Hot End Maintenance: When should I replace parts?

[justphred 0]

Just got an Ultimaker 2 go about a month ago. and have been printing on it just about every day. I have been using XT filament from color fab so I have been running the temp up at roughly 240ºc.

I have done some pints recently that have made me wonder when I need to replace or perform maintenance on the hot end.

The print on the left I did about a week ago, and the print on the right I did a day ago (note, the print on the left has been lightly sanded with 400 grit paper, but nothing else) these prints were done upside down from their current orientation, with no supports and with a 12mm brim. I am not sure what is causing such a jagged wall on the right print. So I am wondering if its just caused by ware and tear on the hot end.

This is the hot end as it looks now. I'm not sure if this is normal, if the temp I am running is causing the Teflon parts to ware out faster. or what the proper maintenance for cleaning the hot end should be.

Any info/being pointed in the right direction would be appreciated.

[jonatanrullman 17]

Wear is primarily going to manifest itself as under extrusion. Friction builds up in several places and at some point it can't keep up anymore.

This is especially true for the non geared feeder on the UM2s. Adding a gearbox will help. Alot. Meduza has an excellent design and I believe that gr5 has done a version of it as well. I have remade my own version with a range of improvements but I have not gotten round to posting it yet.

The bowden tube and nozzle is going to wear out. Though that will take quite a while so if yours was new then that is probably not a major issue for some time.

The thermal paste will also go bad. I can't say how quickly though but every once in a while its a good idea to dismantle the head completely, clean everything and apply new paste between the steel coupler and the lower part of the heatsink and bottom plate. Be sure to use something that can stand the temperatures, regular thermal paste for computers won't cut it. I used copper paste that was advertised for use with car brakes.

I think the main culprit here is the teflon coupler. At 240 it is going to deteriorate quite quickly.

I don't think you would get more than a couple of hundred hours out of it. My first teflon coupler, which was almost new when I bought my second hand UM2, I used at something like 230 degrees and I think it lasted about 200-250 hours.

I would suggest that you dismantle the head and have a look at the coupler. The bottom part will most likely be burnt and it is probable that you will find that the hole has decreased in diameter. This causes quite a bit of friction but can be dealt with by cutting off a small slice. This can be done a couple of times before the coupler needs replacing altogether.

I would however suggest another course of action as well. Since you are in the US, have a look at gr5s store at thegr5store.com and search for the i2k spacer. Well worth the investment, especially if you are going to print at those temperatures. And replace the coupler when you're at it as well, so that you are starting fresh.

As for cleaning. The nozzle looks a bit ragged. I have an olsson block on my printers to I simply heat up and remove the nozzle and do an atomic pull with it loose. Otherwise you can do an atomic pull in the regular fashion. Doesn't hurt to do it once in a while.

The exterior of the nozzle I usually clean with a bit of paper towel as needed.

On a related note. You might also want to look into replacing the fan shroud. It was designed for the dual extruder upgrade that never got past beta and as such it is less than perfect for single extruder I'm afraid. I've been using Laberns fan shroud pretty much since day one and it works incredibly well. Though I always have a spare one on hand because if something goes wrong in a print the shroud will take quite a bit of damage and will need replacing.

I hope I covered all the ground and didn't make it too confusing. I'm sure others with more experience will chime in as well.

Cheers

Edited May 30, 2017 by Guest