Effector Weight and Precision

I've been following many of the threads here for some time and have decided to start my new delta printer build. While I know this topic has been discussed other threads and there is postings on the wiki, I still have a couple questions related to my project about effector weight and extruder options. I'm working on a larger delta using 875mm linear rails and around a 300mm build plate diameter. The construction will be mostly if not all metal and I am planning to use Igus rod ends. My priority for the printer is print quality over speed. I am very happy for a print to take twice or three times a long since I am not printing for production volume. While designing it I am trying to figure out which extruded setup I want to go with. Right now here is what I am looking at:

Bowden with a heavier extruder (maybe a Bondtech or Bulldog XL). I'm concerned about issues related to retraction due to the z axis height and required Bowden tube length. It seems Kuhling and Kuhling was having issues with this according to Tom (https://youtu.be/v6v65UxDRiI) and went to direct.

Direct extruder mounted on the effector with a light extruder (E3D Titan with pancake motor).

My questions are:

Would retraction be a significant issue with Bowden for this size of printer?
Some have mentioned additional wear due to direct extruder extra weight on the effector? How significant is this?
Would the E3D Titan be a good choice for direct mount? It seems some like other light weight extruders such as the PG35L.
How much weight makes a significant different in effector stability? 5g, 10g, 50g? I know this will depend on arm spacing, etc. but is there a general guideline?

My delta has 1m high verticals and 300mm build diameter, so I guess it is about the same size as your build. I use a Bowden extruder with the extruder drive mounted about half way up one of the verticals. The Bowden tube is 650mm long, which isn't ideal but I find it manageable.Retraction is about 6mm to avoid blobs. Using extruder pressure advance in the firmware helps with print quality. See link in my signature for more details of my build.

Another option you haven't mentioned (and I haven't tried yet) is a flying extruder.

Edited 1 time(s). Last edit at 07/29/2016 12:15PM by dc42.

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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].

The wear on the effector and rods mainly depends on the acceleration values. Since you accept to print slow, you can try direct drive.
I'm building one right now and find it difficult to use the whole width of my bed, because the pancake/cycloid gear extruder collides with the rods at some points.

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o_lampe
The wear on the effector and rods mainly depends on the acceleration values. Since you accept to print slow, you can try direct drive.
I'm building one right now and find it difficult to use the whole width of my bed, because the pancake/cycloid gear extruder collides with the rods at some points.

Here is what I am working on for a Titan effector. Based on 3d modeling, a pancake should clear the rods but it will be sometime before I can test it. Have you been able to print with yours?

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dc42
My delta has 1m high verticals and 300mm build diameter, so I guess it is about the same size as your build. I use a Bowden extruder with the extruder drive mounted about half way up one of the verticals. The Bowden tube is 650mm long, which isn't ideal but I find it manageable.Retraction is about 6mm to avoid blobs. Using extruder pressure advance in the firmware helps with print quality. See link in my signature for more details of my build.

Another option you haven't mentioned (and I haven't tried yet) is a flying extruder.

I think I have ready your entire build/blog. Great stuff! I will also be using an E3D V6 hot end and I noticed you mentioned only 2 mm of retraction is needed, that doesn't seem too bad. Have you had any issues with the 3:1 extruder?

I didn't mention a flying extruder because I think it adds a bit more complexity than I want to deal with right off the bat. Also, I am not sure if I trust the extruder just bouncing around all the time. I might try it eventually though.

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Kewdtz
Have you been able to print with yours?

Yes, it prints well, but I'm still testing how I can retract faster. The output shaft started slipping until I got milled an aluminum dowel pin holder.
Now I'm at 60mm/s retraction and still testing...

Also I had to reduce the outer radius of the bed levelling gcode to avoid rod-collision with the stepper at certain points..

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o_lampe

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Kewdtz
Have you been able to print with yours?

Yes, it prints well, but I'm still testing how I can retract faster. The output shaft started slipping until I got milled an aluminum dowel pin holder.
Now I'm at 60mm/s retraction and still testing...

Also I had to reduce the outer radius of the bed levelling gcode to avoid rod-collision with the stepper at certain points..

That is pretty impressive. I am attempting to print the 1.75 mm v0.3 version now. I am not sure if I will be able to achieve the tolerances needed, however, our local makerspace just picked up a Tormach CNC mill so I may be able to mill my own parts too. Hope your testing goes well.

Alternate solution would be to use a very lightweight extruder with a remote stepper, like the Zesty Nimble.
(full disclosure, see the signature. :-) )

This allows you to use a direct drive extruder with no weight penalty. The Nimble weighs around 33 grams.
It also allows you to easily print flexible materials like NinjaFlex. That is something a long bowden setup struggles with.
Finally, because it is designed that way, you can flip it over and add a second one next to it, if you want dual hot ends. How close you can get the 2 hot ends together depends more on the hot ends than on the extruder.

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Lykle
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Co-creator of the Zesty Nimble, worlds lightest Direct Drive extruder.
[zesty.tech]

@Lykle
Would two of them fit on an E3D-Chimera? (not sure what the filament inlet distance is from them ?)

@Lykle

It looks like an interesting design and a good potential option. I noticed you are planning to launch a crowd funding campaign to cover mold costs, how long do you think it will be before the extruder is available?

My only concern about the Nimble is the apparently direct driven extruder gear. The flexible shaft must be huge (and stiff/heavy ) compared to the Flex3Drive?
The flex shaft is shown nowhere on the website. ( I didn't sign in to see more details )

Hi guys,

Yes it uses a flexible shaft, so it is light and not stiff.

2 will fit on a Chimera, yes.

We are working on the price as we speak, but it is tricky. Taxes, import duties, shipping, it all matters.

Lykle

Flying extruder isn't that complex and if you use a titan with 20mm stepper its 250g of which only pure z lift moves actually have to deal with the increased inertia. The extruder bouncing around is no problem, just make sure you have a little downward pull from the bowden tube.

The improvement in print quality is marked. Just try a 80cm bowden versus a 10cm one. I accept you can tune a bowden to a good degree but unless the bowden tube is frictionless and the filament fits perfectly within it, and is not flexible itself you will only beat flying extruders with flexible drives or direct drives.

Consider the titan with small motor (for 1.75mm) as a direct drive, it's reasonably cheap, light and reliable.

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Simon Khoury

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