Page 1 of 2

Zesty Nimble extruder technical thread

Posted: Sat Oct 29, 2016 8:33 am
by mhackney
I'm starting this thread for technical discussions around the recently announced Kickstarter for the Zesty Nimble. My original announcement thread is here.

One question I have off the top - what should we call this class of extruders? Something like "remote direct drive"?

Re: Zesty Nimble extruder technical thread

Posted: Sat Oct 29, 2016 9:04 am
by Qdeathstar
What makes it different from the flex3drive?

Re: Zesty Nimble extruder technical thread

Posted: Sat Oct 29, 2016 9:16 am
by mhackney
A good question and one Lykle can jump in and answer. There are a couple of differences that appealed to me:

The flex3drive has a much higher gear ratio at 40:1 that affects top end print speed (significantly) and extruder acceleration configuration. The nimble has a 30:1 ratio (validated with Zesty).

The Nimble is really small and designed so it is ambidextrous - you can position 2 of them back to back to use with dual extrusion. The flex3rive has many different models for different printers and especially for dual extrusion so you can't reuse a single extruder version you already have.

And the Nimble has breach filament loading so starting filaments should be really simple. For those of us that do a lot of filament swapping, little details like this make a big difference.

All this said, the Nimble is still in production so none of us have tested one! But I was impressed with the attention to the details and the compact size, gear ratio and breach loading.

Re: Zesty Nimble extruder technical thread

Posted: Sat Oct 29, 2016 9:49 am
by Qdeathstar
Aren't the gear ratios related to torque? So while it has faster speeds it's torque is reduced?

I also thought he said the worm drive was an off the shelf component, so by buying a different worm gear you get a different ratio... Eg, not unique to the nimble.

I'm not an expert here so my assumptions might be wrong.

Re: Zesty Nimble extruder technical thread

Posted: Sat Oct 29, 2016 9:56 am
by mhackney
Absolutely but even a geared stepper at 5:1 has plenty of torque. The Bondtech with it's 5:1 geared stepper is the gold standard in my opinion. I don't know the reasoning for the big ration on these remote drive extruders, it might be related to the limitations of the worm gear.

I am not sure what you are trying to say in your comment "not unique to the nimble"?

Re: Zesty Nimble extruder technical thread

Posted: Sat Oct 29, 2016 10:33 am
by morgandc
Can the flexible drive cable be trimmed to length? What length comes with the kit?

Re: Zesty Nimble extruder technical thread

Posted: Sat Oct 29, 2016 12:44 pm
by ramai
It was mentioned that the retraction was not an issue, as the rotational twist is absorbed by the 30:1 gear ratio. I'm curious if the rostock max will require a longer cable and if that increases the rotational twist. Thanks!

Re: Zesty Nimble extruder technical thread

Posted: Sat Oct 29, 2016 1:53 pm
by 626Pilot
How much hysteresis do you get with the metal cable in the Bowden tube, and what are the mitigating factors?

Re: Zesty Nimble extruder technical thread

Posted: Mon Oct 31, 2016 9:08 am
by Zesty_Lykle
Hi guys,

Hmm, I was pretty sure I posted here before on some of the questions, but must have failed to do it properly.
2nd attempt.

what should we call this class of extruders? Something like "remote direct drive"?

Yes please, that is exactly what we were calling it before we picked the Nimble. Remote Direct Drive, aka RDD. We also had DoubleD but RDD is better.

What makes it different from the flex3drive?

As Michael mentioned, we are lighter, and a lot more flexible. Flexible in the sense of positioning, applications and add-ons.
Not only are we a lot lighter, now 28 grams, the breech loading system makes filament loading easier than ever. You open it up, see the whole filament path down to the hot end, slide the filament in and close the breech block with a click.
Our shape makes it possible for planned add-ons. Like a filament sensor (together with David Crocker), a brush to clean the hobbed wheel, a little bracket to make a "reverse bowden" to the filament spool. Those kind of things.
The 30:1 is relevant, as it allows a greater extrusion speed. We found that some boards were struggling to deliver the steps needed, especially with a Volcano 1.2 mm nozzle on 1.75 mm filament. We tested from 20:1 to 50:1 and found the best combination of response and speed in 30:1.

