[sshroff100]

Hi
My new machine is responding to command, like M3,M4,M5,G00 X2....Now i need to setup machine home limit?
Should i move machine on manual mode and bring to all axes + side and set home limit , what number i setup, X-12" Y-19" Z-5" A-5",or different? is that any material? can help?
any one know how or any idea?:idea:

[sshroff100]

No one know how to set up reference or home position on mach3,
shop master don't have limit switch, so home reference is important to set,
machine need to know home position.

[j2mariashop]

No one know how to set up reference or home position on mach3,
shop master don't have limit switch, so home reference is important to set,
machine need to know home position.

The Shopmaster does not have physical limit or home switches but you can set Soft(ware) switches. What I did on my 2012 machine was:
1) jog each axis to the spot that you want to designate Home. In my case, Z Home was at the tailstock end (Z++), X Home was the furthest away from the spindle-tailstock center-line towards the operator (X++), and Y Home was at the top most position of the mill head. (Z,X and Y here are from Mach3 Turn's perspective). All movements are then in the -ve direction.
2) Select Machine coordinates in Mach3 Turn's Manual screen and then click Set Home Z and Set Home X. The axes DRO in the top left should now be 0.0.
3) From this position I also set Soft Limits in under Config/Homing Limits. My Soft Max for both the X and Z axes was 0.0. The Soft Min for the Z axis is -12.5 and for the X axis -6.7. I did not move the Z axis to the very end near the tailstock as I wanted some clearance in front of anything I mounted in the tailstock. At the other -ve end of the Z axis, my -12.5 Soft Min was a function of allowing a safe clearance between my LH tool and the chuck jaws.
4) In the Auto Screen, turn on Soft Limits On/Off so that the light is green.
5) Click Auto Override in the Diagnostic Screen so that you can jog off a limit though this is for physical switches.
You have to, I belive, reset Home each time you turn the machine on so that Z and X Home Referenced lights turn on in the Manual screen.

I am in the process of fitting physical limit switches on the Patriot. I am a complete beginner but learning a lot as I go along. I will keep you posted on my Limit switch journey!!

[j2mariashop]

These are notes I - a complete newbie - made to digest my understanding of home and limit switches. These are probably very basic for the users of this forum but it was my way of understanding all the nuances. It took me only about 3 painful weeks to figure this out and lost much hair in the process. If there are any errors please correct!!

Installing Home and Limit Switches in Mach 3

There is no real need for physical home and limit switches as Mach3 can replicate these switches virtually in the software. Mach 3 scans the GCode to check if the max. and min. limits of axes travel is within the soft limits (see below for how to set). If any movement is outside the soft limit, the code signals this and does not run. The only risk is you forget to turn on Soft Limits (see below) and then the axes drive motors could crash against the ends of an axis. Physical switches can prevent operator error causing damage.

Setting Soft Limits

The Shopmaster does not have physical limit or home switches but here's how I set up soft limits on my 2012 machine:

1) jog each axis to the spot that you want to designate Home. In my case, Z Home was at the tailstock end (Z++), X Home was the furthest away from the spindle-tailstock center-line towards the operator (X++), and Y Home was at the top most position of the mill head. (Z,X and Y here are from Mach3 Turn's perspective). All movements are then in the -ve direction.

2) Select Machine coordinates in Mach3 Turn's Manual screen and then click Set Home Z and Set Home X. The axes DRO in the top left should now be 0.0.

3) From this position I also set Soft Limits in under Config/Homing Limits. My Soft Max for both the X and Z axes was 0.0. The Soft Min for the Z axis is -12.5 and for the X axis -6.7. I did not move the Z axis to the very end near the tailstock as I wanted some clearance in front of anything I mounted in the tailstock. At the other -ve end of the Z axis, my -12.5 Soft Min was a function of allowing a safe clearance between my LH tool and the chuck jaws.

4) In the Auto Screen, turn on Soft Limits On/Off so that the light is green.

5) Click Auto Override in the Diagnostic Screen so that you can jog off a limit though this is for physical switches.
You have to reset Home each time you turn the machine on so that Z and X Home Referenced lights turn on in the Manual screen.

