Eamon McQuaide on December 17th, 2014

As the complexity of the part increased from our initial support design study : http://open3dp.me.washington.edu/2014/12/diy-support-study1/, the support we originally made was no longer suitable for use, as it would get trapped within the lattice structure we created, and be impossible to pull out. Now things are getting interesting..

100_3195

 

We noticed two things from our prior experiment:

1.  We wasted time and filament making solid support.  We needed to turn the support into a shell to reduce heat, and wasted material.  This will also make it easier to break out later.

2. We needed to add thin sections in the support to make it weak enough there to break apart to get it out.

Here is what the completed part looked like from the bottom:

100_3197

 

You can see now that the support was hollowed after it was designed in by using a “shell” command in Solidworks. We used a .5 MM shell thickness, which was a bit overkill.  It could have been done with .3 with equal success. The gaps between the part and it’s support was consistent with the last setup.  You can see in the foreground that there was a built in stress riser (thin spot about .05 MM thick) up the middle to aid in breakout, and the results were the support came out in two equal pieces.  The results were excellent!

100_3199100_3198

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Eamon McQuaide on December 17th, 2014

I don’t know.  But I do know that in practice I’m not all that impressed with the performance of blue painter’s tape either.  It doesn’t have a very strong adhesion with the print bed (it’s adhesive was designed to be easily removable), so there are two cases in which I have had issues:

1.  Long parts.  If you lay down plastic in a straight line on your print bed, a certain percentage of that length will be lost to linear contraction of the material as it cools.

2. Heated build beds.  Blue tape was designed to be put on walls and trim around your home as a mask that won’t leave behind a residue.  It was not designed to be stuck to a surface, and have that surface heated up to 100 degrees C while maintaining it’s full adhesive properties (common ABS plate temp).  Especially with our ABS builds, we have had problems not only with the plastic not sticking to the tape (wrong nozzle zero height setting) but with the part actually pulling the tape off of the bed under contraction.

I set out to find a solution to this problem, and found with a bit of searching, High temperature masking tape (MCMASTER PART # 7627A27).

The tape comes in 3″ X 60′ rolls, and costs about 18.50 a roll.  It claims to be stable up to 325 degrees F. It’s not cheap, but it’s also been very durable.  Our issues with part adhesion have gone away completely with the use of this tape, as well as the thermal degradation of the tape adhesive when used on a heated build plate.

NO WARP3

NO WARP1

 

 

The nice thing about masking tape, is it is not as sensitive to nozzle Z height adjustments as Kapton tape is. I’m guessing this is due to it’s slightly “fuzzy” texture that the liquid plastic bonds to kind of like velcro, or just the fact that it is not smooth, and therefore has more surface area for the plastic to adhere to.  This means with the many, many people who use our printers (with highly varying degrees of…..ehem….ability), we don’t have to re-level the beds constantly.

There are some things to be careful about when using this tape:

1. Don’t heat the build plate above 25 degrees C with PLA!!!!!!!! You will never get your part unstuck without damaging the tape!

100_3139

2. Consistent with above, you may need to experiment with how close to set your Nozzle Z-zero height to get your desired release strength.  The plastics I have used tend to stick better to this tape than the blue tape.

NO WARP2

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Eamon McQuaide on December 4th, 2014

One of the most challenging things to do and maintain print quality with an extrusion style printer is to print a solid object (100% fill).
A student recently came into our shop to print some small parts in PLA. They were 15mm long with solid connecting tubes 4mm in diameter, and he insisted that they had to be solid.

hex_4mmDi_15mmL sidehex_4mmDi_15mmLfront

After a few attempts using support created in Makerware, it was obvious we were going to have to create our own solution.  The issue ultimately came down to cooling time. There was just no way to run the part slow enough to prevent warping, and permanent bonding of the support to the part.  We modeled in a solid support with a gap to the part of .3mm to start.  The part fused solid, so there was definitely not enough gap. We bumped it up to .4mm for the next print.  We saw positive results on the sloped surfaces, but the horizontal surfaces still fused solid.

On the left, first attempt with our own support.  Much improved, finish, but still fused solid.  On the right, another attempt With .1mm layer resolution.  This put way to much heat into the part.

On the left, first attempt with .2mm layer height, and our own support. Much improved, finish, but still fused solid.  On the right, another attempt With .1mm layer resolution. This put even more heat into the part, making things worse.

Eventually we found the equilibrium.  A gap of .6mm between support and part on horizontal surfaces, and .3mm on surfaces at an angle worked great.

The final settings were .2mm layer height minimum, 215 degree nozzle, 20mm/min print speed.  I accidentally left MW support on without any ill effects.  Support broke out cleanly, and parts were beautiful.

