More test prints and fine tuning the heated build platform

So we have been able to play around with Hydra's FDM toolhead some over the past 3 days and have gotten some pretty exciting results. After doing several small test parts we moved on to some larger parts to test out the long term functionality of the machine as well as the anti-warping techniques we had implemented with the heated build platform. The first slightly-larger part we did was the whistle v2 off of Thingiverse. It was really neat how the ball is printed inside of the enclosed whistle. Here are a few pictures of the end result. The quality, as before, was very good compared to machines I have used in the past.

As you can see from the first pictures, the machine was able to span the gap across the top of the part amazingly well. It took lots of tweaking on my old machine to get this to work along with an active fan for cooling, but somehow it worked on the first try here. The resulting whistle actually functions very well so kudos to whoever designed it on Thingiverse.

The next part we tried to print was a MUCH larger part that is about 3 inches wide and 4 inches tall. The part is also from Thingiverse and is a bust of the famous Walt Disney. We didn't have much plastic left on our one small spool of red filament, but we decided to try it out anyways. Mostly, we wanted to see if we could print a part this big without any positional errors or warping. Here are some pictures of the finished print when the plastic ran out.

I also uploaded a time-lapse video of the build in progress. It can be found on YouTube here: http://www.youtube.com/watch?v=eSThg1k-VVE

I was amazed with the final print quality. So much detail on this tiny part. It was really a shame that we ran out of plastic before finishing. I think we might merge the end with the brainy walt on Thingiverse so we can print the brain in a different color.

Onto the heated table. Before printing the above head, we had been experimenting with exactly what temperature gives the best result from the heated build platform with a Kapton coating. We actually tried printing Walt on a 100C and 110C heated table, but both times the part failed around the 6 or 7th layer. The above print was done as 120C and had zero problems. It seems that there is a very fine line between being too cool and too hot with this platform. We had done other prints around 135C and noticed that the part actually seemed to deform and was a little too soft. From what we can tell, there seems to be a 10 degree window where the parts come out really nicely. Anything above or below that doesn't seem to work very well. Thankfully, we have dual PID control implemented in the v1.4 firmware so keeping the table and nozzle temperatures stable to about 1-2 degrees is no problem. I have had lots of trouble in the past with the Reprap firmware that I eventually traced back to temperature fluctuations. I have tried to solve this in the v1.4 firmware in 2 ways: First, PID control is used to offer much better temperature stability instead of the single threshold on/off switch the Reprap firmware used back in the day (not sure if they are still using this now). The second improvement is that the v1.4 firmware also offers the ability to have a slave Arduino hooked up the Arduino Mega via the Serial1 connections that can handle all temperature control. This way, the slave Arduino is constantly monitoring and regulating the temperature while the master Arduino Mega is free to handle the command processing and movement calculations. Using these 2 methods we are able to maintain temperatures extremely well. It has definitely helped improve our overall print quality. I will try to release the v1.4 firmware over the next week or so as there are LOTS of improvements and additions in both the host GUI and firmware. For now, it's back to the machine for more test prints!