Flying Extruder Damper

I've had this idea kicking around for a while, and finally got around to building it.

The idea is that it damps the oscillations that can affect a flying extruder. This means that your flying extruder won't wobble around anymore, which means less ringing in your prints.

It's easy and cheap to make, and seems to work quite well.

[www.thingiverse.com]

As one of the delta masters round these parts, what do you think of my plan: attach a spare stepper to the uppers, set it to reflect Z height and basically just reel the extruder up as the print goes. Bowden would only need to be long enough to reach the outer edges from the middle.

I don't know about delta master, but I think your idea would work.

You'd need a bit of compliance in the linkage though, because the distance between the stepper and the extruder will change based on where the print head is on the build plate. You would also need to locate the extruder on the X-Y plane to stop it flopping around on fast changes in direction.

An easier idea is to just use a clockspring, as found in key retractors or tape measures. Note that you still need to locate the extruder in the X-Y plane.


I've been considering using a key retractor to stop the carriages falling down a bit when the steppers turn off. 0.9 degree steppers have a lot less detent torque than 1.8 degree steppers, as I've just discovered!

Edited 1 time(s). Last edit at 01/24/2017 03:47AM by nebbian.

You are certainly a delta master Nebbian, I don't think many people have spent as much time gaining deep knowledge of how to iron out those inaccuracies in this platform as you have. I have been copying/learning from your posts all the way along.

The dampers are an excellent idea, they all say this, but I was just looking into using RC car dampers on my flying extruder, but couldn't find any long enough, when I saw your post here.

I was thinking of elastic - damper - elastic but was concerned this would be no better than just elastic alone.

---

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

I thought the meaning of the flying extruder would be to make the extruder follow the printhead but without the added weight?
Now you want to fix it in XY direction? That would mean you need a longer Bowden tube?!
I'd let it swing and also use the winch to keep the tube short. Maybe add a damper ( or 3? ) to make it perfect.

The clockspring is a nice printer project btw...

Edited 1 time(s). Last edit at 01/24/2017 02:14PM by o_lampe.

Quote
o_lampe
I thought the meaning of the flying extruder would be to make the extruder follow the printhead but without the added weight?
Now you want to fix it in XY direction? That would mean you need a longer Bowden tube?!
I'd let it swing and also use the winch to keep the tube short. Maybe add a damper ( or 3? ) to make it perfect.

The clockspring is a nice printer project btw...

A longer bowden tube... well my bowden is about 6 cm long, how much shorter do you want to go???



A flying extruder should follow the printhead, but it doesn't have to actually move, only rotate to point the outlet at the head. If it moves to follow the printhead, then you're back to square one, because the printhead is dragging around a heavy weight, and trying to stop it when it overshoots (which causes ringing in the prints).

I think we're on the same page though, by 'locating' I just meant to use a damper of some sort to stop it flopping around and banging into everything. Which it will do if it's not located in some way. In the end we still come back to the flying extruder design.

@nebbian
Your extruder is hanging below COG. That makes it harder for the effector to " point the outlet" to the hotend.
Have you considered using a stepper bracket where the springs are attached closer to COG?

Centre of gravity of what? (loaded question)

Moving the attachment points down, (which moves the stepper up), makes the bowden longer. Note that the bowden plays a role in tilting the extruder as well.

It's printing very nicely at the moment

Quote

Moving the attachment points down, (which moves the stepper up), makes the bowden longer.

What about longer springs?
With COG I meant the COG of the flying extruder. Have you seen my "swinging extruders"? The tubes are longer, but there is almost no force or side load on the hotend/effector.

I've seen prints of you and they are superb!
But right now there is more "dragging" force than necessary.

Hmm. Interesting point. I might be able to turn the attachment points on the extruder mount upside down, that would move the point down by 15mm or so.

I've seen your swinging extruder, it looks nice. I'm keen to keep the bowden as short as physically possible, however.


I think a lot of people get hung up on "weight on the effector", without considering that it's actually "coupled mass", not "weight" that's the issue. Tilting an extruder to follow the effector doesn't take much energy. Physically accelerating that extruder, however, takes a lot of energy, even if the extruder is fully supported with a cable to the top of the frame.

I've recently lifted my flying extruder so it's a bit higher. The bowden is longer but only 17cm, but the extruder mass has less of a bearing on the effector acceleration. Oddly the slightly longer bowden tube doesn't seem to have a detrimental effect on the filament control.

I wonder if anyone's done any relatively scientific testing on effect of length of bowden tube on filament control, perhaps the effect is not as linear as I'm inclined to presume it is.

---

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

The negative effect of the tube length can't be linear:
#1 The longer the tube, the more room for the filament to compress.
#2 Longer tube has more friction, that's a factor to the compression problem.
#3 More compression means longer retractions and adds ooze-time.

