3d printing rookie trials and tribulations - Prusa MK3S+

[BuggyDad]

Update... 

Benchy got to roof level then came off the bed. 

So technically a failure but I would say quality overall looks fairly decent, so on the assumption that ambient temperature is my problem, solved by moving rooms, I'm having a go at an arm. 

Would you 3d printer pros raise any other issues (other than the curling up)?

It's mesmerising watching these things work. 

[BuggyDad]

And, with that, A THING is born! 

Cutting the cord and wiping up the bodily fluids took but a moment, and it's a healthy arm. 

It feels pretty solid actually, but I know how brittle PLA is, so I don't see this as a runner. However it does make me a bit more confident that with changes to both material choice and orientation there's a reasonable chance I can make something fairly strong. 

[Honza]

10 hours ago, BuggyDad said:

Benchy got to roof level then came off the bed. 

The prints shouldn't come off that easily. The smooth PEI sheet ha very good adhesion for PLA (and too good for most other materials), so there's some problem.

Take a look at the bottom, check if you have nice, uniform layer. My guess is that the initial layer is set too high, which is visible on the bottom of the bow. Unlike newer printers, that tap the print sheet directly, MK3 is sensing the steel plate below, and the offset has to be set manually.

Check this article

https://help.prusa3d.com/article/live-adjust-z_112427

Also, here's manual for Benchy to evaluate your result:

https://www.3dbenchy.com/wp-content/uploads/2015/04/3DBenchy_Broschure_3DBenchy.com_.pdf

Also, if the nozzle is crashing to the print regularly, it's sign if over extrusion. Check some tutorials how to tune flow.

[BuggyDad]

1 hour ago, Honza said:

The prints shouldn't come off that easily. The smooth PEI sheet ha very good adhesion for PLA (and too good for most other materials), so there's some problem.

Take a look at the bottom, check if you have nice, uniform layer. My guess is that the initial layer is set too high, which is visible on the bottom of the bow. Unlike newer printers, that tap the print sheet directly, MK3 is sensing the steel plate below, and the offset has to be set manually.

Check this article

https://help.prusa3d.com/article/live-adjust-z_112427

Also, here's manual for Benchy to evaluate your result:

https://www.3dbenchy.com/wp-content/uploads/2015/04/3DBenchy_Broschure_3DBenchy.com_.pdf

Also, if the nozzle is crashing to the print regularly, it's sign if over extrusion. Check some tutorials how to tune flow.

Thanks. I'll have a look at all those things. The arm I printed subsequently was better, in higher room air temp, so I think that's a factor, but perhaps I should print another Benchy in good temperature and refine. I also intend to print a temperature tower to understand the impact of nozzle temperature a bit more.

Looking at the bottom of both prints, would you say from these pictures that my bottom layer is set too high?

I can just see a small gap between the runs on both, but the base of the arm feels smoother than the benchy. To the naked eye I think the lines are less visible on the arm too. The settings change between the two was to move the printer to a warmer room, but it's also the case that the arm is an easier print with a big flat base and I added a 5mm brim to aid adhesion further. 

[Also thread title updated] 

[Honza]

24 minutes ago, BuggyDad said:

Thanks. I'll have a look at all those things. The arm I printed subsequently was better, in higher room air temp, so I think that's a factor, but perhaps I should print another Benchy in good temperature and refine.

The lower ambient temp increases warping of the print, if you start with bad adhesion, it makes the issue worse.

It shouldn't have any effect on measurements, because the printer preheats the bed first.

24 minutes ago, BuggyDad said:

Looking at the bottom of both prints, would you say from these pictures that my bottom layer is set too high?

Yes, it's definitely too high on both prints. I'd guess around 0.1mm. There should be no visible gaps. The arm looks better thanks to long regular infill lines, but I'd say that the first layer is same as on Benchy.

If you got more sheets with the printer, check the menu, if you got right preset for the smooth sheet.

Then proceed with the first layer calibration , or check the first layer while it's printing and tune live-Z.

I don't think you need to print another Benchy, you've already identified the issue. That is, unless your target is to have one completed 😃

[BuggyDad]

4 hours ago, Honza said:

The lower ambient temp increases warping of the print, if you start with bad adhesion, it makes the issue worse.

It shouldn't have any effect on measurements, because the printer preheats the bed first.

Yes, it's definitely too high on both prints. I'd guess around 0.1mm. There should be no visible gaps. The arm looks better thanks to long regular infill lines, but I'd say that the first layer is same as on Benchy.

If you got more sheets with the printer, check the menu, if you got right preset for the smooth sheet.

Then proceed with the first layer calibration , or check the first layer while it's printing and tune live-Z.

