Hi all, first post here. I have not found a quite similar topic, so excuse me if this has been asked before.
I am making a light diffuser, embedding pieces of frosted drafting mylar into a frame. Here is a CAD cross-section of one corner of the frame (there will be 15 layers of mylar). I have the vertical dimensions set up to be all multiples of the .2mm layer height
The recesses are two .2mm layers deep, and I put a pause at the beginning of the first overhanging layer so I can place the pre-cut piece of mylar. Here is the slice at the end of the second “recess” layer
I then place the film in the rectangular recess and resume the print.
I have wall order set for outside-inside. The first overhanging layer does indeed start from the outside of the part but then jumps away from the new outer wall
This does not work, because the filament does not adhere to the frosted surface of the drafting film. The unattached free-hanging filament causes much stringing and a non-functional print.
I am using Bambu Studio 2.3.1.51 with an H2D printer, Sunlu High-Speed PLA2.0.
But what I really want to know please is if there is a setting to make outside-to-inside really mean outside-to-inside. I need those “inner” overhanging filaments to be progressively printed next to the anchored “outer” ones.
I don’t know how many wall loops you have, but I think the blue line on your last image is the outer wall. The printer was doing exactly what you asked it to do.
When printing overhangs, it is better to be in the order of inner→outer wall.
Also make sure the overhang is not too much that it becomes unsupported floating regions that causes printing mid-air.
Don’t think so complicatedly, think in FDM. The material is flexible. Create a design with snap and slots. Bend the plate Mylar slightly, let it snap into place, then slide it in. You can then still print on it, but not on the Mylar itself, rather on the snap and slots.
Instead of solving the fundamental problem, you’re trying to tinker with it. That may not be the answer you want to hear, but it’s probably the most honest one on this topic. This is not a slicer or setting problem, but a design problem.
A possible quick solution: Stop trying to make it perfectly round your overhang. Instead, draw wavy lines so that about 30% is on the Mylar and 70% is on the object to be printed. There is no logical reason to make it perfectly round and print it 100% on the Mylar. Instead of waves, jagged edges are also possible, of course.
And I was thinking that the overhang isn’t in the real world an overhang, because there is a piece of material the slicer doesn’t know about that the new layer is resting upon… i would just like the printing to be monotonic, rather than jumping around. If the mylar was “stickier” it would not be a problem, but I haven’t thought of a surface treatment that would not mess with the light-diffusing properties (no glue stick, etc.)
@RetroSharky , thank you for your reply. The material is indeed flexible–.004”/.1mm. I have seen embedded window concepts that use thicker material–.25mm or so thick that are reasonably rigid. But this is the consistency of a piece of paper and not totally flat. In fact, I have gently been holding it in place with a small engineering ruler until at least the corners are tacked down (we have the door sensor disabled)
Instead, draw wavy lines so that about 30% is on the Mylar and 70% is on the object to be printed.
That is an interesting concept. Put “tabs” on the first layer above the recess and then full layers above that. I will give that a try after I stop typing here. I do need a full light seal around the mylar strips–this will go into an ultrasensitive piece of optical lab equipment.
I would try to orient this on it’s side, even if it needed to be split and joined.
On topic, this object, since it has a hole in the middle, has two outer walls. So despite telling it outer/inner, the ordering of WHICH outer will be a small bit up to the slicer. “Outer” meaning a skin path that touches external air vs “inner” being repeats of that contour but inside filled space.
The middle of your model is hollow, so there are two outer walls, one on the outermost and the other the innermost. The slicer did treat it as overhang, as indicated by the blue color. If it were a normal outer wall (without being an overhang line), the color would have been the same orange color as the outermost line on your image.
