Home/Limit advice, please

More
10 Jun 2020 23:11 #171007 by blockbuffer
More (potentially) dumb questions - sorry!

Pushing to hard stops sounds good, and that lines up with advice I've been able to dig up, over in the wiki.

But...This is a Taig, and the hard stop for (say...) X is on the right end of the table, along with its stepper.

This leaves things feeling backwards, as my HOME position value should probably be 11.7", vs 0.0", when up against the hard stop on the right.

Seems like I should probably reverse the axis coordinates, so that the hard stop on the right becomes 0.0". Am I misunderstanding this?

And if not, there's the matter of how to do that so that the physical axis and its GUI and DRO representations are consistent. Suggestions?

Thanks!

- Bob

Please Log in or Create an account to join the conversation.

More
11 Jun 2020 00:46 - 11 Jun 2020 00:46 #171027 by andypugh
Replied by andypugh on topic Home/Limit advice, please
It's simpler if the home / stops are at or around zero, but that just means that you configure so that _machine_ coordinates of that axis are negative.
Nearly every Z axis is configured with zero at the top of travel.
You don't work in machine coordinates so don't even notice.

Do _not_ reverse an axis. That will mean that G-code males mirrored parts.

So, it is quite normal to see home 0, max 0 min -127mm
Last edit: 11 Jun 2020 00:46 by andypugh.

Please Log in or Create an account to join the conversation.

More
11 Jun 2020 07:36 #171084 by bbsr_5a
Replied by bbsr_5a on topic Home/Limit advice, please
you can set the numbers to your need
even REF to the right and stop in center
[AXIS_1]
TYPE = LINEAR
HOME = 235.0
MAX_VELOCITY = 20.0
MAX_ACCELERATION = 120.0
STEPGEN_MAXACCEL = 200.0
SCALE = 100.0
BACKLASH = 0.1
FERROR = 1
MIN_FERROR = .25
MIN_LIMIT = -235.0
MAX_LIMIT = 236.0
HOME_OFFSET = 474.000000
HOME_SEARCH_VEL = 3.000000
HOME_LATCH_VEL = 3.000000
HOME_FINAL_VEL = 5
HOME_SEQUENCE = 2

Please Log in or Create an account to join the conversation.

More
12 Jun 2020 15:27 #171266 by blockbuffer
Thanks, gents!

Seems stable now, and it *might* be ready to move on to cutting air - here's an update. Any thoughts?

One of the issues I was having earlier was that I'd test moves in MDI and not get consistent behaviors. I was *assuming* that moves would be incremental. Nope. I think there may be a random-mode-default generator in the background. :-) Once I started setting G91 explicitly in MDI, that settled down and I started to get the incrementals that I expected.

The mill currently passes the simple test of moving a given distance on an axis, and then returning the same distance, to its hard stop. This for all of XYZA.

I did take advice to just bump the axes at the hard stops and pass on using switches. That's the advice in the wiki for hobby mills as well - just took me a while to find it. Yes, the steppers make some noise if they stall, but apparently, no real harm done.

This is a Taig 2019CR-ER mill, so the table's a bit larger than the original.

X Axis
The motor and its stop are on the right side of the table, so from the stop position (table hard left), the only way the table and workpiece can move, is to the right.
Home = 0.0
MIN_LIMIT = -11.75
MAX_LIMIT = 0.0
HOME_OFFSET = 0.0

Y Axis
The motor and its stop are on the front of the table, so from the stop position (table hard to the front), the only way the table and workpiece can move, is inward, toward the Z pillar.
Home = 0.0
MIN_LIMIT = 0.0
MAX_LIMIT = 5.0
HOME_OFFSET = 0.0

Z Axis
The motor and its stop are at the top of the Z pillar, so from the stop position (headstock hard up), the only way the headstock and tool can move, is downward, toward the table.
Home = 0.0
MIN_LIMIT = -0.0
MAX_LIMIT = 6.0
HOME_OFFSET = 0.0

One oddity, is that for the Z axis to pass a move-out-then-move-back-home test for some given distance, the MIN_LIMIT had to be "-0.0", because "0.0" would fail with a complaint about hitting its soft limit. That got solved, but it's peculiar...

Thx!

- Bob

Please Log in or Create an account to join the conversation.

More
12 Jun 2020 15:35 #171269 by tommylight
For a mill, the X and Z axis are set wrong, X should always move on the positive side and Z on the negative.
So for X
min limit can be 0
max limit should be positive value of how far can that axis move.
For Z
min limit has to be the bottom of the travel, so -6
max limit should be 0

Please Log in or Create an account to join the conversation.

Time to create page: 0.078 seconds
Powered by Kunena Forum