Musings and Experiments on the Art and Science of 3D Printing

Recent Posts

How not to knock your socks off...

By Michael Hackney → Tuesday, July 18, 2017
A gent named Scott Smith posted on his blog and FB a few months ago about modifying the E3D V6 silicone sock to prevent it from grabbing the printed part and either pulling it off the bed or pulling the sock off the hot end. At the time I scoffed. I had 1000s of hours of printing with the sock on multiple printers without a single sock-related fail. That was with printing PLA, Nylon and ABS. 

Late last year I started printing a lot more PETG - especially the Atomic Filaments PETG Carbon Fiber Extreme (my new go-to filament for mechanical things). Turns out my sock experience parallels Scott's – the sock grabs the print and little bits of the sock get torn from the opening. I've observed that PETG is much sticker than PLA and ABS and grabs the sock. This can result in a tear, small pieces of sock broken off, parts ripped from the print bed and even – gasp – spontaneous mag ball disassembly (SMBD).

Scott's simple modification has worked perfectly. He carefully removes the inner diameter around the nozzle opening as shown here:
Use a new X-acto knife blade to carefully cut out the disk. I now have 100s of hours of PETG printing without a single fail. The sock still does its primary job of insulating the heater. But the secondary task of minimizing filament stick (for PLA and ABS) is lost. But now I get to do this again: Polishing nozzles for improved layer quality.

UPDATE - not even an hour after I posted this a follower mentioned that E3D now offer their sock with the large opening exactly like this! They still carry the other version and call it the "Pro" version.

First week with the Mosaic Palette

By Michael Hackney → Monday, July 3, 2017
Well, maybe it has been a few days longer than a week! That's partly because it has taken a little tinkering to fit my UltiBots D300 delta printer with Palette due to the large Z axes. The Palette requires that the tube from the Scroll Wheel to the extruder (in my case, this is the UltiBots Micro Extruder mounted on the effector) have as gentle an arc as possible. Not an easy task for a printer with a 450mm range!
(scroll wheel mockup)
But with a little experimentation I came up with a great solution that will work on any delta.
(that's not a real snake on the palette)
The Scroll Wheel - circled in green in the middle of the photo - is mounted on a rotating base. This allows the tube to seek a natural and gentle bend as the delta's effector moves up and down and across the X-Y plane. I've published the STLs on my Thingiverse page: Mosaic Palette Swivel Scroll Wheel Mount.
(Scroll Wheel swivel - there is a bearing inside)
The swivel mount is attached to a 4th column positioned between the X and Z columns and offset about 150mm. I used a 10x10 aluminum extrusion for this. I will post my mount STLs but I have to figure out how best to hold the column in place since I can't find anything that will slide into the slots on this small extrusion. Once mounted, I ran a few movement tests to find the optimal position for the Scroll Wheel. Turns out that halfway is ideal.

The next challenge was the attachment of the Scroll Wheel PTFE tubing to the effector. The Palette comes with a mount that attaches with industrial strength Velcro. This printer has magnetic ball arm joints and attempts to fasten and remove that adapter resulted in multiarmdisconnectitis (the condition of multiple arms spontaneously disconnecting simultaneously and causing great angst to the unsuspecting user). It is nearly impossible to stabilize a mag ball mounted effector while putting substantial push/pull force on it. So a new solution was in order. I designed a threaded adapter that gently holds the tubing and can be easily removed and attached with no multiarmdisconnectitis. The folks at Mosaic are testing it out now and I'll post the files on Thingiverse soon. You can see it in the green circle at the right of the photo above. Here's a closeup:
Ok, so now I had the palette attached, it was time to learn to calibrate and print. Calibration is actually straightforward once you understand what is supposed to happen. In my case, I believe my Scroll Wheel connector was not attached completely to the Palette so it did not register when filament moved through it. Jonny and Brennan at Mosaic were very helpful and answered my emails at all hours on the weekend to help me get up and running. Brennan even spent an hour on the phone with me to describe in technical detail how the Palette works. After I sorted out calibration I chose a simple and quick print to test, the Multi-color Citrus Coaster. I chose to do a pink grapefruit version for my first print.
With this first print behind me it was time to start working on my own project. For a couple of years I've had a desire to 3D print a US flag themed red, white and blue fly fishing reel. I decided to start with a simple "coaster" version of that to work out the details. I realized that Canada Day (July 1st) and the US Fourth of July were coming up in a few days so I expanded my design to include a Canada Day and a Fourth of July Coaster. You can get the STLs at Thingiverse: Fourth of July Coaster, Canada Day Coaster.
These were printed in a new PLA filament I'm testing: Filamentum Extrafill Nobble Blue, Extrafill Signal Red and Extrafill Light Ivory. I ordered mine (plus a few more colors) from filamentone.com (tell them SublimeLayers sent you of you order).