You can definitely try other designs such as that suggested by RetroSharky. I personally am not a fan of pausing the printing to insert something. Too much work for me
Ah, that is an excellent suggestion. Make the slots vertical, than just one pause to drop in the pieces of mylar before capping. If RetroSharky’s wavy-tabs idea does not pan out (part is starting to print now) I will try that. Or I might try it as an alternative anyway, because it is only 1 pause and not needing to babysit the printer every 4 or so minutes…
Part is just starting, I’ll know in about 5 minutes or so…
This is working perfectly, at least for the first two of the 15 inserts. thank you again! I am still going to try Bullock’s sideways orientation–I can use my original STEP file and just put one pause… Even though the printer is just across the hall from my office, I find myself just staying over there between pauses to watch it…
Hey, for me it’s a chance to play more with the new 3D printer at work. This is my first job that uses pauses… I’m an R&D mechanical engineer, but have personally been into CNC machining for the past 20 years. I’ve used Carbide3D Nomad desktop milling machines for 10 years now, and just bought and CNC-equipped a Taig 5C collet ballscrew lathe (both in the living room of my 1-bedroom apartment now…) The Carbide3D community is wonderfully supportive, and I definitely am getting that vibe about this forum.
Well, the extruder nozzle flicked out the 6th sheet of mylar when I was out of the printer room, and by the time I discovered it the part was ruined… Starting Bullocks’ “on end” print now. I oriented the bridge layer near the top so that the filament lies across the ends of the mylar sheets. If that works, it has the additional benefit that I don’t need to anneal/flatten the mylar as I have been doing for the past couple of days, just slip the pieces into the fully-formed slots…
If it were me, being lazy and not wanting to do any work mid-print, I probably will make the model in two parts.
The first is the base with slots for the 15 mylar sheets. It will be printed vertically so no support or bridge or overhang is involved. The base will probably be printed in TPU and will be designed with very tight toleance so the mylar sheets, which will be inserted after the base is printed, can fit snuggly with no play and no gap for any light to leak out.
The other part will be the cap part to lock onto the base via some kind of simple locking mechanism.
I may have the mylar sheets to be slightly extended over the top the the base and have slots on the cap for these mylar sheets to go into as part of the locking mechanism to have a more secure locking.
Thank you for your continuing thoughts. I am enough of an FDM newbie (up to about a year ago I had never touched an FDM machine) that the only things I have designed/printed in TPU are flexible air ducts, and I could not describe any of them as tight tolerance. Functional, yes, but I will need a whole lot more experience to get to that point.
But I am thinking that (since we have a laser marking machine down in production that might be able to cut the frosted mylar) I might be able to make pieces of mylar that are serrated around the perimeter, and then just run a straight line of filament across the serrations to lock in the pieces.
Designing parts for FDM is way different than just thinking “CNC in reverse” and I am enjoying the constant learning curve. Our other mechanical engineer suggested a T-shirt for me saying “DON’T WORRY, THE NEXT ONE WILL BE BETTER”…
The reason I think of TPU is that it is flexible, so on the base part the width of the slots for the mylar sheets can be made the same or almost the same as the thickness of the mylar sheets. This will allow the sheets to be held tightly after inserting. The sheets will not be potentially sagged, curved or bent after a while due to the edges not being held tightly by the frame.
One can try other filaments, too. Maybe PLA or PETG will also work after a few iterations of trying different tolerance to find the right fit.
But this is off the top of my head on what I would do. Furthermore, I don’t know enough about what you are designing for so it may not work. It is only a suggestion.
I’m sorry about that–it’s an ongoing development project so I wanted to stay really focused on the immediate fabrication issue. I do appreciate all your input. My go-to filament is PLA because I’m really used to it, only use PETG or ABS or ASA or PETG-CF when a part seems to warrant it. And I have a couple of rolls of PA6-CF I’m wanting to try. And I’ve read that PEBA is flexible like TPU but easier to deal with, so I will probably get some of that to experiment with.
I am sure this will work out one way or another. Don’t hesitate to ask for info or a second opinion whenever needed. There are enough people here willing to share their experience.
A quick followup. It turns out that printing a 2-layer thick “membrane” of white PETG with a black spacer surround works as well as the drafting mylar insert and involves less user interaction.
I do need a full light seal around the mylar strips–this will go into an ultrasensitive piece of optical lab equipment.
So despite telling it outer/inner, the ordering of WHICH outer will be a small bit up to the slicer. “Outer” meaning a skin path that touches external air vs “inner” being repeats of that contour but inside filled space.
(character filler)
