Homing Switches & Routine

[RJS100]

I am assembling a small panel consisting of:

-Acorn board
-Three closed loops stepper drivers (Stepper Online CL86Y)
- One 12 Nm closed loop stepper
- Two 4 Nm closed loop steppers
- 70V/35V Toroidal transformer
These will be used to convert a PM-728TV or PM-833TV to CNC.

I wired and tested each axis one at a time and it appears that they are working well. The panel is shown in image "Panel". The X,Y & Z move appropriately as I press the X, Y and Z jog buttons. I also wired and tested the E-stop and drive fault input. I am getting ready to wire and test the homing switches and have the following questions:

1. If I am correct, I can either use n/c micro switches wired in series and connect them to one input (see image "Microswitch") and select "home all" for the appropriate input on the wizard or if I would like to use proximity switches, I would need to assign each proximity switch to its own input (see attachment "Proximity"). The wizard has several input selections FirstAxisHomeLimitOK and FirstAxisHomeOK. Which of these is correct? Is there documentation on these selections? I could not find any.

2. I am leaning toward using proximity sensors for the homing switches. If I want to simulate the action of each (I did not buy them yet), can I simply connect the common to the corresponding input to simulate the action of the NPN proximity sensor?

3. Lastly, the wizard differs slightly from the older videos regarding the homing & Travel. When I watched older videos, the homing sequence appeared to home each axis one at a time. During my present bench test, when I press the "Park" button, the X & Y axis move simultaneously, once these axis stop, then the Z axis moves. Am I confusing "Parking" with homing? It looks like I need to have the wizard create the homing macro (cncm.hom) to establish homing direction and sequence prior to actually homing. Does this all sound correct?

Thanks again... Richard

[ShawnM]

Hi Richard, glad to hear you got everything moving, and in the correct direction. That's a big first step for some.

1. You can wire the N/C proximity switches in series as well. I have one of my machines this way as it uses only a single input. If you are short on inputs this is the best way or order the Ether 1616 for more input/outputs. If you wire them up on individual inputs then "FirstAxisHomeLimitOk" is the correct choice as it's you home switch AND your limit switch. The second axis is of course "SecondAxisHomeLimitOk" etc. You can then set your "soft limits" for the opposite end of travel without the need for more proximity switches and inputs.

You can buy a 5 pack on eBay for $19 from a US seller here:
https://www.ebay.com/itm/5PCS-SN04-N2-N ... SwfRdZJUvI

2. You could short or jumper the limit switch inputs closed until you have them or simply do not assign that input until you have them wired up. If you short/jump them and they are assigned the machine will try to home to them but it wont stop as the input is shorted closed. You'd have to open the input for the machine to stop the homing sequence and mov to the next axis in the homing sequence.

3. As for Park, if I remember correctly that will bring each axis within 1/4" of the home position (after you home the machine of course) before you shut down. I have a custom park.mac file that parks my machine (router) at the rear, center of the table so it's out of the way. I just forget the OEM park location exactly but that's how it works. For the record you should change your homing sequence to move your Z axis up first then the x and y axis. This way you don't crash into anything. Get the z axis out of the way before you do any rapid x,y moves. My "park" sequence is Z axis to top by itself and then X and Y together at a rapid rate I set to the rear center of my router table. Homing moves one axis at a time and park moves them together because you already homed the machine.

You HAVE TO HOME the machine at startup as you know. Just starting out you can let the wizard generate the home program for you. It moves each axis towards the switches (you can set the direction in the wizard if it's backwards) one at at time and then zeros out the DRO and sets that as home. Set the "homing type" to automatic and it will home to your proximity switches. Below that in the wizard is the homing direction, the X and Y will normally be negative and the Z will be positive. This is how my router is so your mill might be different depending on how you want it.

Be sure and set your "software travel limits" in the wizard as well for the max travel of your table. This saves you from having to use more proximity switches and it works flawlessly.

I hope this helps and others with more experience will chime in to help also.

[RJS100]

Shawn,
Thanks for the quick and detailed reply. Very much appreciated! I am new to working with proximity sensors and did not know that you can wire them in series. I like the idea, and cannot think of any negative to doing so. I have attached a schematic of how I think they would be wired in series. Can you confirm that this is how you wired yours? Also, thanks for the link to the proximity sensors. These were exactly what I planned on buying!

Thanks again... Richard

[ShawnM]

You certainly can and please use 24 volts to power them. They have a voltage drop per switch that you have to overcome which can be a few volts each. Using 24 volts to power them this wont be an issue. I've never had an issue with mine.

I'm using Input 1 but you can use any input you like, just set it to "HomeAll".

Your diagram is correct, here's a pic of my modified Centroid drawing showing how I wired mine and some notes at the top of the page in red.

Here's an informative video that's been posted before.

[RJS100]

Prefect! Thanks for the schematic. That is exactly what I had in mind. I actually bench tested it this morning and it worked great. I can't think of any negative associated with wiring these in series as opposed to using a separate input for each. Thanks again for your thoughts. Now I just have to decide which of the Precision Mathews mills I am going to convert. I have been thinking about the PM-728TV, PM833TV and PM840V. I think I am going to put this in another post to get some feedback. I am totally new to this.

Richard

[ShawnM]

Glad it’s working out for you. As for the mill choice, I’m sure there are many here with their input for you on which one. I have a Grizzly G0704 and it looks just like some of the PM mills. Good luck.

[MakerMarc]

Could someone help me with a problem? I have also used Proximity sensors in my setup. The X and Y axis are Homing perfectly. The only problem is the Z. When it homes it moves in the right direction, triggers the endstop, goes back to clear the signal, but then moves right back up in the direction of the sensor causing an error: “Homing routine failed” due to double triggering. Is There a setting for this? I can not find this in the .hom file.

Board: Acorn control board
Software: CNC12
Motors: 4 closed loop nema 34
Sensors: NO PNP Proximity Switches

Greetings!

[ShawnM]

Not sure how X and Y are working if your sensors are NO PNP when they need to be NC NPN switches per all centroid wiring diagrams. PNP switches are not compatible unless you switch the output with a relay or transistor. Limit/home switches should be NC.

[MakerMarc]

Okay, thanks for the quick respons. I will try the NC Proximity switches and see of the problem still persists.

Marc

[ShawnM]

Okay, thanks for the quick respons. I will try the NC Proximity switches and see of the problem still persists.

Marc

They need to be NPN also, no PNP switches.