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PharmDDan

Avoiding Mid Print Bed Height Adjustment

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Posted · Avoiding Mid Print Bed Height Adjustment

Hey Guys,

 

1st post here, so I'm excited to be part of the community. I'm new to 3D printing, but have been messing around with my Ender3 and CURA for a few months now dialing everything in. I find that to get good 1st layer squish I need to have the bed closer to the nozzle than the next layers. If I do not change the bed height manually after my 1st layer is down with the 4 adjusting screws, my subsequent layers will over extrude and feel rough and not smooth. By lowering the bed manually mid print, I get good first layer smoothness and squish, and then smooth subsequent layers.

 

Is there a way to tell CURA to print the first layer closer to the bed than the rest of the layers of the print?

 

I've played around with "Initial Layer Height" but it seems to make my issue worse.

 

Printing on Ender 3 with Glass bed.

 

Attached is the PLA profile I have tuned over the last few months.

 

 

PLA Profile.curaprofile

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Posted (edited) · Avoiding Mid Print Bed Height Adjustment

Hi @PharmDDan

 

You don't need to adjust your print bed height after the first layer, In Cura under the Quality settings, adjust the setting "Initial Layer Height" you have it matching the normal layer height and its better to have it set bigger so it pushes down to the print bed more for the first layer. A good setting for this would be 0.20 mm

Edited by Carla_Birch

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Posted · Avoiding Mid Print Bed Height Adjustment

As Carla said, the best option is to set the initial layer height.  You can also push the "Material / Initial Layer Flow" up to 110% or 120% BUT that would mean more plastic in the way for the subsequent layers and you would still have over-extrusion symptoms unless you back the flow off to 95% for layers 2 to 5 or so.  I've gotten very consistent at leveling the bed and I run Initial Layer Height at .20 and Initial Layer Flow at 105%.

Those layers just above layer#1 generally get covered right up by infill or another layer.  I like to concentrate on the first layer because it is so important to a good print.  A little over-extrusion on inside layers is a good thing.  Under-extrusion can lead to weakened parts.

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Posted · Avoiding Mid Print Bed Height Adjustment

Thanks for the suggestions guys. I increased first layer flow to 120% and rest of the layers to 90%, top layers to 93%. Seem to be having great results. Printing an X-Wing Now, and its looking great so far.

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Posted · Avoiding Mid Print Bed Height Adjustment

That's... strange.  I've never had to adjust flow for PLA.  The bottom layer I've done tons of adjusting on in every possible way (thickness, flow, adjusting screws, initial horizontal expansion) but not the subsequent layers.  I've been printing for I think about 8 years?  I have 5 active printers.  I mean I *have* adjusted the flow but I always end up back at nominal, 100% flow.

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Posted · Avoiding Mid Print Bed Height Adjustment

Yes sir, but you have 8 years experience.  Those of us starting out need to build confidence and getting consistent good first layers does that.  Pushing the flow seemed an easy way to get good plate adhesion and good bonding between the lines of mesh.  Compensating for the over-extruded first layer by under-extruding a couple of layers seemed a small price to pay for getting some kind of system that worked.  As I get better at this I've reduced the initial layer flow to only 5% over and the subsequent layers run at 100%.  That has helped get rid of the elephants foot too.  It comes together.  Troubleshooting is still a pain when things all of a sudden go south on me.  It seemed like it was always something different, but when all was said and done - I'd be back rebuilding and cleaning the hot end and everything would be OK.  I think that these are both the simplest and most complicated machines I've dealt with.  Tuning a set of Weber carbs is a piece of cake next to these.

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Posted · Avoiding Mid Print Bed Height Adjustment

The bottom of the nozzle has a flat area around the hole.  Like an iron.  so if you overextrude (up to around 200%) it will still flatten it out (if it fits) such that the bottom layer is no thicker than it's supposed to be.  I suppose in practice it's possible that the bed/stage is pushed down a bit and the bottom layer is thicker.  But I don't think there is enough pressure through that tiny nozzle tip to do that so mostly the filament should slip a bit in the feeder to compensate for some overextrusion.

 

I personally compensate for the "elephants foot" by using "initial layer horizontal expansion" set to a negative value.  This allows the bottom layer to be squished nice and hard for good adhesion yet avoid the elephants foot.  For a 0.4mm nozzle I set this to about -0.25mm but it matters how much you are squishing that bottom layer and you have to be aware that if your part has small features on the bottom layer they might not get printed at all which will give very bad results (second layer printed over air).  So check the bottom layer in PREVIEW mode.

 

The second layer is usually fine for me without any flow adjustment.

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Posted · Avoiding Mid Print Bed Height Adjustment

I do some things with fine relieved text on the bottom.  So far there haven't been any problems with loosing definition of the letters.  I usually hand code speed changes into the Gcode file so the first few layers are slow and then after the lettering I speed things up.

My inconsistencies with leveling have pretty much gone away since I started using parchment paper.  At .04 thickness it gives me more control over first layer thickness.  Theoretically, when I tell it to make the first layer .2 and I've leveled with a piece of printer paper at .1, the nozzle should be .3 above the surface.  At any rate, somewhat more than .2mm.  I think that was where my first layer under-extrusion was coming from  I'd be loose on the leveling and the first layer may have been closer to .35 or .4.  Not enough squish.  I'm much better at adjusting the bed while the skirt / brim is printing, but at first, I was worried about dragging the nozzle so I just pushed more plastic to fill the large gap (instead of closing the gap).

I once tried using a feeler gauge of .1mm with the nozzle at Z=.1 hoping for an exact zero on the Z axis.  That didn't work out I think because I was trying to cut things too fine.

There is no BLTouch in my future.

All in all I'm pleased.  The $220 Chinese POS printer is accurate if not terribly dependable.  It now has near 500hrs on it at the cost of a hot end, and 2 fans (1 was my fault).  I've had to take it apart probably 6 or 8 times to fix various problems.  It's a learning curve.

Some of the pieces on the motorbike were my first attempts at printing and I think there are about 60 separate pieces on it now.  I was a machine tool designer in a former life.  I've been running AutoCad for decades and have some experience with Gcode.  What I don't know about 3d printing fills libraries, but I've been involved with Gcode CNC machines since the late 60's and used to market my own software for monitoring lab equipment and racing timers via serial ports using MSExcel and VBA.

 

I'll close here with some compliments.  Cura dazzles me.  The support here is excellent even though there are numerous non-Ultimaker products being discussed.  I also appreciate the fact that there is very little "look at my mini" or "see how fast I can print" stuff here.  It's a nuts and bolts kind of site.

Now go back to work.  I'm tired from hi-jacking this thread.  I think I'll have a nap.

 

776175944_ABike2.thumb.JPG.6d23189a16e5aa610258895b02aef79a.JPG

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Posted · Avoiding Mid Print Bed Height Adjustment

There is a z-offset plugin in the marketplace that can allow your first layer to be closer to or further away from the bed to help with first layer adhesion.

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