Thanks Slashee. You are a detail person (like me). Love it.
This is really useful. I'm going to attach a slightly different stl file so you can replicate what I'm looking at.
First issue. When i print all at once, I get these nasty drags across the coin. I've mucked about with retraction (I'm printing PLA/silk), but for this project, I just can't get it printing well. After trying 2mm,3mm,4mm I ended up retracting 6mm and seems I never went back to 2mm.
One at a time is the way to go. I find that if i print a bunch of these then snot builds up, burns and drops off the nozzle. One at a time tends to solve that problem. Temperature and Retraction are an issue, but I can't consistently get it right. Some days it prints well, others (like today) it's rubbish! My other coin project is much simpler (one colour) and printing one at a time solves heaps of issues that I found hard to control doing all at once. Hense I'm seeing if I can do that here.
Image below shows the two travels in each layer. one to get from the wall to the center (why it does this is beyond me) - i want it to start in middle and go outwards. On some models it will actually do the wall of one, then the wall of another and then come back to complete the centers. Drives me nuts. The second travel is to move to the wall of next object. this gives me a seam I have to remove from the edge and sometimes an awful surface that I can't clean up with a file (because the letters on the top are there too)
I like the suggestions on the widths, but actually the letters print well. The text gives a slight calligraphy effect which I'm going for, and it looks good, so I don't want to play with the line widths - I already spent time getting that as I want, but actually helpful to see the line widths you go with - that will save a bit of tinkering next time!!
The model comes from FreeCad if you're interested. This stl you are now looking at doesn't touch walls. I actually print the outer wall completely separately now, and then press this inner piece into the outer to make the whole "coin". This stl is thinner as I didn't like the height, so you are right about that, but I gave you an old file. I already fixed and you see it is thinner, so we are thinking alike!
Anyway, I was also thinking of the two models idea, but freecad wont let me split the model as you suggest. the bottom half will be fine, but the top half will be two shapes, an X and a 5 which freecad doesn't like, so I would need to find another way to do that. Not impossible, but that's probably what I'll end up doing.
I tried the support blocker for the same effect, but that doesn't quite work as I intend.
Happy to manipulate gcode. I was already starting that, but it's a painful task of tedium where I worry about the extraction values and pasting into the right place. It made my head hurt after two models, and with 18 more to go I gave up.
Anyway, breaking into two models. This could be the way to go, just need to find a way to split them. Doesn't seem there is a native way within CURA to this without a bit of working around. Would be nice to have "print up to height" and "print from height" setting for each model - I could then overlap them and achieve the same thing. or use the support blocker and have "model blocker" option so i can add a "don't print here" shape. but maybe i just need to play with the stl....
Anyway, curious for additional thoughts. thanks for the reply and sorry for the essay 🙂
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Slashee_the_Cow 410
Howdy! It's always more helpful if you can post a Cura project file (.3mf, get it set up then go to File > Save Project) rather than just the model so we know what printer and settings you're using. 🙂
What filament are you using? PLA should be able to retract well enough if you're using the right settings and you've got your machine properly tuned.
I don't think combing takes layers below it into account, and even then, if it's impossible to make a route which meets the combing setting, it'll avoid as best as it can.
You need to get your retraction right, assuming you're using a material that retracts well *subtle glance at spool of PLA sitting on other side of room*. If you're using PETG or TPU (squishy coins are fun) avoiding strings is like finding a parking spot in the Sydney CBD. Specifically, you can't. And if you're using ABS, you probably shouldn't be. (Shouldn't be using ABS, that is.)
If you're not retracting properly, Z hop won't have any significant effects on stringing.
It doesn't help that your design is kind of awkward as it slices (I'm using standard quality settings here because I don't know what you're using):
→ Blue arrows: Parts where due to thickness it has to switch between one thick line and two thin lines.
→ Yellow arrows: Parts where it's thick enough to generate an inner wall.
Both of those situations require moves. Inside the x it handles it reasonably gracefully, around the 5, not so much.
So what can we do? If I set Walls > Minimum Wall Line Width to 0.24mm (the narrowest you can reliably pull off with the "standard" 0.4mm nozzle) that improves the situation a lot to begin with:
Although that does give us a small dislocated section off the x:
If I turn on Walls > Print Thin Walls that reconnects it:
It's also added a tiny section of inner wall to the inside of the x there, which isn't a problem stringing wise (it just does a non-retract move and does the outer wall.
