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[Solved] MK4 Wishlist  

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Noble Member
RE: MK4 Wishlist
Posted by: @neal-p

I lost over half of my MMU jamming issues when I moved my spools up to a broom stick spanning across the floor braces in my basement's ceiling. Gravity assists pulling the filament off the spool and into the tubing that I have held in place with threaded eye loops screwed into a piece of pegboard flat against the wall. I had to clock the MMU bottom up 45 degrees to eliminate the extra turn in the filament's travel path. I think this method also somewhat uncurls the stiffened shape that only curls more severely as you reach the end of the spool. I will always place my filaments high and directly above the printer from now on. It is easy to catch the last part of the filament as it leaves the empty spool because it will curl and wrap around any rod that is there for it to spring around

We are talking about two different issues here. What you are dealing with in that setup is your filament path and the result you are having is smoothing the flow which allows the system to better form it's tips. The jamming you were experiencing during a tool change before doing that was due to poorly formed tips. I happen to hang my spools above my printer as well, though that is for convenience/space rather than any gravity assist.

What we are talking about with a geared extruder and heat break are actual jams in the hotend due to design choices. The first is that the direct drive gears in the stock extruder allow heat from the motor to travel to the filament and soften it. This can result in filament not being effectively fed into the extruder. The second is the heat break, which under heavy retraction prints, can build up a blockage that can't melt at normal printing temps. The issue gets worse as your layer heights get smaller.

If you don't happen to do prints that run into heat creep or retraction issues, absolutely don't go changing your printer just cause someone says it fixes a problem you don't have. There are a lot of us, however, that do run into these problems and Prusa could very easily fix them in new printer (or even a slight redesign of the current extruder).

MMU tips and troubleshooting
Stop SL1 tank leaks with a simple o-ring...
Posted : 30/06/2020 4:34 pm
Laura F Farrell
Trusted Member
RE: MK4 Wishlist


To be fair I had this issue with a particular filament (Colorfabb Pa-CF low warp) and nothing I did including switching to a standard e3d heatbreak would fix it. And to be honest, I have also a CR10 which just about printed that filament until I changed my hot end to an e3d V6 so I'm not entirely sure that problem is entirely on the Prusa side - seems to me to be more to do with the e3d  than Prusa per se.

Perhaps offering an option of other extruders/hot ends that are more friendly to high temp filaments might help - Bondtech, Mosquito, whatever.

The Prusa does pretty well for a sub 1000 euro printer, so wouldn't get too fussed about not having some features - given that you can easily pay nearly 4 times the price for an Ultimaker or others. I think Prusa does quite well given the cost.

Posted : 30/06/2020 6:27 pm
Eminent Member
RE: MK4 Wishlist

Hi gnat

I know it was two different issues. Moving the filament up above was not intended to be under the heat break discussion but a departure still under the broader MK4 wishlist title.

I once tried honeycomb and came home from work to find my extruder was forced into a corner by a part that shook off the plate. It was like an upside down volcano. Plastic squirted up and caked over my extruder, destroying the whole thing. My extruder was destroyed and I rebuilt it with a titanium straight through heat break. I moved the filaments above my printer well after that.

I think my failure that destroyed my extruder was many things wrong going bad at the same time because I am self taught and didn't know what I was doing. So under the wishlist topic and not heat breaks, I would like to say what I did about vibration. 

I wasn't home watching to see why my part left the heatbed and I didn't see how things got forced into the corner. But if vibration was a factor, then I need to eliminate vibration from the possible causes when I have more prints go bad. I happened to have 6 heavy steel brackets for hanging drop down televisions and I never did anything with them. They were big enough and heavy enough to hang from the underside of the printer through holes in a board of MDF to preserve flatness. 

After I got that chore done, then I knew failures were not caused by the printer sitting only on those rubber points. My printer was mounted to a base that was too solid and heavy to shake. My guess was the next part failure was going to be belts getting worn. If the printer can't shake then that energy will need to go somewhere. I guessed it would wear out the belts. I was wrong. My next problem was the magnets shaking loose from under my heat bed. I didn't notice what was happening until 4 fallen magnets found each other and jammed up the y axis. I think some of that Kapton tape should be used as extra prevention to hold in the magnets. I am going to try hot water heater tape I found at Home Depot as a cheaper alternative. If that doesn't work I will buy Kapton.

This post was modified 1 year ago by neal.p
Posted : 01/07/2020 3:24 pm
Reputable Member
RE: MK4 Wishlist

1) larger color screen

2) 32 bit with integrated wifi. with advanced features like duets


Posted : 28/07/2020 4:50 am
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