Move Machine to inside soft limits when Probe Basic on

Hi,
So I am trying to move the machine to inside the Soft Limits as when I put the mill/cnc back together the limit switch limits have been breached. I have tried to switch off limits, however, what is the easiest approach to put the X, Y and Z in mid point so I can complete a homing process.

What is the process to move the X, Y and Z axis back to mid point, when the machine says cant because limits activated?

In addition, how do I make sure that the correct positions, X, Y and Z are Min and Max.

Are the following correct?
Left X = Min, Right X = Max
Front Y = Min, Rear Y = Max
Top Z = Max
Bottom Z = Min

Thanks.

on the sidebar WCS tab there is a button called LIMITS OVERRIDE. this will only be active if a limit is currently triggered.

for your min/max soft limits, this is set in the ini file. min is to the negative direction max is to the positive direction. these directions are relative to the spindles direction of travel through the work and the layout of an XYZ cartesian coordinate system. in other words if it is a moving head type configuration (gantry type machine with fixed table) the X+ is to the right and Y+ is to toward the back and Z+ is up.

if it is a moving table such as a VMC, X+ is table motion to the left (making spindle motion through the work in X+ dynamically to the right), and Y+ table motion to the front making spindle motion dynamically towards the back. and Z+ remains the same moving in the upward direction.

how home position is set can be different ways as long as the axis motion is always changing in the correct positive or negative direction relative to the spindle motion dynamically.

aikiaviator wrote:

What is the process to move the X, Y and Z axis back to mid point, when the machine says cant because limits activated?
 

I think you have this a bit wrong. Home switches need to remain triggered until the end of travel. That way, Linuxcnc know which way for initial homing movement. Take the case  of the X axis, Say the home switch is 40mm from end of travel on the left and it stays triggered to the end of travel. If the home switch is triggered when homing starts, Linuxcnc knows it must travel to the right to find the home switch edge. HOME_OFFSET sets the final position. If this is a shared home/limit switch you need to move to the right so the switch is no longer triggered otherwise it will trigger a limit switch error once homing finishes.

If you have seperate home and limit switches, the final position can be in that 40mm where the home switch is held triggered.

good points Rod!

Firstly, I have a PM728vt, using a MESA 7i96S.

Ok, so through some trial and error I have come up with the following for homing, and it is working correctly (i.e. zero out home etc..), however, I have two questions. The one relating to the bottom set of config elements:

These are the current config and are working and displaying on the correct orientation on Main on Probe-Basic. (i.e. tool path direction).

[JOINT_0]
MIN_LIMIT = -480
MAX_LIMIT = 0
MAX_VELOCITY = 10
MAX_ACCELERATION = 4
TYPE = LINEAR
SCALE = 320
HOME = 0
HOME_OFFSET = 1
HOME_SEARCH_VEL = 4
HOME_LATCH_VEL = -1
HOME_FINAL_VEL = 1
HOME_SEQUENCE = 0

[JOINT_1]
MIN_LIMIT = -180
MAX_LIMIT = 0
MAX_VELOCITY = 10
MAX_ACCELERATION = 4
TYPE = LINEAR
SCALE = -320
HOME = 0
HOME_OFFSET = 1
HOME_SEARCH_VEL = 4
HOME_LATCH_VEL = -1
HOME_FINAL_VEL = 1
HOME_SEQUENCE = 1

[JOINT_2]
MIN_LIMIT = -172
MAX_LIMIT = 0
MAX_VELOCITY = 10
MAX_ACCELERATION = 4
TYPE = LINEAR
SCALE = 320
HOME = 0
HOME_OFFSET = 1
HOME_SEARCH_VEL = 4
HOME_LATCH_VEL = -1
HOME_FINAL_VEL = 1
HOME_SEQUENCE = 2

At present it homes and just offsets by 1mm to create 0 home. So machine is sitting in the Right (x), Front (y), Up (z) sections of the machine. What I would like to do is home to the centre of the machine and wanted to know if there was a convention for the limits setup. In other words, should it go from say an example of -150 through 0 to +150, or is convention, 0 to 300.

I feel that I would like to "centre" the machine after homing and wanted to check if the following changes would provide for this. And is this best practice?

[JOINT_0]
MIN_LIMIT = -240
MAX_LIMIT = 240
HOME_OFFSET = 240

[JOINT_1]
MIN_LIMIT = -90
MAX_LIMIT = 90
HOME_OFFSET = 90

[JOINT_2]
MIN_LIMIT = -86
MAX_LIMIT = 86
HOME_OFFSET = 86

The second question is that I have limit switch for the other end of travel, and wanted to know how I can configure the home switch to be both Home and limit without causing errors. I have not been able to get it working as a combination switch, but would like it to function that way.

Once this is done, will be configuring up the Probe and a tool touch off.

Any help welcome. Thanks.

Setting middle of table as home isn't advised in my opinion. This tends to be the desire of new cnc users for some reason but will present some complications down the road once you've started actually machining. It's always best to use 0 home at full movement of an axis, especially if you plan on taking advantage of mdi use. When you use g90 for motion in mdi with a transition it's will require an extra bit of head math. Just a suggestion, but no industrial machines use that centered method.

Ok, so at the moment I have it homing right hand side of X (i.e. moves table to left cutting to right to home), Front of Y (Y- table comes towards front, cutting to rear, to home), and Z (Z+ moves up to home).

The reason for the front homing is I was not comfortable reaching end of travel at the base of the Z upright. But happy to be dissuaded.

Home switches are located X right hand side, Y front, Z top.

So if this was to change, could you please document out the placement for the homing switches, and the values that should be applied? I believe that it needs to progress to rear and right for cutting purposes. Z I believe is correct orientation, but settings on the home, offset etc... I must admit, I have been confused.

For Z for example, is this 0 at the top and homing at the top??

Could you please provide some direction and numbers that would adjust and orientate effectively?

Thanks and appreciated.

Ok, so it should be 0 to max travel correct? And that means homing switch is on the left, table moving to the right. Allows for cutting moving from 0 to max travel. Y is confusing for me as I could not work this one out and have correct orientation on the screen. Z, homing was recommended for the top, correct? So how is this configured normally. Does anyone have an example config? Standard xyz mill.