I printed a couple of these, each better than the previous as I tuned in slicer settings. Sidebar on this: The Palette worked completely predictably during these tests and print quality issues had nothing to do with it. Palette only supports two slicers right now, Cura and simplify3d. I really don't like either slicer but support seems to be better for s3d so I went with it.

Soapbox This does not imply that I will be advocating or recommending s3d anytime in the near future, I still have significant issues with both the company and the heinous bugs that have not been fixed for several years - including my old friend the "corner artifact bug" I reported exactly two years ago and was told "it's not a bug". No other slicer has a problem with this geometry. And here it is again in the US coaster - you can see it makes the stars look horrible.

I was not able to get a clean print of the star field in blue in the Fourth of July coaster due to the s3d bug. I going to try Cura soon to see if I can tolerate it more.

Next, just for giggles, I decided to print this multi-color owl. I'm not that into printing figurines but I wanted to test some more Filamentum colors and this seemed like a good model. The owl is printed in Filamentum Vertigo Grey, Metallic Grey, Ivory and Gold Happens. I really like this filament - it prints beautifully, the colors are rich and not overly saturated and they really hide layer lines.
Now I'm working on the US flag fly fishing reel that's been bouncing around my head for a few years. I'll be using Cura to slice it since it's critical that the stars look perfect. I'll make a post showing how Cura, Kisslicer and Slic3r PE handle these stars compared to s3d.





First week with the Prusa MM Quad Extrusion Kit

By Michael Hackney → Saturday, June 24, 2017

Last Sunday I had a leisurely afternoon to myself – a rare occurrence around here! I took the opportunity to upgrade my Prusa i3 MK2/S with the MM (multi material) kit. The job was straight forward and took about 3 1/2 hrs start to finish. The kit includes four new extruders that use Bondtech dual drive gears, here they are:
This is the cool Prusa Super Switch – it interfaces to the mini RAMBo card and drives the four new extruders by multiplexing their step and direction signals over the original E0 connector. Clever.

The kit includes filament racks for four spools of filament along with a new E3D V6 hot end that was customized for the MM kit. Once it was all together, this is what it looks like from the top:
The filament racks are paired, so there are two of them. The four new extruders sit on top of the Prusa arch – again in pairs. The filament is delivered to the Y Splitter via four short Bowden tubes (ironically, I've been working to eliminate Bowden tubes from my delta printers!) you see in the lower half of the photo and here is a closeup view. The four filaments feed into the top of the Y Splitter and the g-code orchestrates the dance to advance the active filament and withdraw the retiring filament.
Other than the space required for four spools of filament, the setup is very compact.

Like anything new, there is a bit of a learning curve required. It is highly recommended that you have solid experience with single extrusion on your i3 before doing the MM upgrade. There are just too many new variables to control and without a firm foundation of success I fear frustration will be your friend.

For my first attempt I decided to print the MM g-code for the Gear Bearing Prusa provides. I chose green, blue, white and orange filament. I have a lot of experience printing the green, blue and white but not much with the orange and it was a little persnickety at the time. This is important! I highly recommend finding four filaments that print very well with your stock i3 before diving into quad extrusion. In my case, I understand filaments and extrusion well enough that I believed I could deal with a relative newcomer filament. How wrong that assumption was!

And the reason for that is buried in the details on how the MM kit does its magic. Conceptually, filament changes are made by removing the active filament and then advancing the new filament. That's easy enough. But deep in the bowels of the hot end and Y Splitter things are not so simple. Are is a cutaway drawing based on my understanding of what's going on:
Assume that the printer is printing your first color – red in the drawing. When it's time to change to the next color the nozzle is moved to the prime block. The nozzle is simply moved back and forth the length of the prime block as the filament is withdrawn up into the special PTFE tube (light blue). This tube is special in several ways – it is not standard 2mm PTFE, it has a precision 1.9mm ID. You can not replace this tube with standard 2mm PTFE and get good results. The lower end of the PTFE is tapered to help shape the soft filament as it is retracted up through the heatsink. The filament retract  continues until the tip of the filament is inside the steel tubing. This tube is a good heat conductor and quickly cools off the filament so it retains its shape – a precise 1.9mm diameter. While it is cooling, it appears that the g-code is jiggling the filament back and forth a little to keep it moving it as it cools. This prevents it from sticking to the tubing.

When the red filament is completely withdrawn into its steel sheath, the next filament (blue in this case) is advanced. The upper end of the PTFE is tapered to guide the filament in. The filament continues its journey to the heat block where it is extruded on the prime block to purge the old color and prime with the new.
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An update: Peter(PJR on the Prusa forums mentioned below) emailed me after reading this post with a few well made comments. I'll just quote him, no use trying to wordsmith a clear description!
The Y-Splitter is actually a multiplexer, although technically it should not be called that it does perform that function.

