GregValiant

"...this issue is caused by some slicer setting(s) that somehow modifies the mesh to create this particular defect." So far as I've been able to tell Cura can't do anything to the mesh itself. In this case the outer walls of the first 5 layers have no overlap. It isn't until layer 6 that the new outer wall overlaps the outer wall of layer 5. That means the outer walls of the radii near the build plate are going to sag. TAN(OverhangAngle) * Layer Height = Step Width and when the step width is greater than the Line Width then there is no contact between the Outer Wall extrusion and the layer below. It is going to stick a bit to the inner wall that was laid down previously on the same layer, but gravity is going to win. Looking closely at the last image you can see that starting with about layer 7-8 then outer wall stays where it was put. No more overhang there. Having your "Outer Wall Inset" at 0.2 isn't hurting anything but isn't helping either. Arc Welder will not work with these radii as they are in the wrong plane. These are PETG on a stock Ender 3 Pro. The inside of the radii look good to me. I printed this one with support so there is some scuffing from the exacto knife where I removed the support. The top print was without supports, and I got that divot/chamfer look. It's because the "overhang" of the first 5 layers have no "overlap" with the layer below and so those outboard extrusions sag and give the impression of the divot/chamfer. The plastic is there - it just didn't stay where it was put.

Here ya go. Github Link

The pocket you create in the bottom of the model must equal the total thickness of your bottom layers. In that case of the poster the stack up of their bottom layers was .96. When you open that project file just import the model. You will see what I did.

The red edges on the walls indicate that there are errors in the model. (Looks like the normals are flipped upside down). If you repair the model it will slice as expected. Right now the errors are confusing the Cura slicing engine as it can't tell the inside from the outside. I have no idea what size it should be but I repaired it in MS 3D Builder. Make sure you have "Remove All Holes" disabled as well.

(The same tree with the same problem showed up on Github. I'm copying my response from there to here.) "When you enable "Spiralize"; Cura automatically enables "Remove All Holes". The implementation of Spiralize in the 5.x versions is different than in previous versions. In the Mesh Fixes settings turn off remove all holes. Because that model has a pocket in the bottom it will not print as it would have in 4.x versions of Cura. The 5.x versions will print the pocket where the 4.x versions ignored it. That pocket really needs to be as deep as the thickness of your bottom layers which I believe is .96 with your settings. That way those interior walls wouldn't print and leave seams in that portion of the model. What you see there is the new "expected behavior" in Cura 5.x. Some people call it a regression. It is different and needs getting used to. If you edit the STL and plug that hole then you can bring in a cylindrical support shape in Cura and use it as a cutting mesh and put a 30mm hole in the floor. The cylinder would be 30 dia x .96mm thick." And then I attached this project file. GV_120mmTreeWled.zip

Thanks @gr5 I didn't make that clear. Top layer for a close inspection. The first couple of layers may be still suffering from trying to compensate for any over or under extrusion of the initial layer do to leveling variances.

And when you asked the class who did it - did they respond something like this?

Time for different firmware. Trying to piecemeal that one together to work with Cura (or PrusaSlicer or IdeaMaker) is going to continue to generate problems. Do you have any idea where the "G00 X Y Z A" came from? I've never seen a Cura gcode with a reference to an "A" axis.

I was typing. I'll post this anyway. That is an odd one. G92 is defined in Marlin firmware as "Set Position" and there is no mention of speed at all. The RepRap Wiki gives the same description in regards to MakerBot firmware. G92 E0 sets the extruder location to zero. The "Extruder Offsets" is the distance between nozzles on a Dual Extruder printer. It shouldn't be making a difference here. G92 E0 is important in Cura as rounding errors can creep into the calculation of the E values and so Cura resets the E (G92 E0) about every 10,000mm³ (about every 4158mm of 1.75 filament). In a large print there will be several G92 E0 lines within the gcode. You may want to switch to "Relative Extrusion" in the Special Modes section. The extruder always starts from 0 and so doesn't need resets. Then you could use the Search and Replace post processor... Search: G92 E0 Replace: ;G92E0 By replacing the line with itself but with a semi-colon in front it becomes a comment and the printer should ignore it. The question comes to mind...How do you reset the extruder in Mach3 if G92 doesn't work? G92 is also used to set temporary locations of the other axis.

You are stuck on that one. The whole thing needs support. You can set the "Support Density" to 0% but that is about it. If you are confident that the support rings won't come free of the bed then you could turn off the support brim. If you really want to get rid of supports then print it as separate pieces except for the main ring. When you slice the main ring put in a Pause at Height at some point where the loop is open enough so you can drop the other parts onto it and then continue the print.

If you were to use Support Blockers you could eliminate the support structure under some areas. Tree supports generally take up less space on the build plate. It's hard to tell without seeing the model and what you are really trying to do. A picture is still worth a thousand words.

It's hard to tell without a project file. Do you have "Coasting" turned on? The Cura preview only shows extrusion moves and there is no extrusion during the coasting portion of a move. Try turning on "Smart Hiding" in the combing section and see if that Zseam straightens out.

Did you do the "Project File" trick to get the printer to install in 5.2.1?

They are HERE on Github. Scroll down to version 5.1.1 and then click on "Assets".

5.0 had issues with the dialogs and slicing. Installing 5.1 is a better choice. It can exist with 5.2.1 and you can run either of them side-by-side. I'm on Windows so a Mac user would be a better choice for advice here. You can try re-installing 5.1 and then create a project file with your chosen printer and open the project in 5.2.1. Maybe the printer will install(?).

