Bed levelling or in true terms bed traming is adjustment to how parallel the hot end nozzle travels across the surface of the print bed.
With frustration and perceverence, I was able to achieve perfect first layer adhesion, reduced z-wobble and good prints.
I would like to share a simple concept and process on how I achieved true traming without continuous adjustments and I only redo this process only if something major disturbs the printer and bed. This is the manual process which I use to tram both my Ender 3 V2 Neo and Neptune 4 Plus. Refinement and fine tuning can be achieved via software and manual spacing.
I am not an expert, but only sharing my observation and results from learning from my mistakes.
The picture above represents a cross-section of the nozzle and print bed assembly with a blue line representing true levelling (traming).
The print bed is made of an alluminum plate. Due to thermal expansion and contraction, metal will become distorted in it’s natural state if without reinforcement. When heated, metal expands and when cooled metal contracts.
Before attempting this process, print and install appropriate adjustment screw locks for your specific printer and that you have calibrated E-Step of the extruder and Temperature. This is the minimum to satisfy your level but not the complete calibration process of your printer.
Levelling process and concept
The first picture shows, the bed is bowed downwards, and all the adjustment screws is all the way down.
All of my 3D printers as they come out of the box, the bed has a downward bow. You can measure this from the middle of your X-axis gangtree if its square down to the bed and repeat from the X-axis gangree to the edge of the bed.
The second picture show, as you wind all the adjustment screws all the way up, force is applied to the edges of the print bed making the bed bow upwards. You can verify this by measuring from the X-axis gangtree as described previously.
*** Take note, the first two pictures is the bed ‘Unheated’.
When I’m traming, I do the usual paper (feeler gauge 0.05mm) technique to get my Z-offset and evenly adjusting the screws between the nozzle (unheated) to tram the print bed before auto-levelling.
From the third picture, the yellow line represents my perceived traming - traming the print bed in relation to true level.
Once I auto-level and the bed heats up, due to thermal expansion, the bed bows upwards. The problem here, is that the Z-offset will compensate for any distortion of the bed, but when the nozzle prints either side of the bow, you may think your layer is level, in fact the first layer is barely adhering, due to the Z-offet has it’s level computed from the bow when auto-leveling.
*** From my experience, this is why I get problems with layer adhesion.
The fourth picture, I adjust my adjustment screws, so my print bed is just a tad below actual level. As you can see the yellow line has a downwards bow. The reason for this, is to compensate for the bed bowing up to achieve true level when the bed becomes ‘heated’ during auto-level.
*** I have reduced Z-wobble because how this process helped to damped or reduced the Z-axis movement and have better first layer adhesion.
Check for level and first layer quality
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Dowload first layer (100 x 100) 3d file and slice.
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Print the first layer and adjusting the Z-offset at the same time.
*** What you are doing is setting the correct filament extrusion for the first layer. What you want to achieve is consistent layer that has no over or under extrusion.
*** For under extrusion, the filament layer is apart from each other and eventually, the further you adjust the Z-offset away from the bed, the filament will not adhere and detatch itself from the bed.
*** For over extrusion, the filament will bulge around the nozzle, causing raises of streaks above the surface of the first layer. The closer you adjust the Z-offset towards the bed, more filament will streak and eventually no filament will be extruded.
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Once you have justified the correct Z-offset, let it finish the print.
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Print another layer without adjusting the Z-offset.
*** If the result of your first layer test is consistent in the layer without under or overextrusion symtoms, your print bed is level.
*** If you find raise streaks on areas of the print, that part of the print bed is high. If you find blistering raises, that part of the print bed is low.
- Adjust as per levelling process above until you achieve a nice first layer.
You can make refinements to the actual bed before auto-leveling by adding alluminum tape or something thin enought to act as spacers if your bed is badly distorted. If you cannot achieve your desired first layer after many adjustments, then there is a probability that part of the bed is distorted enough you need spacers.
To fine tune after auto-leveling you can use bed meshing software like klipper if you have it on your printer or have modified it have these priviledges. I only use this method to really hone it to get a perfect print. But in general manual levelling will be suffice.
Please let me know if this has helped
You can just slap a dial gauge on the gantry and move the X/Y manually to see exactly what the deviation is. A decent second-hand dial gauge on eBay will run you $20 shipped.
If you get into the weeds, there is not an accurate method of triggering any form of mechanical stop that involves touch or a hall effect probe. You must get into optics for real accuracy, but that is nonsense for the materials and scope of printing. You would need to eliminate many other variables like the filament accuracy and how backlash and step accuracy are eliminated as issues.
As a former owner of an auto body shop with employees, most people do not know what clean is or how tooth is required. Like isopropyl alcohol has its place but is ultimately extremely weak at real cleaning problems. In automotive paint, silicone is a major problem. It primarily comes from tire dressing that makes them look slick black. The amount of effort it takes to remove that junk for automotive quality work is insane. Most chemicals just lush the junk around but leaves or dilutes the issue often making it worse. One of the big tricks in automotive stuff is (to use a a chemical cleaning step first but -) a few drops of dish soap in the wet sanding bucket. The light soap will keep the sand paper clean and working longer, but also makes most work also cleaning work. Anyways, dish soap can be very effective. Acetone occasionally on a surface is also effective. Virgin lacquer thinner is the strongest common solvent but it can react with lots of stuff and you are unlikely to find true virgin solvent. The recycled stuff has a paint stripper component in it that will cause epic nightmares and reacts with almost all plastics. Acetone is much cleaner and consistent unless it is sold for junk like nail polish.
The general rule of thumb is to assume a mechanical tooth adhesion is the primary form of bonding unless there is a catalyst involved (2k/urethane primers/clear). That rule can easily apply to 3d printing and bed adhesion. I see a lot of the same types of effects from different surfaces and filaments. There are even special adhesion promoters like Bulldog for spraying plastic automotive parts. I had other tricks too like a mist coating of clear coat. The main trick is to know what grit or “tooth” each thing you’re spraying wants to grab onto and prep accordingly. So I use the general safe bet of sanding my smooth build plates to 600 grit. With sanding, do not start dirty, like you’re trying to embed junk into the surface. Start clean, then knock off the shine to a smooth and consistent matte finish on the entire surface. When it comes to sanding like this, edges and any anomalies are absolutely forbidden. Never touch your edges until last when everything else is done. Edges are always thinnest and most vulnerable to causing issues especially for the inexperienced.
Clean it with acetone like once or twice a year and then sand it to matte, clean that with dish soap, then alcohol with each print. That will completely eliminate contamination as a cause.
Perfect first layers are possible with enough fussing with the software. If you really want to level the bed with hardware, use a dial gauge clamped to the extruder. That will remove all of the averaging and inaccuracies from probing. You would need to get into optics for true accuracy like with closed loop control systems that are an order of magnitude more expensive than 3d printers. These are precision machines with no accuracy. The 0,0 home location is always slightly different, but all measurements are based upon this location. This issue becomes relevant with IDEX and CNC. Going we beyond these, in optics accuracy requires a defraction grading and alignment of light patterns. I so want to get into that one to grind my own telescope mirrors.
If you have v-roller wheels on extrusions, one other major potential issue is that extrusions have a relatively large twist tolerance component in their specification. It is extremely difficult to detect this kind of twist, but it is a major potential issue.