The "SuperSwitch" is actually a demultiplexer.

During the tool change, about 10mm of the previous filament is "rammed" into the hot end which has the effect of cooling the tip of the filament for clean withdrawal.  Withdrawal must be fast, but not too fast such that a ball of filament is left behind (below the MUX).  If the temperature is too high, then stringing will occur causing a blockage.

A steady (or better, slowly increasing) purge speed allow the best possible purging of filament and uses about 60mm of filament.

I have a feeling that the cooling tubes are actually 1.95mm internal diameter.  The primarily tip forming is carried out by the PTFE.  Early beta tests were using standard 2mm PTFE and 1.85mm cooling tubes; the tip forming was then carried out by the tubes.

The problems may start when the PTFE start to wear.
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Simple right! What could possibly go wrong? It might be better to ask "how does this thing even work?" It does and quite nicely – once you understand the mechanics described above and the properties of the filaments you are using. PJR on the Prusa forums posted a well done Blockage troubleshooting thread that is a must-read for anyone upgrading to the MM kit.

During my first print, the extruders were sounding out that tell-tale click-click-click of skipping steps. This is virtually unheard of for Bondtech dual drive gear extruders so something must be seriously wrong! Even a Bondtech extruder can't push filament through a wall – and that's the clue. In my case, that orange filament was not retracting cleanly and leaving a long string as it was pulled up into the steel tube (this is somewhat hypothetical although I did disassemble the Y Splitter several times during failed test prints to find a blob and string of orange filament in the bottom of the splitter). This blocked the next filament from entering the hot end. I replaced the problematic orange with a known good gold filament and was off and running making some reasonably nice multi color test prints.

The above illustrates why its good to have some printing experience under your belt and choose four filaments that perform very well. The filament must be well behaved as it melts and cools during the change-over process – extruding at elevated temperatures is the kiss of death and will likely result in blockages as described in PJR's post.

I don't have a lot of experience yet but I am over the initial learning curve and I'm starting to slice my own MM objects. Prusa provides a post processor for Slic3rPE but I'm using KISSlicer (the unreleased 1.6 beta 1 that should be out in the next week or so) and a post processor written by the same PJR mentioned above. It works beautifully. Here's a 12 hour MM snake I printed last night in gold, white and red PLA. This gold is known to string at higher temps and I forgot about that when I sliced. So I did have a fair amount of stringing of the gold. Next time I'll reduce extrusion temperature to 190° or 195°C for it. This print was 200°C, 3 perimeters, .1mm layers and 50% straight infill.

Here's the belly of the snake, not a bad first layer.




Six months with the UltiBots D300VS delta printer

By Michael Hackney → Tuesday, June 20, 2017
A few years ago I built an UltiBots K250 delta printer from printed parts and a hodgepodge of purchased parts from UltiBots. I wanted a smaller delta to take to my presentations on 3D printing and it was the perfect size. This printer was also my original test platform for trying out the Duet .6 controller and David Crocker's dc42 RepRapFirmware. It turned out to be a perfect storm of delta nirvana! The K250 was the most reliable and most precise delta printer I've owned, period (until now).

So flashing forward, I came across the new UltiBots D300VS delta printer kit introduced in November last year (D=delta, VS = V-Slot). This printer's build of materials list read like a whose-who of top-notch printer components. Here's what I mean:

  • Duet WiFi controller with RepRapFirmware
  • Authentic E3D V6 all metal hot end
  • FSR sensors and JohnSL board for probing (delta auto-calibration)
  • all metal (aluminum) frame and corners assembles quickly and precisely, the towers are 20x40 extrusions for excellent rigidity
  • OpenBuilds Delrin carriage wheels
  • Hadyn Huntley's carbon fiber with magnetic ball delta arms
  • .9° stepper motors offer 2x the precision over the standard 1.8° steppers
  • Kapton bed heater with an aluminum heat dissipator and borosilicate glass build plate
  • 24VDC power supply
  • UltiBots' direct drive Micro Extruder - no Bowden tube!
  • top mounted filament spool holder
  • LED lighting
The Duet, .9° steppers, FSR probing and all metal frame caught my attention. But my main interest in this printer was its massive size - 445mm Z x 290mm bed diameter (it's actually a bit larger than that). The only "must have" not included is a PEI print surface – but one is available and can be purchased with the kit.
I ordered my D300VS kit not realizing it was one of the first sold and documentation was sparse. No worries though, I've built a lot of 3D printers and the only unique item was the Micro Extruder. I was actually on the fence about it and my initial plan was to swap it out for a Bondtech QR extruder and Bowden. Brad (UltiBot's owner) convinced me to give it a try for a few weeks and I'm glad he did!

I started to document my build with a lot of photos with the plan to help document the build. But as I got into the build, my excitement grew and I wanted to get this printer commissioned as soon as possible.