Quote
o_lampe
The negative effect of the tube length can't be linear:
#1 The longer the tube, the more room for the filament to compress.
#2 Longer tube has more friction, that's a factor to the compression problem.
#3 More compression means longer retractions and adds ooze-time.

That's all true, but:

#1 can be mitigated by using 1.8mm ID tube instead of 2.0mm. This might increase friction too much for a long, curved Bowden tube, but should be OK for a relatively short straight Bowden tube.

#2 I doubt is a significant issue with a short straight Bowden tube.

#3 can be mitigated by using pressure advance. When necessary, pressure advance will start retracting before end of the extruding move.

Edited 1 time(s). Last edit at 01/25/2017 12:15PM by dc42.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

So would you say David you can tune a bowden to beat/equal the print quality of a direct extruder such as a titan?

---

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Quote
DjDemonD
So would you say David you can tune a bowden to beat/equal the print quality of a direct extruder such as a titan?

Although I get acceptable print quality with my 600mm Bowden, I doubt that I could match the print quality of a direct extruder. What I am saying is that I don't think a short straight Bowden tube need be a significant handicap if it is set up correctly, and if it helps to decouple mass from the print head, it may give better results than a heavier print head and no Bowden tube at all.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Im running counterweights over bearings on the top of each tower, that almost completely decouples all extruder swinging from the frame and also removes any swinging influence from the carriages.

Quote
dc42

Quote
DjDemonD
So would you say David you can tune a bowden to beat/equal the print quality of a direct extruder such as a titan?

Although I get acceptable print quality with my 600mm Bowden, I doubt that I could match the print quality of a direct extruder. What I am saying is that I don't think a short straight Bowden tube need be a significant handicap if it is set up correctly, and if it helps to decouple mass from the print head, it may give better results than a heavier print head and no Bowden tube at all.

Agree entirely, my flying setup has a 17cm bowden tube but it makes little difference as its mainly straight and short. I think I was merely pointing out that its a noticeable improvement over my 60cm bowden I had originally on my mini kossel, which was a big improvement over the 80cm one I had when I bought it (top mounted extruder, moved to mid way up one of the verticals). It just seems that the effect of shortening a bowden tube is not linear in the gain you make. I wonder if anyone has scientifically tested bowden tube lengths, to determine at what point it makes no difference shortening it. I suspect 10cm or less is probably indistinguishable from direct, but that's only experience/intuition and I know how wrong that can often be.

---

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Quote
dc42

#1 can be mitigated by using 1.8mm ID tube instead of 2.0mm. This might increase friction too much for a long, curved Bowden tube, but should be OK for a relatively short straight Bowden tube.

Have you actually used 1.8 diameter tube? It's a pain. When you change filament, the plug at the end of the filament is 2mm wide, and sticks hard to the sides of the tube. I have 5m of 1.8mm diameter tube in my junk box, marked "BAD". I'm never using it again.

Quote
dc42

#3 can be mitigated by using pressure advance. When necessary, pressure advance will start retracting before end of the extruding move.

Have you tried printing a flexible filament such as TPE with a long bowden tube? Let me know how you go with that

Quote
nebbian

Quote
dc42

#1 can be mitigated by using 1.8mm ID tube instead of 2.0mm. This might increase friction too much for a long, curved Bowden tube, but should be OK for a relatively short straight Bowden tube.

Have you actually used 1.8 diameter tube? It's a pain. When you change filament, the plug at the end of the filament is 2mm wide, and sticks hard to the sides of the tube. I have 5m of 1.8mm diameter tube in my junk box, marked "BAD". I'm never using it again.

I have that problem with 2mm tube and a genuine E3D hot end already. On that machine I always change filament by flushing the old filament through with the new.

Quote
nebbian

Quote
dc42

#3 can be mitigated by using pressure advance. When necessary, pressure advance will start retracting before end of the extruding move.

Have you tried printing a flexible filament such as TPE with a long bowden tube? Let me know how you go with that

I'm not advocating a long Bowden tube, I'm saying that a short straight one shouldn't be a problem,

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

im with DC42 on this, I also have a 600mm bowden and I dont feel the need to do flying extruder and sacrifice my speed...I dont even use the pressure advance ( Did not quite catch how its working in RRF or how to active/tune it) and my retraction are pretty good using s3d and guess what a e3d clone I rework. I dont even Wipe , I have little coast at the end like .25 and thats it.

I tried many brand filament and I have to say the quality of filament is a important factor in this, the retraction on the colorfabb pla/pha or ngen is way better than some regular Esun and need less tuning or even no tuning, I trierd pla + esun its not as bad as regular one but not as good as colorfabb. my unknow brand cheap roll is almost not usable I have the tune the crap out of it to get a good but not great quality.

