Jump to content
Puerlin

Circles in Cura

Recommended Posts

Posted · Circles in Cura

I have been using Cura for over two years now and I have started to notice that if the first layer has any circles to print they don’t get fully printed. I’m not sure if this is a new thing or not. I should note that I’m using Cura with a Raise3d N2 Dual printer. 

 

When end I look at the animation of the first layer in the slicer it does draw complete circles but when I watch it print the print head moves to somewhere else before the circle is complete. In other words it’s not like the extruder is failing to extrude at the end the printer just doesn’t finish the circle. 

 

I’ve attached a picture to show it. There are supposed to be three wall layers. 

05EB2DF2-D241-4E78-A9E6-11B7995132B4.jpeg

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

You might need to clean that print bed (is it build tak?).

 

But more likely you just need to move the nozzle closer to the build plate.  Is this easy to adjust?  On the UM2 you just turn 3 screws all equal amounts by hand and presto - the printer will be leveled perfectly for the next few months.

 

It's hard to say how thick this bottom trace is but it looks much too thick.  You need to SQUISH that bottom layer or you get just what we see here.

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

The build plate is a brand new sheet of buildtak. The nozzle is 0.8 mm so I guess that is why it looks too thick but it is squishing onto the plate just right. 

 

The point is that I was looking at the nozzle when it was printing and it never attempted to print a full circle. It got that far around the arc then went off to a different place. 

Share this post


Link to post
Share on other sites
Posted · Circles in Cura
7 hours ago, Puerlin said:

The point is that I was looking at the nozzle when it was printing and it never attempted to print a full circle.

Okay.  But what you see in slice view is what you get in gcode.  So either your printer firmware sucks or you need to video it and watch one more time.  Consider dropping the gcode into the website: gcode.ws  which will show you for sure if it's supposed to be drawing the full circle.  You can see travel versus extrusion moves quite clearly (although cura slice view shows it also - why trust cura if you don't have to).

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

Thanks for the advice. I’ve dropped it into gcode.ws and it shows that full circles are in the gcode. I’m going to create a smaller simpler model and see if I can get to the bottom of this. 

 

Cheers

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

I am getting the same exact behavior with Cura 3.5.1 running Marlin 1.1.9

 

Anyone else notice this for small circles on the first layer?

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

The problem with small circles like this is is that the extruder changes direction quite abruptly at the en of the circle. Unless the buildplate adhesion is very good, the nozzle yanks the last bit of extruded material along with it, resulting in a non-complete circle like this.

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

Ah.  So probably the print head is too far from the build plate and not squishing the filament hard enough onto the build plate to get it to stick well.  And looking again at the photo above that seems to be the case.

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

ah..  the 'solutions' posted for this are frustrating.  I have tried all of this and different nozzle sizes, different pla, 23,487 different heat bed adhesion techniques and materials.  i have spent incredible time leveling beds with many different distances..  

 

two things happen with small circles..  well.. any line..  just very obvious in small circles.  and more obvious in older version of cura.  but still pretty obvious even in 4.0

 

1. When creating a new line, there is no 'wait period' that the printer uses while the extruder is beginning to advance material.  The X and Y are doing their things with almost perfect precision, while the extruder is trying to move a sticky, viscous semi-liquid through a microscopic hole.   Short lines are particularly sensitive to this delay.  At 20mm/s, a half second delay to build up the pressure needed on a 20mm circumference circle leaves half the hold 'printed'.  there are some 'pre loading things' and such, but these are so hard to tune when you really need the tuning for the small circles only.

 

2.  When the pressure in the nozzle finally gets to smooth output, the printer stops that line to move to the next.  then it can retract or not retract.  either way.  pressure needs to be built back up for the next line.  the trouble is, that the movement is much faster than the previous material can cool down.  it also tends to leave that hole very abruptly, quickly, and tangentially which sort of makes it rub past the freshly printed plastic which has probably not set yet.

 

its almost like there needs to be 'initial layer circle identification', where cura creates a specific plan for circles where the the gcode is written to navigate to a circle start. pause, pressure filament, then start to make the circle.  i would say to make two passes here.  Or "initial layer circle id wall thickness' setting to adjust this.  then after it is time to make the next circle.  pause for a quick moment, then leave that circle in a perpendicular way to the next line.  repeat.

 

i notice that the second layers are usually a bit better here.  so maybe a easy way to solve this is to have a single layer fill of small circles that can be cut out later with a knife.  i have had great success with this purposefully adding 0.2mm circle fill to the initial layer so that no circles show up in that layer.  subsequent circles are then perfect...  but this is a total pain in the butt to do and really mucks up the cad file.

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

Can you post a picture please?

 

A few things occur to me right away:

1) Try turning off combing for all layers (certainly for the bottom layer).

2) Maybe your leveling is off (I know - you tried different leveling).

3) I don't have problems with circles so something is different about your circles.

 

Please post a picture of the problem.

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

My models are full of small circles and tiny features, and they print fine, both in PLA and PET. This is a keychain-miniature of dental models used in the hospital. I tend to print these things rather slow (25...30mm/s) and cool (195...200°C for PLA; 210...220°C for PET), bed temp 60°C for PLA, and 80...90°C for PET. Bed is leveled rather close so the first layer is squeezed well (manual leveling on old UM2 printers). Everything else is pretty much default (I am using an older version of Cura).