Once I had the printer commissioned and operational it was time to take a test run. Most who read this blog and my forum posts know that I am into fly fishing and developed a 3D printed fly fishing reel. I like to use it – nine printed parts – to test extruders, hot ends and printers because they can be challenging parts to dial in. So I loaded up the models and sliced an entire platter of all nine parts. This is the 3D printing equivalent of a Hail Mary, especially for a first print! I carefully prepared the new PEI surface, brought everything up to temperature and allowed to stabilize for 15 minutes then crossed my fingers and clicked Print...

As soon as auto-calibration completed (I run auto-calibration in my g-code header for nearly everything I print) and the first layer started I could tell this was going to be a special printer. And that's the precise moment that I fell in love with the D300VS! Take look at the photos below. These parts are each challenging on their own and even more so combined into one platter and printed simultaneously. As you can see, the first layers went down flawlessly. Two of these parts are printed with an "open mesh" that is very challenging to print reliably and flawlessly. The D300VS printed them flawlessly the very first time!

Here are the completed parts. Let me describe these and the challenges they present to the printer (and operator).
Starting at the upper left is the foot – that long skinny object. It is the part that attaches the reel to the fly rod. This part has very little surface area to stick to the print bed and is always a challenge.

Below it are two disks with a central post. These are the side plates and are the parts with the open mesh design. Here's a photo of one printed in pink PLA so you can see the detail more clearly. These parts are the most challenging to print. If the first layer height is off even a little it significantly affects the aesthetics (smoothed weave is obvious and looks horrible) or the part peals from the bed (layer too thick). These parts are perfect.
To the right of the spool pates are three cylindrical parts. They have very little contact area with the bed and must be printed very precisely to hold their dimensions. The larger of these has a gear-like feature you can see clearly in the photo of the pink parts. Those teeth are a major challenge to print flawlessly.

Below these is a large ring. Nothing significantly challenging on this part or the small part at the lower right. 

In the lower left is the reel back plate. This part has all sorts of challenges to print. The tall pillars are magnets for stringing and are a real test of extrusion and filament. They also create havoc for layer registration and part cooling for most printers.

The D300VS has continued to perform like this from the very first print. I knew what to expect from the Duet, .9° steppers, FSR bed leveling and other features but the Micro Extruder was an unknown entity. I've now done enough printing and testing to come to understand that direct drive extruders blow Bowden filament delivery out of the water on these large delta printers. I have been so impressed with part quality and the ease of dialing-in slicing to eliminate strings and blobs that I've gone on a mission to eliminate Bowden tubes from ALL my delta printers. I'm glad Brad convinced me to give it a try and now with six months of continuous use I can say the Micro Extruder has been very reliable and trouble free.

Sidebar: I'll post details about this later – shortly after building my first D3000VS several other direct drive extruders have become available. The E3D Titan Aero, the Bondtech BGM, the Zesty Nimble (remote direct drive) and of course the Flex3Drive (remote direct drive) has been available for a couple of years. I've spent a lot of time learning to get the best performance from Bowden filament delivery using 1.8mm ID PTFE tubing, Bondtech QR extruders and a host of slicer tricks. It wasn't until I saw (and experienced) the results from the Micro Extruder that I realized just how big of a compromise Bowden filament delivery really is. For small deltas like the Mini Kossel and K250 the length of the Bowden is manageable but the loooonnnggg Bowden's on large deltas like the SeeMeCNC Rostock Max and UltiBots D300VS have significant limitations. Over the next few months I'll post about these options. Back to the D300VS...

The only significant criticism about the D300VS was the lack of good build documentation. This is not an issue for experienced builders but is a bit of a non-starter for folks looking for a first 3D printer. Recognizing this, Brad asked if I'd write a professional build guide for the D300VS and I agreed. He sent me a new kit to use to photograph and document the build. The UltiBots D300VS Build Guide is now complete and getting great reviews – and more importantly, helping a lot of first time 3D printer builders get off to a great start.

At the end of the day, the D300VS is an excellent delta printer with top-notch features. It's geometry lends itself to precision construction and printing. The Duet WiFi controller is excellent and its stepper drivers are are dead quiet. Everyone always comments on how quiet my D300VSes are. The RepRapFirmware with its integrated Duet Web Control interface is the best open source firmware there is, especially for auto-calibration performance, usability and overall print quality. And the D300VS is a great value too with its quality components and construction and print build volume.

I'll leave you with a few more photos showing what the D300VS is capable of doing.








When it rains, it pours: Prusa multi-material quad kit arrived!

By Michael Hackney → Friday, June 16, 2017
Last week I got the Mosaic Palette to explore printing with four colors of PLA on one of my large delta printers. Yesterday I got the Prusa quad multi-material kit for the Prusa i3 MK2(S upgrade) I ordered with the printer last October. In fact, the only reason I bought the Prusa was to get my hands on the quad extrusion kit! Turns out the i3 MK2 itself is not a bad little printer within the limitations of its 8bit RAMBo mini controller and firmware. But it produces nice prints reliably (not as nice as those from my delta printers running Duet Wifi and RepRapFirmware, but nice).

