PLA Heat Resistance: Confirming What I Already Knew

Making 3Dprinted pinhole cameras requires opaque materials. I have had difficulties finding and maintaining a supply of suitably opaque PLA filament for my designs and customers. This unusual situation has been blog-flogged HERE. A side effect of this is a stockpile of filament for non-photographic applications and the occasional translucent camera.

I recently designed a 6x9 version of my OSKAR Tuxedo camera, and printed it in Matterhackers Gun Metal Gray (now called Jet Grey). Only afterwards did I discover that the filament (and the resulting camera) was not longer opaque.  I have received excellent customer support from Matterhackers. This is not an indictment of them in any way - They were apparently mortified that their product had changed without their knowledge. I have since received replacement spools, which I have yet to test.

However, I found myself in possession of a useless camera. So, I found a use.

I have long cautioned people to treat their 3Dprinted camera with the same respect they would afford the film inside it. I specifically caution people not to leave their camera in a car on a hot day because the melting point of PLA is lower than other thermoplastics. Today, I tested this assertion.

I donned my Schlab coat, eye protection, oven mitts and tossed the big OSKAR onto the dashboard of my Prius. The dash is dark grey, the outside temperature is in the mid-seventies (a little more than 20 degrees Celsius).  In a dutiful nod to my all my chemistry teachers, at close to sea level, I effectively tested this at STP (Standard Temperature and Pressure).

terraPin OSKAR 6x9 tuxedo body on Prius Dashboard

I ran to the grocery store for some soup ingredients (I'm making a mushroom-bean chili; I am very excited about it).  The camera was left on the dashboard for approximately thirty minutes.  During the short drive, the air conditioning was turned off and windows rolled up. In the interest of parking efficacy, I parked the car pointing toward the north, and not facing the noonday southerly sun. I did not measure the temperature on the dashboard, preferring to relate a cautionary tale based on qualitative findings. 

When I was done shopping, I hopped in the car to observe a very slight drooping of the unsupported front wall of the camera. It yielded without much resistance when I pushed on it. I assessed its rigidity by twisting it. The thicker structure in the bottom of the camera wasn't soft enough yet to twist out of shape, but I easily pulled the camera body apart, stretching and deforming the softened PLA. 

Manual deformation of softened PLA camera body I

I can easily imagine someone ruining their camera in a similar situation, solely through indifferent handling. Based on this experiment, I would suggest that 30 minutes is a general threshold for exposure to the high temperatures found in the sunny day dashboard environment. An assembled camera, with the caps in place, could possibly withstand this temperature extreme if handled very cautiously and deliberately while hot. Any deformation of the front of the camera could easily compromise the shutter's ability to move and/or keep light from the film inside the camera. 

A lengthy hours-long interlude on the dashboard, in similar circumstances, could conceivably reduce your camera to a pile of slag. I may test this next - I have an identical camera body from the same batch of filament. 

Manual deformation of softened PLA camera body II

I repeat: Treat your terraPin 3Dprinted pinhole camera as you would the film inside of it. 

The Curious Case of Vanishing 3Dprinting Filament Pigment

TL;DR: Finding opaque PLA filament has proven almost impossible. Opacity should be considered a critical specification, and filament manufacturers should report same.

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3D printing is rapidly evolving as a competitive market. What once was solidly a hobbyist's niche is now expanding as school kids (and their parents) are exposed to the technology. More and more 3D printing-related companies are entering the retail space and the expanding competition is great for consumers. Prices for machines, parts and filament have been driven down as a result of predictable market forces.

My first 3D printer, the Printrbot Plus, came as a basic laser-cut kit of parts for about $750.  You can get a genuine Prusa i3 Rep-Rap machine, with all kinds of sexy, for less than that today (It's open source and you can get a clone for less than $200!!). In a world where people will pay $800 dollars for a phone - a PHONE!! - cost is quickly evaporating as a barrier to entry for many people. I can only imagine the development of 3D printing in the hands of brilliant young minds that grow up it. Take any outlandish predictions you hear with a grain of salt, but know that the reality will exceed them in both scale and scope.

I design and 3D print pinhole cameras. When I got my first 3D printer, I really had no idea what I would do with it. I taught myself 3D design, made a lot of mistakes, and eventually applied my skills to another hobby: photography. The results vastly exceeded my expectations and I have approximately forty pinhole cameras (plus miscellaneous variations) and related devices posted on Thingiverse.  They are all available for download, by anyone, and they are used by photographers all around the world.

