A question about extrusion widths - UM2

[uma 0]

Hello,

I am trying to print a cool iphone cover design for my wife. But i am unable to print without any holes. i figured that its a matter of extrusion width after reading illuminarti's post about extrusion width in Slic3r. But my problem is still not gone. let me explain. I set the extrusion widths to .4 because thats the nozzle size. When i tried to slice the model at that settings there are lot of holes in the model (see Repetier host screenshot) infact i printed the model and it came exactly like that.

Then i changed the extrusion width to .2 (half of the nozzle size) thinking that i will be able to print these small designs. The repetier screenshot shows very little holes which made me happy. Unfortunately, i faced major problems while printing.

1) The first layer had extreme difficulty to stick. After a heavy layer of gum I was ok.

2) It almost seemed like the flow rate was not enough as i could see the lines were not sharp. The design looked disastrously bad even though repetier showed a clean picture.

I am wondering whether i will be able to print a smaller extrusion width using UM2? is it even physically possible? How else can i print this intricate design? Are there any other settings that can help. i tried different infills, angles and a lot more combination. Almost all of them failed during the preview in repetier itself.

Will i be successful in printing this design if i change the nozzle to a .2 diameter. What are the pros and cons?

I appreciate your help. I need to print this gift quite soon.

holes

No holes @.2 width

 

[illuminarti 18]

It all comes down to how small the gaps are that are left, after the outer walls are printed, and how well the slicer thinks it can fill them. These are some pretty small details, so there's not a lot of room for the slicer to get the head in to do the infill.

Changing the nozzle width setting to 0.2mm isn't going to work very well, because the actual hole is still 0.4mm, so you will simply be extruding half as much plastic as is needed to fill that space. You can't really control where it comes out, so you will get a rather poorly defined bead that doesn't fill the available space, or stick, as well as you might like. Now, actually having a smaller nozzle would help a lot, but you'd have to print very slowly, because the pressures required to extrude through that tiny hole would be even higher (and, AFAIK, no one has any UM2 nozzles less than the standard 0.4mm). While you can get away with declaring a nozzle size smaller than the actual size, I think in practice, the limit is about 75% of the actual size - and it's still not going to be ideal.

What you might try instead is printing with just a single perimeter, if you aren't already; that might leave enough room inside for the printer to set up a proper linear infill pattern. Failing that, you might try other slicers. Kisslicer in particular has a feature for filling in the small gaps like these, but not sure how well it works in practice.

 

[gr5 2,266]

Which slicer did you use? If kisslicer, try cura. If cura try kisslicer.

Consider redesigning this and making the pattern twice as thick. Or 50% thicker. Same exact pattern though - just larger.

I've printed pretty intricate details in the past on the bottom layer:

 

Check out the edge of the arm. I don't know how I managed to get Cura to do single dots like that but it did.

 

This was printed on an old version of steam engine (Daid's newer slicer). He has drastically improved "thin walls" since then. That's what he calls it "thin walls".

 

The above shot is a test piece meant for a cell phone. Later I printed the actual phone with lady liberty in purple and the phone case in white. It came out great. I increased the flow for the white area and that improved things over this photo.

 

edit: Also this was printed on a UM1 on kapton tape and also I had levelling issues - when I fixed that the purple infill met the walls in ALL regions instead of just some.

 

[uma 0]

@illuminarti: thanks for the feedback. i did try printing at perimeter =1. The gaps were still there. It looks like i am pretty much stuck with a .4 nozzle.

@gr5 thats one hell of a print.

two questions

1) Is that a dual extruder or did you change the material mid way

2) What is the nozzle size for the print?

It would be sweet if you could share your print settings.

thanks

 

[gr5 2,266]

edit: I don't have a dual extruder. I just changed the filament between the "two" prints.

Nozzle is .4mm. Done before the UM2 existed.

I printed a very thin layer (.2mm I think) of purple then when print was done I printed the cell phone on top using white. I had to get leveling perfect because after the first try one side was thicker (darker) than the other. There was maybe 20 minutes where the printer was off in between the two prints. Print the bottom layer of the cell phone thicker - .2mm.

The software to make the purple part was here:

http://www.thingiverse.com/thing:66115

 

I think I cut off the bottom/base using Cura (cut off bottom feature).

There's more details of how I did it all here:

https://www.youmagine.com/designs/galaxy-s4-ballistic-case

But if I were to do it again, for the white part, I would just print a "normal" part "on top" but with thick bottom layer (.3mm). Of course I used a UM1 which doesn't skip on the extruder just because there isn't room for all that PLA to flow. I guess on a UM2 I would print the first white layer at 240C to reduce likelyhood of the extruder pressure getting too high and having it slip and then underextrude for a bit.

 

[illuminarti 18]

You can see the same basic approach as George used in my 3D printed Xmas cards from last year; I printed the writing and QR code first, using two layers of 0.1mm, and then printed the card base over it as a solid piece, with a 0.3mm first layer.

 

 

[uma 0]

I am just blown away by the video! Wow. I need some clarifications here.

1) Is the material change done in between the print? did you use a cura plugin to do such a thing.

2) How does the printer know to start from the right Z height. I assume its one single program which waits for the user to change material.

3) What i am impressed with is the uniformity with which the layers are laid. Is that a Kapton tape? I am struggling to get the alignment right over the size of what you are printing.

Finally, are there any posts that you have done to discuss the settings used? the slicer used etc? I am truly blown away by this stuff.

 

[illuminarti 18]

Lol, thanks. I used the PauseAtZ plugin to Cura to insert the appropriate filament changes points.

For the base layer, I created the QR code as a graphic, and then converted it to a DXF file using Illustrator, then imported that into my CAD package, and extruded it up into a 0.2mm high solid. Sliced that in Cura.

The text was drawn in Illustrator, and then converted to coordinates using an open source CAD/CAM package, and then I manually calculated the e-coordinates for each line segment using a spread sheet, and produced the gcode manually for that part, using a text editor to add it to the end of the QR code gcode. That was printed as one file, iirc.

Then the main card was modeled in my CAD package, with the various parts extruded out to different heights, and then sliced in Cura, with the pauses added for color changes. It was printed after the first file was finished. As I mentioned above, I had a thicker first layer for that one, so that the filament flowed over the black part as it went down.

When I actually produced the cards en masse, I manually duplicated the blocks of gcode and and shifted the origin between each one so that I could print 4 cards at a time, to reduce the number of filament changes needed.

Yes, it was printed on cold Kapton tape to give a nice smooth bottom. Unheated Kapton tape works ok for prints with lots of surface area and not too much height. Anything taller than a few cm will likely come loose though, unless you use glue, perhaps.

 

[illuminarti 18]

And if you look closely, you'll see that after printing a vase, earlier, I forgot to re-enable the solid top option in Cura, so that the final red layer only draws the outlines, it doesn't add any infill.... ;-)