The final settings were .2mm layer height minimum, 215 degree nozzle, 20mm/min print speed. I accidentally left Makerware’s support on without any ill effects. Support broke out cleanly, and parts were beautiful.

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Eamon McQuaide on December 4th, 2014

I’ve noticed over time, that there are certain situations where slicing software has a hard time finding a solution to, or just completely ignores geometry that needs support built under it. This is usually due to a kind of loophole created by rules stated within the slicer. For instance:
There is a setting in every slicer that determines the maximum angle a feature in your model can be relative to the build plane. Imagine you build a standard pyramid shell with all sides 25 degrees from vertical. Most extrusion printers can build surfaces more than a 60 degree angle sans support without issue all the way to the top. Nothing amazing here.

tpvis 1 makerware
Now take the top of your pyramid and turn it back in on itself. Now you have an inverted pyramid pointing back down towards the build plane. This feature obviously needs support. Otherwise when the printer gets to the tip of the inverted pyramid hanging out in free space, it will have nothing to adhere to, and the print will fail.

tpvis vinverted1
But according to the slicer, this feature falls under the standard setting in most slicers of 45-62 degrees from vertical. The slicer ignores the feature, or creates an extremely thin support structure which is sure to move around and break off during printing. Think about the load applied to this structure by the extruder nozzle part way through printing:

tpvis inverted2
This is the point where adjusting your overhang angle settings can solve the issue. But that can waste a whole lot of material,  and be tedious if not impossible to remove. Another obvious solution is to rotate your part to print in a different orientation, but this write up is addressing the situations where there seems to be something wrong with every orientation you put your part in. At this point, with a little creativity, the best results are to be had by modeling in your own support.

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Every good calibration starts with a pile of new materials, a daunting task, a ridiculous timeline, and our favorite ingredient…caffeine.

 

The 3:00am breakfast of champions

The 3:00am breakfast of champions

 

How many of these ingredients are for the tester and how many for the printer? The gummy worms, sour straws and energy drinks were for the Humans. The jello, alginate, bone meal, laxatives, joint support powder, mystery tub, and ABS plastic were for the Bots. It seemed like a fair balance.

 

The task at hand was to come up with a reasonable recipe and calibration for a bone gelatin hybrid.

 Recipe:

Equal parts by weight

Bone Meal (extra fine)

PolyEthyleneGlycol (PEG) aka smoothLAX (coarse)

Jello (fine)… yes unfortunately you have to by the little packets. Royal (extra coarse)

 

Why the little packets?… because bulk pack Gelatin is a coarse grind, not a fine grind. You can either ball mill the stuff down to size or simply purchase the smaller more expensive name brand stuff.

 

Coarse grain/mesh size leads to a rough print. The flying particulate can jam the heads pretty quick

Coarse grain/mesh size leads to a rough print. The flying particulate can jam the heads pretty quick

 

Print resolution is dictated by the coarsest material in a batch. Variance in grain size can cause continuous failures in the print resolution as the layers perpetuate upwards. Long story short, try to get ingredients that are the same mesh size, or ball mill them all together until there is a homogenous consistency [Seen below].

 

Test batches are run in the small bins. Note the fine grain/mesh size of the printable media.

Test batches are run in the small bins.
Note the fine grain/mesh size of the printable media.

 

If calibration seems close, the next step is to test scalability.  Then do some more intensive troubleshooting.

 

The printer is laying down clean smooth sheets, and the head is drawing uniform bitmaps.

The printer is laying down clean smooth sheets, and the head is drawing uniformly.

 

1st Calibration depowdered.

1st Calibration depowdered.

 

Remember gelatin is a protein. Proteins take advantage of water to do some ridiculous tricks like folding, coiling, cross-linking, and hydrogen bonding. Normally we are used to seeing this happen in a warm pot of water…100 degrees C warm. The printer is unfortunately not that warm. In order to get to that kinetically favorable part of the jello [ie structural jello-y goodness] we must apply heat. Hence there is a take and bake aspect to the recipe.

 

The test bars should be square. This meant that the baking process was both time and temperature dependent.

The test bars should be square. This meant that the baking process was both time and temperature dependent.

 

After parts have been depowdered they are put into an oven. The oven is set at the lowest temperature possible, which measured by thermocouple was ~180-194F   or ~82-90C. Then parts were baked for 15 minute per inch or 25mm of thickness. Unfortunately nothing we print in real life is uniform in thickness… so as always… use your best judgement.

 

Like cooking anything… the baking specs. are dependent on thickness on the rate of heat transfer.

Like cooking anything… the baking specs are dependent on thickness on the rate of heat transfer.

