Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: boydage on June 20, 2017, 02:55:24 AM
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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.
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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
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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
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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
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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.
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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
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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!
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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
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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.
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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
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Aw I dunno! Its all about moving with steps instead of pushing a wheel around by hand mate. I am getting fantastic results except for the glitch previously mentioned. I guess that my experience with my cnc router has put me in the position I am in. What I am achieving is kind of a manual lathe operation but done by a pc.
Not sure how it could be improved. I can put CAD into a piece of material.
Hey but thanks Rich
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The lathe is different than the router. Frankly I think it is more complex because of the tool geometry and all that goes with it. Also the screen set is different and has additional buttons and DRO's. Yes, one may find a certain way that things
turn out ok. Like Clint said " Tell Me, feel lucky today". ::)
Have fun,
RICH
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Hi. Umm ok?
I am always respectful of experience and knowledge. All I know is I have managed to find a solution to machine parts in an automated and accurate way without having to sit there manually taking lots of small cuts. Not to mention the beautiful way a radius can be cut by cnc.
I dont understand here I am lucky with results? What am I missing?
I do apologise if I am seemingly simplifying whats going on with my lathe but the only problem I have had is the one that has disappeared. I did read the threading writeup. But in all reality to require tolerances so fine you are talking about perhaps an aircraft turbine level? I am an aircraft engineer by trade. There is nothing else I have come accross since that needs such fine work. What I am working on is woodworking machinery. My own.
Hey but thanks for wishing me luck from up there on the soap box.
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Happy that it all works for however you work.
Not a soap box... just some thoughts about threading:
As an engineer you know the importance of proper application of standards and the required tolerances to create a properly fitted bolted or screwed joint
and how the standards can be used in the manufacturing of components.
Most folks just machine a screw and the nut goes on and life is good. Life is good, they are happy, so am I for them if that's what they want to accomplish!
Code defines tolerances, my writeup just makes one aware of them and address why one may not achieve the tolerances.Threading was screwed up for a long time
and and working with Art we were able to fix it. We had to achieve lead tolerances and FIG 4.4.5 gives the basis.
What most folks DO NOT know is that calc's are done and there is a lot to designing, specifying, and getting the proper components to meets specifications.
They don't care, the nut goes on! You can't take that approach if your presenting basic threading information.
Thoughts from a process / mechanical engineering designer,
RICH