Hot End Break-In Period?
July 02, 2012 12:39PM
I recently swapped out the 0.5 mm MakerGear hot end that I was using with a 0.35 mm version as part of an upgrade to my MendelMax printer. At first I was extremely disappointed with the results and I thought that maybe I had gotten a bad hot end, but after a few test prints, the results started to get pretty good. The prints improved drastically without me changing any settings in Marlin or in Slic3r.

Do the hot ends have a break-in period? The only thing that I can think of is that maybe the fire-cement has to go through a few heat cycles before reaching its desired properties? Has anyone else seen behavior like this? I don't remember seeing this on my previous hot end, but that was when I was still calibrating the printer, so I doubt I would have noticed.

Re: Hot End Break-In Period?
July 03, 2012 07:11AM
The thermistor takes a several heat cycles to settle down to get a consistent temperature. Happened on my print bed too.
Re: Hot End Break-In Period?
July 03, 2012 11:33AM
Everything mechanical has a break-in (or wear-in) period. The trick is figuring out what is changing. With your hot end, there are several posibilities.

1. Debris. Tiny bits of something or other that we may not see, sometimes has to work its way out of the nozzle.
2. Thermal hardening of the soft parts. PTFE liners and such will expand and contract with each cycle of use, and this will cause some re-alignment at the molecular level, releaving stresses, or maybe creating stresses.
3. Opening of the nozzle. Surely this must be going on all the time. Afterall, there is friction there at the tip, however small.
4. If you had to take anything else apart to install the hot end, that too may need to break-in. One of the reasons I oppose frequent PM schedules is because of this. When you clean and adjust machines too frequemntly, they seldon have time to wear in an perform at the optimal level.
Re: Hot End Break-In Period?
July 03, 2012 01:17PM
Fire cement is conductive until it is dried out fully. If the thermistor is embedded in fire cement it needs to be baked for some time before it will give an accurate reading.

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