This guide will help you replace the hot end and heatsink on the SK175.
As you use your 3D printer different parts will undoubtedly wear and break unexpectedly. This guide will show how to replace the hot end and heatsink assembly for the SK175 tool end from Lulzbot.
For this replacement the hot end was obtained through Lulzbot.
Tools used in this guide
|Side Cutters - 1691-1037-ND||iFixit Driver Kit - 2434-145392-1-ND|
|Pin Extractor - WM9937-ND||Cable Ties - 1436-1591-ND|
|Bits - 2mm Hex, 2.5mm Hex, 2mm Flat|
Before you are able to disassemble the tool head, it will need to be removed from the carriage. First check that power is disconnected. Next you will need to disconnect the connector assembly at the top of the tool head assembly.
If the tool head is not resting on the bed, you will need to hold it while removing the screws. There are two screws on the top and one at the back of the carriage. Once removed, the tool head will be free to remove.
After the tool head is removed from the carriage, you can now extract the pins from the connector. First you will need to cut the cable ties around the sleeving and the backshell. You will need to locate to the two wires for the heater element, in this case they are the two yellow wires.
Using the extraction tool, WM9937-ND, insert the square tip into the front of the connector on the side of the contact. Turn the tool clockwise and counter clockwise a couple times and repeat on the other side of the contact. The first contact will now be able to be removed from the housing. This motion will push the locking tabs back into the contact. After the first contact is removed repeat the process for the second heating element contact. With both of the contacts extracted from the housing, you can now remove the wires from the bundle and disconnect the thermistor connector.
With the wires for the hot end removed, you can now start to disassemble the tool head to remove the hot end. In this next step there are nine screws that will need to be removed. First remove the screw securing the blower fan, here you will need the 2mm hex bit. Next use the 2.5mm hex bit to remove the four screws securing the fan to the heatsink. Once the fan is removed from the heatsink assembly remove the four remaining screws securing the heatsink and the tool head.
With the screws removed from the heatsink, the blower shroud and the heatsink can now be removed from the tool head. Note that as you remove the heat sink, there is a filament guide that may fall out.
The bearing from the old heatsink will need to be removed and placed into the replacement. Using the 2mm flathead bit, push the bearing from the outside of the heatsink. Once the bearing is free, press it into the same location on the replacement part. Fit the filament guide onto the replacement with the PTFE tube towards the hot end. You are now ready to start the reassembly of the tool head.
With the filament guide slotted into the replacement heatsink, position it over the feed assembly. You may need to adjust the heatsink back and forth to get the filament guide into its holder. With the heatsink now in place use two of the screws to secure the top of the heatsink using the 2.5mm hex bit. Next secure the blower fan to the tool head using the 2mm hex bit, do not tighten this fully as some movement will be needed to mount the blower shroud.
As the blower shroud is reattached to the tool head note the cable bundle location in the left image. The blower shroud will need to be positioned as seen in the above third image. There are two screws that are used to secure the shroud to the tool head.
There are two screw lengths for connecting the shroud. The shorter screw on the left corresponds to the bottom left location on the next image and the longer screw to the bottom right. With the shroud secured the fan can now be secured to the heatsink and the blower fan screw can be tightened.
With the hot end assembly now secure to the tool head, connect the thermistor connector to the mate that we previously disconnected, this connector is keyed. For a clean cable bundle, work the heater element wires through the bundle as they were like the previous wires. Once the wires have been fed through the backshell, you can now orientate them to be inserted in the connector housing. The contacts need to be inserted in the housing open side up. In the above third image you can see the guides in the connector. The contacts on the yellow wire need to be inserted into the same positions from earlier when we extracted the contacts. When inserting the contacts, you should hear a faint click, this will let you know that the contact have been fully seated.
With the contacts fully seated you can now move the backshell over the connector housing. Use the two cable ties, 1436-1591-ND, to secure the sleeving and trim the excess length. Now that the tool head is reassembled it can be remounted to the carriage on the Lulzbot. There are the two screws on the top and one at the back. Reconnect the connecter and you are ready to load filament start printing again!