Strengthening 3D printed parts… with Holes?..

Hello, Sunday!

 

Silence reigns as it rains down on this blog, but bear with me, for I yet persevere through my final year.

I’ve been doing a lot of 3D printing recently on my self built CoreXY “ETA”, and I had to make a case for a portable speaker I have. The speaker in question had rudimentary loops for tying it to something, but was rather insufficient for actually wearing on a belt. Having a 3D printer, I decided to print a case for it.

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The blue object is the case, and the black body is a mock-up of the speaker

I quickly modeled a case for the speaker on Fusion 360, it’s a simple design where you slide the speaker into the case from the top, and a pair of clips snap onto indents on the speaker. Pretty straightforward, but during self review, I ran into a little problem. The case was 3mm thick on most sides, and as FDM/FFF 3D prints by nature are weak along the vertical Z axis, the clips looked like they would wear and break fairly quickly.

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This is the orientation at which the print would be on the bed. The thin section just below the clasp is the weakest section, as repeated bending would result in it snapping off eventually.

Traditional knowledge would lead one to assume the simplest solution would be to increase the thickness of the section, or add structural elements like ribs to strengthen it.

Practical knowledge would assume that it would be unlikely that I would want to repeatedly remove the speaker from it’s case. Perhaps there could be better designs that would have eliminated the flaw entirely. However, I came up with a little trick to take full advantage of my medium, Fused Filament Fabrication, and exploit the way slicers work.

I started with making a void in my part. Yes, I plan on making it stronger by removing material. Removing material is typically used to maintain strength while keeping the weight down like with I-beams or fullers. However I use it here to induce a certain feature in the slicer. I created a side profile of the weak point in question, and hollowed out a tiny sliver, 0.1mm thick.

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A sectional analysis of the case reveals the paper thin void modeled into the case

“What’s that going to change?”, you may be asking your screen, but rhetoric questions to a monitor aren’t going to get you answers, scrolling down will. This is the result when the model is sliced in Cura.

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The original shell thickness would have been 4 shell lines + the infill, but here it’s 8 shells, which should result in greater strength and bonding.

In my experience, infill has a marginal influence on strength. Around 15% is good for structural integrity, 30% for decent rigidity, and about 50-70% if you really want it as strong as possible. However, increasing shells is also an effective way to boost strength. By creating a hollow inside the weak section, the slicer prints additional shell lines in the area, and the shells fuse together to make it stronger.

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Here you can see just 4 lines, infill, and 4 lines again in Cura’s Layer mode

Here is a view of the same layer in another section of the part, which is not reinforced with a void. You can see that when compared to the previous image, the number of perimeter loops is nearly doubled, effectively making the weak areas a nearly solid part.

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Here you can see a close-up of the part being printed. The clip on the left is nearly solid, whereas the wall on the right is hollow but for the infill.

If this case was to be injection molded, it’s strength would be vastly superior to a 3D print of the same. However, by exploiting the nature of 3D printer slicers, we are able to selectively increase the strength of our prints in areas where it is required without increasing the entire part’s material and time cost.

 

I hope this little tip aids you in your designs, please let me know your thoughts via the comments below, and if you would like more tips and tricks in 3D printing.

Thank you, and have a great week.

~Adithyaa

Maker: Venus de Venus

My printer ETA just finished a sculpture I designed a while back, which I called “Venus de Venus”. It stands 27cm tall, and took 11 1/2 hours to print, the largest object I’ve printed on ETA thus far.

A little back story on this piece. I had a class on wood and metal working a while back, and for that class I carved a statue of Venus de Milo, an ancient greek sculpture, with a little difference.
The head is an oblate spheroid, to represent the planet Venus, from whence Women are said to have originated from, for there are two mysteries that have always, and presumably always will elude man, and that is the eternity of space, and Women in general.

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A close-up of my hand carved piece

TL:DR Classical Medium vs Contemporary Medium, the ongoing battle of mediums since classical times.

Until next time,

Adithyaa

Poem: Printer O’ Printer

Printer o’ printer,
whirring by the window,
laying layer by layer,
arose by rows.

O’ Eta o’ mine,
what’s ETA of thine?
with silky strings that shine,
laying line after line,

Spinning through the day,
weaving through the night,
what fine lines you lay,
till dawn’s breaks light,

Precision machine,
makeshift in green,
with rods a’gleam,
layin’ lines so clean,

Till time’s end we make,
for a maker’s sake,
for a creator’s crave to slake,
O’ Eta, Awake and bake.

~Adithyaa Raghavan

 

Hello, Sunday, I’ve been expecting you,

To anyone who doubt’s a maker’s obsession with technology, show them this. Worry not, I have a good psychotherapist, and he worrying enough for everyone.

Either way, I just wrote this yesterday, after nearly a year working on and off on my printer Eta.

Signing off,

~~Adithyaa~~

Project: FFF 3D Printer “Eta” Part 9

Hello, SUNDAY!

