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.

Venus de Venus (24)

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

Projects, Plans and Procrastination

Heello, Sunday!

 

It’s good to see you again, I feel melancholic when I don’t update my blog or write poetry, and I haven’t done either in such a long time now. Since my last post, quite a lot of things have happened. I finished another year in college, started an internship, and organized my lab.

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Well, Organized for the most part…

I’ve earned the title of “Scrap Collector”, to all those who know me well, and it is a title well earned. I’ve accumulated a hoard of parts, gadgets, stationary, components, bric-a-brac, and scraps for over a decade, and it’s reached a point where I had to toss out all the things I perceived were not immediately useful to me. My remaining collection is still somewhat wasteful, albeit neatly organized now, and it includes but not limited to, a kilo of plastic strip files, 10kg of e-waste, miscellaneous toxic chemicals and mixing pots, fasteners and random tools, more piping and hose than a Shakespearean reproduction, enough plasticine clay to build a kindergarten, a hot pink toilet seat, and some of my lost marbles (only 3Kg of them).

Regardless of the phrase “One man’s trash is another man’s treasure”, I believe the 10-year’s worth of spring cleaning was slightly overdue.

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ETA, Chilling on the bay window

On the project front, I’ve begun Plan Wololo, a plan to convert Project ETA’s HBot kinematics to CoreXY, using non crossed belts. I’ve already done the CAD work, and I should receive all the parts in a few days. While designing ETA, I’d made sure to include the tolerances for when I transition to CoreXY kinematics in case HBOT’s accuracy was insufficient, so it should go somewhat smoothly.

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Various random concepts for the moon clock

I’ve also started Project Moon clock, a desk or wall mounted gadget which indicates the current phase of the moon, for those who don’t like stepping outside or have cloudy weather. It’ll have a little ball representing the moon, and will use a NodeMCU and a servo motor to rotate said mini-Moon, and indicate how lit it is. It’s a quick little project, as a present for someone.

That’s all for now, but I am going to restart weekly updates on this blog of mine, so please, stay tuned and let me know thy thoughts.

 

Signing off,

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 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~

MiniMake: Benchtop PSU

Hello Sunday!

So as I’m working on Project Eta right now, I need a source of power while I’m prototyping. Historically, I’ve been using 9v batteries and AA battery holders to provide power while prototyping, but obviously, that is less than perfect as a solution. So I had a couple old computer ATX power supplies laying around, and I decided to turn one of them into a benchtop power supply, as these handy little supplies provide 12v, 5v and 3.3v in neatly regulated cables. This project takes less than a weekend to finish,  and presumes you have basic skills with soldering connections and a grounded understanding of how electricity works.

WARNING! POWER SUPPLY UNITS CONVERT WALL OUTLET ELECTRICITY INTO LOW VOLTAGE HIGH CURRENT. ELECTROCUTION HAZARD AND DAMAGE TO YOURSELF/YOUR HOUSE’S WIRING/YOUR PSU AND YOUR PET GERBIL IS POSSIBLE. UNDERTAKE THIS PROJECT ONLY IF YOU KNOW WHAT YOU ARE DOING. KIDS, DON’T TRY THIS AT HOME.

Components

  • Computer PSU, 2nd hand works well, ATX preferred.
  • LED/bulb for indicator
  • Switches
  • 2.1mm plugs, screw fit connectors, crocodile clips, etc.
  • Heat shrink tubing & solder

Tools

  • Multimeter
  • Drill
  • Sheet metal snips and tools
  • Soldering Iron
  • Wire Stripper

On Choosing ATX PSUs-

Most PSUs should work ATX works well because they usually have a bit more headroom for circulation, and they’re the most common and cheap. It’s advisable to use a second hand PSU for this project, as long as it works. Some old PSUs require a minimum load on the 5v line in order to properly regulate the 12v line. This can be fixed by adding a resistor onto the 5v line, but at low current applications it shouldn’t be an issue.

Benchtop PSU (2)

Here’s my PSU’s specs, and I doubt I’d be reaching anywhere near the limits

Procedure

Start by unplugging your PSU and leave it alone for around 15min, just in case the capacitors have any remaining charge in them. Remember to exercise caution and possibly even common sense while working.

Unscrew the 4 screws on the top of the box, and remove the upper shell. The PSU has two U shaped shells, one upper and one lower, which forms the body. The lower one has the electronics, fan, power port, and cables attached. If you want to paint your PSU afterwards, peel off the labels now, and give the upper shell a thorough scuffing with sandpaper, 120 should do it.

Now plan your layout for what you plan add to the box. I’m using 3 sets of crocodile clips, a 2.1mm jack for arduinos or the like, a 2.1mm port, a potentiometer, an indicator bulb and a power switch. You may want to adjust this depending on your anticipated usage, maybe using header ports instead of barrel plugs, your choice.

Use a marker or scriber to mark your layout, then use a drill to make the holes. Keeping a scrap of wood under the sheet metal as you’re drilling will prevent it getting dented or damaged as you drill. After drilling,  I used a pair of snips to cut a square hole for the main switch, and clean up the edges of the circular holes.

