The Fourth Layer

I’ve learned a lot about the first layer from excellent YouTube channels like MWT and have achieved beautiful first layers at last. But I am far from satisfied. Can we talk about the fourth layer?
I’ve been printing for close to a year now. I have an Ender3v2, with a MicroSwiss clone hot end, a BMG clone extruder and a CR Touch. Everything is well tuned; extrusion tests come out exactly on the spot with 100, 200 or 500mm of filament. When I set the ZOffset nicely, the first layer is excellent.
Printing PLA with a 0.4mm nozzle with 0.2 layer height, I print four layers for the top and bottom. (Typical Cura Standard Quality)
Assume the print has a rather large, rectangular bottom surface. As I print the second, third and fourth layers, a large amount of goo builds up and gets pushed around by my nozzle. By level four there are many ridges at least 0.1mm high and a lot of obvious excess material on the model. I have experienced this with quite a few different filaments, nozzles and nozzle sizes. The filament is dried before and while printing.
As the print progresses, it recovers. As infill prints the obnoxious globs disappear. The final print looks fine and is strong. However, the bottom four layers form an extended elephant foot which is about 0.1mm wider than the rest of the print on all sides. The four solid layers at the top do not create this bulge, perhaps because they have some room to expand downwards rather than outwards. If I print 8 layers of bottom, the bulge is 8 layers thick. Interlocking parts don’t fit together without lots of post-production work.
I’ve begun using Cura’s ChangeAtZ script to back my flow rate off for layers two through four. Layer one’s over expansion can be absorbed in a brim. I find I have to back the flow off to 80%, and that’s still a bit high. I plan to try 75%. That’s a huge delta! BTW, if I adjust my esteps down by 80% and print normally, the print is brittle and obviously under extruded.
Can anyone print a solid piece of PLA that is, say, 20x20x1mm that has an acceptable top surface? I’m intensely curious, because I don’t hear of anyone else experiencing these issues.

This sounds like “elephant’s foot”. You could try this: in Cura, look under the Walls section of the Settings panel for a setting call Initial Layer Horizontal Expansion. Enter a small negative value here and see how it affects the print.

The next thing I would try if it was my printer would be to lower the Flow rate. I would likely lower if by 10% the 1st time, just to see if it has an effect.

Thanks, Ender5r!
OK, the second image would have shown Initial Horizontal Expansion’s effect, which only applied to the first layer and the bulge remained quite similar. Pieces do not fit together.

Finally, I used ChangeAtZ gcode post-processing to set the flow to 90% for layer 0, 75% for layer 1, and 100% at layer four. I got a pretty nice cube whose walls met the bed in a straight line. I could assemble something with this, but this kind of processing isn’t any good for ‘Print Sequence: One at a Time’ because the layer number doesn’t reset to zero with each part.

Now, if I change my overall flow rate to 75% the bottom is fine, but the top is clearly under-extruded and I can easily crush the model in one hand. The infill doesn’t fuse and the print is a mess.
I’ve retuned e-steps over and over again, and they’re correct. 100% flow rate looks perfect for everything but the first few layers.

Are you certain the layer # doesn’t reset to zero? If it really doesn’t reset I would consider that a bug and I would submit it as such.

Good idea; I found Cura makes it easy to report bugs and was half way through doing so when I realized I needed to do more testing first. While I clearly saw layer numbers constantly increasing in the Cura preview and on the printer display, I did not test to verify that ChangeAtZ did not somehow compensate for this and do the right thing.
I’ll do something crazy like expand by 10% on layer 1 and print several copies in One at a Time mode to verify that there’s an operational problem first.

This problem is a puzzler. From the description, it seems like a slicer setting. Can you post all your Cura settings?

BTW, thanks for the excellent pictures and descriptions. Very helpful.


