robertcedwards/grbl-steps.txt

## grbl-steps.txt
Step 8: BONUS! Math!

Here's a quick mini tutorial on finding out the value to put into your GRBL settings for the correct amount steps for translating designs into the real world accurately.

A typical stepper motor has 200 steps PER revolution. These are known as FULL steps or 1.8° per step. This setting has the most torque and is the fastest, however not the smoothest.

Most of these machines will list the kind and size of lead/ballscrew it has. On my 3020, the lead screw is 1404.

14: 14mm diameter of the screw thread (OD)

04: 4mm pitch (or the distance between threads)

We are mostly concerned with the 04 number since it describes the amount of linear travel something connected to the lead screw will travel with ONE revolution. So a 1205 thread is 12mm diameter and 5mm thread size, so on and so forth. This also applies to ball screws, 1603 is 16mm diameter and 3mm thread size.

--

Now we can connect the two numbers together.

Stepper: 200/rev

Leadscrew: 4mm/rev

The settings in GRBL call for a PER mm number so its a simple math really.

200/4 = 50 steps to make something travel 1mm

(if we have a 3mm thread, it would be 200/3 etc etc)

50 is the number I put in GRBL

--

Heres where we get fancy, micro stepping.

I have my CNC machine set up to be 1/8 micro stepping, which means each step is divided into 8 microsteps.

200 steps x 8 micro steps = 1600 total steps/rev

The same math applies

1600/4 = 400 steps to make something move 1mm (again, if your thread is different, than the divider number will be different)

400 is the number I put into GRBL

--

The more steps the smoother the motions, but slower it will be and less power on the torque.

THANKFULLY, the Chinese CNC machines are all metric, which makes this math very simple. If these were ACME threads, there would be some metric/imperial conversions which would result in some very odd numbers.

--

Ok now go cut yourself something fun!
	Step 8: BONUS! Math!

	Here's a quick mini tutorial on finding out the value to put into your GRBL settings for the correct amount steps for translating designs into the real world accurately.

	A typical stepper motor has 200 steps PER revolution. These are known as FULL steps or 1.8° per step. This setting has the most torque and is the fastest, however not the smoothest.

	Most of these machines will list the kind and size of lead/ballscrew it has. On my 3020, the lead screw is 1404.

	14: 14mm diameter of the screw thread (OD)

	04: 4mm pitch (or the distance between threads)

	We are mostly concerned with the 04 number since it describes the amount of linear travel something connected to the lead screw will travel with ONE revolution. So a 1205 thread is 12mm diameter and 5mm thread size, so on and so forth. This also applies to ball screws, 1603 is 16mm diameter and 3mm thread size.

	--

	Now we can connect the two numbers together.

	Stepper: 200/rev

	Leadscrew: 4mm/rev

	The settings in GRBL call for a PER mm number so its a simple math really.

	200/4 = 50 steps to make something travel 1mm

	(if we have a 3mm thread, it would be 200/3 etc etc)

	50 is the number I put in GRBL

	--

	Heres where we get fancy, micro stepping.

	I have my CNC machine set up to be 1/8 micro stepping, which means each step is divided into 8 microsteps.

	200 steps x 8 micro steps = 1600 total steps/rev

	The same math applies

	1600/4 = 400 steps to make something move 1mm (again, if your thread is different, than the divider number will be different)

	400 is the number I put into GRBL

	--

	The more steps the smoother the motions, but slower it will be and less power on the torque.

	THANKFULLY, the Chinese CNC machines are all metric, which makes this math very simple. If these were ACME threads, there would be some metric/imperial conversions which would result in some very odd numbers.

	--

	Ok now go cut yourself something fun!