Of course, I 3D print, assemble, and test every camera I design, and there is a growing demand from people who want to buy a camera from me. I have mixed feeling about this. 3D printing is really about distributed, one-off, or customized production; Anyone can download the files from the Internet and make their own, and make it to their own preferences. This is the perfect model.

However, the intersection of film photographers and people with access to 3D printing is a relatively tiny group of people. The more cameras I make for people, the fewer I can make for myself and friends. On the other hand, I've seen enough of my cameras bodged by indifferent assembly or out-of-whack printers to know that I am going to print and build the better camera. I've sent people cameras with defects (light leaks, weak parts, poor fit, etc.), and it's morbidly embarrassing, albeit educational.

One of the primary issues I've seen is 3D printing filament (the raw material, kinda like weed-eater line) that isn't opaque enough for photographic use. I started with ABS, the same plastic LEGO are made from. Optically, it's an ideal material for a camera - it's opaque, flexible, and strong. It also stinks like cancer when you melt and extrude it. It's also fiddly to print, requiring absolute control over ambient temperature to prevent warping and cracking. This becomes really difficult in a poorly heated space like the Schlaboratory. When I got my Lulzbot, I found that, even with a box and a 300W light bulb inside the box, I couldn't get clean prints. That's when I switched to PLA.

PLA, or PolyLactic Acid, is a bioplastic that is compostable, benign, and dimensionally stable when 3D printed. It's the same stuff your fork is made from (by city ordinance) at Seattle area take-out restaurants. It literally smells like maple syrup when melted in the printer. PLA comes from plant-based starches, like corn, and is completely renewable. It comes in vibrant colors, but it's often not opaque.

I started my love affair with PLA using a budget-priced black filament from SHAXON, made in China. It worked well for many months, even though it's quality and dimensional accuracy (and, presumably, purity) were in question.  Then one day I designed and built a box camera that didn't work as expected. I wracked my brain trying to find the defect in the design that caused the photo-destroying light leaks present on my images. At some point, it occurred to me that maybe the filament wasn't fully opaque. I tested this with a bright LED flashlight, and, sure enough, a dim purple spot of light glowed faintly through the body of the camera. Well, shit... I had a dozen spools of the stuff and they all failed an opacity test.

I resolved that this was what I should expect from a bottom-feeding price point product, and began spending more for my black filament, in a quest for higher quality. For a while, Makergeeks "Dark as Night" filament worked perfectly. Then suddenly it wasn't opaque. I got some Matterhackers filament in black and dark grey. The black wasn't opaque, but the grey was! Then it wasn't. JustPLA sold me a spool of perfectly opaque black PLA, so I bought a 5 kg spool. Not opaque. Then I used many spools of Rigid.Ink filament with fabulous results until it quit being opaque also.

I devised an opacity test tool, and posted it on Thingiverse. I pleaded into the depths of the Internet for a crowd-sourced black PLA opacity test. My standard is no detectable light through 1 mm of solidly printed PLA when proximally back lit by a 70 lumen light. The following filaments have been tested and essentially all have not been found to e opaque enough for photographic applications:

MatterHackers Pro Gun Metal Grey PLA Mixed results by batch
Rigid.Ink Black PLA                                   Mixed results by batch
JustPLA Black PLA                                    Mixed results by batch

Additionally, it has been reported by a Flickr user that these filaments are opaque at 1mm or less:
eSun Black PETG from HobbyKing            (not opaque for me)
eSun Black PLA from HobbyKing
Metal composite PLA from HobbyKing
__

Shaxon Black PLA                                      Formerly opaque; NO LONGER
MakerGeeks Dark As Night PLA                Formerly opaque; NO LONGER
Inventables Black PLA                               Not opaque
Lulzbot Black PLA                                      Not opaque
Hatchbox Black PLA                                   Borderline, but super-shitty quality
MatterHackers Pro Black PLA                   Not opaque
MatterHackers Pro Midnight Blue PLA     Not opaque
Ultimachine Black PLA                              Not opaque
Atomic Deep Black PLA                             Not opaque
Laywood-Flex                                             Not opaque

Recently I sent an email to a dozen filament manufacturers describing my application and the problems I have had in sourcing a consistently opaque PLA filament (in 3.0 mm). I have received replies that variously assert that, "of course our black is opaque", "opacity is not a reasonable expectation", or suggest filaments mixed with erosive additives like carbon fiber. I did receive two samples, but in 1.75 mm.  I have a small scratch-built printer that takes the smaller size, but I need to repair the extruder before I can test.