If we want to remove those bits of wall the "hit it with a hammer" approach is to increase Walls > Wall Transitioning Threshold Angle. If I set it to 38° it gets rid of them, and adds a bit of detail back to the x at the expense of those detailed bits being fat single walls requiring their own starts (but now we don't have tiny bits of inner wall that do):
I'm not sure you'd be able to do much better than that when it comes to avoiding travels. Those changes again were:
But I would say the most important part is make sure you're using a filament that retracts well and get your retraction settings right. Reducing the number of travels and starts/stops might result in less stringing but if your aim is "none" then you need to be retracting properly.
If you need to figure out your settings there's an awesome plugin (just look in Marketplace at the top right) called AutoTowers Generator which can print test towers for retraction. Although it hasn't been updated in a little bit so if your printer has a direct drive extruder you might need to install OpenSCAD so it can generate a custom retraction distance tower (I usually retract PLA 0.8mm on my Ender-3 V3 SE) - don't worry, not hard to get that set up, just a little bit of extra work).
=== AND NOW THE PART YOU MAYBE OR MAYBE NOT SHOULDN'T TRY AT HOME ===
Oh, I forgot the bit about wanting to do all the bottoms first then all the tops. Not that hard with gcode manipulation, actually, if you know what you're doing. The easiest way would probably be to split the coin into two separate models (top and bottom) and slice both in one at a time, making sure the top half is at the correct height. You'd need to turn off "drop down model" in the move tool and turn off Mesh Fixes > Remove Empty Bottom Layers to get them to slice in midair (and check the preview to make sure they're in midair at the correct height). You'll also need to insert a pause after the last layer of the bottom half.
So with those two files, open up the file for the bottom half and delete the end gcode, should be after pause. Open the file for the top half, and copy everything after the start gcode except you need to make sure you have a G92 E0 line at the start of the top half and there's usually one at the end of the start gcode so keep that. Paste it at the end of your first file (after the pause) and you should have a combined file that does the bottoms one at a time, pauses, then does the tops. The key rule here is if you're not sure if you're doing it right, don't do it. If you want to post some combined gcode for the boffins around here to look at before you run it, feel free.
=== AND NOW THE PART WHERE SLASHEE FLEXES HER DESIGN MUSCLES EVEN THOUGH NOBODY ASKED HER TO ===
Let's look at your design. I don't get what software people are using that exports circles with so few faces, but I can count the number of faces on the edge of the ring using just my digits and those of the neighbour I totally don't have the body of stashed in the freezer 😕 But that one's probably not your fault, it's from the software you're using.
The first thing that struck me: the height. 4.5mm. That's one fat coin. Not sure about other countries but the thickest coins we have here are 2.8mm high ($2). Poker chips are usually around 2-3mm.
Second thing: it's not a very big coin. Diameter-wise the $2 coin is actually the second smallest coin currently in circulation (20.5mm, the smallest being the 5 cent coin at 19.41mm diameter and 1.3mm thick). Diameter-wise (technically wrong since it's a dodecagon, not a circle) is the 50c coin at 31.65mm.
I don't have any $2 coins on me (it's 2024, be amazed I have any cash) but for comparison purposes, here's a pile of four 5c coins (representing your coin), a poker chip and a pair of AA batteries:
Third thing: the height of the text, and then the height of the wall around it. Your text is 0.4mm high (or should I say short) and then has a whole 1mm of just wall above it. It's going to get lost in there. Being that short makes it hard to see to begin with, put it in a well and you've got no chance. If you were to make the text 1mm high it would be a lot easier to read and then you'd only have two layers of wall around it. Unless you make your whole coin shorter... which you should. On the poker chip in my photo, if it had text on it, ideally it would be about the same height as the ribbed ring around the edge.
Fourth thing: font. Even in a different colour, thin text does not stand out very well in a 3D print, especially at this scale (the scale where it can barely print the text with any consistency). You should go for something a bit thicker. I'm not saying it has to be in IMPACT BOLD but something with a bit more body to it is going to be easier to see.
Fifth, and just a minor one: try to avoid making your design touch the edges: if the walls join with the walls of the outer ring it generally looks pretty messy, especially if you're going to make the ring go higher.
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