Messages

1671

LazyTurn / Re: I am having trouble with tool size

« on: March 04, 2014, 01:54:48 PM »

The inscribed circle ( IC) definition is incorrect on page 16 of 50 - Rev 8 of the Lazyturn Manual.
The inscribed circle, diameter in the cataloges I looked at, is inside and tangent to the tool's edges.

By default, a button tool is round thus IC = the button tools diameter.
A button tool can't have a different sized radius. Also a  square tool can't have a IC equal to it's width.
So if you have a odd ball shaped tool not represented by the standard insert tool selection then you may want
to use say a groove tool and limit the flank cut depth.

Just remember that LT uses tool info to check and apply anti gouging so if you trick the software gouging is affected.

So the value you input for IC should be the button tool diameter.  The program won't allow you to
input a radius value for the Tip Radius of a button tool and will default to the input diameter as you replied.

Tip Radius applies to other tool shapes since they can have different tip sharpeness even though the IC's are the same.

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Now note the following:

Page 19 of 50 in the LazyCam Manual states:
"Use Tip Center - When selected will discriminate between using Mach3's offset registers with compensation , or
just to create the code pre-compensated using the tip radius as that compensation from the tip center."

I generated the code both with and without checking  "Use Tip Center" and the generated code was exactly
the same. In the generated code, only a G40 was generated, thus compensation is cancelled. Upon backplotting the
code one will find that it is all pre-compensated with the cutting edge away from the profile a distance equal to the
button tools IC and not it's radius.

See attached pic.

RICH

1672

LazyTurn / Re: I am having trouble with tool size

« on: March 04, 2014, 05:56:23 AM »

pstenabaugh,

I'll get back to you with an full explaination on what LC actualy does rather than post something from memory since it's been a while since I used LC and want to verify what I post.  

Later today............,

RICH

1673

Show"N"Tell ( Your Machines) / Re: Chiron FZ12 on its way sometime soon(ish)

« on: March 02, 2014, 07:23:15 AM »

Hey Hood,
Surely you must have a good feeling about the machine. Lots of work,time, and money but it is great when a plan comes together and the shop has new capability.

 RICH

1674

General Mach Discussion / Re: smoother circles?

« on: February 27, 2014, 08:33:15 PM »

Echo what Ray said.........heck, I'ill go one step more......dump the "etch a sketch" programs and get a CAD program.
LC is just an importer and garbage in = garbage out!

RICH

1675

CS-Lab / Re: Lathe Threading

« on: February 27, 2014, 01:40:22 PM »

Russ,
Just some more stuff .......

In the simple threading wizard the pitch for a 48 tpi thread would be rounded to  =1/48=0.021 if you input 0.0208,
but, the generated code uses whatever you input and you will see the F value in the G32 code.

So if one knew or had an idea of a tweak and wanted to adjust the feedrate some in the Gcode to account for some lead error you could do it.

...............

Pulling out cleanly would best be done with a pullout over a rev or two. Don't think instantaneous pullout is possible.
Again you can experiment some. It will realy show on say a two start thread and should  be 180 degrees out from each other with no burrs. Sort of the same idea as using a scribing on the disc at the start of a thread. You can take this to another level by adjusting the start location and playing to see how the lathe accelerates from a distance.

....................

Again in general.......threading will only be as good as the "LATHE SYSTEM" and the better you want it to be the more you need to pay since  you pay a lot for increasing accuracy.

RICH

1676

CS-Lab / Re: Lathe Threading

« on: February 27, 2014, 09:06:11 AM »

Not sure how small your talking about Russ.

There is a real challenge on single point threading ( better to chase maybe ) for very small threads.

A good example is a 0-80. For a class 2a the lead tolerance / allowable error for a length of 0.1" is
only 0.00052". Then also consider some other tolerances like the diameter, tool radius, accuracy of setup, etc.
Depth of the thread is only 0.01083" for a truely sharp pointed V tool, but any tool has a radius, say 0.001 to
0.003 no matter how one sharpens it, thus dosen't take much to screw up that kind of thread if trying to
achieve a certain class. The pitch diameter range is only 0.0018". So setup based on the tool to be used becomes very important.

