There is no shortage of 3D printers on the market, the problem that hobbyist run into is that typically you get what you pay for. Logically thinking, if you buy a 3D printer that is cheap, you are going to get low-quality parts. That doesn’t have to be true and a lot of the issues that come along with low-quality 3D prints are slicer and setup issues and don’t have a lot to do with the machine itself.
For my fill time trade, I work as an aerospace and defense Quality Inspector and CMM Programmer. This means that my full-time job is to inspect metal machined components and verify that they were manufactured to the desired specifications. Basically, dimensional accuracy is the world that I live in and I am very good at measuring things.
Obviously, there are features that come with a higher cost 3D printer that will increase the accuracy and quality of your prints such as linear rails vs belt-driven linear axis, self-leveling bed, and upgraded extruders we will talk a lot more about these further in the article.
How Accurate Should A 3D Printer Be?
A 3D printer should generally be able to hold a linear tolerance of +/- .020 inches or .50 mm without any major modifications or printer strategy edits. If you want more accurate prints then you will need to modify your slicer settings to compensate for shrinkage, material composition, and machine capability.
FDM
FDM Printers will have the hardest time holding dimensional tolerances. Materials such as PLA, PETG, ABS, and PETG have a tendency to shrink and this can be seen more dramatically depending on the size of the part. With an FDM printer, you will also struggle to hold accuracy due to layer height which is typically .05 – .3 mm
SLA
SLA printers are far more accurate due to the laser projected image has a much higher resolution than FDM. SLA printers also have a much finer layer height of roughly .015mm – .020mm. SLA does have shrinkage that can be highly unpredictable depending on the material that you are using.
If you are seeking accuracy with an SLA machine it is highly advised to print a 1” test cube or a 1” test puck to check for shrinkage compensation before starting a print that requires accuracy.
SLA printers are incredibly accurate for printing models and figurines. If you are wanting to print game pieces or D&D pieces an SLA printer is the way to go.
What Tolerances Can A 3D Printer Hold?
If tuned correctly and shrinkage is compensated for most 3D printers can hold a tolerance of +/-.002 linearly, a true position of .005, and a profile of .005. The toughest tolerance for a 3D printer to hold is surface roughness.
When checked with a profilometer the surface finish is too high to even register on a standard roughness scale. If I were to guess I would say that a standard finish for the side profile of an FDM printed part is probably around 500 uin.
What Makes A 3D Printer More Accurate?
For FDM printers there are many factors that affect print quality, printing speed, layer height, bed level accuracy, extruder quality, XYZ motor accuracy, and whether your machine is rail driven or belt driven will all affect accuracy.
How Does Shrinkage Affect 3D Printer Accuracy?
Shrinkage can dramatically affect 3D printed part’s accuracy depending on the type of filaments. PLA shrinks 1-2%, PETG shrinks .5-.8%, and ABS shrinks 1-7%. All plastics will shrink some when 3D printed so if you need to achieve a higher accuracy then it is critical to select the right material.
PLA – FDM Printer
PLA shrinks 1-2% depending on your filament, if you print a block that is 1″ wide after shrinkage you should expect your part to measure .990 – .980. For general use on non-critical parts, this probably isn’t an issue but for critical features this is basically a mile.
I know that doesn’t seem like a lot but think of it this way, a piece of paper is roughly .003 thick, so if your part measured .980 you would have to stack 6 pieces of paper onto your part (.018 thick) to achieve your desired thickness.
To compensate for this print a 1″ test block and check it for accuracy with a pair of calipers. If you see that your part is ~.990 you need to scale up your model to %101 and if you see that your part is closer to ~.980 you should scale up your model you 102%.
PETG – FDM Printer
PETG shrinks .5-.8% depending on your filament, if you print a block that is 1″ wide after shrinkage you should expect your part to measure .995 – .992. PETG is one of the most stable 3D printed PLA Materials. If you are trying to achieve tight tolerances it will be much easier to dial in with PETG.
PETG is a great choice for prints that are going to be in your vehicle. I wouldn’t use it in the engine because of the heat but in the cabin of a hot car, there shouldn’t be any worry of heat distortion. If you are creating prototype parts that need some level of strength PETG is a great choice. A common product that is made of PETG is invisalign braces alternative.
ABS – FDM Printer
ABS shrinks 1-7% depending on your filament, if you print a block that is 1″ wide after shrinkage you should expect your part to measure .990 – .930. ABS is widely used because of its incredible heat resistance and its strength. If you are seeking dimensional accuracy you should use a different material.
ABS is a great material for prints that are going to see a lot of abuse. Legos are a common household item that is made of ABS. If you are printing moveable parts such as gears or mounts for cameras ABS might be the best choice. The large downside of ABS is that it is prone to warpage and will often require a higher-end 3D printer due to the high temperatures required to print.
Resin – SLA Printer
SLA printers will experience shrinkage just like an FDM printer. Shrinkage can be more unpredictable on an SLA printer depending on the material that you are using. Resin on an SLA printer can shrink up to 8%.
SLA is by far the most accurate form of 3D printing. The main thing that you will need to compensate for is material shrinkage and once you get a good hold on that you will have great quality highly accurate prints.
Most Accurate 3D printer under $300
FDM
Creality – Ender 3 V2
This printer is a beast for someone on a budget. I think the only machine that can even compare at this price point is the Ender 3 V1 Pro which is basically just a downgraded slightly cheaper version.
If you are wanting to do larger prints then this is definitely the best sub $300 machine for accuracy.
SLA
ANYCUBIC – Photon Mono
Currently, once you add in the wash and cure machine it is just over $300 but this is hands down one of the most accurate machines for under $300. If you are doing figurines or smaller parts this is the way to go.
Most Accurate 3D printer under $1000
FDM
Original Prusa i3 MK3S+
$999.00
Prusa is a tried and tested brand that has been at the top of pretty much everyone’s list for years. In all reality, it is an Ender 3 with all the bells and whistles. Auto bed leveling, filament sensor, metal rails, and a slightly larger bed.
SLA
Anycubic Mono X
$808.00
If you need accuracy. Buy this printer. It is the whole package of accuracy, bed size, and affordability. If you are doing larger models this is the way to go
