Weird scars on surface of print  

RE: Weird scars on surface of print

Not really no.  Warping upwards can be a continuous process, it doesn't just happen at the start and as it warps up the space available for the filament gets less and so causes a continuous problem as the amount extruded is calculated based on the assumption that there is zero warping of the part.  Once its starts it can propagate upwards if there's nothing in the geometry to act as a 'firebreak'.

Fix your bed adhesion, change your printing environment to minimise the possibility of warping such as drafts etc or redesign the part to reduce warping factors.  Preferably all 3 and anything else that can contribute.

RE: Weird scars on surface of print

Agreed. This is a textbook example of warping.

RE: Weird scars on surface of print

I really doubt it. The 'warping' was worse in another corner where the effect was minimal and well, see the pictures:

I really meant it that its a marginal error. Next to that I wouldn't know how to increase bed adhesion. The bed is cleaned with alcohol and I've increased the temp. 

RE: Weird scars on surface of print

I really doubt it. The 'warping' was worse in another corner where the effect was minimal and well, see the pictures:

I really meant it that its a marginal error. Next to that I wouldn't know how to increase bed adhesion. The bed is cleaned with alcohol and I've increased the temp. 

RE: Weird scars on surface of print

Large rectangular models are prone to warping. Things to try:

• Wash sheet with dish washing liquid and plenty of hot water
• Add Mickey Mouse ears to the model corners or a brim all around
• Use an adhesive agent such as Layerneer or Magigoo
• all of the above

RE: Weird scars on surface of print

Oh, it's a Mk4 so you may try to manually adjust live z down by -.010 when the print starts by holding the knob, to give it a bit more squish. 

RE: Weird scars on surface of print

Wolph your second set of pictures clearly show the warping.  While your first layer looks ok you can clearly see a difference in that top pic of the bottom, there are lines there that are obvious to me where the layers above that are solid, have peeled those small first layer patches away from the bed in the corners.  They look like lines/almost watermarks.  Wish I had a photo editor so I could outline what I mean but look at the bottom rectangle third from the left, its really noticeable there but theres indications that the entire corner has lifted up.  you just have to learn what to look for.

I'll also agree with Fuchsr that cleaning with detergent and HOT water is better than alcohol.  IPA dissolves greases and can leave behind a thin layer, detergents and hot water remove greases when the detergent is rinsed away.

RE: Weird scars on surface of print

thank you all for the feedback on warping (I do see the 'watermark' edges, thats why i said there is some warping). Ill do this next time. HOWEVER...I really don;t think that this is the cause as you can see in the 2nd picture, the 'warping' effect is completely rectified alreay I few layer higher. I've had other warping issues where indeed the effect worked its way up, close to the top but even there I've not seen this scarring issue I get here. Hence im inclined to say that there is little to no correlation between the insignificant warp and the scarring on top. I have picture of another project if you like with massive warping; also square (equal size) object and no scarring. 

RE: Weird scars on surface of print

If I hadn't seen these patterns a hundred times before... 

RE: Weird scars on surface of print

You ask, we reply.  Its up to you what you do with that information.  Or not.

As I said previously much of this depends on the geometry of the model in question and the way it is sliced.  If there is space for the excess filament to go inside with a warped up part then you may not see any external effect at higher layers.  If there isn't then you can.  This is the firebreak principle I mentioned.  As you haven't provided a project with the model and settings we cant slice it and check the preview to see if this is a possibility or not.  We can only go on your provided picture information.  

RE: Weird scars on surface of print

and all the feedback is very much appreciated! thank you for that. To answer your question directly: I use 20% infill, I've check halfway print and the infill is nice and smooth so it appears the warping issue is fixed in the between layers. Note that the 'warping' was similar in this print. 

In the mean time I've tried the same print but for the top layers I've lowered the nozzle temp 10C and the effect, while still there, is much less. So it could be a temp. I'll try a third part, but lower it further. 

Any other suggestions are still most welcome!

RE: Weird scars on surface of print

You could try reducing the extrusion multiplier to 0.97 or 0.95.  The ripples are caused by trying to put down more filament than there is space for - this is usually caused by warping, but if, as you suggest, the warping is fully resolved by the time you get to the top layer, it may just be that you have a filament that is a few percent bigger than the settings are expecting.  For infill layers there's plenty of room for excess filament, but not on the top solid layers.  You could try tuning the settings for your filament with something like this, or you could shortcut that and just see if a lower multiplier solves your problem.

if, as you suggest, the warping is fully resolved by the time you get to the top layer, it may just be that

No.  The OP is missing the point; there is no room or allowance to break the warping effect so it's the classic wrinkling when the correctly calculated amount of material is laid in a space that is now too small for it.

Cheerio,

RE: Weird scars on surface of print

My last comment on this topic: Easy enough to test. Different ways to address warping have been listed above. If those fail, I'd be open to alternative explanations. Adjusting EM would be a kludge at best.

RE: Weird scars on surface of print

the EM is a good tip and makes sense, I'm currently printing the next one, I've also lowered the temp for the top layer by 20C and additonally set the EM to .95. 

RE: Weird scars on surface of print

ok status update: cleaning the bed with soap did indeed help with adhesion, though there still was some minor warping in the corner, but much less. Overall its about 3 layers where I see slight deformation and then none further. lowering the the EM and the temp to 200C also helped with the scarring, but there is still some noticeable scarring in one corner. It did introduce another issue though and that is that the support layer I used was nearly impossible to remove. 

RE: Weird scars on surface of print

Hi,

I had the same issue sometime ago and I had help from prusa to solve it. You have setup the temperature too high for the first layer. Reduce it by 5°C until it's good.