Whew, it’s been an unfortunately long time since my last post, I’ve had to move my base of operations and un-discombobulate everything, and much is still a mess. However, this move comes with it’s benefits, as now I have a dedicated areas for my computing, electronics, metal, resin, wood, plastic, and 3D printing work. This compartmentalization allows me to quickly finish tasks in any field, so I should be clipping along speedily henceforth.

On the topic at hand, Printer ETA is finally fully online and mechanically sound (for the most part)! I had to disassemble Eta to move it, so I used this opportunity to upgrade the X & Y axes with shiny new bearings and carriages, which now means I have more accurate and precise prints.

Here are the upgrades I’ve installed,

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Printer feed is a sensitive area, and feeding dirty or dusty filament is asking for a jam. To fix this, I hacked together a rudimentary but very effective filament cleaner (could be used to oil it too :] )

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New Y axis carriages, printed in ABS by my dear friend Balaji, equipped with 3 LM8UU each to counter the HBOT mechanism’s XY torque.

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A new belt clamp, to allow me to remove/adjust the hotend without loosening the belt.

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As much as I like to wave around my successes, I’m open with my failures, so that others may gain from it at the very least. Here, I miscalculated the offset between the two belts, leading to a bend in one side. Luckily, this did not affect print quality.

Moving forth, I’ve setup my printer on the bay window in my room. Even though my printer’s bearings and steppers are extremely quiet, I can detect it’s movements by placing my ear to the walls even a floor away due to it’s discreet vibrations transmitted through the building. Truly a highly advanced monitoring system.

Now that we’re done with the nerd stuff, we move onto seeing what I’ve been printing!

I’ve been calibrating and printing, and Eta’s functional enough at this point for me to simply select the print job and leave. That said, keep your eyes and ears on your printers, they apparently  suffer from separation anxiety and are prone to spontaneous self injury.

I’ve also  started using very watered down PVA white glue to coat the print surface, and I’m extremely happy with it. With plain heated glass, I had to amp up the temperature to get anything to stick, and even then, lines getting peeled off were far too common on even small prints. However, first coat of PVA I slathered on instantly fixed all of that, and parts detach perfectly afterwards. If I need to reapply the coating, I simply take the glass out, pour water over it, and scrub it after a few minutes, then reapply the coating with a sponge.

I’m looking forward to working on many projects using Eta, so keep your sensors scanning the horizon for more to come!

That’s it for now, but stay tuned, there may be additional posts flying in very soon!

Singing off,

~Adithyaa~

 

Project: FFF 3D Printer “Eta” Test print Timelapse

Hello, Sunday!

We meet once more, this time to spectate the video of mine 3D printer, Eta, printing a tiny calibration cube.

It still has room for improvement, but what do you think?

Project: FFF 3D Printer “Eta” Part 8

Hello, Sunday!

So Eta was on hold for a while as I was awaiting a few parts, and where I left off last I was having hotend problems. It was a Chinese clone of the E3D v5 and it was jamming harder than an amateur jazz band, and I had to blowtorch solidified PLA out of it several times.

However, my grandfather, Jairam Thatha came to my rescue and brought me a E3D lite6 from America. The lite6 installed easily and worked like a charm, easily extruding PLA once calibrated. However, as you all should know, problems present themselves like hydras, lop off a head and two more shall sprout. In this case, it was Z axis wobbliness!

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I used LM8UUs fixed into the Z axis bed platform with a little hotglue, so there was a minuscule amount of play in the fitting, but this meant that the platform could pitch back and forth about ~5mm. When the threaded studding rods lifted or lowered the platform, it would cause a slight variance in the height of the bed. Not by much, but I’m trying to lay down plastic lines 0.4mm thick, so a minute wobble is all you need for it to not work.

Hence, Once more, we venture into the fray! IE,  SJP road.

Having returned from SP road with flanged bearings, I set about installing them into place in Eta. They didn’t have many flanged bearings in stock, so I just about managed to get two LMK8UUs and two LMF8UUs, which works out fine for me.

 

I also had a small issue where the bowden tube & hotend cables kept flopping over, so I devised a highly sophisticated mechanical construct to keep it upright.

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Ahem…

The flanged bearings nearly completely eradicated the the wobble, and while I was installing them I also straightened out the Z threaded rods by placing them against a pane of glass and gently rapping them while turning them to find the high spots. #highlyadvancedproblemresolution

I’m certain no one found the the double the in the prior paragraph. 🙂

Next, I spent a lot of time just banging about Marlin’s parameters, and trying to bludgeon the bed leveling code to work. No matter what I try, the Z axis kept getting muddled. I made a Z probe using contacts glued to the bed’s glass, and the nozzle itself as the contact, which worked splendidly as long as the nozzle isn’t covered with plastic. However, the leveling code itself is still non-functional. Any suggestions welcome.

I started Eta at the start of this year, just after the clock struck 0000, I decided to go over to my computer and resume some reading I was doing on 3D printers, and then I decided to go along and design and build one. 5 months, on and off designing and reading about them, and then 6 months buying parts, waiting on deliveries, and prototyping.