Here's what arrived in a Tyvec package:
And here's what's inside the main box, the motor and multiplier pox has 4 steppers and Prusa's innovative multiplexer/driver:
Under all of the parts were the two components I was most interested in. Shortly after I ordered my kit last Oct. Prusa announced a shipping delay because they were not happy with extrusion and hot end. The net result was, they worked with Martin at Bondtech and decided to use the excellent Bondtech dual-driven drive gears in their extruder update. The magic here is the Bondtech dual drive do very little damage to the filament surface. I've been talking about this for several years so it's great to see an application where this is critical. Prusa is sourcing the drive gears from Bondtech.

They also worked with E3D to address the issue they discovered with the hot end that affects the quad kit but not normal V6 operation. This is because the quad kit does its magic by pulling the active filament completely out of the hot end in order to insert the next color in! That's a lot of movement, especially when the end of the filament is a molten blob that can get unglanceable up as it cools and solidifies. 

So I anxiously removed bags of parts until I found these. The Bondtech drive gears - they are as beautiful in a Prusa bag as they are in a Bondtech QR or BGM extruder!
 
And the E3D V6 hot end:
So it will be a fun weekend of tearing apart my i3 MK2 again (I had to tear it down for the "S" update last month) to install the quad system. I'lll post photos, impressions, results as they come. Meanwhile, take a look at these prints from Prusa, if these don't make your heart skip a beat (except for those unbearable Benchies) you are either 1) dead or 2) disinterested in FFF 3D printing!
(photo linked from http://www.prusaprinters.org/update-multi-material-upgrade-2)





Mosaic Palette - the journey begins

By Michael Hackney → Wednesday, June 7, 2017
I've been watching the Mosaic Palette since its Kickstarter and have come close to buying one on four occasions. But each time I hesitated and moved on to other projects and challenges – a little gun-shy from the shipping delay and lack of time. So what, you might be asking, is the Mosaic Palette?
(photo used with permission)
That 290mmx170mmx140mm (11.4"x6.7"x5.5") white box above is what it looks like in case you haven't seen one. But the all-important question is "What does it do?"

In a nutshell, you feed four different colors of filament into Palette and it chops them up into short segments and fuses them back together to make a single multi-colored filament. Here's a little graphic to show the concept:

The length and position of the colored segments are calculated from an object's g-code file. It delivers this sequence of chopped up colored segments to your 3D printer, with its standard extruder and hot end, so it can print objects in up to four colors. If that isn't difficult enough, it does the cutting and fusing in near real time as the object is printed. It's a fascinating concept and it isn't difficult to imagine the technical challenge to pull it off. Is it art, technology or black magic (or a combination)? Over the next few months I am going to find out.

Due to a combination of a successful Kickstarter campaign and some last minute technical challenges, Palettes were scarce with a long waiting list. That was one of my deterrents for jumping on board; I tend to be opportunistic due to my very busy "life schedule". I can't predict what I'll be doing and how much time I'll have next week let alone six months from now! But while I faltered Mosaic stuck to it, resolved the technical issues one by one, and finally caught up shipping to backers and those patient early buyers.

I was a bit surprised when I made my monthly pilgrimage to the Mosaic web site this week and found they were offering a 25% discount to the first 50 new customers. That was just the extra kick I needed - well, that and having seen Jetguy's Palette at the Midwest RepRap Festival in March. I knew it was just a matter of time before I got my hands on one to see exactly what it can do with visions of four-color 3D printed fly-fishing and spinning reels dancing in my mind. I placed my order at 12:45pm yesterday and today at 12:30pm this package arrived at my door:
An amazing feat when you realize that Mosaic is in Toronto, Canada and I'm in Boston, MA USA. The tracking showed my package routed through Cincinnati, OH! Less than 24hrs from order to delivery - your mileage may vary :)

Inside the box, packed in paper any molded foam, is this purple box (one of my favorite colors):


Inside the purple box is the Palette. It might be a good omen that a postcard from my all-time favorite filament designer – Proto-pasta – greeted me when I opened the box!
Over the next months I'll post updates on my progress, tests and prints as I install and learn how to use this unique device. My plan is to commission it on an UltiBots D300VS large delta printer modified with an E3D Titan Aero direct drive extruder. The Aero should provide very precise filament delivery without the issues of Bowden hysteresis - an issue that some early delta Palette users have discussed on the SeeMeCNC forum.

Please be patient though! I have a lot on my plate so progress might be slow. But I'll get there... 

Friend's don't let friends use oil...