Terminology Basics for Limit and Home Switches

Normally Closed (NC) and Normally Open (NO) Switches

A normally closed (NC) switch is exactly what its name says: under normal operation of the machine, when the switch is ON, the circuit is closed allowing voltage to flow through the circuit from the power source to the ground. When a normally open (NO) switch is ON, no voltage flows through the circuit as the open switch prevents the circuit from being completed.

Active High and Active Low states

NC and NO switch systems can be designated as Active High or Active Low. Usually in the transistor-transistor logic (TTL) circuits found in a PC, a high voltage is between 2.8v to 4.8v and could be assigned a binary value of 1, while a low voltage is between 0v and 0.8v and could be assigned a binary value of 0. Input pin #s 10 through #13 and #15 take voltage inputs from the machine to send signals to the software.Pin #s 1 through #9 and #14 send signals out of the PC to the machine. In my wiring system, pin #2 is used to send PC power (4.8v) to the limit switch circuit and pin #11 is used to receive an input from a limit switch.

In an Active High system, under normal operating conditions, the voltage measured at an input pin (#10 through #13, #15) is Low since the high voltage is bled away to ground before reaching the input pin. When a limit switch in an NC system is activated - the switch is now Active - the circuit opens and the high voltage is redirected to the input pin changing it from its normal operating Low voltage state to an Active High state. This kind of a system is called a NC Active High system.

The advantage of using a NC system is that if a wire breaks, the circuit opens, lowering the voltage and triggering an alarm. In a NO system, a broken wire is viewed as just another normally open "switch" in the circuit. NC systems are also better at managing electrical "noise" that might confuse the switch because a closed circuit has low impedence. Another problem is that a NO Active High system (tells the machine to do something when the voltage is high) can be accidentally triggered by a voltage spike.

In an NC Active High system all the limit switches can be wired in a series (from one to the next to the next and so on) and connected to just one input pin. This kind of a system (a series of 6 switches on my machine) is called an "OR" system. If either switch 1 OR switch 2 OR ...switch 6 is triggered open, Mach 3 will recognize a Limit or Home switch has been activated. Under an OR system ,in the Diagnostic Screen, the LEDs for all 6 switches will light up when any one switch is tripped.

Hardware setup:

Wiring the Switches

My switches were bought from Dan Mauch of Camtronics (Camtronics, inc. -- CNC with Dan Mauch). Each switch has a NC, NO and Com prong (see photos at the link below). On my 2012 Patriot, each axis has an NC limit switch on one end and a second NC switch that doubles as a Home and Limit switch at the other end. All 6 NC switches are wired in series as follows: the wire first goes from the NC prong in switch 1 (Y++ Limit and Y axis Home) to Common (COM) in switch 2 (Y- Limit), then from NC of switch 2 to COM of switch 3 (X- Limit),and so on to X++ (X++ Limit and X axis Home), and then to Z- Limit and Z++ (Z++ Limit and Z Home at the top of the mill. Finally, NC of switch 6 is connected to the V-ground on the CNC power supply panel which for my 2012 Patriot also has a black wire that connects to pin #12 (power supply ground) on the Gecko 540 board.The COM of switch 1 is connected pin #2 on the Gecko 540 board. None of the NO prongs is connected. The circuit is as follows: 4.8v PC power from pin #2 flows through all 6 NC switches and goes to ground at pin #12 (power supply ground) on the Gecko 540 board through the V- ground onthe CNC power supply. When a switch is tripped, the circuit opens and 4.8v is diverted from ground to pin #11 (now Active High) and tells Mach 3 to stop the machine.

https://picasaweb.google.com/1169829...MfNg5G004XGIA#

I use 16 guage wire inside plastic protective sheaths, kept at least 1" away from any stepper motor and power cables to prevent "noise". The longest run for a wire is less than 4'. I did not use shielded cables. Finally, protective plates are mounted over the switches to keep swarf and any fluids off the rollers.I used a multimeter to check continuity each time I added a switch. After the system was wired, I measured approximately 4.5v across each switch (Active High). Since the voltage was more than 4v, I did not need the 470 ohms "pull-up" resistor shown in the Mach3 manual that should be added to the wire before it goes to the v- ground. After each switch was connected I checked for continuity.

