Sometimes I amaze myself.  

Re: Sometimes I amaze myself.

Hi Sean,

Thanks so much for sharing you experiences. It helps a lot for a newbie like me to know what I’ll be dealing with and things to try once I get my mk3.

What do you use for the retraction test? Do you have a link to a thingeverse “thing”?

Thanks

Re: Sometimes I amaze myself.

Hi Sean,

Thanks so much for sharing you experiences. It helps a lot for a newbie like me to know what I’ll be dealing with and things to try once I get my mk3.

What do you use for the retraction test? Do you have a link to a thingeverse “thing”?

Thanks

I've actually never printed one.

Basically anything with 2+ "small diameter" towers.

I was going to print a 4 tower one. https://www.thingiverse.com/thing:2489319

But I could not tell you if it's any good or not. 😛

I when I have any issues, the first thing I do, is print a "standard" calibration test I use.
https://www.thingiverse.com/thing:1622868

I print 2 of those at the same time, and if they are "tight" I need to lower extrusion, and if they are loose, I need to increase extrusion. I noticed my MASSIVE under-extrusion when checking this.

If your extrusion is wrong, EVERYTHING is wrong. So before "tuning" the printer, the extrusion MUST BE PERFECT.

I never got to the retraction I thought it was... because I isolated the issue before that test. 😉

PS: My retractions look rough... I' going to be doing a full retraction calibration here in the next few days, once I get my extruder rebuilt.

PS2: My entire Extruder asssembly, is custom. Many of the issues I'm having, is becuase it's still in early testing, and has design flaws here-and-there. (and I'm replacing old parts, with older revision parts, until I get the full thing reprinted... which is what I'm doing right now. ETA 5 hours!) 🙂

Re: Sometimes I amaze myself.

This is an area I need to understand, the different parameters that affect the print. I undertand print temperatures, but extrusion and retraction rates? Where are these done?

Re: Sometimes I amaze myself.

Thanks Sean. Great info.

Re: Sometimes I amaze myself.

This is an area I need to understand, the different parameters that affect the print. I undertand print temperatures, but extrusion and retraction rates? Where are these done?

Ummm... from your post count, I would have assumed you would know this... but... I don't care to type this out anyway. 🙂

There are MANY *MANY* Parameters you need to learn to "master" your printer.

The prusa's hardware is setup VERY well, and you don't need to mess with the hardware parameters, but I"m gonna start with those and explain what they do, and why they are relevant.

Steps per mm
E-axis (extruder) - This is figured by "how many steps per linear mm of travel of the filament going into the printer. If you tell the printer to feed 100mm of filament, you want it to, actually, feed, 100mm of filament. Not 80, not 120, not 95. Exactly 100mm of filament. This number is 280 steps/mm on the Mk3. (And that's what it should stay) ((I have a 3.5:1 gear reduction, and it is set to 980steps/mm))
XYZ axis - This is just how many steps the motor needs to turn, to move the belt/extruder-assembly/bed/X-assembly every mm. I'm not sure this number off the top of my head.

Then there is the "Acceleration" and "Jerk" settings. I'm starting to work on configuring these on my printer. Messing with these parameters, will change how fast/slow the movment happens. This is most relevant on X and Y. I don't understand enough about these to explain it to anyone. I don't have a clue what I"m doing regarding them... lol!

There are even deeper variables to change the amperage of the motors, which can help increase/decrease many other issues... The community is just now learning of these, and I'm not posting them here. I do not understand them myself yet.

There is another variable, I'm not sure what it's called, but it adjusts Linear Advance. I think I have an issue with that right now honestly, and I need to fix it... ... ... That's another story. I know VERY little about how this one works as well. (Not enough to even ballpark know if I need to increase or decrease it to "try" to fix my problem... No idea...

THOSE are your hardware variables, that you can mess with your printer with. (and seriously mess it up) Chances are, messing with these, will not yeild much improvement, as Prusa has them set VERY well. (I think... lol)

THIS is where I will start explaing my process of "tuning" my printer.
In your Slicer. (I use Slic3r, not Cura, or S3D, ask someone else for help in those)

The *FIRST* thing I would do if I was to "start from scratch". Is get the first layer to stick. DO NOT TUNE THIS YET. Just get it to stick. That's all we are going for at this point.

Next Print THIS two at a time. And keep printing them changing your extrusion multiplier until they "hold" together lightly, but not have to "push hard" to get them together. (If they won't "hold together" you have a problem.

EXTRUSION MULTIPLIER TUNING
Print the above file x2.
Let the print bed COOL COMPLETELY.
Take both the pieces off, and attempt to stick them together.
TIGHT -- If they are too tight, and do not slide together easily, you are OVER EXTRUDING.
LOOSE -- If they don't have any "stick-tion" holding them together at all, you are UNDER EXTRUDING.