I don't think you need to print another Benchy, you've already identified the issue. That is, unless your target is to have one completed 😃

Ah ha. Thanks. It seems to me with this that while it's quite easy to change settings there is no substitute for an experienced eye when it comes to knowing what you're looking for, and knowing which of the many variables to adjust and in which direction. So your advice has been very valuable and time saving. Thank you. 

I've done a couple more first layer calibrations and moved it down 0.07mm, 0.1mm seemed to ridge up between the runs a bit more, although it did eliminate the mid-run gaps between the runs when viewed from beneath. 0.07 doesn't quite create a uniform flat surface but it is close. 

So next is a temperature tower, which can miraculously come into existence while I walk the dog. 

[BuggyDad]

Surprisingly (to me) my PLA+ seems to print best at a temperature that's off the bottom of its quoted range of 210-230°c. To my eye 195/200° look better than any of the higher temps, so it troubles me slightly that the best result is at one extreme of my ladder, and also that I've got a result as a beginner that differs substantially from expectation - that just smacks of my error. 

However, the only issue I'm seeing anywhere here is the stringing, so I don't know whether there's something else I'm not seeing. What is the downside of "lower than optimum" temperature? I think it's reduced layer to layer adhesion, which would be bad but invisible and not testable without destroying the experiment. Perhaps also poor bridging, which I can't really see here. 

[NB poor visibility of the numbers is just my bad photography - resolution/quality of the print is decent, the numbers are pretty clear throughout with the 235 being just a shade worse than the rest] 

[Honza]

16 hours ago, BuggyDad said:

What is the downside of "lower than optimum" temperature? I think it's reduced layer to layer adhesion, which would be bad but invisible and not testable without destroying the experiment. Perhaps also poor bridging, which I can't really see here. 

Exactly, too low temperature will result in low layer adhesion. This can be also influenced by cooling. But printing too high also reduces quality, because the plastic will degrade. You need to hit the sweet spot in-between.

Don't be afraid to break the tower. You already have results regarding quality, so now it's time for destructive tests. The little spike is meant for that, tenps with poor adhesion will break easily. Then you can try to break the larger portions and look for breaks that run accros the layers.

[BuggyDad]

2 hours ago, Honza said:

Exactly, too low temperature will result in low bed adhesion. This can be also influenced by cooling. But printing too high also reduces quality, because the plastic will degrade. You need to hit the sweet spot in-between.

Don't be afraid to break the tower. You already have results regarding quality, so now it's time for destructive tests. The little spike is meant for that, tenps with poor adhesion will break easily. Then you can try to break the larger portions and look for breaks that run accros the layers.

Ah ha. Gotcha. So it seems to me that strength between layers is increasing all the way up the temp range, so temperature choice is quite subjective in that even if you're already stringy, you can choose to go hotter for strength while accepting even more stringiness. Therefore, for a really simple model with the nozzle staying engaged with the same part all the time, so little opportunity to hang these strings from section to section, you might choose to do this. 

I am oddly struggling a bit with a temperature tower in PETG. It's printing nicely but on the screen it is still showing the starting nozzle temperature of 265° on section 3, which should have gone down 2 jumps to 255°. I did exactly the same gcode work as for PLA. 

[Honza]

Now I noticed I wrote bed adhesion instead of layer... Well, you got it 😃

What did you do for temp towers? I manually add M104 S(temp) in the slicer - it's a little tedious, but I can check the temperature change in slicer before printing.

[BuggyDad]

31 minutes ago, Honza said:

Now I noticed I wrote bed adhesion instead of layer... Well, you got it 😃

What did you do for temp towers? I manually add M104 S(temp) in the slicer - it's a little tedious, but I can check the temperature change in slicer before printing.

I did the same (slider to the right layer, right click the cross, add that code in the dialogue box, repeat, slice again, export). It's very odd - I can see the changes in the slicer, and I've done it before successfully with the PLA, but with this it just seems to print at 265 all the way up. 

I've repeated the whole exercise from the start twice as well. 

It'll be some stupid rookie error but if I can't work out quite quickly what's going on I will do some individual smaller prints at 10° steps I think, because it's only these tests that need that kind of gcode tinkering. 

[Honza]

That's weird, especially if it worked before and shows in the slicer.. Looks like some sort of bug, did the G-code changes write correctly into the file? 

You could make individual tests, but a single tower is faster and gives you direct comparison on the same object.

I don't think that G-code tinkering falls I to rookie category 😁 it took me a while before I started with calibration models.

[BuggyDad]

1 hour ago, Honza said:

did the G-code changes write correctly into the file? 

Good question. I had to work out how to look at a gcode. Opening both my files in Prusa gcode viewer (PLA top, PETG bottom):

It looks like while both have icons on the slider to show something is happening at the temperature change points, only the PLA one is showing different temperatures by layer. 

