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Author Topic: Lathe Threading. Fantastic but just need one final answer. Sorry, two!  (Read 2657 times)

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I love the threading wizard in Mach 3.

I think I do understand that both axis need to move for a preliminary handshake to be formed between the spindle speed and the cutter. So I begin a cycle, the X and Z both move in a direction, then come back, and begin the thread cutting operation.

My first question is, what determines the direction the cutter moves when it is, calibrating itself against the spindle? Today, I set it up to thread and once I started it, the cutter instead of moving away from the chuck  and in, decided to go towards the chuck.

Also second, when I was threading a large pipe, the cutter went a very long way before returning to begin threading. Why so far? Poor encoder?

Just wondering what I can do to resolve or if someone can help me understand would be fantastic please.

Offline RICH

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Have a read of the write-up Threading On The Lathe-Mach 3 Turn. Should find it in the MAch3 directory and if not it's in Members Doc's.

RICH
HI Rich. This is a post you are referring too? I looked at quite a few posts and could only find problems etc. Also I was not aware of Members Docs, I will take a look. Thanks mate.

Boyd

Offline RICH

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My first question is, what determines the direction the cutter moves

A negative thread length input in the wizard and   the tool moves towards the heads stock, and positive value it would move towards the tail stock, if you have your axis direction set correctly.
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This is a post you are referring too

Look in the Mach3 directory where mach3 is installed on your computer since  the write-up  was included with the installation, if not there, then look in Member's Docs.

RICH
Hi Rich. Yes I understand that mate. As of previous though, when I press cycle start, the tool will move in and towards the tail not cutting. Then it returns back to the workpiece to start cutting a thread towards the headstock. This first movement I believe allows Mach 3 to synchronize with the heads speed?

My problem now, is that when I hit cycle start, the tool moves into the head. Know what I mean?

Anyways I will have a readup.

Offline RICH

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I don't know how you  are setting up to machine a stock and  and that may be why your getting the movement.
You should allow approx. length of 3-5 x pitch before actual cutting takes place.

Now if you read the write up I explain in Section 2 / Page 4 how threading works in detail.


RICH

 
Hi Rich,

Mate I read a lot of the write up. I was unable though to find anything about what my tool-post decides to to prior to entering the workpiece to begin threading.

Very strange. Today I needed to make a piece. I set it all up as normal and now, when I hit "cycle start", the tool moves away and back from the chuck. It then came back to complete a thread that I found satisfactory.

So its working now, but I am still no clearer why last time it went so wrong!

Offline RICH

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How do you reference your machine, set home position, and define where the part is away from home?

Here is what I basicly do to set up for a job with no switches , front tool post being used:

1. Set Machine Coordinates 0,0 and home to the same location. That location is based on using the master tool and
   far enough away from the stock for a change of the longest tool, but minimizing the travel from home to
   the stock. So Machine coordinates 0,0, home position, and tool change location are the same.
   Note that those locations are relative to the master tools controlled point.    KISS !

2.Define where the stock is. A G54 work offset is created which is the distance from home to the stock.

All GCODE for part machining is based on the parts center line and end / face of the stock. Thus the parts location
is just the G54 work offset from home. If you look at the first few lines of code you will see that the first move
is always from home to the parts first path.

Be home when you open the wizard and I also set G76 set to G32 code output so I can monitor the pathing.

Must note that I use a custom screen set and probing is done to automate most of the above.

FWIW,

RICH
Hi Rich.

Thanks for that. Mate you know what? I don't reference anything! I did install a home switch at the rear of my tool post and also in the middle of the bed but actually dont believe I have used them.

I guess what I have been doing is to just face off a piece and work from there. Ok. I will stop being so lazy and actually set my lathe up instead of just using it lol.

Although yesterday was very satisfying making up a part with several cuts and then threading the end without having to pull out my die set.

Offline RICH

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I don't reference anything!

One MUST understand the basics of CNC. I know where your coming from.
Using a cnc machine in that fashion is like driving a car in the dark with no lights.

RICH