The next biggy is the CNC lathe as it must exceed the requirements. X axis repeatability must be better than the
tolerances  your trying to hold, spindle runout can come into play, same for the Z axis but it also is controlled by the index. You can check the total Z axis repeatablility by scribing a very small tick mark 1/2 to 1 thou on a trued thin disc and seeing how much it varies say for  a number of tries and the mean average will will give you a good indicator of repeatability for YOUR Z axis. Actualy you can do it with a double disc and compare the start to the finish of the thread, say 1" for a 0-80, do some math ...measure with a microscope....meticulous / time consumming but good to keep one out of the bars. A different approach is to do multi start threading as it is similar to just mentioned test.

So in summary, small and accurate requires all the stuff associated with threading to be good and there is not much room for error.  

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Practicaly speaking, I have cut 0-80's on the Sherline into 1/16" dia weld rod but the converted Atlas was more conistant / privided better therading and that would be expected.

---------------------------------
Electronic gearing is realy neat. Using an encoder on spindle and slaving the Z  to the spindle ( done with IMS, which i used a long time ago) one could turn the spindle by hand and could cut small fine threads. So if you wanted to spring pass a thread,just rock / trun the spindle back and forth and you could almost polish the thread and you had complete control of the x feed. The carriage just tracked in sink with spindle perfectly with the slightest movement.

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Art said electronic gearing would be possible, Mach code would need to be reworked, and a defined developement procedure would be rquired and that was a few years ago.

FWIW,

RICH

 

1677

General Mach Discussion / Re: DRO doesnt match gcode move

« on: February 23, 2014, 06:43:07 PM »

Check for backlash and also make sure the steps per are accurate.
Movement is only as accurate as the components that mechanicaly drive it.
RICH

1678

Tangent Corner / Re: About Motors

« on: February 23, 2014, 06:40:04 PM »

You got my curiousity Russ.

Don't have any rpm checkers here that are accurate enough to check the motor rpm.
If you get a loan of one make sure you know what the % accuracy since don't think some of cheaper ones will give you +-1 rpm at 1750.

Way back, when we were checking the index on my lathe, we used  a very accurate pulse counter and compared index input to Mach vrs displayed rpm and pulses sent to the axis and it was very close. I know that varying belt tension on say a stepper that it will change steps per unit, but the steps per unit are repeatable per rev.

I do have faith in the DRO readout as being accurate, again based on what Mach is being told.
The problem is one needs to isolate each step for comparison, as you simply did, but that must be compared to a known / calibrated standard. IE. indexer puts out x pulses compared to an electronic device that is more accurate then the index output.

RICH

1679

General Mach Discussion / Re: Lathe Threading - RPM inconsistent

« on: February 23, 2014, 06:03:14 PM »

Russ,
3.042 is corrrect. 

RICH

1680

General Mach Discussion / Re: Machine running in slow motion

« on: February 22, 2014, 05:35:48 AM »

I am still trying to understand what Rich said

.

- cruise control - 60 mph on the turnpike....constant speed and no direction
--        "                    "                         going north  velocity  / motion in a direction ( velocity is a vector quantity)

- sitting at the light with the car, revving her up, pop the clutch, 0 to 60 in 4 seconds - zero velocity to 60 mph in 4 sec ........ acceleration
-- 60 mph on the turnpike going north......floor the gas peddle ..60 to 80 mph in 3 sec - change in velocity in a time frame

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Acceleration and velocity are related and frankly it gets complex quickly since what we are realy talking about is the ability of the
motor to make the axes move. Mach controls how the motor is going to spin but the machine and machining  limits the motor
movement. 

So in general you have the following:

In practical applications one defines an acceleration desired and finds what is required to achieve it ….or ….. accepts the value based on some other parameters. One could say that they are either designing a system to achieve the task or they accept their system
“ as is “ and the acceleration is defined by what they have.

RICH