set this in the Ideamaker - does not allow to set flow rate for raft, only for support (trying to print it right now).

Also, there are several filament profiles to choose from, two of them are named "... V2 Hot End" not sure if I am supposed to choose these two ? There are no print profiles under them :/

Any hints appreciated...

Jetguy
Posts: 1793
Joined: Tue Mar 22, 2016 1:40 am

Re: ABS + HIPS dual extrusion layer height problem

Postby Jetguy » Mon Aug 14, 2017 2:07 pm

Diameter of the ABS thats printed from the left nozzle is roughly 0.5mm
However, the HIPS printed form the right nozzle is around 0.66
(idle head hovering over platform, extruding into the air)

It's called die swell and is not really a factor in your problem. This is material specific factor because the very chains of the plastic polymer to not untangle at high extrusion speeds. So plastic does not act like a pure liquid and takes on "plastic properties" one of them being die swell, the plastic flowing out of nozzle expands in diameter some percentage of original raw unmelted diameter. This is again because the polymer chain "remembers" the shape and size. As you slow down extrusion to realistic printing rates, the filament is heated longer and slower and has more time to untangle the polymer chains and thus reduces real world die swell.
As a fact, loading speed of extrusion is nearly 3 times even some of the fastest infill rates in a typical print.

Remember, you print at 1/2 to 3/4 nozzle diameter as layer height to intentionally smash this round extrusion oval to stick to the previous layer and squish and bond to side by side adjacent infill layers.

It's more likely that your problem is one of 2 areas
#1 Your filament on the spool diameter effects the output volume so do the exact measured with calipers diameter of the ABS VS hips match?
#2 your nozzle leveling ALSO has significant effect on dual extrusion layer height.

Jetguy
Posts: 1793
Joined: Tue Mar 22, 2016 1:40 am

Re: ABS + HIPS dual extrusion layer height problem

Postby Jetguy » Mon Aug 14, 2017 2:13 pm

Again, the rule is for best dual extrusion results- simply don't
I know that seems like a contradictory answer but no- really listen, if you are new to 3D printing- use dual extrusion as a LAST RESORT.

If you have to dual extrusion, it is going to be messy- hence the above guidance.
You have to perform best case scenario usage.
Use 2 well matched materials that are nearly the exact same material diameter feeding into the extruder- not exiting the extruder.
Why? Because as you see now, the Marlin firmware stock does NOT allow for different rates.
Further- back to a long standing suggestion about how Ideamaker works- flowrate should be a modifier and change the gcode lengths, NOT post a command in the gcode telling the firmware to change the lengths.
Obviously, the nozzle leveling must be perfect- that's hard for people even with experience to tune and we have threads for days about this.
Wipe walls only go so far and the 25mm spacing of nozzles in X will cause the unused nozzle to cross over into the print. There is no magic fix here.

Jetguy
Posts: 1793
Joined: Tue Mar 22, 2016 1:40 am

Re: ABS + HIPS dual extrusion layer height problem

Postby Jetguy » Mon Aug 14, 2017 2:24 pm

Also, about profiles.
There is nothing trick about V2 profiles. I avoid them. The only difference was the default temp was lowered by about 10C from non-v2 profiles.

Again, more likely than not, you are facing PHYSICAL factors and adjustments NOT SOFTWARE.
You focused time and effort on a factor you should not be measuring or adjusting for (die swell of open fast extrusion).
You found limitations of the overall software and system architecture- limits to specify firmware based flowrate multipliers independent for nozzles left and right.

Tips to dual extrude:
#1 adjust an relevel the nozzles to exact matching height and then readjust the bed leveling and Z gap. It must be done in that order. Leveling the nozzles results in a slightly higher or lower combined nozzle height- so that's why you level nozzles first, then level the bed, then adjust Z gap.
#2 Measure filament diameter at your spools. Know them and mark them on filaments. Due to limitations, attempt to use well matched filament diameter. Again, since the stock ideamaker has limits here, you have to limit the physical variables as best as possible.
#3 consider using an alternate slicer software that does allow individual filament diameter and flowrates and those values manipulate the gcode extrusion lengths VS telling the firmware to modify it on the fly using flowrate commands.


Jetguy
Posts: 1793
Joined: Tue Mar 22, 2016 1:40 am

Re: ABS + HIPS dual extrusion layer height problem

Postby Jetguy » Mon Aug 14, 2017 2:42 pm

Also, just basic 3D printing tips that apply to single or dual extrusion.
#1 Proper initial first layer G-gap and overall bed leveling are the single biggest key to successful printing.
#2 By getting the gap right, you should not ever use rafts. Rafts are the "training wheels" way of giving a cushion to improper Z gap and leveling. It wastes time and material and is never as high quality as a properly setup print on the direct bed surface.
#3 If you need more adhesion for specific print, use brim rather than raft. Brim still makes a defect in the model edge but is far less invasive than full blown raft.
#4 clean the bed with alcohol to remove fingerprint oils and dirt and dust for maximum adhesion.

sunraise
Posts: 7
Joined: Mon Aug 14, 2017 8:01 am

Re: ABS + HIPS dual extrusion layer height problem

Postby sunraise » Mon Aug 14, 2017 3:11 pm

Hi Jetguy,

I sincerely hope you copied the answers, as thats quie a lot of text in such a short amount of time !

I releveled the bed about 10 times, cannot count how many times i releveled the heads.

I Started with the heads leveled to the exact same height ( .. well, the best i could) but the right nozzle was hitting the prints and kicking it off the bed. I asked the Raise3D via email, and Vicky replied that it is better to have one of the heads a bit higher, so I spent dozens of hours trying to figure out the best height difference, but without any luck.
I am using a solid block of aluminium and gauge sheets (10,15,20) for the measurements, but as I wrote earlier, no luck there. Thats why I thought that the HIPS height could be the problem.

I'll be getting new ABS spool tomorrow, (as I runned out during the testing) will recalibrate the heads, then the bed using the dial and document the results thoroughly as to the height difference between nozzles..

Thanks for your help

Michael

sunraise
Posts: 7
Joined: Mon Aug 14, 2017 8:01 am

Re: ABS + HIPS dual extrusion layer height problem

Postby sunraise » Mon Aug 14, 2017 3:13 pm

Also - I wanted to use Cura, or Kiss slicer, which were both working fine with previous printers, found some profiles for the printer in the forums, but the results were crazy.
Would be nice if Raise3D shared the required settings so we could use it properly.


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