Finally, HenriETA, my printer, IS COMPLETED! nearly, at least. I still need to add-on a few parts, like a print cooling fan, but for the moment, it’s functional and that makes me happy. I’d like to thank my parents, Jairam thatha, all Indian online electronic parts stores, and the entire opensource community on the internet. Wouldn’t have been possible without all you guys =)

Stay tuned for the next post, which will have a talk about Eta over a timelapse of it printing a test object 😀

Singing out,

Adithyaa~

 

Project: FFF 3D Printer “Eta” Part 7

Hello Sunday!

I’ve been a bit busy repelling the fusillade that is life, with varying success. Those of whom live in close proximity to me may have experienced paranormal sounds and or mumbled exclamations emanating from my lab-cave, but worry not, its just me trying to get my printer online.

A Series of Iterative Incidents of Murphy’s Law

Where I left off, It was 4 weeks ago (Five weeks now, time really does fly), and I had just finished the physical construction of my printer. Most of it, that is. I started by installing the endstops onto the smooth rods. I used microswitches for the Xmin, Ymin,Ymax, and Zmax endstops, and an opto endstop for the Zmin, to ensure accuracy. As my system is a Hbot, I decided to use both min and max endstops to help prevent any accidental crashes.

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I attached them using zip ties and strips of latex cut from surgical gloves,  to prevent them from slipping on the smooth rods.

All the wire I used was twisted for convenience, neatness, and signal clarity. Next, I began configuring the software tool chain for controlling my printer. I used Marlin, an open source firmware for the RAMPS 1.4 control board, Pronterface for direct printer control from my computer, and Cura for slicing.

Attempting to configure a printer is akin to teaching a baby how to move, and then trying to catch it as it bolts off the dinner table headfirst. Eta did ram her print head into the boundaries several times until I got it to understand which axes were which and which endstops applied to what, but it turned out all right with no damage.

MOSFETS and overthinking solutions

I spent a better part of my time planning figuring out how to power the obnoxiously large heated bed that I decided to use, due to its high rated amp consumption. 30A is no joke, and my lack of electrical engineering skills could very well jeopardize my printer, and possibly my continued presence in my house.

After much research, a good deal of headbanging and SP road trips, I finally settled on using three IRLB8743 Mosfets to switch the current to my bed. The RPF ‘fet on my ramps board was simply unsuitable for the task, so I didn’t even try it out in fear of combustion. I soldered the fets to a PCB, wired them up in parallel using thick housing wiring, added a 10k resistor to keep gate at ground, and slapped the largest heatsinks the shop had to offer on fets.

It’s pretty self explanatory what’s going on here. To all of those facepalming about why I’ve mounted a PCB in a metal box, its so that it is less likely to catch fire. The PCB is mounted on a biscuit of wood, and everything is fixed down. With zipties and hot glue. Clearly brilliant engineering.

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A rough diagram I drew when I was visualizing how the mosfet circuit would be made.

Finally, I bolted down all the connectors, checked every joint and connection thrice, and finally turned on the 12v 50A PSU and activated the heated bed!

But nothing happened. Or more accurately, nothing bad happened. I ran the heated bed for several tests, it heated up properly, no melting, no fumes, nothing. The mosfets were room temperature even after running the bed for 30 min. I somewhat suspect that the heated bed is drawing approx. 14-18a, judging by ohm’s law and the PSU’s fan’s duty cycle. On the flip side, the system I engineered could possibly take up to atleast 60a at 12v.

Better more than less, I suppose.

More software tweaking was done, I installed the LCD control screen into a large box, and hooked it up as well. The fourth box as enough space for more additions as well, like an E-Stop button or arduino.

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Here we encounter another incident of Murphy’s law, where my computer decides to crash. Permanently. After a quick series of diagnostic tests, I decided to abandon the 14 year old PC, and instead use an old laptop I had laying around, so that was quickly solved. I like to use Linux mint for my lab computers, due to its lightweight, features and speed.

Worse congestion than a cold in Monday traffic

I’m using a e3D v6 clone, featuring an all metal body. I hooked up the hotend, bowden tube, and the extruder body, and started running configuration tests. The hot end heated up, fan ran, and everything was peachy until I tried to extruding plastic. The filament went smoothly in, and then the extruder gear began grinding like a lion with anxiety. I unwound the filament, and then tried pushing it through manually, and it kept hitting something inside the hot end.

If that wasn’t bad enough, thermal creep started, and the plastic melted in the colder part of the hotend, which is bad because that can’t be cleared easily. With my plastic firmly frozen in the upper heatsink, I was forced to disassemble the hotend to clean the jam, and use a blowtorch to burn out the filament in the heater block and nozzle.

This proceeded to occur with mildly different scenarios three more times. Finally, after the pneumatic press-fit joint proceeded to join the rest of the hot end in failing miserably, I decided that I need to take a short haitus from building Eta, while I wait for the replacement parts to arrive.

I estimate that I’m about 90% done with Eta, as I just need to install the new hotend, calibrate, and slap on the final safety features. Until then, I’ll be working on other projects, Comic con is approaching!

Signing off,

Adithyaa~