By Michael Hackney → Friday, June 2, 2017

Back in the dark ages when humans knew not the subtleties of FFF 3D printing, many tried elixirs, potions, broths, salves, incantations, and many other unscientific and unproven so-called remedies.

It was a dark and dangerous time – especially for those unknowing and unenlightened followers. The "oil myth" started in the early days (circa 2013) of the full metal hot end; that which we know and love today called E3D (taking a bit of liberty here, historically, the oil treatment was developed by a Replicator 2 user as best I can tell. But the word spread fast to the delta community who were grappling with those long, filament-strangling Bowdens). The early E3D was a slightly different beast than the then-current J-head state-of-the-art hot end. And many unwittingly assumed the E3D and other all-metal hot ends of its ilk would work exactly the same, but only better. They did not understand the subtleties of a short melt transition zone that is the hallmark of these all metal designs.

So they continued to blindly slice with long and rapid retracts. And lo, as they printed, the filament – most notoriously, PLA – would jam. "It can't be my beloved slicer or filament or my lack of understanding so it must be this cursed hot end" proclaimed many. "We must lubricate it into submission. If it wants to jam, then let's oil the darned thing." And oil they did - Canola, peanut, corn and many other oils were used. And "good results" were exclaimed by those silly enough to go down this path. Until, that is, until other, more challenging problems arose – first-layer adhesion problems, inter-layer adhesion problems, gummed up extruder drive gears and a general unkempt appearance on and about the 3D printer.

Meanwhile, a few brave and hardy soles were determined to study and understand the problem. They invested 1000s of hours collectively (and some of us individually) to hypothesize and test – you know, the scientific method that seeks truth above all else. And lo, these pioneers discovered that retracting molten filament past the short melt zone and into the heat exchanger is bad, very bad. And more importantly, does not fail catastrophically 100% of the time so the unwitting could not correlate the results to its cause with certainty. However, those brave and determined few DID correlate the results to the cause. They dissected hot ends and nozzles and heat breaks by slicing them latterly after quenching in liquid nitrogen. They invented the "cold pull" test (blush) to study the shape of the melt zone and nozzle geometry, and they came up with theories, testable theories, to determine once and for all what was really going on.

Meanwhile on the forums and groups, the oil-mongers propagated their myth at a time when many, many new 3D printer users were entering the field. Not knowing the hows or whys, these noobs saw the exuberant claims made by the oil-mongers and fell prey to them. Creating a new cycle of perplexed and frustrated users.

It was just at that time when the results of all the hard and scientific work were made known after much collaboration and cross-checking and verification. The cry went out "No oil, no oil good people! It is not necessary and actually creates more problems than it solves." Data and results and explanations were shared. And the nascent hot end manufacture took note and rather than get defensive they embraced, welcomed, understood and appreciated the work and dedication to truth and understanding. They tested and verified the results on their own and went the extra steps to make changes, changes that would later propel them to the top of the hot end market for performance, reliability(!) , functionality, innovation and design aesthetics. They realized the minor flaws in their earlier designs that might lead users down the slippery oil-covered path and fixed them, saving countless others from the "oil myth" of 2013-2014.

You can read about this here: E3Dv6 Release Announcement & Design Details. And the all-important quote that tickled and caused this author to blush slightly:

• Fix niggling reliability issues.

v5 has a great track record of reliability with less than a fraction of one percent of users experiencing issues due to manufacturing issues, however we really wanted to eliminate any chance of future defects.

1.75mm Bowden users were experiencing a disproportionate amount of problems, which was traced back (with much help and hard work from Michael Hackney) to nozzle geometry in certain situations needing high extrusion pressures that resulted in starvation of filament flow.

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The first reference I can find to the use of oil for preventing PLA jams was posted on the MakerBot Operators Google Group on 1/14/13. I have not found an earlier reference, if you do please let me know!


Everything you wanted to know about the Zesty Nimble remote direct drive (RDD) extruder

By Michael Hackney → Tuesday, May 30, 2017
I've been a "delta fanatic" for over 4 years. Like all things in life, delta printers have tradeoffs compared to their Cartesian counterparts. In exchange for very fast movements in all three dimensions, the extruder is mounted remotely and the filament delivered through a long PTFE tube called a Bowden tube, typically 2mm ID for 1.75mm filament.

Delta Musings
The early delta printers were fairly small (Mini Kossel) and the length of the Bowden was not too problematic. But as delta sizes increased - like the SeeMeCNC Rostock MAX and the more recent UltiBots D300VS - the length of the Bowden also increased. Long Bowden tubes have more friction for the extruder to overcome, especially if the extruder roughens the filament surface with its drive gear. Another issue is that long Bowden tubes introduce more hysteresis into filament retracts due to their inner diameter being much larger than the filament diameter. This results in print quality issues like excess stringing and blobbing.