Wracking my brains to think what other differences there might be, my starting settings were defined by "generic PLA" filament settings then "generic PETG", so perhaps there's something else hidden in the PETG filament profile that precludes doing this. Assuming there's no other difference between the stp files (don't see why there would be) I can't see any other difference in my process. 

Anyhoo, individual levels are quick to print and I think there's a fair bit to learn from printing just 240, 250 & 260. I note that the base adheres better and is flatter at 260 than 250 and at 230 I had problems. Even at 260 the model is not as stringy as PLA over 220, and that can be reduced to almost nothing without going below 240, so I think this filament is best printed at 240-260, while the range given on the packet is 230-250. I think I'll go 260 first layer then 250 to err on the side of strength. 

 

First layer settings might change though, with a textured bed incoming. Thus far I've been printing on Pritt Stick. 

Meantime I'm having a go at an arm, up on its side for layer orientation. A more challenging print. It failed at the stock setting of 230° with poor bed adhesion and filament balling up on the nozzle, but I'm hopeful at higher temperature. 

[Honza]

27 minutes ago, BuggyDad said:

Good question. I had to work out how to look at a gcode. Opening both my files in Prusa gcode viewer (PLA top, PETG bottom):

It looks like while both have icons on the slider to show something is happening at the temperature change points, only the PLA one is showing different temperatures by layer

You can view G-code directly in the notepad - it's just a text file with readable commands. Since it's indicated in the viewer, there should be some extra gcode command, so it's weird it's not recognised. 

The 250° is the right temp for me as well, it seems that PETG is not as varied as PLA. 

1 hour ago, BuggyDad said:

First layer settings might change though, with a textured bed incoming. Thus far I've been printing on Pritt Stick. 

I use satin sheet (I didn't want another sheet just for PETG and satin seems the most universal) and it works great, so I don't think you'll need to change anything, apart from Z-offset - petg can be quite sensitive to proper first layer.

Stick glue can be quite tricky, for me, it was hit and miss - sometimes I needed to dissolve it to get the print off, other times, I couldn't get the print stick.

[BuggyDad]

5 hours ago, Honza said:

You can view G-code directly in the notepad - it's just a text file with readable commands. Since it's indicated in the viewer, there should be some extra gcode command, so it's weird it's not recognised. 

The 250° is the right temp for me as well, it seems that PETG is not as varied as PLA. 

I use satin sheet (I didn't want another sheet just for PETG and satin seems the most universal) and it works great, so I don't think you'll need to change anything, apart from Z-offset - petg can be quite sensitive to proper first layer.

Stick glue can be quite tricky, for me, it was hit and miss - sometimes I needed to dissolve it to get the print off, other times, I couldn't get the print stick.

I'm very pleased to have concluded the same temperature as you. That gives me some confidence. 

I've just run a couple of prints on the textured sheet. It gives a perfect finish and just the right level of bed adhesion. My two smooth beds are pretty well used and I intend to print a lot on PETG so I felt it a worthwhile investment. 

And I've printed running arms. Finish a bit rough because these were designed before I got the message on print orientation, so there was a lot of support material. 

They won't be the world's strongest arms (I need to move to something chunkier and simpler for home printing) but my intention was to get the car back running ASAP, so I can improve it at my leisure, and then they'll do as spares. And they were a good test. 

[Otis311]

Glad you changed the print orientation on those arms. Another suggestion for printing symmetrical parts, like the left and right suspension arms, would be to mirror one in the slicing program. That way if there is any discrepancies in the printing they will be cancelled out.

As far as your first layer goes. I want to say you need to lift the build plate a tiny bit. I prefer to have my first layer "elephant foot" a little. Definitely helps with adhesion but requires de-burring after print is complete. Parts need to be cleaned up anyway so I don't mind. I also use clear glue stick if I really want it to work. I should add I only print with PLA at 200*C with the glass plate at 60*C.

[BuggyDad]

7 hours ago, Otis311 said:

Glad you changed the print orientation on those arms. Another suggestion for printing symmetrical parts, like the left and right suspension arms, would be to mirror one in the slicing program. That way if there is any discrepancies in the printing they will be cancelled out.

As far as your first layer goes. I want to say you need to lift the build plate a tiny bit. I prefer to have my first layer "elephant foot" a little. Definitely helps with adhesion but requires de-burring after print is complete. Parts need to be cleaned up anyway so I don't mind. I also use clear glue stick if I really want it to work. I should add I only print with PLA at 200*C with the glass plate at 60*C.

Good idea on the mirroring. I'll try that out. Not sure I want to squish the first layer of PETG anymore though - mine is sticking nicely and has a uniform finish now. There's almost no first layer on those arms because of their shape, but Mk3 arm will have a big first layer. 