 

After the prints have been baked there will be a diffusion gradient. A level where the prints absorbed some water but not enough to achieve full strength. This outer casing should flake/crumble off fairly quickly when compressed or picked. If the parts have been over cooked they will be darker, blistered, and it may not be possible for the casing to be removed.

 

Curing/Baking gradient on a real part.

Curing/Baking gradient on a real part. Blue is ideal… Red is burnt

 

The prints after desiccation will be rock hard, but will solvate in water, because 2/3 of the ingredients are gel-like substance.

 

Printed scaffolds calibrated and ready for testing

Printed scaffolds calibrated and ready for testing

 

What are the applications for printing in jello? This is the cheap way to test bone hybrids for tissue engineering. Jello, basic gelatin, and collagen have similar printing behavior but maintain different levels of biocompatibility. When it comes down cellular science the biocompatible materials are very expensive. The more preparation that can be done with ingredients that are similar, cheap,  and readily available… the more real science can be done with the expensive materials.

 

Printed Bone/Gel Hybrid [Fully Calibrated]

Printed Bone/Gel Hybrid [Fully Calibrated]

[Read more about other 3D printing applications]

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Eamon McQuaide on November 18th, 2014
Half-Stepper weight reduction Mod

Half-Stepper weight reduction Mod

Half Stepper cooling nozzle

Half Stepper cooling nozzle

When I tell people we don’t make use of our second extruder on our FlashForge machines the response usually goes:

“But Why not?  Think of all of the cool things you could do with two extruders!  Don’t you like lot’s of colors, and dissolvable support material?”

My response is usually an astounding:

“Mehhhh…”

The reason for this is two fold:

1.  The case of a print that lifts off of the bed, or thin flat features that bend upward from lack of cooling time (nearly unavoidable in some cases). The second nozzle has a tendency to drag across that raised portion and break the print, and or detach it from the build bed completely.  The latter results in a sort of stalactite piggy back ride, in which the extruder Keeps on extrudin’, the head keeps on movin’ and the part keeps on growin’.  Usually up into the extruder assembly, creating a huge mess.

2. With the shear volume of printing we do (much of it overnight, and un-attended), and the many students setting up and printing with the machines, it doesn’t make sense for us as a shop to make things any more complex than they need to be. To quote a great mind:

“Make everything as simple as possible, but not simpler.”

Albert Einstein

So with that as a goal, many hours of measuring, modeling, and a few iterations,

Design Progression

Design Progression

have resulted in a mod I have dubbed

“The Half Stepper”

A bushing  was added to help support the guide tube.

A bushing was added to help support the guide tube (red).

the coling duct wraps around two sides of the nozzle.

The cooling duct wraps around two sides of the nozzle (blue). It is held in by an o-ring in the now un-used left nozzle port.

the fan shroud/air guide made a significant difference in efficiency.

The fan for the left extruder (grey) is re-purposed as the cooling fan for the right nozzle. The fan shroud/air guide made a significant difference in the fan’s efficiency (pink). And now the fan won’t cut your fingers open!  Yay!

an attempt was made to create a ducted fan to maintain air velocity.

An attempt was made to create a duct of consistent volume to maintain air velocity.

I have been running versions of this mod on all of our PLA printers with excellent results.  I have yet to measure the amount of weight it dropped off of the extruder assembly, but it’s minus one stepper motor, extruder mechanism, heater block, heater, and thermistor.

Want your own? You can find the STL Files Here:

http://www.thingiverse.com/thing:551916

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Eamon McQuaide on November 18th, 2014

With the addition of the semi-enclosed build chamber in our ABS Printer came one particularly annoying issue. The clamp bar that secures the X-Axis belt kept going soft and losing it’s grip on the belt resulting in a failed print part way through. Even when the screws were completely tight.  Given the location of these parts (under the stepper motors, next to the heated nozzle, and right above a 110 degree C build plate) it’s really asking a bit much of an ABS part to stick it here.  As soon as the belt fell off a few times, I just removed the extruder assembly and drilled two holes through the clamp and the belt, and installed two counter-sunk screws with backing nuts though the whole assembly.  If the screws were to back out, they would just run into the bottom of the stepper motors, so they are pretty much trapped there. “Try backing out now, you stupid……grumble, grumble….”

No more loose belts.

No more loose belts. The washer on the left is used to tilt the extruder assembly to give the left extruder tip more clearance.  (We don’t bother using the left extruder)

 

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Eamon McQuaide on November 18th, 2014

When I first started printing with it, I was convinced that ABS really stood for something besides “Acrylonitrile butadiene styrene”.  My mind  three particular expletives were inserted in a certain order (A!B!S!) to describe my feelings about the material relative to printing it.  Delamination, shrinkage, pulling tape off of the bed, clogs, you name it.  Most of that kind of attitude, applied to any situation stems from frustration due to mis-understanding.  In this case, material properties.  Here is what I did with our dedicated ABS printer to try to alleviate two major issues, which are delamination between layers, and warpage.

