My cnc minilathe

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19 May 2011 21:31 #9939 by willburrrr2003
I have my machine running now, still a few bugs to work out....but very happy with it so far. This video shows my first automated cut, and then at end I pan out showing my lathe, control panel, and pc screen.



This was done with my first g-code program running, just a simple facing cut but I am happy to be learning fast and getting better with the machine and making the machine better too. If you can see the point on the end of the work piece, that is not supposed to be there. Turns out I was loosing steps on the x-axis due to a setting on my controller board. I have fixed that problem I think, and will know when I get my tool post mod done and mounted back on the cross-slide. I got rid of the compound piece of the compound cross-slide, so that I could turn larger materials on the lathe. I can comfortably turn 4" roundstock with the mod I am doing...and just happen to have 4" roundstock ready to make a fly reel ;) once up and running....
Regards,

Will

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24 May 2011 20:02 #10033 by andypugh
Replied by andypugh on topic Re:My cnc minilathe
Looks good.

Can I just point out that that is an awful lot of workpiece protrusion, and also an awful lot of tool protrusion? Typically you would try to cut a lot closer to the chuck, and a lot closer to the toolpost.

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24 May 2011 21:59 #10043 by willburrrr2003
Replied by willburrrr2003 on topic Re:My cnc minilathe
Thanks Andy, I am pretty new to CNC so any other advice you wish to throw my way is most welcome! If in the future I have to turn stock that long for a particular part, is it ok to do so like that or should I setup the tail stock to hold the protruding end? I will set up my tooling closer to the tool post on my next cut (have to wait for modified tool post mount to come back from my friend, I am modifying so I can work some 4" aluminum stock I have to make a fly reel...)

Regards,
Will

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24 May 2011 22:19 #10044 by andypugh
Replied by andypugh on topic Re:My cnc minilathe
I tend to use a tailstock centre for anything with more than 4x final diameter protrusion.
(But bear in mind that I have no formal machine-shop training either).
You will find that if the work sticks out too far you will tend to get a taper, as the work deflects more away from the chuck than near it. You are also likely to get chatter.
If you don't have the tailstock adjusted right, though, that will tend to force a taper too. Tailstocks are generally adjustable at right-angles to the bed specifically to allow the turning of shallow tapers. (That does involve turning the old-fashioned "between centres" way).


If you are machining a thick bar down to a long, slender diameter then something that you can do with CNC is do a series of very short operations, at the extreme that would be machining to a diameter with a sequence of facing cuts which stop short. That way the slender diameter is always supported by the remaining material.

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25 May 2011 07:44 #10053 by willburrrr2003
Replied by willburrrr2003 on topic Re:My cnc minilathe
Thanks for the tips Andy :D , I managed to get enough free time tonight to install and test my z axis limit switch and z-limit/home switch. here is the results of my work tonight.



I started at 0.0, and issued the home command. The switch triggers at 1.0, then it backs off to 0.0. My other limit switch triggers at -9.085, should I set my axis travel to be just shy of the switch...or at the point the switch trips (....z table dimensions are -9.0 to 1.0 or z table dimensions are -9.085 to 1.0) ?

Regards,


Will

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25 May 2011 09:35 #10055 by andypugh
Replied by andypugh on topic Re:My cnc minilathe
EMC2 will stop the axis exactly on the travel limit. You probably want to be sure that the limit trip doesn't trip at that position.

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26 Jul 2011 11:53 - 26 Jul 2011 11:55 #11867 by BigJohnT
Replied by BigJohnT on topic Re:My cnc minilathe
Will,

Looking good... I can't tell but it looks like your limit switch is mounted so that in case of over travel it might be damaged.

In this photo of an over simplified lathe set up you can see that the carriage can travel to the limits without damaging the switch.



John
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Last edit: 26 Jul 2011 11:55 by BigJohnT.

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26 Jul 2011 12:07 #11868 by andypugh
Replied by andypugh on topic Re:My cnc minilathe
elvistaylor wrote:

Can u know the limit trip time for that machine running to shop..


Sorry old chap, I don't quite follow your banter.
Could you consider rephrasing the question?

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27 Jul 2011 19:54 #11927 by willburrrr2003
Replied by willburrrr2003 on topic Re:My cnc minilathe
BigJohnT wrote:

Will,

Looking good... I can't tell but it looks like your limit switch is mounted so that in case of over travel it might be damaged.

In this photo of an over simplified lathe set up you can see that the carriage can travel to the limits without damaging the switch.



John


Yes they are positioned where if an overtravel ocurred then the switch could / would be damaged. I figured that 1) the hard limit would prevent the over-travel, and 2) the Soft limits would prevent the travel reaching the limit switch. and with these two conditions in place that the possiblity of crashing into my limit switches would be extreamly slim.... I can look into re-mounting as you showed in your example, as it would be a better way of doing the same funtion...

Regards,

Will

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27 Jul 2011 20:14 #11931 by BigJohnT
Replied by BigJohnT on topic Re:My cnc minilathe
I just mentioned it as all the few machines I've seen are set up so the limit switch will stop the machine traveling at a rapid rate before it reaches the hard stop, which sometimes means going over the switch some as it slows to a stop. If your talking a stepper machine with little power and the hard limit stops it before damage is done to the switch your risk is lower.

John

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