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Author Topic: The Arc Command  (Read 12416 times)

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Offline ger21

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Re: The Arc Command
« Reply #20 on: February 24, 2016, 03:03:16 PM »
Curl the fingers of your right hand into a fist with your thumb pointing out (like the Fonz). If you point your thumb in the positive direction of an axis, your fingers point in the direction of positive rotation.
Gerry

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Offline BR549

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Re: The Arc Command
« Reply #21 on: February 24, 2016, 03:55:38 PM »
I am popping the corn right now (;-)

(;-) TP
Re: The Arc Command
« Reply #22 on: February 24, 2016, 05:02:11 PM »
If I may make a comment when you write gcode as an example it is always best to define teh values in teh normal format and order.  Yes it is OLD school AND some controller can ONLY take a certain format but it does read  much better in my opinion.

Now teh controller will load in Line elements in the order it was programmed to do so to IT order does not mean much But for reading purposes it makes it more clear.

You articles are very good by the way. And will be very helpful to new users.

G02 X0.000 Y0.000 I0.000 J0.000  F123

Instead of

G2 X0 Y0 I0 J0 F123

Just a thought, (;-) TP


Sorry I missed your suggestion. It is a good one and I will make the changes now.

Thanks,

Rick

Offline stirling

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Re: The Arc Command
« Reply #23 on: February 25, 2016, 04:09:15 AM »
LOL - I don't mind admitting you had me convinced it was a bug and now you have me convinced it isn't.

Offline RICH

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Re: The Arc Command
« Reply #24 on: February 25, 2016, 05:19:30 AM »
 rgsparber,

Added your article in Member's Docs called Arc Command - Mill here is the link:
http://www.machsupport.com/forum/index.php/topic,32004.msg222697.html#msg222697

There is an existing thread about arc's for the Lathe, thus wanted to distinguish between the two threads.

For Turn see this link:
http://www.machsupport.com/forum/index.php/topic,11932.msg76353.html#msg76353

RICH

Offline BR549

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Re: The Arc Command
« Reply #25 on: February 25, 2016, 11:28:20 AM »
Trying to explain G18,G19 arc orintation can be confusing . Even Smid makes it very confusing in teh 2nd edition page 240 (;-). His pictures LOOK good until you realise his axis orintation is NOT what you see standing in front of the machine. You would have to flip and rotate his picture for it to fit a normal machine for G18,G19.

Best way to figure it out for yourself is to stand in front of your machine then program it both ways and SEE for yourself where is goes. THEN write it down, draw yourself a picture.

I would refrain from doing an explaination based on standing behind teh machine. Give your examples as standing in front of the machine assuming teh Right Hand rule.

(;-) TP

« Last Edit: February 25, 2016, 11:33:01 AM by BR549 »
Re: The Arc Command
« Reply #26 on: February 25, 2016, 12:13:43 PM »
People learn in many different ways. Some click with the right hand rule so I have added that explanation. But I, for example, prefer having a consistent viewpoint. In this case, looking in the -Y direction.

Thanks,

Rick
« Last Edit: February 25, 2016, 12:27:29 PM by rgsparber »

Offline BR549

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Re: The Arc Command
« Reply #27 on: February 25, 2016, 12:43:29 PM »
IF you only look in teh Y- direction you cannot define G18 arcs as the arc is inline with your veiw.

Here is how I look at it.  Always start by standing in front of teh machine. In G18 teh Z+ is up and teh X= is right. ( For Quadrant #1 that is, but Quads are a different chapter.)  Program a G2 andG3 and see where they go. Draw a picture or write it down.

NOW for G19 assuming a right hand approach MOVE to teh right hand side of teh machine and veiw it. Z+ is UP and Y+ is right. Program a G2 and G3 and note the motions

THen when you are creating 3d Gcode ( and few ever do by hand) refer to the Example veiws.  

Trying to explain it in a way that is not based on a standard gets very confusing as everyone has a different approach and some are backwards to others.

Not saying any way is wrong as long as you get the idea.  Kinda like drawing in CAD there are dozens of ways to draw a simple part. And the finished part will look the same.

BUT IF you are going to explain it you need to reference a KNOWN standard that is defined by the general CNC world.

(;-) TP
« Last Edit: February 25, 2016, 12:51:13 PM by BR549 »

Offline BR549

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Re: The Arc Command
« Reply #28 on: February 25, 2016, 01:27:21 PM »
NOW according to SMID  The arc swing is a mathematical reference NOT a machine plane reference. (;-)

2nd edition Page 240


(;-) TP
Re: The Arc Command
« Reply #29 on: February 25, 2016, 07:06:13 PM »
I certainly agree that the XYZ axes and associated rotational movements are defined by math. In all cases clockwise (i.e. positive) rotation is defined by looking in the negative direction along the axis that is not part of the plane. No exceptions. As commonly defined on mills, the Y axis points away from the operator and towards the column. Looking along the Y axis towards the XZ plane puts you behind the mill. Can't help that...


Rick