The model isn't as simple as you believe. The top of the model isn't flat. In addition, there are steps on the sides and the model has errors. This is a view in MS 3D Builder. You can see a step in the top surface (and it isn't the only one). At 0.02mm it isn't much, but depending on your combination of Layer Height + Initial Layer Height, Cura can notice. The model on the right is yours. The model on the left has been altered to be 6mm tall with a flat top. So alter the model to make it correct or just change the Initial Layer Height until the anomalies disappear. EDIT: Before clearing the build plate I decided to flip this over and check the bottom. Here is the slice with the model "upside down". The bottom isn't flat either.

You can do this with support blockers. You might be able to configure the Bridge Settings to do something like this as well. I set this up with a Line Width of 0.6 at 0.3 layer height. The support blocker is configured to Modify Settings for Overlaps and then as a Cutting Mesh (Infill mesh didn't work). I selected "Top/Bottom Line Width" as the lone setting. The block is "Layer Height" thick and the bottom of the block is flush with the bottom of the first layer above the support interface. You can see the difference in the line widths here. The wall division is caused by the Cutting Mesh which I kept in the middle of the supported area to show the difference. The layer above this one has 0.6 Line Width and no wall lines dividing the surface. Another option for you to investigate is to enable the Bridge Settings and see if you get something usable. Setting the Bridge Skin Support Threshold to 100% makes Cura treat the first layer as a bridge. The main problem is that your air gap from the top of the Support Interface to the model has gone from .2 to .3 so there is going to be more sag no matter what you do. In this model the first layer over the support is cantilevered and so it is going to drop .3mm to the top of the support interface. As a consequence the second layer will be under-extruded as the real world layer height at the cantilevered end will be 0.6.

Mostly Cura prints according to the defined line type. Outer-Wall, Inner-Wall, Skirt, Infill, Support, Support-Interface, and a few more. You can open a gcode file in a text editor and search for ";TYPE:" and you will see the order that they are being printed in. That can change depending on if the particular layer has islands or if it is contiguous. Putting aside the Skirt/Brim/Raft - If there is Support on a layer, and if that support has "Support Outer Wall Line Count > 0" then Support Outer Wall will print first. If the Support Density is high enough then the Support Infill would print next and then on to Support-Interface. If there are "Inner-Walls" on this side of the model and "Inner-Walls" way over there on the other side of the model, and they are not connected, then there will be a travel move from over here to way over there. When the Inner Walls are finished everywhere then Cura starts on the Outer-Walls. The order of line type can be changed (for example if you enable "Print Infill First") but it's basicly going to print all the line types on a layer as groups. Settings like the Z-seam location, the Combing Mode and Combing Distance settings, Avoid Printed Parts when traveling, etc. effect the path that Cura generates. Then there is the Outer Wall. With the Wall Order set to "Inside to Outside" Cura will finish everything but the last path and it will be continuous so as not to have blemishes on the outer surface of the print. So any little areas within the wall structure will be traveled to and finished before that last loop goes down. The only blemish should be the Z-seam. If you are in Basic mode I suggest you switch to "Custom" and then to the right of the Search Settings box is an icon with three lines on it. Click on it and set the visibility to "All". You can make changes to a lot of different settings that will affect the generated path. In the end though, if you are printing a horseshoe shape and don't want stringing across the opening then there is going to be a lot of travel based on the Z-seam location and the Layer Start coordinates.

If the printer definition file you are using with Cura allows for 2 extruders then yes, this can be done. Go to the Cura Marketplace and under Plugins scroll down and install the "Printer Settings" plugin. You will need to quit and restart Cura. When you are in "Custom" mode - the Printer Settings group will be last in the settings list. Scroll through the settings and enable "Extruders Share Heater" and "Extruders Share Nozzle". That should get you printing. There will be a lot of tweaking to get the Tool Change Retraction Distance correct and there are more settings in the "Dual Extrusion" section. If the Printer Definition file you are using does not allow for a second extruder, you can load the Lotmaxx Shark. You can make changes to it's settings (and change the name) so it will match your printer (build plate size and things like that).

I think you can still get this on E-Bay. Lucas sold a lot of it. Maybe there is a cross-reference to the UM part.

No, don't do that. Are you slicing once and then running the same gcode on different machines? Do you have a different machine profile for each printer? I don't think I've ever seen a Z=0 in a gcode file so something is going on to make the nozzle hit the bed. Load a simple model (a calibration cube will work) and set Cura up to slice. Use the "File | Save Project" command and post the 3mf file here. Maybe something will jump out.

I've been fooling around with Dual extrusion and the problem definitely exists. If I start with extruder 1 there are 5 tool changes. If I start with extruder 2 there are 68 tool changes.

Well...that might leave me as the only one around here still nursing a steam powered video system. I just can't bear the thought of giving up my Commodore though.

The endstop switches are the same so try swapping the Y endstop switch with the Z endstop switch and see if it makes a difference on at least one machine. The Endstop switches aren't very "repeatable". When you auto-home and level the bed and then the printer sees the "G28" in the StartUp gcode it homes the Z again. There is no guarantee that the "Z = zero" position is going to be the same location as when you leveled the bed. It should be OK with ABL but I gave up with my paper leveling and my start gcode has G28 X Y so it leaves the Z where it was during leveling.

The Z-offset is typically a printer firmware thing. Are you using a plugin in Cura to set the Z-Offset? Maybe there is something in your startup gcode that affects it? Is the actual number value of the Z-offset changing or is the printer simply doing something different (even though the number is the same)?