Hotend preheat tempature keeps flucuation at print tempuatures.  

The extruder software is intened to maintain temperature with filament extruding - taking away some of the heat, not standing idle.

Cheerio,

RE: Hotend preheat tempature keeps flucuation at print tempuatures.

That's true but in this case the temp changes enough that I can't print anything because the printer is waiting for the hot end to settle. 

RE: Hotend preheat tempature keeps flucuation at print tempuatures.

Based on what you're telling us I'd think it's 1 of 4 problems.  Either the thermister is bad and needs to be replaced, the heater cartridge is bad and needs to be replaced, your connections are loose as you've indicated, or your power supply isn't providing sufficient and consistent power.

You might want to do some troubleshooting with a multi-meter https://www.help.prusa3d.com/en/article/multimeter-usage_2117

Cheers

-Bob

RE: Hotend preheat tempature keeps flucuation at print tempuatures.

Posted by: @lewis

I dusted of my MK3S+ after 6 months and tried to print something in PETG. When I did, I found that when I preheat the hotend to 230C, the temperature started to fluctuating about +- 15 degrees. This is without motion. When the printer is at room temp it is very stable. I tried to run the PID auto calibrate routine but with only minor differences. I had something similar happen last year and found that the connectors for the thermonuclear at the control board was the issue. In that case, the temp was changing at all temperatures.   

I was just wondering if anyone else has ran into an issue like this before.

Thanks

     Lewis                                                               

 

RE: Hotend preheat tempature keeps flucuation at print tempuatures.

Mine is a MK3S+ kit, sat for about a month do to a lack of M3nS nuts to put in a new fan shroud, a nut that is NOT in the available part list. So I had to buy 100 of these special thinner nuts from ebay. The nuts fit and I got it back together, and the first print was excellent. But I needed 3 more copies, 2nd copy had yards of stringing on the inside of a cylinder, so did the third. Deleted that profile in cura, then added it fresh, tried a 4th copy.  This is all in PETG , which needs 230-250 nozzle temps and 80C bed temps. It warmed up to about 225 then fell to 215 in the next second, then started to rise again, but a second later was up to 268, a second later was 299 and the fire alarm went off. powered it off & let it cool for half an hour. Turned it back on, ran it up the pole to clean the nozzle, and set the nozzle for 230C, instant playback as soon as it got to 220C, reading totally crazy from one second to the next, 20 to 60C errors given the thermal lag involved, made zero sense to this retired engineer,  Do I have a bad thermistor or a second bad rambo? I've also had a bad time with leakage, so I would probably need the whole hot block assembly due to the heater and thermister being welded solidly into the block by burnt filament deposits.  This kit did not come with an si sock for the hot block, which lead to the premature warp-age failure of the part cooling duct.

So, what do I do next?

RE: Hotend preheat tempature keeps flucuation at print tempuatures.

I'd make the same recommendation I made to the original poster, break out your multi-meter and do some testing: https://www.help.prusa3d.com/en/article/multimeter-usage_2117#_ga=2.7637946.948193057.1644243758-26707886.1637250706

When you talk about leaking, is it oozing up between the heat block and the heat sink?  If so you need to work on your nozzle tightening:  https://www.help.prusa3d.com/en/article/changing-or-replacing-the-nozzle-mk2-5s-mk3s-mk3s_2069

Regards

-Bob

RE: Hotend preheat tempature keeps flucuation at print tempuatures.

The nozzle is tight and there is a gap between the nozzle and hot block.

And I am  CET, with 40 years of keeping a tv station on the air, much of it by myself so I'm quite fam with a multimeter, a 4 channel, 350 mhz bandwidth digital storage scope, VNA's to several gigahertz, TDR's, etc etc.

Since it has to get above 210C before it miss-behaves and its a MK3S+ kit, I assumed I would be graced with a link to a replacement part or parts. Finding where to order parts on your site isn't exactly easy. Nor is using a mastercard with a several thousand balance to pay for them. The last time took a phonecall.

Thank you, take care and stay well.

RE: Hotend preheat tempature keeps flucuation at print tempuatures.

Umm, I don't work for Prusa.  Like many others here I'm a product user.  You missed.

Cheers

-Bob