Electrical insulation for J-head hotend

I've got a j-head hot end that I had planned to use on my next printer but I'm having such terrible jamming problems printing PLA I've decided to commision it early.

Now I was wondering is silicon tubing suitable for electrical insulation of the thermistor and power resistor wires prior to crimping to longer cables, the thermistor leads are wrapped around the heated block ( I was planning on roughly following [tvrrug.org.uk] )

For the PLA jamming I think it's to do with heat transference upwards, the hot end I'm using is [www.nextdayreprap.co.uk]
I've also got always-on active cooling using a 40mm fan using [www.thingiverse.com] but if I use any retraction at all the flow soon stops

Printing: 3mm Faberdashery white PLA
Temp: 210C - any lower and the extruder starts skipping steps extruding manually
Active cooling: yes

Richard

Can you supply a photo of your setup. How tight is your filment extruder. You might be making the filment square which is making it harder to push through the 3mm peek tubing. 210 seems a bit to hot for pla. I do 180 for mine. As you have an extra heat you might need to set your fan at 100% instead of letting slicer or skin forge control it.

Richard,

What kind of firmware are you using? Have you PID tuned your hot end yet?
Few things to look first.
1) Using the correct thermal couple in the FW. Does the values in the host software match up (some way of comparing two temps_.
2) PID tune your hot end (Marlin). I have a budda, and out the box I was having hot end temp issues. I later found out that Marlin FW PID is default on, and the values are set for a makergear hot end (way different then my budda). After I PID tuned my hot end and put the correct values in I have had no issues.

Another thing to look at is the way you are cooling your hot end. The thingiverse part you sent looks like it ducts the full fan force across the whole hot end. With a J-head you only want to be cooling the PEEK part (not the brass). I have found anywhere between 10-20deg drop if a fan is set too high and cooling the melt zone. What could be happening is that there is a temp difference between the outside and inside of your melt zone due to the fan cooling the brass. There is not much material around the nozzle so it is very easy to cool it too much causing filament stripping. By adjusting the temp up and up to compensate for the fan cooling the outside you in turn are causing the inner temp to rise as well liquefying the PLA. My suggestion, try to find a different duct that cools just the PEEK, and possible a second fan ducted for the PLA. Else look into insulating the melt zone (brass) to prevent the fan from cooling it by accident.

In theory yes, but why not use existing high temp (500F) wires that are designed for this purpose?
You can also use kapton.

I use silicon tubing on both the thermistor leads and the resistor leads. Beyond the soldered joints at the end of the original leads I just use normal heat shrink.

So... thanks for all the responses first of all

I've attached a picture of my setup. The 40mm fan by the duct is always on 100% when I'm printing or waming up currently for a start. I did initially have it setup to be controlled by Slic3r but instead have just setup direct M106 and M107 command buttons in pronterface.

I do have the bolts tightened pretty tight onto the filament mostly because I was having issues with the filament not driving through into the hotend, I've also upped the stepper voltage slightly to try to assist as I was getting a bit of skipping. I did try reducing the temperature but as soon as I do I get the motor skipping.

I'm using sprinter firmware that came pre-loaded as I bought the printer as a complete kit from www.nextdayreprap.co.uk and so far I've made no adjustments to it at all so I don't know about tuning it.

I don't have any experience (or know where to get) high temp wires from, the main issue is the wires very close to the hotend and how to insulate those effectively. I heard even soldering that close could fail hence I got some ferrules to clamp over the connectors. So wrap/solder/ferrule/heat shrink is the plan to connect to the cables away from the x carriage. I was wondering if the silicon can take the heat of being in direct contact with the hotend long term - mainly because buying very short lengths of ptfe tubing seems silly expensive for the amount I need.

Richard