# Need help understanding Acceleration units (in/s²)

03 Oct 2023 04:14 #282117 by Sray69
Trying to fine tune some settings in my INI. I have figured out the velocity settings and what they do/mean. BUT the acceleration settings being inches per second squared makes my brain hurt. Can someone explain this in a dumbed down way so I can understand what I am supposed to use for my settings? Inches per second or per minute, I get. And when I put a number in those sections I understand exactly what that means and how fast or slow it is. But I am not sure about the in/s² and what the numbers mean or where to start?

Much appreciated!

03 Oct 2023 04:30 #282118 by Sray69
Let me clarify a little more. I understand the basics of average acceleration and what it means but I am struggling to understand how to determine what to use in my settings.

Here is a basic, dumbed down explanation that helped me in case there are others that are trying to understand as well.

Average acceleration refers to the rate at which the velocity changes. We divide the change in velocity by an elapsed time to find out the average acceleration of anything.

For instance, if the velocity of a crazy ball increases from 0 to 60 in/s in 3 seconds, the average acceleration of the ball would be 20 in/s/s (in/s²). Therefore, it means that the velocity of the marble will increase by 20 in/s every second. The table given below will help you understand better the operation:

Time (Seconds)     Velocity (in/s)
0                            0
1                          20
2                          40
3                          60
4                          80

03 Oct 2023 05:31 #282124 by rodw
Velocity is inches per second. Accelelration is the change per second
So accelleration of 1 in/sec/sec from rest would mean it will be travelling at 10 inch/second after 10 seconds
Sometimes people refer to Accelleration in G or even milliG's which is the accelleration from gravity.
In a metric world, 1 G is 9.81 m/sec/sec which is about 32 in/sec/sec.

From a CNC sense, a lightweight stepper driven plasma machine might have  0.3 g (approx 3 mm/sec/sec) but on a milling machine there is a lot more inertia to overcome so accelleration might be set less to avoid missing steps. Often missing steps will ocur on uptravel of the Z axis as it has to fight against gravity in addition to the mass off the axis. The solution is to slow it down but the accelleration is the main one

03 Oct 2023 17:35 #282180 by JPL

.... And when I put a number in those sections I understand exactly what that means and how fast or slow it is . But I am not sure about the in/s² and what the numbers mean or where to start?

You may  also try this velocity calculator to get a better idea of the meaning of the numbers you need to enter: www.calculatorsoup.com/calculators/physics/velocity_a_t.php

03 Oct 2023 18:57 #282192 by PCW
Note that in dinosaur units 1G=~386 in/s^2
The following user(s) said Thank You: tommylight

03 Oct 2023 21:49 #282217 by rodw

Note that in dinosaur units 1G=~386 in/s^2

ooops, my memory from the 70's of conversion factors let me down
That kind of thing has been known to loose spaceships!

04 Oct 2023 21:00 #282315

Note that in dinosaur units 1G=~386 in/s^2

ooops, my memory from the 70's of conversion factors let me down
That kind of thing has been known to loose spaceships!

And land passenger planes on car race tracks, while the race is on!
The following user(s) said Thank You: rodw