I submit this: Opacity is a fundamental property of (3D printable) plastics. Engineers have used various plastics for applications that demand opacity for more than a hundred years. This is not an esoteric nor exotic requirement for a material that might be used in an infinite number of ways. Filament manufacturers specify properties like "glass transition temperature", dimensional variation, and other technical data every day, yet no one publishes a spec for opacity.

I have a backlog of people who want to buy one of my cameras, but I don't have a suitable PLA. I am considering converting my Lulzbot to 1.75 mm to increase my options. Painting the inside of the camera is both a cheap hack and a temporary fix as the paint eventually wears off in spots.  I can't get hardened nozzles for my Budaschnozzle extruder, so carbon fiber is a no-go.

I want a genuinely opaque black PLA in 3.0 mm. I've used it, so I know it can be done. I will gleefully pay more for a filament that consistently meets this spec. The market needs to respond to both ends of the price/quality curve. As a 3D printing evangelist, I beseech someone to rise to this challenge. I can't be the only kook out there with this requirement.

Thank you, Internet, for any and all help!

Todd Schlemmer
theschlem (at) gmail.com

With heartfelt apologies to H. W. Longfellow

Excelsior, a poem written by Henry Wadsworth Longfellow in 1841, has long been the subject of parody and reinterpretation. Submitted for your perusal, my pinholish take:

RECTILINEAR

The sun was dipping in the West,

Gazing upwards, the light to test,

A man, a tripod in his hand,

Seeking vantage, as shadows fanned,

RECTILINEAR!

In his grasp, a brass and wood box;

The halves, now one, and interlocks.

Inside, the film, the ISO

One hundred, neither fast nor slow.

RECTILINEAR!

A satchel hung around his neck,

Swinging, thumping, impeding trek.

Bicycles, buses, cars rolled past,

The crosswalk clear, he moved at last.

RECTILINEAR!

“Spare change,” a grimy vagrant said,

Standing, blocking, eyes ringed with red.

A shrug and laugh, “I wish I could.

I must press on; the light's still good!”

RECTILINEAR!

“What is that thing?” a child cried,

buckled fast in her stroller ride.

“Photos it makes, with film. You know?”

The blank look clearly answered, “No.”

RECTILINEAR!

Emboidered badge: “The park is closed!”

The photog's thought: I think I'm hosed.

“I'll be real quick. Only one shot!”

I hope this works, the photog thought.

RECTILINEAR!

Unfolds the tripod; meters sky.

Composes landscape; aiming high.

A furtive glance eastward when he

Opens shutter; minutes twenty

RECTILINEAR!

Bearing down, diff'rent rent-a-cop

“What is that box? You need to stop!

You have to leave.” “I need more time!”

Defiant: “Pinhole is not a crime!”

RECTILINEAR!

Taking time, putting on a show,

He packs his kit, painfully slow,

A tapping shoe, the guard's arms crossed,

The shutter snaps, the shot's not lost!

RECTILINEAR!

Pinhole Making Resources

When designing a pinhole camera, I use a Windows app called PinholeDesigner. It also runs well on Linux under WINE. I don't know how to run it on iOS.  LINK

There is a setting for Constant that is "Lord Raleigh" by default. I have been advised that the square root of two (1.41), or 1.51 works better. Then I round down.

On a wide angle camera, the aperture is going to be "too small" for the distance from the pinhole at the corners. If you see crazy color effects or weird diffraction effects, your aperture is likely too small. 

To drill my pinholes, I use this methodology:  LINK

I use brass shim stock, 0.001 inch thick for my pinhole stock. This is a lifetime supply for most people:  LINK

Finally, I check my apertures for diameter and roundness with a digital microscope with a measurement tool, like this:  LINK

I make a LOT of pinholes, and I strive for 0.01mm accuracy. I achieve that about 25% of the time, so I have of extra pinholes that are just a little too big or small for my applications, but I save them and hand them out to people building cameras. Let me know if you need a pinhole, and I'll dig in my box of brass. 

This is a digital microscope view of a 0.30 hand-drilled pinhole in 0.001 inch thick brass shim stock.

 0.18mm pinhole "drilled" in 0.001 inch (0.0254 mm) brass shim stock, 150X