Perimeter layer gaps, not connected

[jimc]

setting the extrusion width lower and increasing the multiplier will result in the printer printing everything out of spec. all your tolerances will be off. you can certainly lower your extrusion width down to your nozzle dia but that also CAN result in poor layer bonding and bridging will tend to be terrible. not that he has any to worry about with this model. the correct ratio is is about 120% of your nozzle dia. thats really the sweet spot then tweak from there. altering the width but keeping the multiplier in place will keep everything calibrated correctly then the software can space the extrusions out accordingly to fit what it can in a given space. lowering the width, if you can do it enough without going too low can possibly make room and allow an extra extrusion in that wall space. in any case the thing to do here is to lower the perimeter #'s to make room so there can be actual infill placed in the wall instead of it being 100% perimeters. thin wall prints are always better off doing that otherwise the ext width has to be perfect so everything fits seamlessly. as in the op pic of the red print..it doesnt.

[spencyg]

I'm printing the model right now with a 0.4mm width setting and a heavier extrusion multiplier and I can already tell I'm over extruding but still have some wall gaps. I did a thin wall test before printing and my 0.4mm width was printing at 0.45mm. Clearly, just adding material isn't fixing the problem as there are still gabs (albeit not as many, much of that due to copious amounts of plastic). I'm going to cancel this print and attempt to go back to a correct width and start playing with line width settings. What kills me is that every model is different and I end up printing 4 of everything when I need it to actually be as good as possible. Needless to say, the example print doesn't fall under this category, but I use the printer to generate prototype engineering level parts so when they need to be right, they need to be right. I have a friend with a UM2/CURA and he doesn't seem to have nearly the problems I'm having....

I'll keep mucking with this....

Thanks for the input folks.

[designfactore]

Hi,

I will admit I only skimmed the responses you've gotten thus far before I offer suggestions.

--have you tried "allow gap fill when necessary"? (advanced tab, thin wall behavior) I have "allow perimeter overlap" at 50% always
--it looks like the problem often happens during a direction change. If the speed is too high and/or the filament temp is too low, gaps can happen because the filament didn't get a long enough chance to stick during the quick moment of the direction change. Slowing things down and heating the filament a bit higher can help it stick better when those direction changes happen. Try slowing the movement and incrementing the filament temp 5 degrees at a time.

[JoeJ]

I'm printing the model right now with a 0.4mm width setting and a heavier extrusion multiplier and I can already tell I'm over extruding but still have some wall gaps. I did a thin wall test before printing and my 0.4mm width was printing at 0.45mm. Clearly, just adding material isn't fixing the problem as there are still gabs (albeit not as many, much of that due to copious amounts of plastic). I'm going to cancel this print and attempt to go back to a correct width and start playing with line width settings. What kills me is that every model is different and I end up printing 4 of everything when I need it to actually be as good as possible. Needless to say, the example print doesn't fall under this category, but I use the printer to generate prototype engineering level parts so when they need to be right, they need to be right.

Just to be clear - you should be increasing ONLY the extrusion multiplier. Do not increase the extrusion width. Set that to a fixed manual value of 0.4mm and then don't change it. Now increase ONLY the extrusion multiplier until your perimeters touch. Also, make sure you aren't trying to assess these things in the first 5 layers, since things may still be heavily affected by your bed leveling and position. Wait until about layer #10 to try to access if the perimeters are touching.

FYI - I've used the software with almost a dozen printers and never encountered this issue before. So I'm not sure how you got here, but it's a very unusual issue to have. Hopefully we can help you get to the bottom of it!

[spencyg]

One thing I find especially interesting about the 3D printing community, and more specifically the resolution of problems within 3d printing forums is that for every question there are at least 2 conflicting answers. Some people say always do it this way, while others say never do it this way, do it that way....round and around.

So I'm seeing some folks say leave it at a 0,4mm width, others say you can vary the width depending on requirements. Some say set the multiplier so when you're printing a particular line width, the finished line actually prints exactly at that dimension while others throw that idea out the window and use the multiplier to make visual adjustments to the line segments.

I'm now in a position where I have tried adjusting the multiplier while leaving the width alone and adjusting the width while leaving the multiplier alone. I go from under extruding to over extruding when the multiplier is messed with, and adjusting line width doesn't seem to have an effect on gap. I'm going to mess around with it more this evening but I'm clearly an isolated case here since this doesn't seem to be a problem anybody has real world experience with. I'll print a few more samples with varied settings and post up some pics tomorrow.

[MichaelHerron]

One thing I find especially interesting about the 3D printing community, and more specifically the resolution of problems within 3d printing forums is that for every question there are at least 2 conflicting answers. Some people say always do it this way, while others say never do it this way, do it that way....round and around.

So I'm seeing some folks say leave it at a 0,4mm width, others say you can vary the width depending on requirements. Some say set the multiplier so when you're printing a particular line width, the finished line actually prints exactly at that dimension while others throw that idea out the window and use the multiplier to make visual adjustments to the line segments.

