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Author Topic: what to do first? set home or calibrate part size  (Read 988 times)

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what to do first? set home or calibrate part size
« on: October 19, 2019, 08:59:06 AM »
Hello Chaps,
I am making progress with my mach3 lathe and am getting more comfortable with it every day.
Short question
what is good practise? should I calibrate the part size before setting "home"
or is it better to set home first then calibrate the part size?
regards

fred
think of the trees-- use both sides of the computer paper

Offline RICH

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Re: what to do first? set home or calibrate part size
« Reply #1 on: October 21, 2019, 09:14:32 AM »
I home first and then set the G54 offset to the part. Said differently, the  software is told where the tools cutting edge is located and I define to the software where the part to be machined is located. KISS!

That can be done a number of different ways and I use a custom screen to make it all simple.
I set up manually using probing to find the lathe center, the part, and tool offsets.

Now as Carrot Head once said.....it's not how you pick your nose but rather where you put your buggers that is important!
So home / reference / cutting edge of tool is Machine coordinate X&Z=0 and safely away from the end of the stock such that the longest tool offset clears the stock. The G54 offset is the distance from the cutting tools edge to the part.
   
RICH
Re: what to do first? set home or calibrate part size
« Reply #2 on: November 14, 2019, 12:59:58 AM »
Hello Rich,
I have been following the "pattern" of sequences as follows.

1.switch on the machine.
2.cancel the flashing red button
3.using the manual screen I set home x then set home z
4. put a 30 diameter stock in the chuck
5. jog x axix so the tool just touches the 30mm dia
6. set dro ( the one on top left of the screen) x=40
7. jog the z axis to right hand of stock
8. set DRO to z=0

Is this an acceptable good practice ?
you said that you had a custom screen to make it all simple
could I please get a copy of that screen?
thank you very much
best regards

fred evans
think of the trees-- use both sides of the computer paper

Offline RICH

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Re: what to do first? set home or calibrate part size
« Reply #3 on: November 15, 2019, 06:56:39 AM »
What is acceptable practice is subjective. As a hobbiest you are the boss of your machine shop and can do as you wish. If you worked in a shop you would find that they have typical procedures which you should follow. That said the following higher level sequences should be considered.

1. Confirm that the CNC lathe is configured for how you want to work and is functional.
2. All the lathe tools that are available for use should be defined in the tool table.
3. My words ....... Reference the lathe. Referencing a lathe is just defining to Mach3 where the lathe
    center is located  relative to the tools. ie; Machine Coordinate X =0.
4. Set home location. Home can be anywhere but logic implies that it should be away from the
    stock such that any tool to be used will clear the the stock.
5. Define the work offset. That is the distance ( G54 work offset ) from the tool to the center / face
    of the stock.
    (Understand that usual gcode for the lathe assumes that X and Z zero is the basis of the gcode       and that the gcode is also based on using radius or diameter mode.)

How do I do the above?
I will always just check basic functionality of cnc lathe before using it and know what modes are active. The tool table is populated via probing, and once done, no need to fool with the tool table. Then I probe to find the lathe center. Then I set an appropriate home position. Usualy I will insert the
stock into the chuck before setting home and minimize the tool travel to the work.

Sorry,no plans on sharing my screen set.

RICH
Re: what to do first? set home or calibrate part size
« Reply #4 on: November 18, 2019, 04:29:35 AM »
Many thanks Rich
Your advice is sincerely appreciated
regards fred from south africa
think of the trees-- use both sides of the computer paper