 

ostrcp_key_v20_zoom.thumb.jpg.c85991865979ff09557a37d9ca6ad20f.jpg

For reference: text caps height = 3.5mm; character legs are 0.5mm wide.

 

DSCN6081.thumb.JPG.b4339d77becd99527d2c1f0e0fbff415.JPG

 

 

DSCN6083.thumb.JPG.6fa2f0776aca10a340718c2065decdbf.JPG

View of the bottom layers. This is transparent PET. The lighting from the back gives some weird highlights due to reflections and defractions in the model, but the circles are printed almost perfectly. They are ca. 2.5mm diameter. The ruler is in mm and cm. The tiny dark spots which look like corrosion pits are caused by salt, as I printed these using my "salt method" (=wipe the glass with a tissue moistened with salt water).

 

This is the routine quality I get, with close to default settings.

 

So there might be something else going on in your printer or settings? A setting that inadvertentie got changed? Or printing too hot or cold? Or a non-optimal bonding? Bed too far away, or too close?

 

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

I'm a Raptor v1 owner and updated to the TM3D 1.1.9 firmware just to be able to save the mesh. after several hours of fault finding of this issue I reverted back to the stock firmware and the issue was gone. I'm using Octoprint.

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

I also have a lot of issues with small holes on the first layer. The biggest issue seems to be that there is always a tiny delay before filament is extruded (from drooling filament as the nozzle moves from the outside of the model to the inside position of the hole. Because the very first circle put down by Cura is a single circle, there isn't anything else to support the circle. The drooling also pulls on the still soft circle and in the majority of the cases the filament from the first circle gets pulled all over the place and gets embedded someplace else.

Cura comes back later and prints more layers of wall and then everything starts to stick properly.

I could add extra flow to the first layer to give the first circles more stick but that usually haunts me on the rest of the first layer.

Possible solutions I could see - extra flow in small first layer features separate from the overall first layer flow when there is nothing else printed that the first circle can hang on to. No idea how this could be implemented <shrug>

Maybe a special extra slow mode when printing that first circle for the hole.

If the holes could be printed from the outside in, that would also help as the inside circle, that is normally printed first, has something to hang on to. Larger circles tend to stay put by themselves.

The kinds of holes that give me issues are 3 mm inside diameter with a 0.4 mm nozzle and a 0.5 mm trace width. I tend to print a lot of those for some reason.

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

I print a lot of 3mm holes on my UM3. 0.4 mm nozzle and line width, typically 0.1 mm layer height. In Fusion 360 I specify these as 3.4mm holes. This has worked well for me with PLA, Tough PLA and Ultimaker Nylon. In nylon the holes are just slightly smaller.

 

The holes adhere just fine. 

 

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

If your "holes" aren't sticking on the first layer it's most likely because the nozzle is too far from the print bed.  What kind of printer do you have?  You want to move the bed closer to the nozzle for that bottom layer.  You want more "squish".

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

The printer is a CR10-S5 with a Duet controller and chimera clone hot end. The rest of the print sticks very well (on glass). Only the first loop/circle of the hole doesn't stick. If I increase the squish, the rest of the print has too much material extruded making it a mess. Height above the build plate is very accurately controlled with a hight mapped bed.

I will play with the height a bit as well as the printing order. Currently it only prints one (inner) circle but if I set for optimized print order it will print the first two circles and that might help.

If I could get the printer to not drool filament as much, I would expect the issue would be reduced as well.

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

 

2 hours ago, jens3 said:

If I could get the printer to not drool filament as much, I would expect the issue would be reduced as well.

As @gr5 mentioned earlier in the thread, you may want to turn off combing. This is what leaves lines during the fast travels between the circles because it doesn’t retract during those moves. There’s also a minimum travel distance before retract

Share this post


Link to post
Share on other sites
Posted · Circles in Cura

I am happy to report that setting 'combing' to 'not in skin' helped .. but the real star was 'pressure advance' which is a function in the controller and not in Cura. I have a very long bowden tube (somewhere around 650 mm) and this caused a considerable delay between the printer starting to print a circle and filament actually coming out of the nozzle. Pressure advance has eliminated this issue and now when Cura tells the printer to put down filament, it actually happens ! 

I am using a Duet controller and the suggested setting for the average bowden tube setup is a value of 0.2. A direct drive printer needs about 0.05. I am using a value of 0.8 (!!!!) and am producing a MUCH cleaner print then before when I was using a value of 0.2.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Our picks

    • Ultimaker Cura 4.0 | Stable available!
      Ultimaker Cura 4.0 is mainly focused on the improved user interface and cloud integration.
      As always, we want to collect your user feedback for this release. If there are any improvements you can think of, feel free to mention it here and help us to shape the next release.
      • 98 replies
×
×
  • Create New...

Important Information

Welcome to the Ultimaker Community of 3D printing experts. Visit the following links to read more about our Terms of Use or our Privacy Policy. Thank you!