Thanks, Alan!
This is the first time anyone has asked me to post my settings. There are quite a few.
If I export my profile, it shows creates a zip format file with two files in it:
creality_base_extruder_0_#2_ployterra_cotton_white_pla_4mm #2
creality_ender3pro_ployterra_cotton_white_pla_4mm #2
…which is odd, because that’s the name of a different profile. But the files contain the following:

creality_base_extruder_0_#2_ployterra_cotton_white_pla_4mm #2:
version = 4
name = PloyTerra Charcoal Black PLA 4mm
definition = creality_base

type = quality_changes
quality_type = standard
intent_category = default
position = 0
setting_version = 19

bottom_layers = =999999 if infill_sparse_density == 100 else math.ceil(round(bottom_thickness / resolveOrValue(‘layer_height’), 4))
cool_fan_full_layer = 2
material_print_temperature = 200.0
material_print_temperature_layer_0 = 205.0
retraction_amount = 4.5
retraction_speed = 35.0
speed_print = 50.0
top_bottom_thickness = 0.8
top_layers = =0 if infill_sparse_density == 100 else math.ceil(round(top_thickness / resolveOrValue(‘layer_height’), 4))
wall_line_count = =1 if magic_spiralize else max(1, round((wall_thickness - wall_line_width_0) / wall_line_width_x) + 1) if wall_thickness != 0 else 0
z_seam_type = sharpest_corner

creality_ender3pro_ployterra_cotton_white_pla_4mm #2:
version = 4
name = PloyTerra Charcoal Black PLA 4mm
definition = creality_base

type = quality_changes
quality_type = standard
setting_version = 19

adhesion_type = skirt
layer_height_0 = 0.2

If there’s a better way to post my settings please let me know.

Another way to illustrate this problem would be for me to show the condition of the top surface of a solid square printed four layers thick. First layer would look beautiful, fourth layer is like a busy pasture after a hard rain. Again, this self corrects as the print continues and most are quite usable, but have a swollen base so they can’t be assembled together.

@Ender5r; I tested ‘Print Sequence: One at a Time’ and found that for three objects each 25 layers tall, the Cura Preview showed 75 layers, numbered as I described.
However, I found that the printer correctly reports layer 0, 1, 2 etc. on the second and third objects and ChangeAtZ kicks in correctly for each.
However, I did find that ChangeAtZ’s ‘Apply To: Target Layer Only’ behaves exactly like ‘Target Layer + Subsequent Layers’ (at least with Change Flow Rate to 50%) so I will report that bug.

At least 1 question is answered.

This may sound crazy, but have you checked/calibrated your Z axis steps/mm? What is your current steps/mm for the Z axis?

Thanks for posting the settings! Nothing looks out of the ordinary (I thought maybe some wall/bottom/infill setting might have been accidentally changed). Is the MicroSwiss a direct drive setup?

Have you tried the “Outer before Inner Wall” setting?

It’s hard to tell with black filament sometimes, but the first layer looks like the nozzle might be a tad too close.


@Ender5r; the Z axis is set to 400 steps/mm. I have never calibrated or (intentionally) changed that.

@Alan; I printed a Benchy at 75% flow. It didn’t look particularly bad, so no pictures. Top surfaces were a little raft-like with the layer below slightly visible through the cracks (like my final four-layer print above.) However, I could easily snap the cabin in half using one hand. Smoke stack and gunwale are easy to crush, not at all like one printed at 100% Flow Rate.
While printing, I could see that the infill wasn’t well fused.

400 steps/mm sounds right.

Stupid question. What is the bed temperature?

It looks like the heat from the bed is keeping the plastic in an elastic state and the weight of the print causes the bottom layers to compress and this sagging causes the bulky bottom layers.

Just remember the heat is not just at the surface. It raises along the side of the part and slower through the inside, by heating the air inside the infill. So the bottom plastic is radiated with constant heat during the entire print, which may be 12 hours or longer in worst case. So if the temperature of the bed is too high, it may stick fantastic, but the side effect is bulky sagging.

If the temperature is 50°C or below, you should check the temperature using some external device. If you use a surface like glass you can go higher, as the temperature at the top is 50-55°C, when the sensor is reporting 65°C depending on the print surface. The sensor if below the bed, while you print not only on the other side of the heater PCB, but there is also a aluminum plate for heat distribution and some spring metal sheet or glass bed. These may cause a five to ten degree difference.

So rule #1! Check the temperature at the top of your print bed to get the real value. Just taking some “I print at 55°C” information from someone else may not work for you and your workspace (room temperature).

You can use a multimeter and a spare thermistor to measure the resistance and use the official resistor to temperature table to see what the real temperature on the surface is. Some multimeters also come with a thermistor and a mode to measure, so you just need to tape the resistor to the top for testing. These “laser pistol” kind of devices may work, too. But those have trouble with glass and reflective surfaces, so keep that in mind when you results are way off.

