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Archive for October, 2016

21
Oct

Thermochromic PLA – MG Chemicals

Thermochromic filament is filament that changes its colour according to ambient temperature. I’ve mostly seen ABS filaments that change colour with even the slightest heat from your hand.

Thus it was with much anticipation at the outcome when I found myself with a spool of Mg Chemicals latest offering of Thermochromic RED PLA. Yep, PLA.

Staying in line with the rest of MG’s new products offering, it’s delivered in a zip lock bag, cardboard sides, and large spool center hub. All pluses in my book.

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I don’t know about the rest of the printing world, but it seems to me that RED filament must be next to impossible to make. Without fail, every red I have seen looks more orange to me than red. In my case, if it’s not fire engine red, it’s not red. So I of course, immediately looked at what MG ascertained was red.

IMG 1840

If you’re mumbling to yourself, that’s NOT red, well, you’d still be correct. Still, let’s look at the spool without a flash from the camera adding or subtracting anything from the colour. And for giggles, I’ll put a spool of eSun RED beside it.

This is MG Thermochromic on the LEFT and eSUN red on the right. MG’s is more in the purple hue range, and eSun is more to the orange. Still, if I have to pick something that at first glance is going to pass for red, it’s going to be the MG. No contest to my mind.

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Printing with the Thermochromic is no different than printing with any other PLA. I used the same temps, same retraction, same speeds. Wasn’t stringy or blobby in any way. Actually the more I use the new MG products, the more I like them. For the simple reason they are extremely consistent across the colour spectrum. I love not having surprises when I print…

One thing that catches you a little off guard though is when you look at the spool during the print job. It’s redish purple. And then you look at the print under the hot end. There’s a slight pink hue to it and other than that, it looks white.

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The beauty of thermochromic filament is of course that it changes colour. According to ambient temperature around it. One would assume that MG would have indicated the temperature range that will affect the colour. Which of course, at the time of this writing is the wrong assumption. There was nothing on the box, nothing on the filament label, no information that I could find that specified the temperature range. An oversight? Lack of data from the manufacturer? I honestly don’t know but it is something that should be addressed.

According to my own less than scientific tests, there’s about a 20F working range. Below is the finished print (Fossil Fish from Thingiverse) and the temp of the top of the print is 123F (50.5C the temp of my heated bed). You can see the tip of the tail fin has started to cool.

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Get down to 115F (46C) and you start to see more areas, again thinner areas cool faster…

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At 108F, 42C, things are starting to really change. Again, the thicker areas retain the heat better so you have to wait longer for them to cool.

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Finally at our human body temp, it’s completely gone through the colour change. This means that you can’t just pick up the print and have your hand affect the colour. If you’re looking for that temperature, MG’s thermochromic isn’t going to cut it for you.

Further, if you scan around the net looking for thermochromic filament specs to find the temperature range for the colour change, you’ll find what I did. Zip. I couldn’t find one company that actually spouted the specs for a PLA temp range for the colour change. All I could find was recommended melting temp. I found this odd, but seems to be the way it is. For whatever reason (plus I’m thinking the guys who dye the stuff have either never heard of Pantone or are colour blind).

Remember I said that this is more purple red? Heres the print from MG Red on the left, eSun red on the right. Natural lighting.

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If you’re like me you’d say the eSun is more red. But lets take the same fish and put them in front of a red toolbox lid.

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Isn’t perception a pain in the butt…so the key to the red/orange/purple thing is lighting, background, and frame of mind. There’s still no hands down colour winner but at least you know what to expect.

To summarize, I really like the new MG PLA. Thus, yet another winner for myself and MG.

The thermochromic is super useful where the temperature range will be hotter than the human body.

Where would that be? A few seconds to search Thingiverse for water tap nozzle should give you a few hints. Imagine you have kids and a PLA printed nozzle, if the nozzle is white the temperature is 115F to 120F+. Don’t touch it! Or jump in the shower unless you want to perform an equally quick jump back out.

Or make an ornament that hangs on the mirror in your car. When you come back to the car in the summer time, a quick glance will tell you if you want to open the door and jump in, or just take a step back as you open the door. Course if the ornament is on the floor mat, best to have someone else open the door, just to be on the safe side.

Something that sits on the mantle over the fireplace…in short, lots of places to use this higher range PLA. Just keep in mind the glass transition point…(60-65C).

Update: MG Chemicals informed me that the Red colour changes to natural at 43 °C / 109 °F. This is a little different than my somewhat unscientific approach with the IR temp gun readings. They stepped up to the plate with the info. Nice.