The 30:1 gear set is custom made for us, as we have a very tight space requirement. Also, the fact that the thing is ambidextrous, creates some special needs for the worm wheel. It needs to be symmetrical in every way, so you don't have to open up the unit and flip the worm over to use it upside down. Or the Australian way as I like to call it.
Of course we looked at off the shelf components, but with each of them there was an issue. Too long, or the wrong diameter, or the gear was to thin, things like that.

Absolutely but even a geared stepper at 5:1 has plenty of torque.

Correct. We can generate about 5 kg of pushing force. (6 kg in static tests, but let's play it safe) So we do not reach the heights of Bondtech, but normally there is no need. The average pressure needed to good flow and clean extrusion is between 2 to 3.5 kg. I have seen a spike to 4 when the hot end was a bit too cold, but that also impacted negatively on the layer quality.

Can the flexible drive cable be trimmed to length? What length comes with the kit?

The standard length we supply is 95 cm. This is a compromise that works best on a lot of printers. My Delta is 1 meter tall and it is perfect for that.
It can be trimmed, but that creates issues. The trick with this cable is that all the layers inside the cable need to be connected very well. It is vital. It is not easy to guarantee that if you cut the cable.
Having said that, if you require a different cable length, we will supply a different cable length. Simple.

stock max will require a longer cable and if that increases the rotational twist.

I don't think you will require a longer cable. As I said, my Delta is 1 meter tall and it looks as if the Max is about the same. The flex does increase a little, of course it does. But looking at the numbers, we will need about 2.5 meters of length to increase the flex far enough to make the retraction go from 1.2 as it is now to 2.2 mm.

If your Delta is 2 meters tall, mount the stepper a little below the middle of a column, and the 95 cm cable is still long enough.

How much hysteresis do you get with the metal cable in the Bowden tube

I have not noticed any. As I said, my retraction is 1.2 mm. I don't set an Extra Restart Distance in S3D.
We clamp the sleeve on both ends to handle torquing effects, but let the sleeve form a natural curve to the effector. Friction is there, but is low.

Finally, the only extra thing I would like to point out is that we recently updated the Nimble (even before we finished the Kickstarter campaign) and it is now smaller, lighter and even easier to use, with a complete new breech system.

Also, we added filament shavings handling. We built in a garbage chute, and a way to empty the garbage without opening up the Nimble. Nifty yes? There are 2 holes in the design, one on top and one at the bottom (preserving the ambidextrous nature of the beast). Blow canned air in at the top and all the shavings come shooting out the bottom.
(Why is it, that the spell checker has an issue with shute, is that the wrong word?) Edit! Found the answer thanks to Mac the Knife. Chute!

OK, give me more questions please.

Lykle

Re: Zesty Nimble extruder technical thread

Posted: Mon Oct 31, 2016 9:17 am
by Mac The Knife
Chute. :)

Re: Zesty Nimble extruder technical thread

Posted: Mon Oct 31, 2016 10:35 am
by Zesty_Lykle
Darnit!
Of course. I tried that in my email, but probably still had that set to Dutch.
Thanks Mr Mac

Re: Zesty Nimble extruder technical thread

Posted: Mon Oct 31, 2016 11:01 am
by DeltaCon
Finally a Dutch friend on this forum... ;-)
Where are you located?

Re: Zesty Nimble extruder technical thread

Posted: Mon Oct 31, 2016 1:02 pm
by rurwin
To add to what Lykle said, it is the gearing that limits hysteresis. Hysteresis is caused by twisting of the cable. Going forward it will wind up a certain amount of twist and when you retract, that has to be unwound and wound up in the other direction before the filament starts to move backwards. However the high gearing ratio reduces the effect. If you get a half-turn of twisting in the cable, and it says on the Kickstarter page that you don't even get that, it is reduced to 1/60th of a turn at the hobbed wheel.

Re: Zesty Nimble extruder technical thread

Posted: Mon Oct 31, 2016 4:01 pm
by Zesty_Lykle
Thank you Rurwin, I will keep that quote and re-use it if you don't mind. Nice and concise.

Finally a Dutch friend on this forum

Sorry buddy, Cyprus. I might be Dutch but I don't live there.