Software setup:

Getting Mach3 to recognize the switches:

I used Mach3 to define the Limit and Home switches. Select Config/Port & Pins/Input Signals. Then click Automated Setup of Inputs. Select the appropriate switch - say, X limit++ at the tailstock end of my lathe - and click Autoset. Now manually trigger the X++ switch. Mach3 beeps, signalling that it has recognized the switch. Select the next switch, click Autoset and trigger the switch. Repeat for all switches and then click OK.

Once all switches have been activated, the Input Signals tab should show a green check mark next to each switch, with the pin #. All my switches are assigned to Port #1, pin #11. There will be a red cross mark in the Active Low box for each switch. This indicates an Active High system - at input pin#11, the default operating voltage is Low, but when activated the voltage at the pin becomes high. Mach 3 now recognizes that there are Active High Home and Limit switches for each axis.

Trigger each switch to make sure the wiring works and that the Limit activated LEDs light up. If they don't, and the wiring has been checked for continuity, change the Active status and test.

Limit Switches in Normal Use

When axis over-travel triggers a Limit switch, the Active High signal to Mach3 stops all movement and the red Reset button will flash. In the Diagnostic Screen, since all switches have been wired in series and connected to one pin, all Limit lights will be on. You cannot move the machine unless:

Auto Limit Override is on in the Diagnostic Screen.This allows you to click the Reset button and then use the arrow keys on the keyboard to jog off the Limit switch. The machine and part need to be re-referenced because stepper motors lose some steps due to inertia and do not know at which machine coordinate they stopped.

Preventing noise from triggering the switches

Unless you have shielded cables there is a fair amount of noise - electrical disturbance - in the switch wiring. Mach3 needs a way to distinguish "noise" from "signal". Debounce is the time a signal must be continually "on" before Mach3 realizes that it is a signal and not just noise. In the General Config tab, in the Input Signal Debouncing / Noise Rejection section in the top right corner, each value in the Debounce Interval box corresponds to 1/kernel speed of time. Since I have my machine set to a kernel speed of 25,000Hz, a debounce interval of 500 is 500/25,000 or 0.02 or 2 milliseconds which is long enough for the computer to realize that it is a signal and not a random electrical disturbance. Since in Config/Motor Tuning I have set my axis velocity to be 50 ipm, the actual distance the machine will move before it realizes that it is a "signal" is 50 ipm * 0.02 / 60 sec = 0.017" of travel beyond the Limit switch. Lowering the interval reduces the overtravel (and damage) but increases the probability of a false signal.

Setting Home:

Home is the location that the machine recognizes as 0,0,0 on the X, Y and Z axes (Machine Coordinates 0,0 which should be displayed in the axes DROs). In Mach3 Turn's Manual Screen, for example, click Machine Coordinates and then click Set Home Z. The machine moves slowly in the z+ direction towards the tailstock. (If the Home Neg box is checked - see below - the machine moves in the z-ve direction towards the chuck looking for the Home switch). When Homing, Limits are not active. When the axis reaches Home, the machine reverses in the -ve direction to move off the switch.Clicking Set Home X will repeat this for the X axis. The machine is now at 0.0 Z and 0.0 X. All movements will be in the -ve direction from Home. This procedure needs to be repeated each time the machine is turned on. The X and Z Home Referenced lights in the top right corner of the Manual Screen will now be green.

If the machine has been referenced to Home on start up, clicking the Home X or Home Z or Home All in the Manual or Auto screen will move the machine to the respective Home location. Clicking Home All first Homes X (moving it clear of the chuck or tail stock) and then Homes Z (in the positive direction towards the tail stock).

If the machine is not referenced to Home on startup, none of the Home buttons will work.You need to reference Home each time you start up the machine.

Diagnostic Screen

All the Limit and Home switche lights in the Input/Output Status Inputs grouping should be off when the switches are closed, and the X and Z DRO should read 0.0 or the value in the Home Off. cell when Homed. The Auto Limit Override switch should be turned on to allow movement off the Limit switches using the arrow keys on the keyboard.

Setting the G28 Home Location

The G28 command returns the machine to its Home position. However, if you share the Limit switch with a Home switch, this would trigger the Limit switch requiring a reset and a re-reference to be done. To avoid this, I set the G28 location to be -0.25" for both the X and Z axes. When the G28 command is issued in a program, the machine moves to -0.25" off the Home switch for both axes.

