Thursday, December 11, 2008


No-curl hair dryer

ABS is a superb building polymer, but it does tend to curl up and delaminate as it's laid down because of thermal contraction. Inspired by Nophead's work and the heated base done by Metalab, I decided to try a very simple solution. I ran a build with a cheap hair-dryer (right) clamped above my RepRap machine blowing on the build.

The result was perfect: there was no curl at all; the part built as flat as a pancake.

I had to insulate the extrude head by wrapping it in fibreglass wool and putting a piece of cardboard on to exclude the draft: the hot air cooled it too much...

The head was running at 240 oC. I put a thermocouple thermometer on the base at various locations around the build as it progressed. The result was a pretty constant 60 oC. Measuring the temperature of the part during the build with an IR thermometer gave 70 oC. Measuring the components of the extruder (including the motor) gave temperatures just below 40 oC; I directed the hair-dryer carefully to minimise the flow of hot air over them and the electronics.

And here is the part fitted (right). This is the prototype granule extruder coming together. The part is the guide that stops the screw-drive rotating as it's driven against the polymer granules. I made the hopper (green) in the Strat as my RepRap was in bits the day after I'd finished the design for that.

Watch this space...

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LOL! Beat me to it. My old hair drier blew up a few weeks ago and my paint stripper is too powerful! Brilliant work, Adrian! :-D

We're getting places in a hurry!
Amazing, I wonder if it works for HDPE as well. Might need to be a bit hotter I suppose.

The air flow below melt temperature should also be beneficial in setting the plastic faster, allowing smaller objects to be made.

I must get my machine working again.
Basically, what Adrian is doing is creating the 80-odd degree environment in which Stratasys prints its stuff without having to have an enclosure. :-)
The hairdryer has two settings - I used the lower. A neat trick might be to use the higher, but to drive it off a Variac to wind the temperature up and down. Not sure what that'll do to the fan motor, mind...
I love how the granule extruder is coming along! It looks a lot like a KitchenAid food grinder / sausage stuffer. :D
In my experience, variacs and AC motors tend to fight with each other. Possibly you ought to put a hockey puck solid state relay in line with the hair drier heater circuit and pwm that rascal. :-)
Very nice. I was just at Target looking at tempered-glass cutting boards with an eye toward gluing nichrome to the underside. I should've just picked up a hairdryer. Seeing as my hair averages 1/2" long, I don't actually have one handy.
Nice! I like the wingnut extruder drive - have to work that into the name somehow...

Don't they usually use two SCR's wired opposite of each other to drive AC motors? I had a look around on Mouser and small ones suitable for this type of thing can be had for like $5. PWM control of a hair dryer would make this project look so much cooler at a Dorkbot meeting!

Nice work, Adrian.

A Triac is effectively two SCRs back to back and they can be used to control AC motors, lamps and heaters.

Probably best to separate the wiring to the heater so it can be controlled while leaving the fan on full blast.

All a hair drier is is some nichrome, a fan and a cowling. We could make our own with a PC fan and some nichrome. Or just attach a power resistor to a CPU heatsink with a fan. Pick the resistor for whatever voltage you fancy and extrude the cowling from HDPE. A good idea to fit a thermal fuse as well to make it safe.
We would need to insulate the fan from the heatsink of course to stop it melting.
For UK reprapers Woolworths have 1800 watt hair dryers going cheap at £6. Get one quick before they close down!
Wow, old thread, but I was about to try the same idea. Glad to see it works! One difference, I found a 12VDC-powered travel blow dryer that I'm going to modify for active temperature control with a MOSFET and thermistor and mount it to the the print head like a lot of the PLA cooling fans.

Any suggestions for an optimum temperature? I was thinking 80-100C would be best, but it sounds like 60C might be enough...
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