What's the difference between LAYER RESOLUTION and Z AXIS POSITIONING PRECISION ?

[dysquare]

I noticed that a printer has the specification of Z POSITIONING PRECISION 2.5 MICRONS and LAYER RESOLUTION 100 MICRONS.
I don't understand that why it can't print at a layer thickness of 2.5 microns?
Or Z positioning precision is just the mechanical movement accuracy of its nozzle? So what's the meaning of it

[curious aardvark]

it means that the bed can move up and down in 2.5 micron increments. But you can only extrude a layer of plastic 100 microns thick.
That has nothing to do with the precision of the vertical movement, and a lot to do with the extruder, the plastic itself and the nozzle.

And to be honest no one in their right mind would want to print thinner layers than 0.1mm with an fff machine anyway.
Can you say three weeks to print anything.
Getting that thin a layer of plastic is seriously hard. Your calibration has to be absolutely perfect as does the temperature and viscosity of the plastic.

hell i don't print anything lower than 0.2.

[Davo]

it means that the bed can move up and down in 2.5 micron increments. But you can only extrude a layer of plastic 100 microns thick.

Well said. Actually, "Layer resolution 100 mcirons" indicates (accurately or not) that the layers can be put down in increments of 100 microns - 100, 200, 300, etc. They probably mean "minimum layer thickness", and they can probably print 150 micron layers as well.

I don't agree about the difficulty, but I do agree about the printing duration. We print most parts at 200 microns, but we have printed at 25, 50 and 100 microns. IT TAKES FOREVER AT 25 MICRONS.

The same print will take 30 minutes at 200 microns, an hour at 100 microns, two hours at 50 microns, and four hours at 25 microns.

The quality improvement is not worth the wait for most of the things we do.

[richardphat]

Precision, accuracy and resolution, don't be fooled by those words, every of them have different meaning.

[dysquare]

it means that the bed can move up and down in 2.5 micron increments. But you can only extrude a layer of plastic 100 microns thick.
That has nothing to do with the precision of the vertical movement, and a lot to do with the extruder, the plastic itself and the nozzle.

And to be honest no one in their right mind would want to print thinner layers than 0.1mm with an fff machine anyway.
Can you say three weeks to print anything.
Getting that thin a layer of plastic is seriously hard. Your calibration has to be absolutely perfect as does the temperature and viscosity of the plastic.

hell i don't print anything lower than 0.2.

Well , can i say that the Z positioning precision is useless ?

[dysquare]

Precision, accuracy and resolution, don't be fooled by those words, every of them have different meaning.

Can you explain them in detail?

[curious aardvark]

Well , can i say that the Z positioning precision is useless ?

you can say that - if you're an idiot.
Okay so the machine only (lol 'only') prints in 0.1mm increments. But in order to do that accurately, layer after layer, after layer, after layer...
You need a very precise and accurate stepper motor - and that's what the z positioning precision is telling you.
If you have low z positioning precision you could find that the error in each layer, could gradually get worse and end up effecting the overall accuracy of the model.

So - yeah it's important and 0.0025 micron precision is pretty bloody good.

[Wolfie]

In general....

Precision - How accurately something can move or measure.
Resolution - The smallest division it can accurately work with or display.

For example, a digital caliper may boast a .0001mm precision and have an LCD display that shows 199.99mm. Its precision would be 0.1 micron but its resolution is only 1 micron. That means it can measure down to .01mm (1 micron) but do it extremely accurately. Make sense?

For the OP, the precision parameter describes how accurately the z axis can return or go to any specific height. If the code says to go to 100mm in the z axis, the machine is capable of going there to within +- 2.5 microns. So it would be somewhere between 100.0025mm and 99.9975mm.

The resolution is the increment of the z axis that it can print at. In this case, down to 0.100mm or 100 microns. But it will be +- 2.5 microns of that 100 microns or 97.5 to 102.5 microns accurate layer to layer positioning. If it was told to print at 200 micron layers (common fine resolution print setting) it would do so from 197.5 to 202.5 layer accuracy.

[Feign]

Precision - How accurately something can move or measure.

Well, that's not really right. (though you got resolution spot-on)
An example of precision is if you have a print head move on and off of one coordinate, how close the head moves to that exact coordinate each time. Almost every printer is very precise.
Accuracy is if you have the head move between two points that should be a set distance apart, how close the two actual points are to the expected measurement. Most printers are very accurate if calibrated correctly and run at a speed their frame can handle.

As a general rule of thumb, parts with high resolution look smooth, parts made with precision look the same, while parts made with accuracy fit together properly.

[Wolfie]

Well, if you want get down to it... As a long range rifle shooter, I am acutely aware of the difference. A precision weapon system and cartridge combination are able to put the bullet in the same place every time. It may not be the right place but its the same place. How big of a diameter that the bullet holes make indicates its precision. Accuracy is the ability to put the bullet group where you want it to go, irrespective of the precision (or lack there of) of the rifle. So, if your weapon system puts a bullet 4" below the target at 400 yards and does so 5 times out of 5, its extremely precise. Its not very accurate (well, unless you are 1200yd away then 4" is darn good). If the same system is adjusted or used in such a way as to hit the intended target in the location selected 5 out of 5 times, its very accurate and precise.

A high precision printer can put the head in the same place every time, or extremely close. Even if its in the wrong place, its the same place each time. I printer that puts the print head 110mm above the print bed within 2.5 microns even though it was told to put it at 100mm, is still extremely precise. Its not very accurate.

Precision is usually (not always) due to design and condition of the physical device. Accuracy can either be user or device oriented. With 3D printers, user interaction is normally what results in poor accuracy. Maladjusted Z stops, bed leveling, etc, all affect accuracy. Its precision remains constant unless hardware damage or malfunction occurs. With a rifle, its precision is by design and the components and methods that were used to produce the ammo. Accuracy is all about the guy (or girl) operating the weapon.

What I stated in my first post should have satisfied the OP's question delineating precision and resolution. He did not ask about accuracy. As such, I rolled them into the single term of precision as most people use the words interchangeably, though incorrectly.

And just so you understand what I by a precision weapon system... Here is my granddaughter behind my Barrett MRAD 300 winchester magnum at 400yd shooting groups the diameter of a 50c piece (yea, thats me at the spotting scope)...


When I shoot it, I generally put quarter sized groups on target from 400 to 600yd. For reference, a quarter is about .95" (24.2mm) diameter. The bullets are .308" (7.8mm) diameter. And I am putting 5 of them in a .95" or less area at 600yd or more.

If you want to get a real look at what these distances involve..here is a close one at only 300yd:
https://www.youtube.com/watch?v=79-agh6Wq3g