I just found the perfect thing to test my idea to get all the

I just found the perfect thing to test my idea to get all the benefit of a heated chamber and more without risking patent entanglement. Some time ago, I came up with the idea for a “warming fan” for ABS to match the cooling fans that can be used for PLA. The idea is that the fan would actively cool the print as with PLA, but only to the optimum temperature (cooling ABS too much creates adhesion issues), and any plastic that falls below that temperature would be warmed back up to it. A heated chamber keeps things warm, but it also makes it take longer for a layer to cool enough to be printed on top of, and this would solve that problem.

I put off testing this because I was thinking of complicated designs involving fabricating heatsinks to attach to power resistors to put in the path of the airflow, but tonight I decided to see if I could find an off-the-shelf part that I could modify to suit my needs. Most heaters run off of AC, which makes them less than ideal, but I found a few cheap fan-equipped heaters (and even a blow-dryer) designed to run off of the 12V from a car’s cigarette ligher. Perfect! All it needs is the car plug cut off and a thermistor mounted in the right place to regulate the temperature of the airflow.

Try first with hair dryer. Mount a pipe in extruder and pipe’s other end at hair dryer.

For the first test, I’m going to go even simpler than that. I’ll just bodge the hair dryer onto my X carriage, pointed just below the nozzle, with a thermistor shoved up inside it. I’ll probably take the thing outside on a cold day to do some comparison testing with and without the device.

Our aim here is to keep bottom layers hot right? wont it effect the top layer quality?

Didn’t Adrian Bowyer try this a long time ago?

Very curious to hear how this turns out. Mounting something like this on a Cupcake would be very simple given the stationary nature of the extruder too.

@Whosa_whatsis - Have a look into TI’s selection of temperature sensors: http://www.ti.com/lsds/ti/analog/temperature_sensor.page

A lot of them have a dedicated “alert” pin of some kind that could be used to control your warming fan.

SparkFun carries a TMP102 breakout board you could use to test things with: https://www.sparkfun.com/products/9418 Only coding required is to set Thigh/Tlow trigger temperatures. Gottcha is the VDD range only goes up to 3.6V.

An even simpler option (with wider VDD range, up to 5.5V) would be the resistor-programmed TMP709: http://www.ti.com/product/tmp709

Here’s what Adrian did: http://blog.reprap.org/2008/12/no-curl-hair-dryer.html (that was four years ago, btw)
For him, it eliminated the need for a heated print bed, so that concept looks pretty promising.

@Thomas_Sanladerer Thanks for the info. I hadn’t seen that. Great minds…

@Andrew_Plumb For now, I was going to use a board set up for dual extruders, and use the second extruder’s temperature control for the fan. I want to have gcode control so that the same apparatus can double as a cooling fan when using PLA, or run at different temperatures for different materials (anyone know where I can find some HDPE filament?).

I think I still have a roll of 3mm HDPE filament from Year 1 Cupcake-era MakerBot.

Maybe collaborate with Filabot to “make your own” HDPE filament? http://filabot.com/

Orbi-Tech has pretty much any plastic you can think of: http://www.orbi-tech.de/shop/Plastic-Welding-Rod/PE/PE-Welding-Rod-3-mm-on-spool-Black::149.html

Two of the German RepRap suppliers resell their ABS, and it’s often praised (e.g. by Alessandro Ranellucci / Slic3r) as the best ABS on the market. I do like their filament, but i’ve had spools delivered that would behave completely different to the other ones.
Plus, since they’re not in the US and HDPE is “on request” only, anything but a batch order will probably cost an arm and a leg per roll.

I signed up for a pound of HDPE from http://www.indiegogo.com/osprintingllc/x/549084 , but I’m not holding my breath for usable filament from one of those. I’ve been doing some research, and proper filament production is a lot more complicated than all of these people think. High pressure, low temperature, oxygen evacuation, long cooling zones… these desktop versions don’t seem to have any of the things needed to make decent filament.

A friend of ours visited @Vik_Olliver 's facility and described how big his machine is. While I’m sure it can get smaller, I don’t think desktop-sized is an option, at least without some radical changes to the process.

HDPE is a particular bugger because it loses a lot of heat when it crystallizes, making it bulge unpredictably metres away from the die nozzle. We hate making it. Also the parts distort like crazy when you print 'em.

Which patents are you worried about entangling? I might be able to help you figure out whether your plan would actually infringe. Source: I am a Patent Examiner. Disclosure: All advice would be informal.

Stratasys has a patent on printing in a temperature-controlled chamber with the motion-control systems mounted outside. It’s a stupid patent that makes everyone afraid to sell fully-enclosed printers until it expires. Simply covering the windows and allowing the chamber to be passively warmed should not infringe, but everyone’s tip-toeing around to avoid becoming the target of even a questionable patent suit.

Abolish patents!

I believe the patent you are referring to is 6722872. I’m assuming you are in the US, but there are similar patents filed and granted in the European Offices.
You seem to be concerned with the idea that a chamber has to be “enclosed.” The independent claims of this patent does not require that the chamber is enclosed. A reasonable person can make the argument that “chamber” does not inherently require an enclosed space. Further, the enclosed chamber does not appear to be the main thrust of the patent. Rather, Stratasys seems concerned with keeping the x-y-z control thermally separate from the heated chamber.
Some other notes: The maximum monopoly that stratasys can have for these claims is 20 years from the date of filings, which appears to be 2001. This is only true if they have continued to pay their maintenance fees. Also, contrary to what you might believe, litigation for Patents is fairly uncommon compared to the number of patents issued each year. Litigation can be expensive, and stratasys would have to weigh the pros and cons of taking an individual or small business owner to court. They may find that it just isn’t worth their time to be able to squeeze very little monies out of you or this idea if you implement it. Also, simple licensing agreements can be a viable option. Lastly, if you believe you can prove that Stratasys does not deserve this patent (since you can prove that some other party did it first) and it is financially beneficial for you to do so, you can work with the Patent Office to invalidate it.
tl;dr: you have a lot of options for ways to work within the system and get what you desire.

@Jacob_Cigna I appreciate your thoughts on that patent. I have been wanting to hear an informed rundown on that patent for years.

The concern, I believe, is from the front runners (as far as sales) in the Open Source 3DP community, which is by a fair bit MakerBot. Since they got funding, they’ve probably had lawyers from stratasys and others waiting to pounce. If for any other reason, to send a message to the rest of us.

Now that I think of it, with MakerBot no longer being open source (give it time), they’re probably a bigger target now.