Lykle

Re: Zesty Nimble extruder technical thread

Posted: Tue Nov 01, 2016 4:13 am
by DeltaCon
Zesty_Lykle wrote:Sorry buddy, Cyprus. I might be Dutch but I don't live there.

Geeft niks beter twee Hollanders dan géén Hollanders ;-)
The Dutch community on delta's seems to be quite small, but that's what I liked on the Rostock in the first place: different!
I would not have mind to drive half way through NL to come look at the Zesty Nimble, but even half way to Cyprus is not going to happen ;-)

Re: Zesty Nimble extruder technical thread

Posted: Wed Nov 02, 2016 7:33 am
by Zesty_Lykle
Well, it is a nice place to visit.

Want me to shoot some video for you? Or do a Skype chat so I can show you around the Nimble? Als Dutch moeten we elkaar ondersteunen, toch?

Lykle

Re: Zesty Nimble extruder technical thread

Posted: Wed Nov 02, 2016 8:22 am
by DeltaCon
Thanks Lykle, I will take a raincheck on that. I have some other problems to solve first, and upgrades to make, but I think the Nimble is sure something to keep in the back of my mind.

Re: Zesty Nimble extruder technical thread

Posted: Fri Nov 04, 2016 2:35 pm
by mhackney
I've been exchanging emails with Lykle at Zesty about mounting on the V3 since it has the new HE280. A couple of back and forths and he has come up with a nice solution he calls the Mad Hatter! It's still a draft and I hope to get the STLs to print and test fit on my V3. I had test fitted an earlier design for the V2 Rostock and it, of course, won't work on the V3. This design is printed in 2 parts. The gold part is the cap (or Mad Hat!) and the green part is the Zesty Adapter.
image.png

Once the design is finalized, it should be very easy to mount the Nimble on a V3.

Re: Zesty Nimble extruder technical thread

Posted: Fri Nov 04, 2016 2:35 pm
by mhackney
Great, while I was writing the above Lykle sent me the STLs to print and test. I'll do that as soon as a printer frees up.

Re: Zesty Nimble extruder technical thread

Posted: Fri Nov 04, 2016 5:34 pm
by Zesty_Lykle
We aim to please.
:-)

The overall shape is good, I think I will want to see if there are tweaks needed in the support structure inside the Mad Hat, to support the Nimble.

Lykle

Re: Zesty Nimble extruder technical thread

Posted: Fri Nov 04, 2016 10:32 pm
by Qdeathstar
Interesting... that was one of my worries was about figuring out an adapter... so it's good to know I can go for it straight away. I donated the money for two in case I decide to go for dual extrusion with a cyclops, but I'm probably going to I've it a go with one first.

Re: Zesty Nimble extruder technical thread

Posted: Sat Nov 05, 2016 7:21 am
by Zesty_Lykle
HI Qdeathstar, thanks.

You know we have an adapter plate ready for the Cyclops/Chimera hot end, right?
It is in the Shapeways shop. We will also be making a DXF file available, so you can download it and have it waterjet cut if you prefer.
We will be publicizing the list of adapters we have available and/or working on soon. In fact, on Tuesday.

Lykle

Re: Zesty Nimble extruder technical thread

Posted: Sat Nov 05, 2016 7:27 am
by crocky
I did for a single one tonight.... Looks good so far...

Re: Zesty Nimble extruder technical thread

Posted: Sat Nov 05, 2016 1:46 pm
by Zesty_Lykle
Thanks crocky!

We just put up a new video, of the Nimble printing 4 very different materials. https://youtu.be/3KL9jXDX3p8

Lykle

Re: Zesty Nimble extruder technical thread

Posted: Mon Nov 07, 2016 5:22 pm
by 626Pilot
You're 40% of the way there with 12 days to go. Now is the time to ramp up your social media presence if you haven't already. I would post on the RepRap forums and deltabot Google group if you haven't already.

If it doesn't get funded, do you have a contingency? I would really like a RDD extruder, even if it means buying the parts from Shapeways and sourcing the rest myself.

Also, the live event is at hours when most people in the US are asleep. This is a HUGE market. You should probably have a second event during a time when we can realistically be awake.