One issue I've just hit is that I've downloaded the files for the IKEA Lack enclosure and with a substantial number of larger parts printing together I'm getting some failures. I may try dropping the temperature to compensate because I think it's filament collecting up on the moves between parts, but I'm not sure. Or could it be too long a time between layers in my cooler than ideal ambient temperature? I might just separate the parts and print them in smaller batches/singles. This would reduce the moves between parts, the time between layers and I'm also uneasy about the risk of an 11 hour print - it's a lot of time and parts down the drain if it fails late in the print. 

[Honza]

If you have too much buildup on the nozzle, you may need to dial back the extrusion multiplier a bit. PETG loves to stick to the nozzle and then pull something with the blob. Btw, silicone sock helps to keep the heater block clean.

A little squish can help. The elephant foot can be compensated. 

You can also try to slow down. I need to check my notes, but I had batch of PETG filament that had similar issues.. but it was a while ago and I cannot remember how did I solve it.

[Otis311]

1 hour ago, Honza said:

You can also try to slow down.

I should have mentioned this as well. It really helps when trying to lay down a very detailed first layer.

[BuggyDad]

I think extrusion multiplier, speed and retraction are all variables that have the potential to help me here. The overall quality of print, bed adhesion etc do seem good so I probably only need a small change but I'll need to go about this scientifically to understand the effect of each variable. 

On extrusion multiplier, it occurs me that already where I have 100% infill I am seeing small gaps within the structure, which will affect strength substantially. I am a little wary of laying down less material in this instance as it's sure to amplify the same issue. Not talking open infill structures by design, which should be strong, rather fissures in the structure which aren't there by design and will bring in weaknesses. Or, perhaps this is showing up some other setting issue - temperature again? 

[Otis311]

Something to keep in mind is the inherent variability of the filament diameter itself. More expensive filament has a tighter tolerance but it is still a tolerance and can result in either over or under extrusion. Not saying that this is the issue you are encountering in this case but just something to be aware of.

[BuggyDad]

2 hours ago, Otis311 said:

Something to keep in mind is the inherent variability of the filament diameter itself. More expensive filament has a tighter tolerance but it is still a tolerance and can result in either over or under extrusion. Not saying that this is the issue you are encountering in this case but just something to be aware of.

Ah yes, I did read something about putting calipers on each filament but it got lost among the gazillion web pages I skim-read. I guess one should really calculate and adjust the extrusion multiplier from that measurement? 

[BuggyDad]

I made some minor changes. Retraction I changed from 0.8mm to 2mm - that was probably the key one - I get the impression that 0.8mm is not appropriate for PETG and am a little surprised it was in the "generic PETG" settings (although maybe it doesn't change when you change filament profile?). I also made sure none of the speeds exceeded 70 mm/s, which meant dialling back just the infill speed a touch. Then with not enough testing to be really confident (I think the issue is greater in a large multi part print, so it's kind of not that testable without doing a large multi part print) I took the plunge and set off an 11 hour print that would mean leaving it running overnight. I'd be awake for the first quite a few hours so I figured I'd get enough of a confirmation that things were OK before I left it alone, so we could call that a test of sorts anyway. 

And it was a success! 

It is nice to have a print without supports and I must say the finish here exceeds my starting expectation of what I could do with this.

These are parts for an enclosure for the printer made with a cheap IKEA table (x3). It should help a little with PETG printing, and also with my sometimes-slightly-too-cold room, and (perhaps most importantly) it's good storage for the printer and its various paraphernalia which is currently spread around the room. 

Next: design and print TD4 servo mounts. 

[BuggyDad]

So after refining my settings for one roll of PETG, I now find that another roll, same brand and spec, different colour, gives me a less good print. My orange prints have a pretty good finish overall I think, and easy to print, while a first print from this new black roll of the same is quite stringy, gives a rougher surface and was very hard to remove from the printer bed. 

First roll:

 

Second roll:

Accepted different angle catching the light may be a little unfair but print orientation is the same.

[BuggyDad]

Well, I dried out the black PETG filament and went to Prusa default temperatures at the same time, so not scientific and I don't know what improved it but something did. 

So I can get a decent enough finish with the black. It's gloss as opposed to the orange's matt, but otherwise nearly (but not quite) as good.

I wonder whether there's a bit of trial and error required before one finds a favourite filament brand/model. 

I've also built the classic IKEA cabinet. Did a bit of extra design to slot the lower two tables together more safely as well. And got a drier and sealed filament storage set up above the printer. Just an LED strip and thermometer to go and my setup will be pretty complete I think. Pretty chuffed with that.