Help please. Dip switches and mach 3 settings

[cropwell]

*once you crush the end it is f***ed (rendered inoperative permanently)* - the switch or the cnc?

The switch.

[Radu_Andrei]

NPN NO inductive proximity senzor, 4mm detection distance, 6-36VDC,300mA,3 wire (brown,blue,black)

[paulus.v]

Hi again.
Shortly after the the 3 weeks old conversation, I received 3 inductive switches, which I.ll install next week.
I like Rob.s approach of also keeping some mechanical switches in place next to the homing ones, but I.m somewhat unsure what.s the best way to wire all this.
I.ve only got 5 pins on the Bob, one being used for the probe. So 4 pins for the remaining Estop, 6 mechanical limit switches (2 for each axis), 3 inductive homing switches (3wires).

So for example (let.s say P15 is the probe)
1. Combine all limits and estop in let.s say P10 and have P11,12,13 for x,y,z home switches.
2. Combine all limits in P10 and all homes in P11, Estop in either P12 or 13
3. Combine the limits and home of each axis in one pin

So what the best wiring option and why?

I have all the limit switches and estop wired in series (NC) to the main contactor that powers everything except the breakout board. One signal wire goes through a spare contact of the contactor to the breakout board to tell mach3 to stop the g-code.

The homing sensors are connected to the same BoB input in parallel as I don't use simultaneous axis homing but need the spare inputs (actually I use one more input on X as I have dual motors and need to square the gantry). The homing sensors are configured as home and limit in mach3.

In 5 years I've never hit the limit switches one single time as the sensors are working as limits as well and never failed.

[Radu_Andrei]

Thanks for the reply.
I don.t get why is the contactor involved in all of this. When you interrupt the signal wire (open the contactor), you also kill power to everything else, except the BoB. Why? Why not use just Bob input terminals?

Could you please post a picture with your limits and homes setup? If not to much trouble even with the whole cnc machine. It never hurts to see a new approach.

[Radu_Andrei]

Another thing that gives me a hard time, is that I have some ballscrew whip. It.s 20mm dia, and 1500mm long, one fixed and on simple end support. On the y axis, on the last 300-400 mm moving towards the stepper, I get some whip. At 3000 mm per min (118inch per min) it.s quite strong. Reducing the speed to 2200 (86) it is very little. I assume lowering to 2000 (78) will kind of fix it. I would prefer 100 ipm.

I found two ways of fixing that online. One is a spring support at the middle of the screw, that reduces somewhat the whip, the second is a change in design to make the ballscrew stationary, and rotate the nut (A LOT OF WORK TO CONVERT TO THAT).

Has anyone encountered this kind of problems, and what solution did you come up with?

P.S. Regarding the pictures with the cnc machine from post 204, please feel free everyone to post some photos with your cnc routers, especially those which used them for some time, as I.m sure you.ve updated your machine design to solve all or most of the problems. This includes you too, Rob. :) You.ve posted a photo with your beautiful limit switches, but I did not have the honour to see the entire cnc, and as you always seem satisfied with its performance, it is of paramount importance to my existence to see your cnc rounter. :)

[paulus.v]

Thanks for the reply.
I don.t get why is the contactor involved in all of this. When you interrupt the signal wire (open the contactor), you also kill power to everything else, except the BoB. Why? Why not use just Bob input terminals?

The BoB input alone is not reliable enough to be used for an emergency stop.

Estop, the emergency stop, that big red mushroom button should be there for emergencies. Water is leaking through the motor electrical connections and on the floor so you could be electrocuted or something in the machine catches fire ... You will be hitting the Estop while running for the door or the fire extinguisher. In those cases you want to kill all power to the machine with that button.
The reason I've put the limit switches on the same loop with the Estop is that I have the sensors for the limit. If the sensor is not stopping the axis, then something should be really bad with mach3 or the motor drive and I want the end switch to stop everything before hitting the end of axis travel.

For minor "emergencies" like loosening the workpiece or hitting a clamp you have the mach3 Stop or Feed Hold buttons.

[Radu_Andrei]

Hi Paulus.v
I also have an emergency estop which cuts power to everything, except the pc and the BoB, but I have never used it. (this being the hardware stop). I did, however used the software estop (input terminals on BoB) a few times, when I messed up gcode programing, and it worked quite well.
Your representation of the work conditions in which the cnc will function are a bit dramatic for a work shop, as I.m quite sure it is not positioned under a waterfall, but as I cannot help notice the flag situated at the left side of your user name it.s quite similar with mine, I think such a Estop described by you, should be very helpful if assigned to our prime minister, leading party and most of the political machine that is running our country. :) Best whishes, and happy national day for 01.12.2018! :)

[paulus.v]

I have read now what problems you had with the grounding and EMF. Are you not afraid to install the homing sensors in your system?
Please do not wire the limit switches as I did! Better wire them in series to a relay coil and from the relay to BoB estop and the stepper drives enable pin if they have it.

If I were in your place I would try to convert all the control circuit to 24V if possible. 24V is the industry standard as it is more reliable and resistant to noise and EMF than lower voltages.

How far is your workshop from the high voltage power lines, measured horizontally?

ps. Our government deserves more than an estop, I wish them many years in jail, and I hope those times will come.

[Radu_Andrei]

A lot of the noise problem was due to improper grounding, which was my fault, but thanks to the patience of the people on this forum, I managed to solve that and many other issues.

I was considering to run the limit swithes on 24v or at least 12v, but they seem to work fine, from the low voltage perspective. They however are very cheap lever switches and tend to have some parts wobble or come loose. I will upgrade to some profesional ones soon in the future.

My workshop is right next to the high voltage power lines. Like 3 meters away. The building existed before the high voltage tower was put in place. I asked a few guys at the City Hall about this issue, but they do not seem to have a problem or an interest in that.

I.m a bit concerned about some aspects of the cnc build, but not afraid. Crashing it, does not seem a big deal in theory, with single drive for each axis.
And it would not be the first time I mess up something in this project. Doing the math, I think I spent around 2500 euro for this project until this point. I bought the components bit by bit, during a few years, with the intent of building it someday. But from this amount, 5-600 euros was the tax for stupidity, representing materials or components, which from lack or knowledge or impatience etc, I ruined. But for the experince aquired, it worth every penny. :)

What I am somewhat afraid, is that, in order to reach a certain profitability with this kind of machine, you need a decent cutting speed, and I might not be able to get that properly. Perhaps I should have bought higher quality components, and make the cnc smaller and lighter. Who knows. I have a few components left from this build so maybe in the future I.ll build a smaller version.

[paulus.v]

Attachment 24669

You are 3 meters away from the double power lines in the picture above? No way!!! There are regulations for a protection corridor of around 30-50 meters along the high voltage power lines. I hope you are not living near... For health reasons it is recommended a distance of 150-300 meters from the HV power lines.

Maybe those power lines are used only occasionally and coincides with the time your CNC starts going crazy. Are you hearing any hum under those lines?