If you are over-extruding, you need to LOWER your extrusion multiplier. This means you are putting out too much filament, compared to what Slic3r THINKS it is putting out.
If you are under-extruding, you need to RAISE your extrusion multiplier. This means you are not putting out enough filament compared to what Slic3r THINKS it is putting out.

Once you get your Extrusion mulplier dialed in perfectly, NOW you go back to your first layer.

I generally take a "10mm test cube" (just a perfect cube that's 10x10x10) and resize it to 0.2mm high, and 40x120mm, from "front to back" to back. (I just find it easier to see this way, to each their own?)
This is when I start dialing in my first layer to the point the "top surface" is neither "smooth ridges" or "feels like sandpaper, sharp ridges".
Sharp ridges GENERALLY means you are too low.
Smooth ridges GENERALLY mean you are too high.

I have a set of DIGITAL CALIPERS.
They are WORTH EVERY PENNY!
If you think you are too low to the print surface, I take my calipers and measure it. I get spooked below 0.15mm (also at 0.15mm I have a terrible sandpaper top-surface)

So now we have our "Extrusion multiplier" and First layer (live-z adjust) done.

At this point, as long as your speeds, temps, and cooling are good, you SHOULD be getting GREAT quality prints.

Notice I do *NOT* measure the filament diameter.
I find it useless to measure the filament diameter, as what if it's oval? What if it's inconsistent? What if...
I measure the "average extrusion rate" with that STL file above, and it gets me the perfect extrusion rate. Regardless of filament size. (I've put some 1.7mm string trimmer string through the printer, and a QUICK test, had it dialed in perfectly.. It's my "dirty secret".

The thing is, many people want to change the "extrusion rate" at the hardware level. (steps per mm) This is a really bad idea, and should NOT be done. It should ALWAYS be done in the Slicer. No exceptions. Anyone who thinks messing with the hardware/firmware variables, is a good idea... they are generally WRONG.

Hope that made more than zero sense. 😛

I ramble too much.

Re: Sometimes I amaze myself.

Once again, Sean that is great info for a completely newbie like myself. Thanks so much for sharing. It makes sense to tune extrusion before perfect height. Few questions:

1) What do you do in the fist step " get it to stick"? I assume that PINDA has to be already tuned, bed is clean, bed is 60C if you use PLA or more of you use other type of filament (eg PETG). Idea is to be "close enough to stick, do not bother going for the final tuning yet".

2) I was thinking of following https://shop.prusa3d.com/forum/prusa-i3-kit-building-calibrating-first-print-main-f6/life-adjust-z-my-way-t2981.html to tune Z. There are many options so might try a few and see which one works best for me.

3) Extremely newbie question: I read that to shutdown the printer you do not just go and turn it off after a print. You have to let the fans run to cool down and then shut it down. When do you decide to unload the filament? If you plan to not print for more than 24/48/?? hours? I will be using PLA and PETG (for now) so I guess it is a matter of how long they can be out in the open before "going bad". What do people usually do?

Thanks
Gaston

Re: Sometimes I amaze myself.

Once again, Sean that is great info for a completely newbie like myself. Thanks so much for sharing. It makes sense to tune extrusion before perfect height. Few questions:

1) What do you do in the fist step " get it to stick"? I assume that PINDA has to be already tuned, bed is clean, bed is 60C if you use PLA or more of you use other type of filament (eg PETG). Idea is to be "close enough to stick, do not bother going for the final tuning yet".

2) I was thinking of following https://shop.prusa3d.com/forum/prusa-i3-kit-building-calibrating-first-print-main-f6/life-adjust-z-my-way-t2981.html to tune Z. There are many options so might try a few and see which one works best for me.

3) Extremely newbie question: I read that to shutdown the printer you do not just go and turn it off after a print. You have to let the fans run to cool down and then shut it down. When do you decide to unload the filament? If you plan to not print for more than 24/48/?? hours? I will be using PLA and PETG (for now) so I guess it is a matter of how long they can be out in the open before "going bad". What do people usually do?

Thanks
Gaston

1. I just keep brining the liveZ down, following the overall concept of how Prusa says to do it. All that matters is.
1a) It sticks to the print bed.
1b) It don't scratch the print bed.
1continuted - Basically you are literally just trying to get it to "stick". It's not about getting it "perfect", just to "stick" enough to print the calibration test. This is a "do by feel" thing, I can't really explain it more than that. If you do it enough, you will understand exactly.

EDIT2: I use the built-in "First Layer Calibration" to do this. Basically as long as the mini-square is "stuck" and not "flopping in the wind", you are good.

