Bondtech or similar extruders (again)
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@preb1
Since the lower layers seem to be fine maybe insufficent cooling? -
@denke Thanks for the suggestion.
I have thought of that but I only print PLA and at 190 to 195 degrees. I only occasionally use cooling if it's got overhangs otherwise I find the layers don't stick together. I have tried all sorts of temps with and without cooling. I usually print a temp tower and use lowest temp that gives a good finish.
This is very weird. -
@preb1
PLA almost always require a fair amount of part cooling, but in some extreme cases, it admittedly can cause the layers to not stick. You should find the amount of part cooling best suited for your printer inbetween. -
I'd be curious how that benchy would look if you aligned the seams, raised your retraction speed and jerk, raised your Z jerk, etc., and most importantly here, turned on your fan. In fact, if you're printing a benchy and seeing this sort of blobbing, try manually cranking the part cooling fan to 100% mid-print from the Duet Web Control and see if it changes.
I know this will sound odd, but if that's what you get when you print a benchy, do you get the same thing if you print two or three benchies at the same time? If you don't, then it's almost certainly a temperature/cooling thing.
ETA: I also just switched from my previous belted 4:1 reduction printed extruder (single drive) to a Bondtech BMG clone, and it's great having that dual drive. I use a bowden feed, and the reliability with which that dual drive can shove filament in and out of that bowden tube for super fast retract/unretract is really great.
Also, have you experimented with pressure advance and non-linear extrusion? I just went through a process of experimentation, measurements, and setting these two up on my printer and I'm getting pretty much the best prints I've ever done now.
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If everything but a benchy prints fine, the moral of the story is
"dont print a benchy"
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@preb1 said in Bondtech or similar extruders (again):
I have thought of that but I only print PLA and at 190 to 195 degrees. I only occasionally use cooling if it's got overhangs otherwise I find the layers don't stick together.
that seem very odd. pla does require cooling normally. does this happen with pla from other manufacturers as well?
can you post your thermistor config? you might be printing at the wrong temperature.
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Thanks for all the replies. Unfortunately I don't agree with cooling for pla. I don't find I need to cool the part. I can print a 20mm single wall cube with no cooling and I get no problems. At 30mm print speed that's just under 3 secs per layer. I always thought you print at lowest temp possible without stringing. This is why I find it hard to believe it's overtemp that's causing the finish on the benchy. Any cooling I use results in layer separation with all makes of pla even if I only use 20% or so.
My jerk is 800mm/s on x,y and z. Accel is 2000mm/s, 3000mm/s on extruder and retraction is 80mm/sec and retraction set at 2mm.
You're right, don't print a benchy but I am curious as to why I can't print them with success.
I am trying now to print 3 at once to see if there is any difference in finish. -
@preb1 said in Bondtech or similar extruders (again):
I can print a 20mm single wall cube with no cooling
A cube has no overhangs.
What kind of fan are you running that any cooling at all results in layer delamination?
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15x50 centrifugal fan
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But does not the cat I printed have overhangs?
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Try the benchy with the fan at 100%, and crank the temperature up to 210-215 to get rid of layer adhesion issues.
Just try it and report back -
@nitrofreak said in Bondtech or similar extruders (again):
Try the benchy with the fan at 100%, and crank the temperature up to 210-215 to get rid of layer adhesion issues.
Just try it and report backThis.
The fan is for bulk cooling, and the nozzle temp is for layer adhesion. The idea of using both at the same time is not an oxymoron; just consider your hotend has a massive heatsink and fan on it right next to the melt chamber. If you don't use a cooling fan for PLA the heat in the bulk print builds up too much and stays squishy. If that's making your layer adhesion suck, then your nozzle temp is too low for that particular PLA. A benchy is totally different than a single-walled cube because in the single-walled cube there's air surrounding every single line you print so the heat can dissipate naturally. With the benchy there's a lot of plastic mass not being cooled, and in addition to the heat of the newly extruded PLA you've got the hot nozzle hovering right over most of the print most of the time radiating heat onto it.
There's lots of stuff I'll print without a fan. I often print PETG with no fan, and always do my attempts with nylon and ASA and whatnot with no fan. PLA isn't one of those things; it needs the fan.
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@sethipus said in Bondtech or similar extruders (again):
@nitrofreak said in Bondtech or similar extruders (again):
Try the benchy with the fan at 100%, and crank the temperature up to 210-215 to get rid of layer adhesion issues.
Just try it and report backThis.
