Issues since Mk3S upgrade  

RE: Issues since Mk3S upgrade

Just an observation - the MK3S cooling shroud and resulting airflow is radically different. So what worked for the MK3 won't print exactly the same on an MK3S.  Many of the issues I see on your block look thermal ... and most folk have added a hot end sock to reduce nozzle temp fluctuations as the print fan kicks on and the extruder moves around a part.   

RE: Issues since Mk3S upgrade

Thanks for the reply. Unfortunately I'm already running with a sock, have run PID, and as it's ABS I'm not using the fan. The thing that baffles me is that one face of the cube is fine, but the face parallel to it (X) is rubbish!

RE: Issues since Mk3S upgrade

Don't really listen to me. I don't have my printer yet...

If I had a cube with one side good, and the far side rubbish - I would suspect belt tension.

Sounds like calibration is fine on Home - but drifts as the axis moves.

RE: Issues since Mk3S upgrade

Try to print with the fan on 30 %.(or 40%)

This because if you print a small object, it has no time to cool down.

or print more objects at the same time.

RE: Issues since Mk3S upgrade

Thanks all, I've narrowed down the problem but not the cause.

It is too hot. That's the issue. All of my symptoms align to having too high a bed/filament temperature. But here's the catch...

...it's too hot on large objects too!

So far I've taken 10C off my extruder temperature without success, and will have to look at whether I lower the bed temperature too. It has me baffled, I've done endless hours of prints on this same Mk3 before the Mk3s upgrade and had zero issues (Fillamentum ABS, PrusaSlicer standard profile for that filament of 240C/110C).

My temperature readings are consistent even when the bed/extruder move.

For comments on the fan shroud, I have always printed ABS with zero fan, so there's no change in airflow, it's nil!

I'd like to think I'm pretty good at understanding why the printer does things, but this has me stumped.

RE: Issues since Mk3S upgrade

Has your room temperature increased?

I would keep the nozzle temp up as you want the best bonding. I would rather print slower. BTW: Big objects doesn't mean slower. On MK3/s you can have pretty fast movements on straight lines.

RE: Issues since Mk3S upgrade

No, and this is within an enclosure. 

For big objects I more meant that the layer time will be higher. 

I cannot understand why I would see such a huge change, and I'm worried that there is an underlying issue I haven't identified. Faulty thermistor maybe? I don't want to reduce my printing speed as that fixes the symptoms not the cause, and I know from experience this printer is more than capable of what I'm asking. 

RE: Issues since Mk3S upgrade

Then I would suggest you watch the print. Check if the nozzle position is correct while printing and what the plastic is doing. It looks like the one corner is off by at least 0.4mm. This should be pretty good visible during the print.

If you changed your extruder then also check if everything is in place and stays in place. My preferred test is by holding (or let the motors hold all axes). Then take the nozzle with your hand and try to wiggle around. Check how much play it does have in all directions.

RE: Issues since Mk3S upgrade

I see any small features or corners readily flex when the nozzle moves near them as they are still soft.

I've checked the nozzle is secure, and I have moved the extruder around to check for any changes in thermistor readings that might indicate bad wiring. 

Thanks for the replies, I'm really stumped. 

RE: Issues since Mk3S upgrade

Has anything else changed? What was your extruder revision with MK3? Maybe you have now a different ambient air flow with the new extruder.

Bad thermistor you would see pretty fast. ABS would start to smell, so I don't think this is the root cause.

RE: Issues since Mk3S upgrade

Nothing else has changed.

My extruder stepper is too hot to touch - the bed actually feels cooler at 100C! I've slackened the tension bolt for the idler right back but it has made no difference.

I assume that when filament goes through the hotend it doesn't fully heat to the hotend temperature? i.e. setting a nozzle at 240C is to get the filament up a temperature gradient, not to get the filament to 240C. If so, then potentially heat creep from the extruder into the gears would result in the filament attaining a higher temperature?

A bit of Googling is showing a bit of a trend for overheating extruder steppers in recent times?

RE: Issues since Mk3S upgrade

So here's an interesting one. Partway through dismantling my extruder assembly to go back to the standard Mk3 parts and I notice that the fixed gear on the extruder shaft is catching against the plastic of the extruder body. It doesn't appear I can move it up or down the shaft as then the feed won't be aligned with the PTFE tube. Very hard to turn the gear with my fingernail with it in place so it's definitely catching.

RE: Issues since Mk3S upgrade

Rebuilt the extruder assembly with no change unfortunately.

Here's how all my benchies/cubes turn out. The rear vertical face is always perfect, but anything else I have a problem with. 

RE: Issues since Mk3S upgrade

And here are how all the rear faces look. 

RE: Issues since Mk3S upgrade

Oh and to answer your earlier question my Mk3 parts are b7.