Also check the bed thermistor for resistance. In cool state it should be at room temperature. If not, a wire may be partly broken and increasing the resistance or the thermistor itself is not in contact with the board and the air cushion makes the printer believe the temperature is at 60°C, while in fact the temperature is 20+°C above.

With “modern” 24V systems the build plate is heating quite fast and you may not notice the problem right away. With a 12V system a bed needs about 12 minutes to reach 80°C (If the bed is insulated) and any problem with the sensor would be noticeable in a massive delay. With 24V this is harder to notice as the heating time is lower in general and a little delay results in a massive time difference.

@Geit; Thanks, this makes sense to me. If my bed is considerably hotter than I believe it to be, that would explain why I always see this issue and others think it’s strange.

I’ve experienced this problem both with the original E3v2 glass build plate, and an inexpensive powered PEI plate that came with a magnetic rubber sticker for the bed.
Adhesion has been a problem for me since the start, and I guess the go-to solution I’ve used to fix adhesion is higher bed temp + first layer temp + brim.
The top views I photographed above I printed at 200C with a 60C bed, but the side views may have been 205/65. But I’ve never calibrated the bed temperature, and with the rubber magnet I often wonder how even the surface temp is.
I’ve got a pocket full of MEMS temperature sensors from home automation projects. I’ll build a little device to make an accurate heat map of the bed, and see what that shows.

I asked above, but is your MicroSwiss setup direct drive or Bowden? Also, have you tried using another slicer, like PrusaSlicer? I’m skeptical that flow rate (especially under extrusion) is the problem.


@Alan; sorry, it’s a Bowden setup. I’ve never used any slicer except Cura. I’ve got a short list of slicers to try “some day.” Maybe that day has come. It would be a good way to eliminate a lot of possible causes, anyway.

Here’s a more fleshed out example of the issue I’m having: today I was printing some opaque holders for lithophanes. They’re 6" by 6", with a hole and pocket in the middle that’s about a third that size, but the front and back pieces are each just 2.6mm tall. Front and back click together to hold the lithophane.
To avoid initial over-extrution I set the first layer to 95% (any less and I can’t get good adhesion) and the next three to 75%, then back to 100%. I printed with a brim, because any warping would completely ruin the print.
To get a successful print I had to set the zOffset to -2.70 for the brim and walls to adhere at all. But I got a mess of a first layer (deeply gouged, tall fins of material near the edges) unless I baby-sat and changed the ZOffset to -2.65 for the diagonal filling. With that change, I got a post card quality first layer. The top layers came out looking excellent at 100%. There were five layers of infill under it.

Maybe this is normal and people just don’t talk about it (tweaking setting while you print.) Maybe I’m making it really complicated instead of pin-pointing the cause.

@Geit; I’ve built a device to measure the bed temperature, but have been printing around the clock the last couple days. A brief test seemed to indicate low plate temperature instead of high, but I suspect I was averaging the plate temp with air temp just above it. I’ll use a very small glass bowl to eliminate ventilation and test soon.

I can tell you that I definitely do not tweak the settings dynamically on every print. Occasionally, I may need to adjust the Z Offset dynamically if I see it’s a bit too close or far away, but it’s not a regular thing.

@Geit; I finally got a chance to measure my bed temperature this morning.
I used an SHT30 sensor and an M5 Stack I had on hand, calibrated the sensor at room temperature, heated the bed to 65C, put the sensor in the center of the bed covered with a small ceramic sauce dish and waited half an hour. The temperature leveled off at 56.4C after about 20 minutes.
The sensor’s range is -40 to 125C +/- 0.2C. It’s mounted in a small enclosure, so it’s not in contact with the build plate, which is a magnetically mounted powered PEI plate, on top of a magnetic rubber sheet, on top of the E3v2 bed. I can’t attest to the accuracy of this reading, but it’s an indication that I’m running cool, not hot.

I’m wondering; if the bed is much too cool (and I do have adhesion problems all the time, thus the powered PEI plate) perhaps the work-arounds I’ve applied to achieve adhesion lead to the effect I’m seeing on the bottom layers.
I could try some tests with a much warmer bed and much less squish, and possibly a cooler hot end.
I need to do a little research to verify the top safe temp for the rubber layer first, in case my readings are invalid.

Has anyone out there verified your build plate temperature? How did it come out? What method did you use?