[1ctoolfool]

How repeatable is the homing function when the machine it powered up?
If I machine one side of a part then turn the machine off.
In the morning I flip the part over, turn on and home the machine, how close will it be and does it return to the same place every time?
So far I haven't had a problem but I wonder if I'm supposed to do this.
thanks
jv

[Mitsui Seiki]

It should return to the same point every time.I have never had any problems with that.

[Al_The_Man]

Most commercial systems capture one edge of the marker pulse (1/rev) of the encoder, which is very accurate.
The main discrepancy would probabally be due to machine growth, The machine in all probabilty will be colder the next day start-up.
Al.

[gar]

070307-1809 EST USA


1ctoolfool:

May be as close as 30/1,000,000" excluding thermal factors with the resolution of the current standard encoders on standard leadscrew machines, assuming zero backlash.

.

[Geof]

To convince yourself do an experiment. Face off a piece of material, turn the machine off, come back next day and home the machine, raise your offset 0.0001", cover the faced off surface with marker pen ink and then face it off again. You will probably just face off a layer of ink and then if you drop your offset 0.0001" and do the facing again you will take off practically all the ink along with some traces of metal.

I have done this to convince a friend that CNC machines are really quite precise.

[pit202]

the homimg of the machine is realized to come near the proximity sensor and find home signal of the encoder , every encoder haas 8192 lines witch is 32768 impulses per revision ( visible at the machine ) , most haas machines has 6mm pitch screw , you can calculate the accuraty of this homing

sory for my poor english.

[mikef137]

I thought the vm machines were 6mm pitch, standard was 8mm, extra rapid option was 10mm, and the ss machines are 12mm?

[pit202]

look at the table, maybe this is a little old , I don`t know.

[DomB]

Hi,

As far as I know when you press power up restart, the machine does not reset the zero position, it just goes back to the home switches to zero the count of encoder rotations so the machine can keep track of where it is, it only needs to know this in complete revolutions as the encoder spins many times as the table travels the full length of the machine. If the zero was set at encoder position 1578 for example it would go back to the home switches to start the count of encoder revolutions to zero. However the encoder would still be using position 1578 at the first rotation as zero. The machine just needs a reference of where it roughly is in complete revolutions, and the precise position comes from the encoder position.

However if you use 'Auto all axis- zero reset' then the machine moves all servos back to the home switches and resets the zeros to whatever encoder position lines up that time, it could be position 517 this time. It is not a problem because all machining will be done relative to that point. In fact the home switches are pretty accurate, but I would not rely on them.

If you set the machine once when the machine is installed, you need never set them again for most use, as long as you always the 'power up restart' button, when you turn on every day. Therefore jobs can be left on the table overnight.

The only time you need to press 'auto all axis-zero reset' is when you change the memory battery on the machine or after a power surge messing all the settings up, or after major surgery like a new processor fitted.

Often when we have a large job that I do not want to move and has a lot of machine hours in it like a mould, i will leave it on the table for several days, even if I put the vice on the bed next to it to do other jobs in the mean time.

Hope this helps
Dom

[Geof]

Hi,

As far as I know when you press power up restart, the machine does not reset the zero position, it just goes back to the home switches to zero the count of encoder rotations so the machine can keep track of where it is, it only needs to know this in complete revolutions as the encoder spins many times as the table travels the full length of the machine. If the zero was set at encoder position 1578 for example it would go back to the home switches to start the count of encoder revolutions to zero. However the encoder would still be using position 1578 at the first rotation as zero. The machine just needs a reference of where it roughly is in complete revolutions, and the precise position comes from the encoder position.

However if you use 'Auto all axis- zero reset' then the machine moves all servos back to the home switches and resets the zeros to whatever encoder position lines up that time, it could be position 517 this time. It is not a problem because all machining will be done relative to that point. In fact the home switches are pretty accurate, but I would not rely on them.

If you set the machine once when the machine is installed, you need never set them again for most use, as long as you always the 'power up restart' button, when you turn on every day. Therefore jobs can be left on the table overnight.

The only time you need to press 'auto all axis-zero reset' is when you change the memory battery on the machine or after a power surge messing all the settings up, or after major surgery like a new processor fitted.

Often when we have a large job that I do not want to move and has a lot of machine hours in it like a mould, i will leave it on the table for several days, even if I put the vice on the bed next to it to do other jobs in the mean time.

Hope this helps
Dom

This did not seem completely correct so I checked on my Super MiniMill.

After the power is turned on POWER UP RESTART homes all the axes and indexes the toolchanger to Tool 1.

After the power is turned on and without pushing POWER UP RESTART ZERO RETURN and AUTO ALL AXIS homes X, Y and A and leaves Z above the tool change position at Z+4.3689 on my machine; it does not index the tool changer. If POWER UP RESTART is then pushed it indexes the tool changer and moves the Z axis to zero.

At any time POWER UP RESTART will home the machine; push it with the machine in any position and it finds machine home again on all axes.

ZERO RETURN and SINGL AXIS only homes the selected axis.

For both ALL AXIS and SINGL AXIS it is necessary to push ZERO RETURN first.

HOME G28 homes all axes, or the selected axis, and it is not necessary to push ZERO RETURN first.