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GerryH

holes/circles first layer

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Many of my 3d printed parts have smaller holes designed into the base.  Cura when printing the first layer prints the outer wall, then tries to print the circles inside the outer wall.  There's nothing connecting these circles and so they frequency don't stick.  Some other slicers print lines to connect the circles to the outer walls.  Is there a way to make Cura do this?  I've gotten so used to using Cura and have it tweaked just right for my work, I don't want to have to use another slicer for some parts.

 

This is an example of what I'd like to happen

Capture.GIF

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When you say "first layer" you mean "bottom layer", right?  So they should stick to the glass, right?  I guess I don't understand the question.  If they aren't sticking to the glass your nozzle is too far from the glass.

 

Maybe show a photo of what cura is doing.

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bottom layer/first layer.  I'm using PLA on buildtak with gluestick.  I don't have any problems on larger lines/circle, but these are 3 or 4 mm circle for screw holes.  I was just thinking that if the circle was attached to something, it would have a tendancy to move/not stick.

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Well isn't the circle attached to the build tak then?  It should stay in place until the print is done.  And then the circle should be attached to another one on the layer above, right?  And so on going upwards eventually connecting to the rest of the part.  Right?  Again, a photo of what it looks like in cura would be helpful both solid view and layer view.

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That's the problem, the circles sometimes don't stick, then the extruder drags them around until they fall off, but then you get some glob of PLA where you don't want it.

 

See how Cura prints the circles after the outer wall.  Compare that to the picture above.

 

I'm guessing this is just the way Cura slices.  Would be nice if there was an "anchor" feature for small features like this.

Capture2.GIF

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At the moment, Cura always prints walls and skin separately and given how the program is structured I can't see that being easily changed. However, I wonder if there is some scope for connecting the inner, circular walls to the outer walls with other walls. That would achieve similar results in terms of adhesion.

 

Personally, I have solved the small circle adhesion problem by printing first layer walls very slowly so I would not have any trouble printing your example above.

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You do not say what 1st layer speed you are using but you want 20mm/s for those circles and as @gr5 says an easy solution is to move the nozzle closer to the bed. If all else fails then you could design your part for the circles to start on layer 2 and then when finished cut out the 1st layer with a Stanley knife. Oh and to make things easy for adhesion print your 1st layer at 0.300 layer height

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8 hours ago, GerryH said:

That's the problem, the circles sometimes don't stick, then the extruder drags them around until they fall off

OH!  You should have said that in the first place, lol.  Instead of the 5th post.

 

Yeah.  As I said and as yellowshark said:  Move the nozzle closer to the print bed.  You aren't squishing the bottom layer enough.  I don't know what kind of printer you have.  On all Ultimaker printers you simply rotate the 3 leveling screws CCW as seen from below to move the glass bed up a bit.

 

Do you have a printer with a heated bed?  If you *do* have a heated bed 60C is good.  I don't think you need PVA glue on build tak - I think that might defeat the purpose a bit but your main problem is not enough "squish".  MUCH more details here:

 

 

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I do understand the problem, as I had that too in the very beginning, when printing on bare glass without any bonding aid, or when printing on a glue-layer that was too thick.

 

But if you try to solve this kind of bed adhesion problems in the slicer, it would create ugly lines through the bottom of your prints. I think it is best to optimise your bonding method, to make the small circles stick by themself.

 

It might be a good idea to post a few close-up photos of the underside, to see what exactly is the problem. For example: build-plate too far away, glue too thick,...

 

Since I started using my "salt method" (=wipe the glass with a tissue moistened with salt water) I don't have this problem anymore. But I think gr5's method (10% white wood glue in water) or neotko's hairspray method, or 3DLAC, or a thin layer of glue-stick wiped with a wet tissue afterwards, should also work well on the condition that the build-plate is at the correct level.

 

For the manual on the "salt method", see here:

https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

 

When using a new bonding method, always stay with the printer for the first prints, and carefully watch if it works well, and what happens.

 

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