Setting Soft Limits:

In addition to physical Limit switches, you can set up virtual Limit switches or Software Limits.In Config/ Homing Limits/Motor Home Soft Limits tab, you can set actual dimensions that specify the maximum and minimum distance the machine can travel on each axis. On my machine, for the Z axis, the Soft Max is 0.0" and the Soft Min is -12.50" near the jaws of the chuck. The corresponding numbers for the X axis is Soft Max 0.0" and Soft Min -6.70".

In the Auto Cycle screen, click the Set Soft Limits On/Off to set Soft Limits On. Otherwise, Mach3 will ignore any soft limits you entered. When a program is loaded in the Auto Cycle screen, Mach3 scans ahead to see the max. and min. of axes travel and if any move is outside the soft limit, a warning pops up and it asks if the program should continue.

Turn Auto Limit Override on in the Settings. In case you trip a Limit switch, this option lets you click Reset and use the keyboard arrow keys (manual motion control) to move off the Limit switche.The movement away from the Limit switch will be at a slow jog speed so that you can react if jogging in the wrong direction.If you release the jog arrow key and press it again, jogging will resume at normal speed.

Override Limits lets you literally override the Limit switches. A red light flashes.

Slow Zone and Speed %

You can slow the machine down as it approaches the Soft Limits or Hard Limits/Home switches by specifying the distance before the Limit the machine should start reducing its approach speed. On my machine, I have set the Slow Zone to 0.20" for both axes which means that Mach3 will slow starting from 0.20" before the Limit.

The speed the machine travels at while in the Slow Zone can be specified in the Speed % cell. In my case, I set it to 10% of the axis speed set in Motor Inputs.This only works when jogging the machine. Even though the shift key is held down to enable fast manual jogging, the machine will slow down when it enters the Slow Zone.It has no effect when a G-code program is running.

Home Neg

This box should be checked if the Home switch is in the -ve direction (at the chuck end for the Z axis or away from the operator on the X axis).

Home Off.

Home Offset is the distance Home (usually Home X) is away from the spindle's center line. Say, using the method below, Home is offset from the spindle-tail stock center line by 4.349". Moving towards the spindle center line will now progressively decrease the DRO reading from 4.349 until it reaches 0.0 at the center line.

What is the advantage of having a Home Off.?

The main advantage is that once a Home Off. value has been input, there is no need to reference the part that is in the chuck. Before you start any GCode program, you need to tell the machine where the Part or Program coordinate is relative to the Machine coordinate. For accuracy, this is usually done using the skim-cut method. With Home Off., the machine always knows where it is relative to the spindle-tail stock center line. Since this obviously passes through the center line of the part in the chuck, the machine knows where it is relative to the part. This removes the need to take a skim cut saving time and effort. Both X and Z axes on the lathe can have Home Off. values. In the case of the Z axis, using the face of a chuck to measure Home Off. removes the need for accurate Home Z switches. There is then no need to take a facing cut to set the Z 0 coordinate.

Home Off. however, works only if the Home switches are accurate and can maintain their accuracy repeatedly. Since I have no idea how accurate or repeatable my switches are, I chose the option of not having a Home Off. value and, instead just input 0.0 in the Home Off cell. This means that I have to reference each part before I can start.

Tool Tables.

If a Home Off. value is set after the Tool Table has been filled, all tools would need to be re-referenced.

Setting Home Off.

Clear any values in this cell and click Machine Coordinates / Zero World in the Manual screen. Click Set Home X which will move the machine to its X axis Home location. Chuck some stock and using the MDI line take a light skim cut. Note the value in the top left X axis DRO in the Manual screen. It should be a -ve reading. Ignore the -ve sign and call the value X. Now measure the diameter D of the machined stock in the chuck.

Home Offset (HO) = X + D / 2
This is the distance Home X is from the spindle's center line.

Go to Config/Homing Limits and in the Home Off. cell for the X axis input HO. Now, click Set Home X and the machine will move to the Home X location. Once it reaches Home, the X axis DRO should read the value HO. Now, take another skim cut off the stock and note the X DRO reading. It should be the same as the stock's radius. If it does not match, either the measurement was not correct or the Step/Unit is wrong.

Auto Zero

Connected to Home Off. is the Auto Zero option. If it is checked, then the axis DRO will take the value that is in the Home Off. cell.

[sshroff100]

Thank you great job.