Layers keep seperating.

[aniyapaniya 0]

Hi, so I've been printing some cookie cutters with a 0.2 nozzle. I chamfer it so it goes from big to small, and on the top part where its the thinnest (where you would be slicing it with) it always breaks off, i think this is because it is too thin. It is 2mm thick with the chamfer starting from the bottom going to the top until it is 0.2mm. Is there any recommendations with what I could do to still keep this sharp edge but not have it break off? My cutter is 12mm high and chamfer is 9, it always breaks off at the top approx. 2mm in. Any help would be appreciated, I've spent all day printing out different heights and chamfer sizes and nothing seems to be helping. I bought cookie cutters that are these measurements but now im starting to think they might have used a different filament. I use PLA and I am trying to keep it as this because I print in my room. Thanks! 

[DivingDuck 97]

You maybe can play a bit with print speed / temperature / fan speeds for your last layers. With such walls at the end of a print the usual settings may not work well and the adhesion will come weak because of not consistent filament temperature.

[GregValiant 1,142]

The problem may also be in the transition between the single line width for the sharp end, and the point where it becomes 2 line widths.

 

I wonder if slicing with the Arachne version would be a better choice?  It is variable line width and might result in the print being closer to the model as it moves up the chamfer.

 

How sharp do you really need the end to be?  You may be able to live with it just not printing the problem layers.  I printed some cookie cutters for Christmas and used .8 wall and a .4 nozzle all the way up the side walls.  They worked fine.

[geert_2 557]

Do the walls need to be slanted for cutting cookies? For injection moulding plastics, for sure yes, for casting silicones also yes, unless the models are very thin. But for soft cookies or dough?

 

If I had to print cookie cutters or plasticine cutters, I would probably first try straight walls, print with a standard 0.4mm nozzle (less risk of underextrusion and clogs), 0.8mm thick walls (=2 lines), print slow at 25...30mm/s, thin layers 0.06...0.12mm, and print cool at the lower edge of the temp range. Printing cool helps prevent the filament from decomposing in the nozzle due to the long transition time. Printing slow gives the molten filament more time to melt the previous layer and thoroughly fuse it. Thin layers give less indents, less entrapped air between the extruded sausages, a better fusion, and smoother surface. All that should give a quite solid and strong model.

 

Then I would cut and sand away blobs and defects, and smooth the side walls with dichloromethane (for PLA and PET) or acetone (for ABS), so they get high-glossy and don't cause friction. Smoothing also makes cleaning much easier, and gives less grip for dirt and bacteria.

 

After smoothing, I would let the models dry thoroughly, so they do not degass the solvents anymore while cutting cookies.

 

Not sure if it would work, but that is how I would approach it. And then optimise further from there, if necessary.

 

[aniyapaniya 0]

8 hours ago, GregValiant said:

The problem may also be in the transition between the single line width for the sharp end, and the point where it becomes 2 line widths.

 

I wonder if slicing with the Arachne version would be a better choice?  It is variable line width and might result in the print being closer to the model as it moves up the chamfer.

 

How sharp do you really need the end to be?  You may be able to live with it just not printing the problem layers.  I printed some cookie cutters for Christmas and used .8 wall and a .4 nozzle all the way up the side walls.  They worked fine.

Sorry what do you mean by slicing the arachne version? See, I use these for clay so I really do need them as sharp as possible, the 0.4mm nozzle ones do work ofcourse but there is alot of clay left uncut because its too flat. I have bought some cookie cutters with 0.2mm top parts and they dont break so im trying to achieve this now myself although not getting very far unfortunately 

 

[aniyapaniya 0]

7 hours ago, geert_2 said:

Do the walls need to be slanted for cutting cookies? For injection moulding plastics, for sure yes, for casting silicones also yes, unless the models are very thin. But for soft cookies or dough?

 

If I had to print cookie cutters or plasticine cutters, I would probably first try straight walls, print with a standard 0.4mm nozzle (less risk of underextrusion and clogs), 0.8mm thick walls (=2 lines), print slow at 25...30mm/s, thin layers 0.06...0.12mm, and print cool at the lower edge of the temp range. Printing cool helps prevent the filament from decomposing in the nozzle due to the long transition time. Printing slow gives the molten filament more time to melt the previous layer and thoroughly fuse it. Thin layers give less indents, less entrapped air between the extruded sausages, a better fusion, and smoother surface. All that should give a quite solid and strong model.

 

Then I would cut and sand away blobs and defects, and smooth the side walls with dichloromethane (for PLA and PET) or acetone (for ABS), so they get high-glossy and don't cause friction. Smoothing also makes cleaning much easier, and gives less grip for dirt and bacteria.

 

After smoothing, I would let the models dry thoroughly, so they do not degass the solvents anymore while cutting cookies.

 

Not sure if it would work, but that is how I would approach it. And then optimise further from there, if necessary.

 

Yes see the thing is that I use these for clay so they do need to be as sharp as possible, when they are 0.4 mm thick it leaves you with alot of clean up at the end.. I have bought some that are 0.2 thick at the top and they dont break so I am trying to achieve this myself but they keep breaking..

[GregValiant 1,142]

The Arachne version of Cura was pre-released a month or so ago for testing because it's a whole new thing.  It uses variable line width so it will fit better into features like your chamfer.  Instead of jumping from .4mm wide to .2mm wide it might start at .4, adjust the line width to make a layer that is .3mm wide and then drop to .2 for the finish.  It's a bit buggy but you can find it here in one of SanderVG's posts on the main forum page.  It may give you the added strength you need.

Another alternative might be to consider mixing up some epoxy and painting it on.  It would enhance the layer adhesion that seems to be a problem with the super narrow point.

[aniyapaniya 0]

Oh wow thank you very much. I will check out the arachne version and see how that goes with my print!

14 minutes ago, GregValiant said:

The Arachne version of Cura was pre-released a month or so ago for testing because it's a whole new thing.  It uses variable line width so it will fit better into features like your chamfer.  Instead of jumping from .4mm wide to .2mm wide it might start at .4, adjust the line width to make a layer that is .3mm wide and then drop to .2 for the finish.  It's a bit buggy but you can find it here in one of SanderVG's posts on the main forum page.  It may give you the added strength you need.

Another alternative might be to consider mixing up some epoxy and painting it on.  It would enhance the layer adhesion that seems to be a problem with the super narrow point.

 

[aniyapaniya 0]

15 minutes ago, GregValiant said:

The Arachne version of Cura was pre-released a month or so ago for testing because it's a whole new thing.  It uses variable line width so it will fit better into features like your chamfer.  Instead of jumping from .4mm wide to .2mm wide it might start at .4, adjust the line width to make a layer that is .3mm wide and then drop to .2 for the finish.  It's a bit buggy but you can find it here in one of SanderVG's posts on the main forum page.  It may give you the added strength you need.

Another alternative might be to consider mixing up some epoxy and painting it on.  It would enhance the layer adhesion that seems to be a problem with the super narrow point.

Do you know weather I have to change many settings in it for it to do that or will they be put on automatically?

[GregValiant 1,142]

I have no idea.  It's under construction and I think they started with an earlier version (maybe 4.6?) and built on top of that.

If you save your file using "File | Save Project" it should keep all the settings for you.  When you open it in Arachne most should transfer over.