My custom Cartesian

wilriker

@obeliks Actually I don't even know that. I guess so because they feel very stiff. But of course it introduces another elastic element besides the belt into the system. So it will at least add a very minimal amount of backlash.

Now that I think of it my ghosting problems with infill visible on the outside of a Benchy might be backlash issues...

OBELIKS

Do you have a picture of that Benchy?

wilriker

@obeliks This is the best one I could find (and not a good one to be honest):
0_1535116706809_1130815247278436466352977980638233011.jpg

Given this is actually printed on the original acrylic frame but sadly the aluminium frame did not improve in this very issue in any way.

And this is not just visible because the filament is a tiny amount transparent but also you can feel it.

EDIT: There already was belt tensioner in use and I used glass-fibre reinforced belts from the start - I never used the steel-reinforced belts that came with the A8.

OBELIKS

This is not really ghosting, what value do you have for the perimeter/infill overlap?

wilriker

@obeliks I knew that this would come up. It's at 10%. And I am using 2 perimeters with 0.4mm each so a total wall thickness of 0.8mm.

OBELIKS

Haha
IDK, usually these kind of issues are down to slicer, temperature, filament errors. But you probably checked those before.
Just one more, is this PETG? I have seen something like that with it.

wilriker

@obeliks No it is PLA actually. But I see the same with PETG. That is one thing I have yet to get rid of - but maybe I need to try harder instead of all the time tinkering on the printer.

Regarding the filament I checked its width and AFAIR it had a little over-diameter but not enough to adjust anything. And temperature was determined by temperature tower.

OBELIKS

You know what. Send me sliced file, I'll try it here. We will be able to definitely rule out slicers if it is all OK on my front.

wilriker

@obeliks Uploaded it to my Dropbox 3DBenchy_75mm.gcode.

Of course you have to adjust start and end codes as for me this simply calls two files in /sys via M98 and temperatures are set at the beginning of the file as well.

OBELIKS

Good news, I have the same result. And I think I know what is the problem. Try disabling Print Infill Before Walls. When it was printing walls I could hear it dragging against the infill and I can feel it. With Slic3r that prints walls before the infill by default I never had this issue.

wilriker

@obeliks First of all thanks for your test print!

I have to check my settings what the actual value of this switch is tomorrow. I know so much as that I am using the default of Cura.

But interestingly I always thought that printing infill before walls was exactly to prevent the issue I am seeing. But my brain had so much input in the field of 3DP since I (only) started end of March in this adventure it would not be unlikely for me to mix something up here.

wilriker

OK, I checked the the default settings of Cura. As you said it will by default print infill before walls. In the setting's description it even says this can lead to infill sometimes showing through. I assumed "sometimes" would not mean "nearly always". Anyway, it also says that enabling it will improve overhangs significantly.

But then I also found a setting "Connect infill lines". From the description of it it might alleviate the issue so I get best of both worlds at the price of some more filament because this basically adds another perimeter on the inside.

I will try both after I switch filament next time because currently this is a borrowed spool that I can use for a specific purpose but I don't want to stretch the generosity by printing an army of Benchies.

OBELIKS

If you need more help from me just say. I can print more tests. Just prepare them for PETG.

OBELIKS

Also. I might be slightly linguistically impared. We have a local festival, so...
I really do not mid to run some tests if you need them.

wilriker

@obeliks said in My custom Cartesian:

If you need more help from me just say.

Thanks! I might come back to this offer in the future. For now I already appreciate that you pointed me in the right direction.

Also have fun at your festival! Drink a beer for me - I would not like it anyway so it is better spent on you!

wilriker

Totally unrelated: I am in the process of rewiring everything. It's going quite slow but it progresses.
Last weekend I replaced the wiring for my Z motors. @dc42 suggested somewhere that for high-inductance motors they should be wired in parallel instead of using the in-series-wired two connectors on the Duet. So I did that and could effectively double the max speed of my Z axis to 25mm/s - this looks totally unreal now when moving longer distances after I got used to 10 or 12mm/s max speed I had before.

deckingman

@wilriker Lucky you. I run mine at 450mm/min which is 7.5mm/sec. I've pushed it to 10mm/sec (600mm/min) but it's not too happy. Mind, it weighs around 8kg and I'm driving it with 3 screws via a single Nema17. With 750mm Z travel it takes 100 secs to go from max to min (not that I do that too often)

OBELIKS

@wilriker Beers were drank, food was eaten, it was good.
Even today it is not too bad.

wilriker

@deckingman But what to do with my luck? Driving Z all day up and down... I could write a macro for it, it's RRF after all.

But still your motor seems to be better than mine plus you probably use 24V.

My X gantry weighs about 2kg (probably much less but easier for the following math) and I have two Z motors and therefore only 2 leadscrews. That makes a quarter of the weight, double motor power and only 2/3 of the leadscrew friction. All together my Z axis should run 8-12x as fast as yours and I only have it about 4 times faster.

But as you also mentioned: when does one need speed in the Z axis?

deckingman

@wilriker said in My custom Cartesian:

@deckingman But what to do with my luck? Driving Z all day up and down... I could write a macro for it, it's RRF after all.

But still your motor seems to be better than mine plus you probably use 24V.

My X gantry weighs about 2kg (probably much less but easier for the following math) and I have two Z motors and therefore only 2 leadscrews. That makes a quarter of the weight, double motor power and only 2/3 of the leadscrew friction. All together my Z axis should run 8-12x as fast as yours and I only have it about 4 times faster.

But as you also mentioned: when does one need speed in the Z axis?

Ahh, but what is the lead of your screws? Mine are fine lead (1mm) so I've probably got better gearing than you.

There is one situation that I could think of where you might need faster Z and this is if you homed to Z max - for example if you want to recover from a power loss on a CoreXY. I don't do that myself as the bed would cool during a power fail and the part would fall off in any case. For me to home to Z max would take 200 seconds (100 seconds to go down 750mm and 100 seconds back up).