how would a machinist program this?

[rhmeng]

This might not be the correct thread but I have a part with some curves/radii in it, and I want to make sure I am dimensioning it as easy as possible for the machinist. The way it is currently dimensioned I know that you can figure out the curves if you do all the math, but how would a machinist actually go about and do this? Do they have a program where they can easily drop these radii in and make them all tangent? Or would it be easier if I gave center locations to all of the radii? Also is it easy for a machinist to program a profile for whether the machine should follow the outside or the inside of the radii? I have several parts like this and i want to make sure the drawings make sense. Please see attached.

 

[JNieman]

Just draw the part accurately and simply and they'll make it work. No two machinists will want the same numbers (radii centers vs radii tangent points vs apparent intersection pts). It also depends on what the controller is, whether it's programmed at a computer on some sort of CAM software, or if it's programmed at the machine using some manual input on the controller.

If you don't know much about machining (and even if you do) you'll do more harm than good by trying to make a funky drawing "made for the machinist" rather than an appropriate design drawing that adequately defines the part and shows the design intent.

The best thing you can do for the machinist is to not over-tolerance your drawing. If a three-place dimension is defined as being +/- .005" then you should really ask yourself if you need that tight of a tolerance on fillet radii.

tl;dr: If there's enough information on the print to /draw/ the part; there's enough information on the print to machine the part. Your desire is great. It's good that you wish to look at your output as if you were the person making the part. That will solve a great many things, but at a certain level 'unintended consequences' arise.

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All that said, the only exception is if you're making actual "shop drawings" at which point you should be asking your shop (and honestly shouldn't have to ask, unless you have a supervisor that can answer them)

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NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[KENAT]

Please don't multiple post rhmeng you have it here and other in GD&T and now have replies both places.

Didn't you have a similar question about dimensioning curves a few weeks back, or am I thinking of someone else?

Dimension it based primarily on functionality as JNieman says.

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[rhmeng]

yea sry i was looking for a reply from both ends, the engr and the mfgr. Too many times I talk to people and they just throw something on a drawing and make it the other guys problem.. they actually somewhat came to the same conclusion as far as how to dimension, saying there is not really a more correct way and just to design to the part functionality. I had a similar question a while back but I wanted input from the machinist point of view, lesson learned. Thanks.

 

[MikeHalloran]

Most machinists can do trig way better and faster than I can, but it saves time and money to help them avoid doing any at all.
... e.g. by providing center locations for radii, and providing coordinates for tangent points. If that results in the part being overconstrained, mark some of the dimensions as reference.
... but first, if at all possible, go find the machinist who will actually make the part, and have a nice chat about how to dimension the part to make manufacture and inspection easy and straightforward.

Bring doughnuts.


Mike Halloran
Pembroke Pines, FL, USA

 

[MikeHalloran]

Oh. Important Shop Rules:

Don't bring food or drink into a temperature controlled shop.
Don't rest drink or food on a machine way or a surface plate.


Mike Halloran
Pembroke Pines, FL, USA

 

[BillPSU]

A machinist would have a print with the necessary information including what needed to be machined and the tolerances. The manufacturing engineer would have defined the methods to be used by the machinist based on additional information.
What is the material? Aluminum, cast iron gray, cast iron ductile, cast steel, cast austenitic stainless steel. Is this a cast part needing milling on the end or a flame cut part or a forged part or a bar stock part?
Is the part heat treated after machining? Is the part plated?
How many do you need to machine one, 10, 100, 10,000?

I was a N/C and a CNC programmer for 12 years and machined many different parts on many different machines. I manually and later used computer assist to program many parts and used paper tape/mylar tape. Machines today have a nice interface and many programming features built into the controls. Many of my programs were manually written and manually put on tape. Give me what you want and I can make you a program. Give me all the information.

Bill

 

[dgallup]

Our machinist respond better to biscuits, might be a Southern thang.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[silveringchap]

A component drawing should provide all the necessary info to manufacture the part. This may mean the machinist reaches for his calculator but he should be able to work out his intersection points with the dimensions provided. But, the machinist will know the programming language and be able to create the program so it may help to know how he would prefer the profile to be dimensioned.

 

[capnhook]

Iges file, perhaps?

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[dicer]

The cnc programmer would import your cad drawing and use it to machine the part. If it is done by manual G code programming all the tangent points that is the angles and start and stop points need to be calculated. If that is how it is to be programmed it will help a bunch showing those calculated dimensions, and scaling up the drawing to a much larger size.