Topic: Hot end replacement mk2
This is a guide for the hot end I've been using for the last few months. It features two heating resistors in a copper block for super fast response. So far it has been predictable and reliable.
Parts & Tools Required
Soldering iron and solder
Thread/plumber's tape
Some heavy gauge wire
Step 1: Grind PEEK Barrel
This step is a must for any Solidoodle owner, even those with the standard hot end. File down the edges of the PEEK barrel, a little at a time and constantly checking, until you can firmly fit a spanner of your choice. I went for 11mm.
Step 2: Insert Brass Barrel
Screw a fitting nut onto the end of the barrel, and then the nozzle behind this. Tighten the two of them against each other, which will allow you to turn the barrel into the PEEK until it's really tight.
Please note: At this stage you should shorten your brass barrel if you are want the new hot end to match another you already have. SCrew on nut on first, then hacksaw and file the barrel down. When you remove the nut, it will re-cut any damaged thread. Be careful to remove any debris from this to avoid an immediate nozzle clog.
Step 3: Drill Thermistor Bore
The standard thermistor doesn't quite fit in the hole provided. You can either re-bore this or drill another. I chose to drill another so the placement was in the middle of the two resistors and close to the barrel.
Step 4: Resistors Side 1
Place the two resistors in the brass block and bend one side of their leads until they touch each other. Now remove resistors and solder the two resistor leads together. Use Kapton tape of another high temperature insulation to wrap the exposed leads of the resistor. The aim is to prevent the leads from ever touching and shorting on the brass block. Continue by soldering some heavy gauge wire onto the resistor leads and insulate everything with tape and heat shrink.
Step 5: Resistors Side 2
Insert the resistor sub-assembly through the heater block and repeat the steps from side 1. After this is done, use the Kapton tape to wrap and insulate the whole thing, making sure to leave the hole for the thermistor exposed.
Step 6: Assemble
Apply thread tape and then screw on the brass block as far as it will go. I like to then screw on the tip tightly, before winding back the brass block against it to tighten them both.
Step 7: Insert Thermistor
Completely fill the thermistor hole with thermal paste. Doing this will ensure accuracy from the temperature reading. If the thermistor is loose in the cavity, it could move and the temperature reading could fluctuate, potentially damaging the printer. Insert the thermistor and use Kapton tape to seal it in there.
Step 8: Minimal Software and Firmware Tweaks
Firstly, if your nozzle is anything other than 0.35mm, set the new value in your slicing software. Mine was 0.34mm.
Secondly, the heating performance of the new unit will be terrible because the PID settings in the firmware are optimised for the old heater. Fortunately this is an easy fix, and requires no firmware flashing thanks to the Sanguinololu's on board EEPROM. This stores some configuration variables, regardless of power outages or firmware upgrades. Using the screen below is the best way to make calibration changes.
Send the manual command in Pronterface or Repetier-Host:
M303 S200 The firmware will now test the heater by cycling it to the temperature you specified, and then give you the best PID settings.
Look for the message pictured and write down the values. You may need to reset the machine at this point. For me I receive errors afterwards.
Navigate to 'Config > Firmware EEPROM configuration' in Repetier-Host. The dialogue box below will appear. Enter your PID values and click 'Save to EEPROM'. A confirmation message will appear in the log.
Please note that even when upgrading the firmware, values stored on the EEPROM are prioritised. The 'Restore factory settings' button will wipe the EEPROM values and then read from the firmware values.
Don't forget to recheck your Z height to avoid smashing the nozzle into the bed.
