[truckeic]

Very Confused about where to mount my home switches...

I put my Z at the top of the column so I would assume it would home in the + direction.
I put my X at the left side of the table which would home in the + direction
I put my Y in the front (closest to me) and it home in the - direction.

What I would like to know is the left front corner the place to home? and if that is so the when homed the X can only go in the negative direction and the Y only in positive right?

[routalot]

Is there some reason why you can't locate the home position as you describe?It appears to be logical and the positive direction of travel for X would be to the right and for Y it would move front to back.Having z homed at the top is also logical and you should generate a homing sequence that has it as the first axis to home.When machining you can locate the part datum and orientation to suit I would imagine.

[truckeic]

Is there some reason why you can't locate the home position as you describe?It appears to be logical and the positive direction of travel for X would be to the right and for Y it would move front to back.Having z homed at the top is also logical and you should generate a homing sequence that has it as the first axis to home.When machining you can locate the part datum and orientation to suit I would imagine.

I guess that was my question...Does it matter?

Since I am new to this just wondered? I assume you would home the machine then mount your work and locate the work coordinates to somewhere in the middle of the X and Y travel right?

Correct me if I am wrong but when the X axis MOVES to the right it is a positive direction correct... and Y is postive going away from you toward the column correct?

Thanks!!

[Jim Dawson]

Correct me if I am wrong but when the X axis MOVES to the right it is a positive direction correct... and Y is postive going away from you toward the column correct?

Thanks!!

Here is the normal layout for mill axes, home position can be anywhere that you want it.



Unless your home switches are very accurate, it is better just to zero off of the part that you are working on. There is really no need for a home position unless you have a tool changer. I don't have home switches on my mill, but I do have the ability to set a floating ''parking position'' to move the Z and table to a convenient location for tool and part changes that is invoked on a tool change command or program end. This is set per the job on the table.

[truckeic]

Here is the normal layout for mill axes, home position can be anywhere that you want it.



Unless your home switches are very accurate, it is better just to zero off of the part that you are working on. There is really no need for a home position unless you have a tool changer. I don't have home switches on my mill, but I do have the ability to set a floating ''parking position'' to move the Z and table to a convenient location for tool and part changes that is invoked on a tool change command or program end. This is set per the job on the table.

I just want to make sure of this....
So if I am facing my Mill and the Table is JOGGED to the right (moving in the right direction) the DRO should be going positive correct? and if the Table is jogged to the LEFT that would show negative direction on DRO correct.
Jogging Y away from me should give me positive movement on DRO and Y close to me would be Negative correct?

I want to make sure my Motors are turning the correct directions and homing in the correct directions.

Thanks for all the help!!

[cncuser1]

I just want to make sure of this....
So if I am facing my Mill and the Table is JOGGED to the right (moving in the right direction) the DRO should be going positive correct? and if the Table is jogged to the LEFT that would show negative direction on DRO correct.
Jogging Y away from me should give me positive movement on DRO and Y close to me would be Negative correct?

I want to make sure my Motors are turning the correct directions and homing in the correct directions.

Thanks for all the help!!

Do the following with a felt tip marker:
-stand in front of the machine, facing it, as the user.
- in the physical center of the table make a dot
- the dot is home.
- draw a line through the dot in the left/right direction, from one end to the other end of the table.
- on the right most end of the line, ON THE TABLE, write +X
- on the leftmost end write -X
- draw another line through the dot, perpendicular to the first line.
Furthest from you, at the end of the line write +Y
Closest to you write -Y.

[Jim Dawson]

I just want to make sure of this....
So if I am facing my Mill and the Table is JOGGED to the right (moving in the right direction) the DRO should be going positive correct? and if the Table is jogged to the LEFT that would show negative direction on DRO correct.
Jogging Y away from me should give me positive movement on DRO and Y close to me would be Negative correct?

I want to make sure my Motors are turning the correct directions and homing in the correct directions.

Thanks for all the help!!

You have to look at it from the perspective of the tool bit (looking down).

Table moving Right = DRO X going Negative
Table moving Left = DRO X going Positive
Table moving Towards the Column = DRO Y going Negative
Table moving Away From the Column = DRO Y going Positive
Tool Moving Closer to the work (down) = DRO Z going Negative
Tool Moving Away from the work (up) = DRO Z going Positive

https://en.wikipedia.org/wiki/Cartes...rdinate_system see the image at the top right on the page.

The coordinates shown are what your DRO should read when the tool bit in the position of the dot.

[cncuser1]

There are two main purposes of limit switches.
1- In the case of any sort of malfunction the limit switch at the end of a travel will be triggered before one part of the machine crashes into another part of the machine. For example, If you are using Mach3 and disable Soft Limits and jog the X or Y axis till it reaches the end of the travel and the motor starts stalling makes noises...this is bad...don't do it, avoid it! Well if you had a physical electrical switch at the end of the travel, it would be tripped/triggered and stop the travel even if there were instructions to keep going, Its a safety mechanism.