The fan is for bulk cooling, and the nozzle temp is for layer adhesion. The idea of using both at the same time is not an oxymoron; just consider your hotend has a massive heatsink and fan on it right next to the melt chamber. If you don't use a cooling fan for PLA the heat in the bulk print builds up too much and stays squishy. If that's making your layer adhesion suck, then your nozzle temp is too low for that particular PLA. A benchy is totally different than a single-walled cube because in the single-walled cube there's air surrounding every single line you print so the heat can dissipate naturally. With the benchy there's a lot of plastic mass not being cooled, and in addition to the heat of the newly extruded PLA you've got the hot nozzle hovering right over most of the print most of the time radiating heat onto it.
There's lots of stuff I'll print without a fan. I often print PETG with no fan, and always do my attempts with nylon and ASA and whatnot with no fan. PLA isn't one of those things; it needs the fan.
+1 on this.
See my picture below, thit is one of my PETG printers, it doesn’t print anything else but PETG. And you will notice there is NO part cooling fan because it doesn’t need one.
Some materials do need external cooling and some don’t, this conclusion is reached through extensive testing.
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@calvinx said in Bondtech or similar extruders (again):
See my picture below, thit is one of my PETG printers, it doesn’t print anything else but PETG. And you will notice there is NO part cooling fan because it doesn’t need one.
In my experience there is a reason for using a part cooling fan with PETG (and similar filaments) and that is when you are printing skin above support. In that situation you would like to have poor layer adhesion and so blasting 100% fan at the skin makes the support easier to remove.
I print various PETG parts and mostly use zero fan but I do have one part that has some overhang and that needs a touch of fan to avoid sagging.
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@burtoogle said in Bondtech or similar extruders (again):
@calvinx said in Bondtech or similar extruders (again):
See my picture below, thit is one of my PETG printers, it doesn’t print anything else but PETG. And you will notice there is NO part cooling fan because it doesn’t need one.
In my experience there is a reason for using a part cooling fan with PETG (and similar filaments) and that is when you are printing skin above support. In that situation you would like to have poor layer adhesion and so blasting 100% fan at the skin makes the support easier to remove.
I print various PETG parts and mostly use zero fan but I do have one part that has some overhang and that needs a touch of fan to avoid sagging.
Interesting. luckily I have not had any issue removing supports.
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Ok. Update.
Tried printing a benchy at 215 degrees and 100% fan. Set fan to come on at Layer 10 (2mm). That was the end of that . No layer stuck after that and no, my cooling outlet is not blowing at the nozzle but at the print.
I printed an overhang test piece firstly with no cooling and 195 degrees. Printed ok until about 50 degrees overhang when it got a bit messy. Then I printed it at 215 degrees and 50% fan. About the same quality but had no strength. Could pull it apart easily. I'm using Sakata 3d filament. Now going to try Rigid Ink filament.
The daft thing is that when this was a standard printer I could print a benchy no problem. Since upgrading to a genuine E3D and a Direct drive extruder I have had all these problems. I guess that is the answer. Revert to original.
As an aside my delta with a duet board and a E3D and Flexidrive extruder also prints a benchy no problem with no cooling.
It makes me think that 3D printing is not an exact science as some make it out to be. -
Do you have the correct thermistor values for the hotend?
Is there something mechanically wrong with it?
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Since you’ve changed the nozzle, are your thermistor settings correct? Looks to me like you’re printing too hot, and over extruding on the return after retraction, hence a zit. As you’re direct drive, retraction should be much shorter than Bowden. Are you using pressure advance too? Something definitely changes after the first 10 or so layers. Is this where solid fill ends and printer speeds up? Was the cat printed with the current setup, or before the change? If current, I can’t explain why it’s so different for Benchy!
Ian
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Thermistor values I think are correct. I did a PID tune and set the values. The temp is rock steady as is the bed which is mains powered heated mat.
The cat was printed with the same setup.
Not using pressure advance. 2mm retraction set up at moment.
Printer is set at 2400mm/min.
I print first layer at 40% speed as I find this gets a good first layer. The outline is set to 40% as well.
So first layer prints at 16mm/s with the outline at 6.5mm/s
Thereafter everylayer prints at 40mm/s with the outline at 16mm/s.
I chose the fan to come on after 10 layers as this seemed a good point to start. -
@preb1 said in Bondtech or similar extruders (again):
I chose the fan to come on after 10 layers as this seemed a good point to start.
Is this still the picture of the Benchy from the first post? Because something fairly dramatic changes at that point. Maybe the fan is causing interference on the thermistor? Or temperature change at that layer? Something about your settings is different for the Benchy from the cat.
Ian