I enclosed and insulated one of our machines.  We had a real problem with larger prints cooling improperly, and destroying themselves by popping apart at the seams.   With a few quick and dirty mods to the machine, we had a semi-enclosed build space that could keep our builds toasty to the finish.  One was a removable polycarbonate  panel for the front sealed with some weatherstripping.  It hangs on the heads of some longer bolts that I replaced the original screws with.  The rest was taken care of with a 3 dollar windshield sun visor and some spray adhesive to insulate the insides.  The top is just the leftovers of the visor with a hole through it that slides around with the extruder. Though not pretty, those mods vastly improved the results of our ABS prints, and eliminated the delamination issue all together.  (FF now sells the Creator X Pro, which comes with polycarbonate panels to enclose the build space.) 

big ass print

Full build space volume print in black ABS.  A little warping visible on the bottom, no delamination.

The interior of the build space sits at about 57 degrees C, solely from the heat of a 110 degree C build plate.  That also means the components inside the space run hotter, which made me paranoid of at first, but everything seems O.K. so far….

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Eamon McQuaide on November 18th, 2014

After a few months of FlashForge use one issue has consistently cropped up.

The extruder assembly has for the most part been great, and extremely reliable.  The only challenge I still get on occasion is heat soak creeping up the Teflon tube inside the extruder, which results in a clog. There are two ways this can happen.  One is just from the machine sitting idle after a print while the hot end assembly is still “warm”.  The other can occur if you are printing at very slow speeds. In this case the filament in the extruder is not purged as quickly, so the heat energy is not being expelled fast enough to control the melt zone.  This can result in the heat traveling up the filament, and melting it up much higher in the tube than it was originally intended to do.  You end up with a filament jamb when heat travels far enough up the filament to distort it as it enters the heating tube.  At this point it basically stops itself like cork in a bottle, and you have to take the fan and heatsink off so you can get in there with small needle nose pliers and remove the clog.

The other issue is the Teflon tube in the hot end.  It clogs after some time, or eventually loses the compression seal between it and the nozzle tip, resulting in leaks around the joining threads and/or filament jambs. As far as I can tell this is mostly the result of issue above,  running low quality filament (NOT WORTH IT!) and/or filament with a much lower melting temp than the standard 230 C extruder temp.  If you have saggy prints, you are probably running your nozzle too hot.

Teflon tube in the hot end clogs from PLA being left to bake inside it.

Teflon tube in the hot end clogs from PLA being left to bake inside it.

I seem to have completely fixed the aforementioned problems  by only running filament from reputable suppliers (We have had good luck with “JustPLA”),  and changing the way I do filament changes.  The latter seems to be extremely effective at minimizing the amount of dis-assembly I  have to do.  My solution?  PURGE, PURGE, PURGE!  Every time you finish a build, purge out a good portion of material (at least an inch or so on the inboard side) either by hand, or using the “LOAD EXTRUDER”  function in the utilities menu.  Then immediately pull the filament completely out of the top of the extruder.  This prevents the filament from sitting in the hot end and baking into a rock hard clog, often rendering the Teflon useless, and sometimes the nozzle as well.  Before re-loading the filament, make sure to clip off the funky looking end so you always start with a clean constant-diameter filament.  As soon as I started doing this simple step, the majority of my extruder issues completely dis-appeared.

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Eamon McQuaide on November 18th, 2014

I have had the well known (According to the FF forums) fatigue failure of the x-Axis Stepper motor harness.  It is the result of wiring that really wasn’t designed for the way it’s being used.  That would be repetitive cyclical bending. One or more of the wires in the harness ultimately fail in a similar way to bending a coat hanger wire back and forth until it breaks.  My symptom revealed itself as a jittery sad sounding noise coming from the stepper, and an extruder assembly that wandered the build space with the confused panic of a child lost in a busy shopping mall.

 

If your machine has a tendency to stop mid-print for no apparent reason as though you paused it, this may be the result of a failing harness as well. The only fix is to replace the entire harness, unless you want to go in and figure out where the break is and replace that one wire.

Replacement harnesses are available on the FF website, but you will have to ask specifically for them.  It’s probably a good idea to just keep a spare around just in case.  An even better idea would be to figure out which harness on your machine is the longest, and buy that one.  Then no matter which fails first, you will have one long enough to replace it.

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