2- limit switches allow the machine to get a rough idea of where it is. If you program your machine to know a switch is at 30 and you trigger the switch, well you just told the machine it is in fact at 30 and not -5. This is a referencing function. But it may not be as precise as you need to machine. So the limit switches may give you a position +/- .5 accuracy, but your machining operation may need +/-.01. So it will be good enough to avoid crashing and maybe rough machining but if you have a jig, you may have to reference off the jig also!

To be honest I don't have limit switches, Soft Limits in Mach3 are good enough for me.

[109jb]

The home position really doesn't matter. It is only a reference position only. You can put the home switches wherever you want or where is most convenient.

[mactec54]

Very Confused about where to mount my home switches...

I put my Z at the top of the column so I would assume it would home in the + direction.
I put my X at the left side of the table which would home in the + direction
I put my Y in the front (closest to me) and it home in the - direction.

What I would like to know is the left front corner the place to home? and if that is so the when homed the X can only go in the negative direction and the Y only in positive right?

If that is where it works best for you then that is where you want them to be, Home switches double as limit switches also and is what soft limits are associated with so are an essential part of any CNC machine operation

[109jb]

There is really no need for a home position unless you have a tool changer.

While it is true that you can get by without home switches, they are very useful for not having to zero every time you turn on the machine. For example, 90% of my work is referenced to the fixed jaw of my vise, which is keyed to the table. I never have to zero the Y axis on power-up because I can just home the machine and it is set to within 0.0005" as the jaw offset is retained. Likewise if I am working on a part and don't finish it, I can just power down the machine, and when I power-up the next time simply home and the zeros are all set and ready to go. Without home switches you are required to re-zero every time you power up or reset the controller.

[Jim Dawson]

While it is true that you can get by without home switches, they are very useful for not having to zero every time you turn on the machine. For example, 90% of my work is referenced to the fixed jaw of my vise, which is keyed to the table. I never have to zero the Y axis on power-up because I can just home the machine and it is set to within 0.0005" as the jaw offset is retained. Likewise if I am working on a part and don't finish it, I can just power down the machine, and when I power-up the next time simply home and the zeros are all set and ready to go. Without home switches you are required to re-zero every time you power up or reset the controller.

You turn your machine off? I just move mine to 0,0 and hit the E-stop.

[dazp1976]

I home mine to the table centre and top of the column.
I don't use limit/home switches just the software limits.
Couldn't be bothered to fit any as soft limits works for me, can be a pain though to get machine co-ordinate 0.0 back exactly if it does go out.

At days end with Mach3 I send machine home G28 and turn off. Next day I turn on and just hit ref all home button and good to go. It's stayed in position.

It would be easier to go to a corner but my Y axis overhangs the base and I don't like to leave it in that position for any length of time.


In my view having a machine home position is important because when G-codes start G28 G91 Z0 it will send the machine home first. If home is incorrect it can cause damage if you have no physical limits unless you change the G28 lines.

[109jb]

Don't confuse homing and limit switches. The OP asked specifically about homing switches and where to home. Home switches can serve double duty as limits, but can also be totally separate and independent switches.

A good homing switch will have good accuracy. I use proximity switches for homing and have tested them to be accurate to within 0.005" (0.01 mm). I have also tested mechanical switches and the ones I tested were only a little worse (0.001" or 0.02mm) accurate. A lot is dependent on the homing sequence and what the homing speeds are set to.

Saying a switch can only be used for the machine to "get a rough idea of where it is" may be true for a crappy switch, but is totally false if using a switch that provides good repeatability.

[truckeic]

Thanks for all the great info and replies. This forum is indeed great..


Sent from my XT1635-01 using Tapatalk

[jurgenM23]

Strange things that you are embarrassed about. I would be embarrassed, literally for one second if several naked girls came to me and jumped at me

[jurgenM23]

Sorry for my hectic fantasy

[alexgold29]

Yes, I certainly would not refuse such an outcome of events Beautiful girls - this is my weakness. I can not do anything with this.

[truckeic]

So just to help out this newbie...

Homing a machine is really on necessary if you are using offsets and fixtures correct? there is no other reason to do it?

[Jim Dawson]

So just to help out this newbie...

Homing a machine is really on necessary if you are using offsets and fixtures correct? there is no other reason to do it?

About half the members here are going to disagree with this so I'll put my flame suit on, but...........

For the purposes of this discussion I define required homing accuracy as +/- 0.0005 inch or better. This only applies to mills and lathes, there is some logic to using homing limits on a router because extreme accuracy is not normally required.

The only reason to home a mill is if you have a tool changer and need to move the head and/or table to a specific location to effect a tool change. Other than that, the zero should be set to the work or fixture on the table and everything should be relative to that 0,0,0 position.

Limit switches are almost required for overtravel protection, but are normally not accurate enough for absolutely locating the machine coordinates. There are limit switches available that do provide micron repeatability, but normally only found on higher end machines because they are expensive. A proper homing routine uses the index pulse on the servo encoder for final positioning. If your machine does not use servos, the homing can not be accurate.

My knee mill does not have any homing provision, not needed. My Haas does home, it has a tool changer. My lathe also homes. Both the Haas and the lathe use the servo index pulses for final home positioning.