Several years ago I recognized these problems and developed a solution to combat them with a combination of using 1.8mm ID PTFE tubing and Bondtech QR extruders. This combination greatly improved my print quality and is highly reliable (1000s of hours of printing without a single problem). The 1.8mm ID tubing has less issues with hysteresis, the primary contributor to print quality issues. But, any significant filament diameter issues or surface damage from the extruder drive gear results in jamming and filament starvation. This is where the Bondtech QR extruder comes to play. It's dual opposing drive gears exert much greater extrusion force with far less filament damage than the common single drive gear/pressure bearing extruders. The combination was very successful.

Then last year I added an UltiBots D300VS large format (300mm D x 445mm Z) delta printer to my stable. My intent was to build the D300VS stock and then replace the UltiBots Micro Direct Drive Extruder with my tried and true 1.8mm Bowden and Bondtech QR extruder. But after a couple of test prints I was so impressed with the results that I decided to put the extruder through its paces. This experience really punctuated the tradeoff we delta fanatics make with Bowden filament delivery - even with more advanced solutions like mine.

The Zesty Nimble

It was exactly at this time that I first learned of the Zesty Nimble remote direct driver (RDD) extruder. This is a different filament delivery mechanism that places the stepper motor (the primary contributor to extruder mass) remote and powers the drive mechanism via a rotating cable - also a type of Bowden. This has the advantage of removing significant mass from the delta effector while powering the filament delivery right at the entry to the hot end like a direct drive extruder system.

I backed Zesty's unsuccessful KickStarter campaign in October, 2016. KickStarters are hit and miss from a funding perspective and to Zesty's credit, Brian and Lykle persevered to bring their super light extruder to market. I kept in contact with the founders through late 2016 and ultimately they asked if I would be interested in testing the Nimble once they had a pre-production unit ready to test. I couldn't say no to that!

I received the pre-production Nimble on March 16, 2017 just a week before I had to leave to attend the 2017 Midwest Rep Rap Festival (MRRF) in Indiana. I was determined to get the Nimble installed and printing so I could bring it to show the crowd. Little did I know when I received it that mine was the very first (and only) Nimble in the wild.

I decided to replace the Bowden setup on a mid-size K250 delta printer powered by a Duet .8 controller and dc42 firmware (my gold standard delta firmware) with an E3D V6 hot end and standard .4mm nozzle. I have 1000s of hours of printing on this printer so I know it inside and out. Rather than print a new mag ball effector (which would actually have been the effector and all three carriages because I only used matched sets printed at the same time to eliminate dimensional issues) I modified the effector simply by drilling two holes for the Nimble mount.

The Nimble is remarkably small and light (appropriately named!) and mounting it was surprisingly easy as you can see here.
 
In addition to its diminutive size, the Nimble's design and engineering are remarkable. The extruder is ambidextrous - meaning that it can be mounted either left- or right- handed. And, it features a really convenient "breech loading" system - the red lever you see in the photo below is the breech lock.

And here's a photo of the remote stepper and drive shaft.
Before continuing, here are the basic stats for the production Zesty Nimble:
  • 23.5mm x 39mm x 28.5mm (WxDxH)
  • less than 28gm
  • 1.75mm filament standard, 3mm is possible
  • 30:1 gear ratio

And now for the part I'm sure you've been waiting for - testing!

My 3D printed fly fishing reel is a great torture test for hot ends, extruders and printers. There are 9 printed parts and each has unique challenges to print perfectly. The reel back plate with its 4 thin pillars and central shaft is a very difficult part to print without excessive stringing. I've spent an inordinate amount of time printing and studying this part and I've become very proficient in diagnosing printer issues with it. So, of course, it was the first part I printed with the Nimble.

My initial experience was a little mixed but understandable. With its 30:1 gear ratio, retracts require a little forethought. I typically retract PLA at 20mm/s but this speed stalled the stepper. A few back and forth emails with Zesty resulted in lowering retract to 10mm/s. The gears in my pre-production Nimble were 3D printed and the production gears would be much smoother and allow faster retracts. I didn't have high hopes that 10mm/s retracts would be sufficient to prevent stringing but I forged ahead. Here is the very first part I printed:
A very respectable part that many would be very happy to produce. But, as you can see at the red arrow, there was some stringing between the pillars. I've printed 100s of these with this PLA filament and know its extrusion characteristics inside and out. This was not a temperature issue, it was a retract issue due to the low retract speed. Otherwise the part was great with smooth, even and well registered layers. I printed a few of these in several PLA filaments with similar results.

For my next print I decided on a gear vase of my own design. I planned to print this at MRRF. It is not extremely challenging but stringing can be an issue for long Bowden delivery systems. This part turned out near perfect.