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Upper shell of the PSU, drilled and ready to receive the components.

After drilling the holes, give your box a gentle scuff of sandpaper to prepare it for painting. For my texture, I decided to go with hazard stripes, a lightning bolt and the word HAZARD on the top shell, and leave the lower shell as plain metal. I painted the entire box black with gesso primer, then I used 1in masking tape to create a diagonal masking pattern on the box. Using a paper cutter,  I cut out the details out of the masking tape strip, and then painted the entire shell lemon yellow.

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After the paint dries, peel off the tape, and behold your work. You can screw in your accessories at this point, I went with an old fairy light bulb for a mildly retro look, a potentiometer and a 2.1mm port.

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Standard Pin layout for the thick wire bundle from your PSU, older PSUs use version 1, mine was v2

Next, we start the fun part, wiring. Observe the tangle of wires on your PSU, you’ll notice one thick bundle of around 20ish wires, and several thinner bundles. Use a wire cutter to cut the plugs off the thinner bundles. All the wires should be colour coded, although the colours vary depending on the manufacturer, but typically the yellow wires should be 12v, red is 5v and black is common. Use a multimeter to check just in case. Leave the PS_on, -12vdc, 5vsb and PWR_OK wires connected to the big plug for now, and cut all the 12v, 5v, 3.3v, and ground cables from the plugs as long as you can, pull them into the case and group them.

Benchtop PSU (5)

12v yellow, 5v red, ground black, 3.3v orange

Next, carefully observe which wires are PWR_OK, -12vdc, and 5vsb, and cut them from the plug. You can either snip these cables as close to the board as you can, or tie them up inside the case. The PS_ON wire is useful because when it is connected to ground, the PSU turns on. This cable is what we will connect to the power switch on the case. The 5vsb provides 5v dc at approx. 400ma even when the PSU is plugged in but off, so it can be used if you want to control the outputs with a micro-controller.

Next, we start soldering. I connected a ground cable and the PS_ON cable to the red main switch, and  I connected one of the 3.3v cables to my bulb, so that when the PS_ON switch is flipped the light comes on to indicate the PSU is live. Two 12v lines went to a pair of crocodile clips and a 2.1mm barrel plug. I used the potentiometer as voltage divider to control the power to one set of croc clips. I like to twist the wires around each other to keep them together, with a little ring of heat shrink at each end to prevent them unraveling. Remember to insert heat shrink before soldering!

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Once you’ve soldered all the wires you’re going to use, curl up the additional wires, zip tie them and push them to the side of the case. Remember, airflow is important inside the case to prevent overheating, so ensure that you haven’t blocked off the fan or its airflow path. Do a final test with a multimeter to check that all switches, plugs and wires function properly. Pull the crocodile clip wires out through the hole in the PSU case, and close up the case. Check that the tabs on either side of the upper shell properly align with the ones on the lower shell, and that its facing the right direction, and tighten the screws.

Thats it! Your PSU should be fully functional now, plug it in and give it a trial run. As a last minute feature, I glued a small strip of PVC foamboard (sunboard) to the rear of the case, and made some impressions in it so that I could clip my crocodile clips to it. This prevented the clips from accidentally touching and shorting out.

I hope you enjoyed this short MiniMake weekend project tutorial log, and I hope it was of use to you. If you’ve got any queries, please do leave a comment and I’ll reply as soon as I can and do consider sharing and subscribing for more weekly content.

Until next time,

Signing off,

~Adithyaa

Project: FFF 3D Printer “Eta” Part 6

Hello Sunday!

This project is the largest I have ever undertaken, and its goal is multifold. Besides the obvious benefits of having a 3D printer, it has taught me a lot of valuable information as a designer. The most recent lesson it taught me was how errors in the initial stages can result in compounded errors later.

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Top view of ETA’s CAD model, Note the two motor mounts in the lower sides.

While designing the rough CAD layout for Eta, I placed the XY steppers on both “legs” of the H formed by the X&Y rods, as it should be. However, I later rotated all smooth rod axes vertically to facilitate easier access to the printing surface from the front. At the time, I didn’t think there could be any conflict, but after around 5 months when I finally finished making, aligning, and bolting down all the axes, motors and mounts, I realized that this arrangement meant that the motors were countering each other’s movement.

You done goofed.

Since both motors were on the same side, one of them turning would have prevented the other one turning in the opposite direction. To correct this, I swapped the motor on left with the idler mount diagonally opposite, which fixed the issue. The problem with large or long duration projects such as this is that you tend to sometimes lose focus of your original goal, or change a system without realizing its effects on another system.

Design life lessons aside, I’ve extended and linked up the cables from the hot end, and now all that’s left is to hook up the mechanical endstops, setup the heat bed, make the fail safe systems, create the secondary control board and relay board, and I’m done!

With the hardware section, that is.

Next up, the software, and how I’m attempting to control a 3D printer with a 15 year old desktop jury rigged into working order with string to hold it together. I’m running linux mint on that PC, so at the very least it isn’t too slow.

Signing off,

Adithyaa