Getting first layer of part to be 0.05? Maybe a raft?
 

Getting first layer of part to be 0.05? Maybe a raft?  

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krb
 krb
(@krb)
Trusted Member

I'm trying to print ring (like you wear on a finger) at 0.05 layer height. I'm printing the ring lying down on the bed, but it isn't a straight up and down wall, and it has some detail embossed into the surface, which ends up on the Z-axis. 

This is my first part with this small layer height. On my first try, I noticed that Slic3r defaults to 0.20mm for the first layer and that is creating an unwanted ridge in the profile of this ring. I'm wondering if a raft will help? I've tried turning on a layer or two of raft but looking at the layer-by-layer view of the sliced result, it isn't obvious to me the first layer of the part will be 0.05. If I leave Contact Z Distance at the 0.1 default, the difference between the last layer of raft and the first layer of my part is 0.50mm. If I set Contact Z Distance to 0.0, then the difference between these layers is the expected 0.05mm.

So, I guess I'm asking both for help on raft settings, but also more generally if this is the right way to solve this problem of trying to get a small layer height for the first layer part itself.

 

NOTE: I'm doing this on the stock 0.4 nozzle right now. I've got smaller nozzles, but thought I would run a few drafts to see how it turns out before swapping nozzles out (which I've also never done)

 

 

 

Posted : 05/08/2020 4:24 pm
bobstro
(@bobstro)
Illustrious Member

Be aware that your bed may not be within 0.05mm across the entire surface. A 0.2mm 1st layer helps lay a flat foundation for the layers that follow. If you are getting the "elephant's foot" effect on your 1st layer, best to simply calibrate to eliminate that than try to compensate for it elsewhere. 

  1. Check 1st layer temp. Too hot can deform 1st layer.
  2. Calibrate your extrusion multiplier. Any over extrusion will build up on solid layers like the 1st.
  3. Try elephant's foot compensation setting. Not ideal, but it can help.
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 05/08/2020 6:02 pm
krb
 krb
(@krb)
Trusted Member
Posted by: @bobstro

Be aware that your bed may not be within 0.05mm across the entire surface. A 0.2mm 1st layer helps lay a flat foundation for the layers that follow. If you are getting the "elephant's foot" effect on your 1st layer, best to simply calibrate to eliminate that than try to compensate for it elsewhere. 

  1. Check 1st layer temp. Too hot can deform 1st layer.
  2. Calibrate your extrusion multiplier. Any over extrusion will build up on solid layers like the 1st.
  3. Try elephant's foot compensation setting. Not ideal, but it can help

Thanks for the reply.  The ring I'm printing is really small. Maybe 20-30mm diameter, I know the bed may vary that much, and I'm happy to have a bigger first layer, I'm asking for advice on how to print object where I need the entire object including the object's first layer (which does not have to be the printed first layer) to be at 0.05 layer height because of detail I want starting at those bottom 3-4 layers. (four 0.05 layers is one 0.20 layer). It feels like a problem others much have encountered before.

I thought a raft might do it, but I have little experience with rafts and so I don't know how to interpret what I'm seeing in the sliced results.

Posted : 05/08/2020 6:57 pm
nikolai.r
(@nikolai-r)
Noble Member

@krb

This is such a small object. Just try to print with raft. You're only one checkbox away 😉 

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Posted : 05/08/2020 7:38 pm
bobstro
(@bobstro)
Illustrious Member

 I neglected to mention that you can't actually print at 0.15mm normally due to the Prusa soft endstop implementation. Unless you override settings, attemps to move lower will trigger an endstop warning message. If you truly need thinner 1st layers, you will need some other workaround.

A larger problem may be overhangs if the outer wall is curved.

This post was modified 2 months ago by bobstro
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 05/08/2020 7:51 pm
bobstro
(@bobstro)
Illustrious Member

ugh - Can't print a first layer lower than 0.15mm. 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 05/08/2020 8:13 pm
krb
 krb
(@krb)
Trusted Member

Thanks for all the replies! So a raft seems like the way to solve this. Raft first layer can be 0.2 or whatever it wants. Then my question is I can't figure out what layer height the actual bottom layer of my ring will be. From my original post:

I've tried turning on a layer or two of raft but looking at the layer-by-layer view of the sliced result, it isn't obvious to me the bottom layer of the part will be 0.05. If I leave Contact Z Distance at the 0.1 default, the difference between the last layer of raft and the first layer of my part is 0.50mm. If I set Contact Z Distance to 0.0, then the difference between these layers is the expected 0.05mm.

Can someone explain the 0.50mm vs 0.05mm difference I see? 

Posted : 05/08/2020 9:36 pm
bobstro
(@bobstro)
Illustrious Member

Rafts are essentially support, and supports in PrusaSlicer are ... not intuitive. I recently did a quick comparison of support underside results. There's a long & convoluted history behind this. Essentially, the slicer generates support, then a layer of bridged material, then your part. Rafts may be a special case in that it's not trying to match a specific layer height. In any case, the gaps between supports and printed parts in PrusaSlicer is not guaranteed to be the same as your contact z distance.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 05/08/2020 9:49 pm
joan.t
(@joantabb)
Veteran Member Moderator

Could you add a 0.2mm disc under the ring, then print the disc in a dissimilar material using m600 to change filament and when finished, peel the ring off? 

I recently made some model boat propellors using PLA for the supports and PETG for the propellor they peeled apart quite easily when cold

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 06/08/2020 2:40 am
jsw and bobstro liked
Neophyl
(@neophyl)
Noble Member

Any chance of posting your ring model or current project ?  I'd kind of like to see the issue and do a bit of experimenting with settings in both Prusa and Super Slicer.

Posted : 06/08/2020 7:17 am
bobstro liked
krb
 krb
(@krb)
Trusted Member
Posted by: @joantabb

Could you add a 0.2mm disc under the ring, then print the disc in a dissimilar material using m600 to change filament and when finished, peel the ring off? 

This is a great idea, I'll try this!

Any chance of posting your ring model or current project ? 

Sure! Attached.

 

 

 

This post was modified 2 months ago 3 times by krb
Posted : 06/08/2020 8:25 pm
krb
 krb
(@krb)
Trusted Member
Posted by: @joantabb

Could you add a 0.2mm disc under the ring, then print the disc in a dissimilar material using m600 to change filament and when finished, peel the ring off? 

I recently made some model boat propellors using PLA for the supports and PETG for the propellor they peeled apart quite easily when cold

regards Joan

Actually tried this in PrusaSlic3r right now using the built in color change feature and I just realized I have to do more than M600, I need a different extruder temp for PLA vs PETG. Does PrusaSlic3r support this sort of manual material change between layers (I don't have an MMU) including extruder temp changes? I don't need to change the bed temp. 

Or, should I just edit the gcode manually? I guess I could do something like M600 then M109

Posted : 07/08/2020 2:29 am
Neophyl
(@neophyl)
Noble Member

@krb

Instead of adding a Mxxx right click the little plus icon and select add custom gcode.  You can then add in the colour change command and any temperature or fan speed changes you need by typing the codes in.

I had a look at this and raft is useless as it always prints the bottom layer of the model at 0.2 height no matter how high off the plate it is and no matter if its detect bridging on or off.  This seems like a serious shortcoming.  Joan's method of adding a sacrificial disc under the part looks to be the only viable method currently.

 

Posted : 07/08/2020 7:18 am
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