First layer infill not complete (...and bridge fill too)

[0110-m-p]

Every day my machine gets a bit more finely tuned, but I'm still having issues with two things...first layer infill and infill between bridges.

I have got the extrusion width dialed in on both ABS and PLA (thin wall cubes measures consistently at 0.55mm-0.56mm), but for some reason the first layer (esp. with ABS) is never completely filled and usually has a small 1/2 extrusion width gap at each end of the part. Also, with a calibration cube, the bridging works fine but when the machine tries to fill between the bridges, the material doesn't make it to the other side completely and just squirts into the gap.

This weekend I was planning on starting the machine calibration over to make sure my Z-heights are all good (worried that my nozzle height is too high for the first layer) and was looking at upgrading to newer Repetier firmware and maybe trying out a new slicer.

Any ideas?

[cope413]

Have you measured your filament precisely? You could try bumping your extrusion multiplier up 5-10% on the first layer. If that fixes it, then it's likely just a slicer settings issue and you need to accurately measure your filament

[0110-m-p]

Yes, I have measured it on several occasions and have gotten it to the point where my thin-walled cube gives the correct 0.55mm wall thickness without adjusting the extrusion multiplier.

Bumping the extrusion multiplier on the first layer would probably do the trick, but I am unsure how to do this...don't see any settings in Slic3r to modify the extrusion multiplier except the global modifier. Do I need to manually change the g-code?

EDIT: Also, what firmware is best currently? I am still running the factory installed 0.80 firmware.

[Lochemage]

If you are sure the calibration of the extrusion width is correct, but your first layer is still not solid, it's most likely that your first layer is printing too high above the platform. Try lowering the first layer (or in rmax case, increasing the max Z height by 0.1 or so).

As far as the bridging, it's hard to tell without a decent picture, but my first suggestion would be to make sure your bridge print speed is very low. I use 20 mm/s, significantly lower than normal print speed at around 60-70. Going too fast won't allow the edges to bond properly.

[0110-m-p]

I know we do the "heat bed/hotend and set Z-height so that at z=0mm the nozzle drags a piece of paper" method of setting Z-height, but is there a true optimal gap between the nozzle and heated bed when z=0?

Reason I ask is because I have a bunch of feeler gauges down to 0.0015" (a piece of paper is usually twice as thick around 0.003"), so I could technically set the Z-height "better" than the standard paper method if getting closer to zero is better.

[Lochemage]

hmm, well I don't know about that much precision, I usually just use the paper method, and then lower the build by about 0.1 and things work. I print layers at 0.2 so that may play a factor.

[cope413]

The 'optimal' distance is as close to the plate as you can possibly get while still being able to measure and verify uniformity at all the points. I use a feeler gauge that's .051mm thick and then make my first layer .05mm lower than my desired layer height to compensate for this.

[0110-m-p]

Guess this weekend I'm going to bust out the 0.0015" (0.038mm) feeler gauge and recalibrate the whole machine.

When you set the first layer height lower than what you desire though, doesn't the slicer adjust the amount of material extruded to compensate for the change in height?

[Lochemage]

Guess this weekend I'm going to bust out the 0.0015" (0.038mm) feeler gauge and recalibrate the whole machine.

When you set the first layer height lower than what you desire though, doesn't the slicer adjust the amount of material extruded to compensate for the change in height?

As far as the slicer is concerned, it 'thinks' that it is printing at the first layer height (e.g. if your layer height is 0.2, then it starts at z=0.2 whether that is actually at 0.2 or not physically). It's only if you actually set your slicers first layer height to some other value that it will compensate with more or less plastic.

[0110-m-p]

So when you tell slicer that layer height=0.2mm and first layer height=0.3mm, then for the first layer it puts the nozzle at z=0.2mm but extrudes plastic for a height of 0.3mm?

[Lochemage]

So when you tell slicer that layer height=0.2mm and first layer height=0.3mm, then for the first layer it puts the nozzle at z=0.2mm but extrudes plastic for a height of 0.3mm?

No, for the first layer it prints at z=0.3 and extrudes about 50% more plastic to compensate for the larger than normal layer thickness.

So, in reality, you want the nozzle to be directly on the platform at z=0, but if you use a feeler gauge or paper to manage the leveling, you actually end up with that much space in between the bed and z=0. However, unless you have an absolutely perfectly flat platform, z=0 actually touching the platform might be too squished in some areas, so a tiny bit of space can help. As far as your slicer is concerned though, it thinks it is printing at exactly the first layer height that you specified, you can use a larger first layer setting but you don't have to.

[0110-m-p]

I'll post back later on the results of my changes, but I believe that the nozzle distance above the bed at z=0 is the source of my problems. I let it heat up tonight and used some feeler gauges to measure the gap and it is right at 0.005" (~0.13mm).

I'm going to do my best to make get the nozzle as close to the bed as possible without hitting anywhere. I really wish I had a dial indicator and mount laying around so I could get an idea of the flatness of my build platform.