Confused over home switches and limit switches

[adamfromscotland]

Hi

I have the acorn cnc board

on my control panel i made i have drilled in 4 x outputs for limits switches

I have for X,Y,Z And a slaved Y - A


Im wondering the best way for me to use my 4 x limit switches

Can i use the limit switches as homing also? or do i have to do those sepratley ive read all the files but im still confused to how to do them?

I want to use 2 x PNP Proximity Sensors on each AXIS X,Y,Z and A = 8 x PNP Sensors in total can anyone please tell me the best way to wire them?
I know its too be normally closed?

But what diagram do i follow?

[grossmsj]

I use 4 proximity sensors (X,Y,Z,A), NO, wired into IN 1. You tie all the BLK wires together into IN 1 (with NO) and use HomeAll. Very simple, only one input is used.
There really is no need to use a limit switch at the other end of travel. Soft limits work great. Just set it up once and you are done.

[cnckeith]

I use 4 proximity sensors (X,Y,Z,A), NO, wired into IN 1. You tie all the BLK wires together into IN 1 (with NO) and use HomeAll. Very simple, only one input is used.
There really is no need to use a limit switch at the other end of travel. Soft limits work great. Just set it up once and you are done.

i second that!

fyi... related. keep an eye out in the upcoming v5.1 of CNC12 for Acorn we added a new input definition called HomeLimitAll this new input allows Limit Switches to act like home switches during the home program (only) and when not actively running a home program the input acts a a limit switch input. this allows the same switches act like limits when you need limits and act like home switches when you need home switches all while only using one input.

[adamfromscotland]

Thank you very much for the reply and it was easy to understand that helps me loads i could never understand the limits and soft limit and homing as they are all similar but i will do as you do power to 4 x axis and tie the blacks into the 1 x input!

Just one thing!!!!!!!!! I read your 2nd reply and should i fit 8 x Sensors? so each axis i have has a pair? 4 x Axis x 2 so one is on each end?


thanks again

Many thanks

[ShawnM]

It's personal preference if you want physical limit switches at the travel limits. They eat up valuable inputs and the "soft limits" work perfectly. It's also more wiring and more configuration that is really unneeded. You can easily get away with 3 home switches with soft limits. You mention the A axis so I assume you have a rotary axis. I've not wired up a rotary axis before so those that have can respond to that. But for the X,Y and Z axis, 3 home switches are all you need as the bare minimum and then set the soft limits for those axis. It just works, is super simple to configure and uses the least amount of inputs.

[centroid467]

Both Keith and grossmj were saying that you only need to fit one switch per axis to set the home position. After that, you can use limits defined in software to prevent overtravel. The soft limits are set in the Wizard and are set as distances from the home position.

[Nigelo]

I have A axis setup on my mill without a home switch and therefore it's homed in whatever position it happens to be. This is not a problem since it has a 3/4 jaw chuck / faceplate. However, in the event of an unexpected stop (power failure, programming SNAFU etc) midway through a job, you may need to use a probe to establish your chosen continuation point.

[adamfromscotland]

I know its been a while guys but im almost finished the build on my CNC Its called Bulkman Ultimate CNC But ive bought the Acorn CNC and upgrade the software to control the A Axis The A Axis is the slave motor to the Y Axis

so The Y axis has two x motors running it Y and A

Im just about to do the Proximity sensors now so bear with me these are the ones im going to use

Panasonic Inductive Block Proximity Sensor, 2.5 mm Detection, PNP NO, 12 → 24 V dc

So i will used up 6 x sensors? 2 on X, 2 x on Y and 2 x On Z ?

[ShawnM]

If this is the standard 4 axis Acorn board you can only use NPN switches, not PNP. This is outlined in the install manual. The Acorn Six can use either type.

You only need ONE switch per axis and NC is preferred for safety reasons. This is also covered in the install manual. You can easily setup soft limits in the wizard for max travel distance. This saves a bunch of switches, wiring and headaches.

[adamfromscotland]

Thanks for the reply luckily i have both PNP And NPN Switches here so can use the NPN on as it is an Acorn standard 4 axis one I'm using and installed