My new PEI bed is working well and warp is a thing of the past, hurrah! However, as they say, I now have a new problem… Take a look at the bottom of this model:
At first glance it looks like under-extrusion (doesn’t it?) but it’s not. There are parts of this surface that are totally smooth. There’s also a weird “pattern” to the holes, like the filament was “pulsing” rather than being delivered smoothly, but only in the centre of the print. Now take a look at these smaller parts:
These are roughly the same Y dimension as the first (about 35mm) but obviously a lot less in the X. There’s a similar drop-out in the fill right in the centre, but it’s much less pronounced and as we get towards the edges it’s totally smooth. I’ve included a view of the top surface for reference - that’s pretty smooth and looks fine, as are the sides. I had another print that’s half this X/Y and the entire bottom surface is absolutely smooth - perfect, I’d say.
All three prints used the same settings. All were printed under the same calibration, no recalibration done between them. All were centred on the bed (so the middle of these parts was the middle of the bed in each case).
I’m pretty sure it’s not calibration, as I’d expect the “gaps” that appeared in the first large model to be in the smaller ones, as it happened in the same part of the bed. I’m pretty sure it’s not under-extrusion, because there are no other signs anywhere in the print (in fact, if anything, there are signs of very slight over-extrusion). So what the heck is going on? It’s as though the printer simply got “tired” in the middle…
All parts netfabbed. All sliced with Simplify3D. Flashforge Creator Pro, ABS. Bed 110C, Nozzle 230C.
@shahramrobotics no, although it did occur to me (I’m aware of how important top quality filament is). To be honest, the filament I’m currently using is of… unknown origin, not from my usual supplier. Do you think it could be variation in width?
Yes, most of the times it’s because of that. One time I was using a same unknown brand filament (like $5/kg) and the width was fine but found out the filament was more dense like every 7~10mm and like 2~4mm long that caused a similar issue. Definitely try another spool first.
To me that looks like slight irregularity’s in the bed height. Only reason I mention it is that one of my printers still has the factory “blue” sheet on it and it displays a similar pattern but if I put on the glass bed it goes away.
No idea if that is what you have but just a thought.
Hi @wirlybird pretty sure it’s not the bed (as sure as I can be about anything!); this is my new PEI sheet on top of a glass plate and I’ve had other prints since fitting it that are dead flat across that area. As @shahramrobotics suggested, it seems much more like an irregularity in the filament itself - something that only becomes visible occasionally and/or when doing longer straight runs and I do know I’m using filament of an “unreliable” origin.
When the opportunity arises I’ll see if the same thing happens with my usual top-quality supplier filament.
I know you marked this as solved but I suspect the source cause may still exist.
I spent months trying to fix something that looked identical to your print.
Now there’s more than one reason that might contribute to this wavy effect but in my case the right side trapezoidal z nut had about 0.75mm vertical play.
The reason that it propagates as a wave like pattern is simple. As the print head moves across the layer all it takes is a tiny bit of under or over extrusion to start the pattern. On the next line the print head hits the side of that spot and because it’s a little loose the head moves vertically as it rides the bump or dip. Then it tends to expand and get more waves as the print head jumps around. Rock each side of your z axis up and down to see if you have some play like I did. Also check your print head as the play might originate there too.