Last week I even tried TPE filament and its was a success with the first print, even without heatbed, I print them slower off course near 25mm/sec infill (recommended speed), little bit less on last perimeter on 3000 accel. The only mod I did was to put a V cut on my bowden tube and put it closer to my extruder drive to avoid the filament getting kink and jam before entering the bowden.

Ill touch some wood but in 10 month of printing I never had any jam even if the bowden because the longer retraction are more prone to that, it never happen so far.


Dont fix whats not broken

here a sample : There a HTC vice lense protector and some square I use to do calibration of flow. Its a unknow TPE fillament I brought at digitmaker.com last month.

Nice prints GroupB! You're doing well to get that sort of speed out of TPE, especially with a 600mm bowden.

The issue (as of course I'm sure you're aware) is that on extrusion speed changes, you get a drawn out blob when slowing down, and a drawn out underextrusion on extrusion speed increases. This can be mitigated somewhat by keeping all speeds/extrusion widths the same, but this is difficult when bridging unless you're very aware of what's going on.

Those are nice prints. Maybe its better to say the flying extruder will improve upon almost all (long) bowden tube setups and is easy to tune to achieve high quality prints, but with sufficient skill and patience a long bowden tube setup can deliver high quality prints also.

For me I was getting nowhere near acceptable print quality with a long bowden tube but with a flying setup, without any effort, I could match a direct extruder easily. Clearly things like pressure advance and coast and other software enhancements will help to compensate for the bowden tube's limitations.

Proper closed loop control of actual filament extruded would be the ultimate enhancement. Still don't know how this can be done.

Edited 1 time(s). Last edit at 01/31/2017 03:59AM by DjDemonD.

---

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Quote
nebbian
Nice prints GroupB! You're doing well to get that sort of speed out of TPE, especially with a 600mm bowden.

The issue (as of course I'm sure you're aware) is that on extrusion speed changes, you get a drawn out blob when slowing down, and a drawn out underextrusion on extrusion speed increases. This can be mitigated somewhat by keeping all speeds/extrusion widths the same, but this is difficult when bridging unless you're very aware of what's going on.

That is precisely what pressure advance is designed to mitigate. But of course it's not perfect.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

dc42 do you have a post somewhere that explain pressure advance and to enable/tune it ? I guess you have to tell RRF the nozzle size etc instead of using only s3d to control that.

I've created a placeholder page for pressure advance on the Duet3D wiki and I'll try to find time to populate it later today. You don't need to tell RRF the nozzle size, just the amount of pressure advance you want. For example, M572 D0 S0.1 sets the pressure advance for extruder drive 0 to 0.1 seconds. The optimum value depends on the length of the Bowden tube, but it is rarely higher than 0.2. Setting high values may restrict printing acceleration depending on your extruder jerk setting, because pressure advance causes extruder jerk.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Is pressure advance also dependant on the type of material used? ie would you have a different value for PLA vs TPE?

Quote
nebbian
Is pressure advance also dependant on the type of material used? ie would you have a different value for PLA vs TPE?

Quite possibly. I've never tried printing with TPE, so I can't say. I was assuming that flexible filaments wouldn't print well with my 600mm Bowden tube until I saw GroupB's post earlier in this thread.

Edited 1 time(s). Last edit at 02/02/2017 04:30AM by dc42.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I dont blame you DC42 I assume the same and never try it before this last month where I saw some half price, then I had to try it, I was ready to move to direct extruder temporary for a project im doing that will require some tpe but It was a very nice surprise to see I was able to do it good enough with the bowden. Off course the part require some cleaning , Im still tuning the retract to avoid that much cleaning but other than small blob not really stick to the side and easy to remove because of my fast travel and spider web it was good enough.


that the filament I used T-FLEX maybe its a little harder than ninja flex and that why it print better ... I dont know. Ninja flex was too pricey for a first time trying TPE.

BTW pressure advance working on old 1.13 firmware right ? Im on radds so I have a old firmware.

Quote

BTW pressure advance working on old 1.13 firmware right ? Im on radds so I have a old firmware.

You know David was kind enough to put V1.17 for RADDS to his github page? They are untested, but I found them stable so far. ( might have to use the bossac-method to upgrade )

Quote
GroupB
I dont blame you DC42 I assume the same and never try it before this last month where I saw some half price, then I had to try it, I was ready to move to direct extruder temporary for a project im doing that will require some tpe but It was a very nice surprise to see I was able to do it good enough with the bowden. Off course the part require some cleaning , Im still tuning the retract to avoid that much cleaning but other than small blob not really stick to the side and easy to remove because of my fast travel and spider web it was good enough.


that the filament I used T-FLEX maybe its a little harder than ninja flex and that why it print better ... I dont know. Ninja flex was too pricey for a first time trying TPE.

BTW pressure advance working on old 1.13 firmware right ? Im on radds so I have a old firmware.

Thanks for the recommendation.

There have been a few teaks and bug fixes to pressure advance, so I recommend you upgrade to 1.17d.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].