2. I said take a 10x10x10 square calibration cube, and slice it to a odd size... That's basically doing what he's doing. He just worded it MUCH better... Except he has the gCode files already for you... ISSUE however.
2a) The issue with this system is you are using a pre-generated gCode. This does not factor in ANY extrusion multiplier tweaks. This is VERY important, as even 2% over/under extrusion, will yeild around 0.02mm differences on the Live-Z.
2b) I don't really worry about the exact "layer height" of the first layer. As long as...
2b-1) I do NOT have elephant's foot. (where the first layer bulges wider than it's supposed to be)
2b-2) I have a good "solid" first layer, without gaps. And the top surface is SMOOTH.

3. Ehhh... It really depends on how... ... OCD you are. This will get you MANY difference responses... and let me just confuse you more with some crazy.

PLA really don't care about moisture. It can last for 6+ months, out of a dry box without issues.
Some PLA hates moisture, and should be kept in a dry box... It can start to "bubble" as early as a few weeks out of the sealed bag.
Some cheap PLA, comes with the vaccuum bags not under vaccuum. Guess what. This stuff is crap out of the bag!

I only have 1 open spool of ABS. and TPU... My TPU *LIVES* in a dry-box when not printing... That spool is worth WAY too much to risk moisture damage. (regardless of the reality of it happening)

I have *ONE* spool of PETG-CF (Carbon Fiber), which I have *NOT* opened yet. (was a gift @ MRRF2018, spool is worth almost 50$, not really sure what I want to use it on, but I want it to be "special" as it's expensive stuff!)

But here's the reality of it. I have...
8 spools of filament stacked on my desk right now. None of which are in any way shape or form, being kept dry... Is that bad? Probibally. (6 spools of ZYLtech PLA, 1 spool E-Sun PLA-PRO, 1 spool ZYLtech ABS)

Some filaments have some kind of "film" or "coating"... or process, on them to help reduce moisture absortion.

HOWEVER

PC, and NYLON, or any thing in those famlies. *MUST* be kept dry. They are left in a dry box, with a bowden tube going to the printer. That stuff is that bad... But chances are, unless you are an idiot like me, and are highly attracted to the low price of PC.... won't go near it. 😉

Oh yes Mr. Dry-box... Just you wait until I get my Multimaterial... Gonna pull 5 different filaments straight out of you Mr. Drybox... ... ... Get ready to have holes punched in you for stiking long tubes on you... .... ...

EDIT: Whoops, I forgot about one of your questions.

Do *NOT* turn your printer off (the switch), until the nozzle temp is BELOW 70c.

If you do this, the "fan" that cools the "E3D heatsink" will turn off, this will allow the E3D heatsink to "heat up", which will increase the temp all the way up the heatbreak. This has the potential to cause the filament DEEP in the extruder to melt, go swell to a point you can't pull it out, and eventually cool/solidify.
The only way to get this out, is 100% disassembly of the entire E3D assembly. This is *NOT* fun. Even if it happens 1/20 times you do this... You are talking, with the "stock" extruder... likely a 2-3 hour "repair" to get your printer printing again!

Re: Sometimes I amaze myself.

Unlimited thanks!!! 😀

Re: Sometimes I amaze myself.

The only way to get this out, is 100% disassembly of the entire E3D assembly. This is *NOT* fun. Even if it happens 1/20 times you do this... You are talking, with the "stock" extruder... likely a 2-3 hour "repair" to get your printer printing again!

I'm going to jump in here with my pet peeve again...

The extruder wiring really should be a flex ribbon cable leading to a breakout board on the extruder. That way, disassembling the extruder would not require taking apart the entire cable bundle and putting it back together, saving a huge amount of time for tasks like replacing the heater or thermistor.

My TierTime (Up and Cetus) printers all use breakout boards on the extruder, and replacing the hot block is literally a ten minute job. It's a complete mystery to me why Prusa doesn't do this, since any heavily-used printer will require replacing a heater, thermistor, or fan at some point in its life. Plus using a proper flex cable should reduce the chances of a wiring failure due to the constant flexing of the wires in the cable bundle.

</rant>

Re: Sometimes I amaze myself.

The only way to get this out, is 100% disassembly of the entire E3D assembly. This is *NOT* fun. Even if it happens 1/20 times you do this... You are talking, with the "stock" extruder... likely a 2-3 hour "repair" to get your printer printing again!

I'm going to jump in here with my pet peeve again...

The extruder wiring really should be a flex ribbon cable leading to a breakout board on the extruder. That way, disassembling the extruder would not require taking apart the entire cable bundle and putting it back together, saving a huge amount of time for tasks like replacing the heater or thermistor.

My TierTime (Up and Cetus) printers all use breakout boards on the extruder, and replacing the hot block is literally a ten minute job. It's a complete mystery to me why Prusa doesn't do this, since any heavily-used printer will require replacing a heater, thermistor, or fan at some point in its life. Plus using a proper flex cable should reduce the chances of a wiring failure due to the constant flexing of the wires in the cable bundle.

</rant>

Next on my to do list is to get a big connector so I can just disconnect everything. It will require splicing all my wires though... Not that I really care. It's part of life.