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Build a Prosthetic Hand Part 4

8/10/2014

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I could not get the Taulman Bridge Nylon to print well on X3REX printer.  It has a .5mm nozzle, which I can't get the Nylon to flow consistently through.  So I decided to print the Gyrobot hand body on my Airwolf3d v5.5 machine which has been printing Taulman 645 Nylon very successfully.

I loaded the print file, and everything was going along swimmingly until ... (play scary music here)  about 85% of the way through a 16 hour print job, I realized that the 5.5 machine does not have the build height required for the hand.  The height of the hand is 114.9mm and the max build height on the this machine is 104mm.
:-(     I let the print continue until the printer got to 104.9mm and I killed the print job.  The hand was complete enough for testing out, but the guides around the index finger joint were missing, so there is the possibility of the finger sliding off to the side.  Another shortcoming of the 5.5 machine is that there is no control over the bed temperature: it is either on, or off.  That normally isn't a problem with ABS since it heats up to a maximum temperature of about 100C.  But the Bridge Nylon has a recommended bed temperature of 70C.  above that, the glue cooks, burns the nylon at the base of the print, and curls up.  So I'm going to have to go back the the X3REX and figure out the settings for Nylon.  X3REX is RAMPS 1.4 controlled, so you can precisely set the bed temperature.  I also have a .35mm nozzle for the Airwolf JRx hot end on X3REX. I'll install that nozzle and use the 645 Nylon slicer config that works so well on the 5.5 machine.

Aside from the base layers getting burned, the Taulman Bridge Nylon printed pretty nicely.  I did notice some layer separation up around 58mm from the base.  I'll have to play with the configuration a bit more to figure out how to solve that.  Maybe a less dense fill rate.  It is possible that this type of printing is just not suitable for the design.
Picture
Back of nylon hand
Picture
Front of nylon hand
Picture
Finger print fail.
Printing the fingers was a small catastrophe.  Since I knew the glue and lower layers were likely to burn, I shut off the heat bed about 30% of the way through the print.  My thought was that by this time, the  amount of plastic between the base layer and the layer being printed, was enough to insulate the them from each other and prevent curling.   Wrong!  Of course I didn't find this out until I got up the next morning to find that the pieces had seperated from the base about 75% of the way through the print job, and I had a nice blob of nylon strands all over the print bed.
Flexy-Hand #Abstract2Actual: 71:51 and counting
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    TJ Emsley

    Lifetime tinkerer.

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