I'm now in a position where I have tried adjusting the multiplier while leaving the width alone and adjusting the width while leaving the multiplier alone. I go from under extruding to over extruding when the multiplier is messed with, and adjusting line width doesn't seem to have an effect on gap. I'm going to mess around with it more this evening but I'm clearly an isolated case here since this doesn't seem to be a problem anybody has real world experience with. I'll print a few more samples with varied settings and post up some pics tomorrow.

I feel your pain! Part of the fun of this stuff is that there are very few good solid laws. Its all rules of thumb with many exceptions and a great deal of experimentation required. (thats also the frustrating part!)

Here's what i've learned:
The extrusion width affects the model slicing--this means that changing the extrusion width affects how closely the slicer spaces the tool paths in your model. It also recalculates the flowrate to try to give you the desired line thickness.
This means that JUST changing this parameter will likely give you largely the same results. it made your lines closer together, but also smaller.
The extrusion multiplier does NOT affect model slicing--only the flowrate. Also, very small tweaks give large results.
Once you have the correct extrusion width, the extrusion multiplier is used to dial it in.

If you are pulling filament around at direction changes, it SOUNDS like the viscosity of the material could be high--raising the temp slightly will help that--but of course that may cause other issues.

do check the INFILL tab: "The Minimum Infill Length" setting that is too high, can leave corner transitions hollow, as your model appears to have. Set this to a very small value and see what happens. Also make sure that the ADVANCED tab has "allow gap fill when necessary" selected.

As always, take forum advice(especially mine) with an appropriate grain of salt--most of us here are learning the same way you are. Enjoy the process and good luck! Keep us posted on your results, too!

[jimc]

yes mike is pretty much on it. the multiplier is flow rate and should be fine tuned so that your actual extrusion is what s3d thinks it is. what s3d thinks it is, is the extrusion width setting. the multiplier isnt something that you just set where you want. you tune it in and thats it. you can fudge it up or down a point or two to make things work out right. it works in conjunction with the filament dia setting to calculate flow. once that is all tuned your done on that end. from that point if you have a 2mm wall with your perimeters set to 2 then a .5mm extrusion width should theoretically get you a solid wall. still though that may need to go up or down .01 or .02 to make that happen. problem is when you have a wall that varies in width. if the wall gets slightly wider in an area then those 4 perimeter extrusions are spaced out to keep the wall correct. there is no on the fly flow adjusting so you get little gaps in those areas. you can avoid all this hassle by lowering the # of perimeters to allow enough room for infill to kick in. if you start bumping up the extrusion width and look in the preview you should start seeing the lines getting wider until they touch in those areas where your having trouble. of course now they will overlap a bit in the 2mm wide wall area causing a little over extrusion. again the best way to avoid the whole thing is reduce perimeters so infill can go in there. even if you have it set to 90-100%. everything will be calculated correctly at that point. if you choose to do a high infill i would suggest going to rectilinear infill. in tight walled areas the infill patterns that are printed every layer can cause some overextrusion.

[Rebekah_harper]

Have you got the factory file?

[billyd]

One thing I have noticed with printing solid walls (walls that end up not having any infill because of the number of shells and the extrusion width setting) is that it is hyper important to make sure these thicknesses are modeled as an even multiplier of the extrusion width.

For example, if you are printing at .4mm width, you don't want a 1mm thick wall. You want a .8, 1.2 or 1.6mm wall.

Someone else already touched on it, but remember that .stl files are composed of straight line triangles, so curves are approximated. Many solids programs allow for altering the output settings such that curves can be broken into very small segments. It takes a little longer to process, but you will get better consistency of wall thickness in a curve if you set these tolerances very low. e.g. 1 degree segments (instead of the typical 5 degree segment) and a very small linear tolerance can help as well. Again this can result in very large files, but if you have a decent computer S3D is pretty fast slicing them anyway.

[mitcheld]

I've had a lot of fun printing with flexible filament (TPU), but over/under extrusion errors can be catastrophic.

If you OVER extrude, it causes the filament to spring up in the hot end and eventually shoot out of the extruder backwards, thus jamming the printer.
If you UNDER extrude, it causes the perimeter to peel off like a snake shedding its skin.

Thus far, I've set my perimeter to 1 layer, but now that I'm moderately familiar with the material, I want to increase this.
The problem is, the outlines are always under extruded and peel off, but if I increase the flow rate, the solid infill of the part causes the filament to shoot out backwards and jam the printer.

Is there no way to change the extrusion multiplier for JUST the perimeter? (or the extrusion multiplier for JUST the infill for that matter).
My temporary workaround has been to never print parts at 100% infill. I usually set it to 90%. This allows me to crank up the extrusion multiplier a bit to account for the thin perimeters without causing the printer to jam while printing the actual part.

This is a "workaround" and not a "solution" because I still have to worry about the solid top/bottom layers. The first 3-4 layers are truly solid, and this can cause problems if I overextrude.

To summarize, is it possible to do any of the following?
- Change extrusion multiplier for perimeter only
- Change extrusion multiplier for infill only
- Change extrusion multiplier for top/bottom layers