I printed in the neighborhood of 40 parts with this setup before, during and the week following MRRF. I gave a lot of thought to how to mitigate or improve the slow retract speed. The "solution", I thought, might be to use a Duet Wifi and decrease the micro steps from 16 to 2. This would reduce the steps/mm from 3100 (1.8° stepper) to 387.5 steps/mm - very much in line with a good extruder steps/mm range. During this time, Brian was experimenting and tweaking acceleration and jerk settings. He was getting much higher retract speeds - up to 80mm/s. He shared his test results and settings. Here's what he came up with:

extruder acceleration: typically 1000mm/s^2 - reduced to 50mm/s^2
jerk (speed changes): typically 600mm/min - reduced to 500mm/min

I made these changes in my config.g and loaded the reel back plate I use to test. This time I sliced with 20mm/s retract. I'm pleased to say that the Nimble performed perfectly with no stringing or other extruder related print artifacts. I continued to test prints and filaments including NinjaFlex (Nimble is excellent for this difficult filament), ABS, PETG, CF filled PLA, CF filled PETG, BronzeFill and WoodFill. Overall the Nimble performed very reliably and produced some excellent looking parts.

Filament changes are a breeze with the breech loading system. My only minor point on this is the breach lock (the red lever) does require a short break-in period. This won't be noticed by many users but if your delta printer is equipped with magnetic ball arms, you have to be careful in order not to pop off the joints. Not harmful but annoying. But after several dozen loadings, the parts break in nicely and I suppose the user develops a process that works without separating the mag joints.

During this time I've kept a relatively low profile about my Nimble results - not because it wasn't performing nicely but because 1) it was not a production unit and 2) I never endorse any product that I haven't personally put through the wringer with testing, testing and more testing. It's easy to develop a product that gives good results "most of the time", it's much more difficult to develop a product that produces great results with 100% reliability. I'm looking for products with 100% reliability to use on my 3D printers.

The Production Nimble
In late April, Zesty sent me a production Nimble to test - again the first one in the wild. There were a number of changes to the extruder body so a complete new kit arrived on my door step. It was a 10 minute job to change over to the new kit. I've printed over 100 of my fly reels (all 9 parts) and countless (well, at least 150) other models to test the Nimble under a variety of conditions and filaments. I am really happy with it's performance and can speak to its reliability over several months of continuous and heavy printing (5+ hours a day).

Here is a photo of the fly reel back plate printed in Hatchbox translucent blue PLA (one of the more stringy filaments I've come across) yesterday. This is an as-is photo still on the print bed untouched and un-retouched.

This is the level of perfection I seek in all of my 3D printed parts and the Zesty Nimble delivers admirably.

Results in a Nutshell
Nimble Pros:
  • very low mass (<28gms): reducing effector mass is critical for a delta printer. Mass contributes to "ringing" - overshooting corners results in imperfect layer alignment
  • very small (23.5mm x 39mm x 28.5mm (WxDxH)): effector space is typically very tight, especially on smaller delta printers. The petite Nimble can fit virtually anywhere.
  • simple filament loading: the breech loading system gives Nimble one of the easiest filament loading systems available.
  • ambidextrous mounting: the Nimble's design allows it to be mounted in either left or right hand orientations.
  • flexible filament: Nimble is the first really good extruder for printing flexible filaments on a delta printer that I've used. 
A Con or two:
  • removable breech lever: the red breech lever detaches easily from the extruder body. If you are careless, you might lose it or drop it during filament loading.
  • price: although not the most expensive extruder on the market, the Nimble comes in at €85.50 ($95.75 as of 5/30/2017). However, for this you get a very well engineered product that does the job and does it well. If you require low mass, small size and the ability to print flexible filaments, it is an affordable option.
Final Remarks
It's taken Zesty longer than many would like to finalize production of the Nimble. But to the company's credit, rather than rush an product not ready for prime time out the door they took their time to refine, test and deliver a well engineered and produced extruder. I give them a lot of credit for that - I know it was frustrating and expensive for them.

Along the way to production, Zesty has developed mounts/adapters for over a dozen printers for their single and dual Nimble extruders and are committed to developing adapters as needed. They've also refined their documentation for assembling, calibrating, tuning firmware and caring for the Nimble. 

The Zesty Nimble produces excellent results with a variety of filaments including flexibles. Flexible filaments are the bane of Bowden tube delivery so not many delta owners have been successful printing them. The Nimble will change that. 

Disclaimer
Although my pre-production and production Nimbles were provided by Zesty, I remained unbiased throughout testing and provided critical feedback to the company. Frankly, I test so many products that I purchase or that are sent to me that I do not feel obligated to provide a good review if the product does not perform remarkably. I have very high standards for quality, reliability and my integrity and I evaluate everything I test to those standards. The Nimble met or beat all of my expectations. 

I am so impressed with the Nimble that I just purchased (full price) the Dual Nimble Upgrade kit so I can test it with the E3D Cyclops dual in-one out multi-filament hot end.