Create Arc Question

[cruzila]

1 hour ago, gcode said:

This is ridiculous.

Solidworks gave me Ø3.0176

Doing it Bird's way in MC2024 I've done it 3 times and got 3 different answers

In SolidWork

Start a sketch,

sketch a circle in space

constrain it to the horizontal line with a tangent constraint

constrain it to the point with a coincident constraint

constrain it to the angled line with a tangent constraint

 

I'm going to ask our Catia designer to solve this in Catia and see what he gets.

 

Mastercam does not have the ability to make these constraints in this manner

 

3 hours ago, Jake L said:

Here's a video showing another workaround to get the arc I want. 

Dropbox - Create Arc Workaround Example

You learn something new every day!!!!

[Aaron Eberhard]

A bit of a shortcut in your method is that you can skip the "extend the two lines to their intersection point" when you create the circle.   Just hit "i" key or AutoCursor > Intersection and choose the two lines, it'll snap to the intersection.

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You need 2 pieces of information to create a tangent arc. If you have those two pieces of information, you can calculate the missing 3rd, right?

There's a critical piece of missing information to solving this, which is either the tangent point (on the bottom line) or the radius.    Without specifying those two, there's an effectively infinite amount of possible answers.

5 hours ago, Jake L said:

Here's a video showing another workaround to get the arc I want. 

Dropbox - Create Arc Workaround Example

When you extend the bisecting angle lines, you're creating the restriction on the radius (1.50881301") so there's only one solution that fits the end point of the slanted line and the center point (Radius), which means you'll get a tangent point on the lower line at X0.57622467".  Unfortunately, unless you have a specific reason for choosing the centerpoint you did (i.e., it's called out by the print to find the bisecting angle between these two features and create the radius centered off of that?) it's just really a random point in space that confirmation bias makes look more likely to be correct   Note that Tom found the solution in solid works effectively the same way, using Constraints instead of the geometry..

If you use Mastercam's Arc Tangent > Arc One Point, you're now constraining two items:  The end of the angled line and whatever tangent position is closest to that line.  Mastercam will make an arc fitting with whatever radius you type into the panel.

You can make a Arc Tangent > Arc Two Entities, which will do exactly what fillet would do, (in the background) it'll extend the angled line to the intersection and fit an arc of 1" (or whatever you specify).

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Basically, you're not asking the right question.  For two lines of N angle, you can ask:

What radius fits between these lines?   Any of them, pretty much.  What radius is a fillet?  How many windows are in a house?

If I give you a point and a line, what radius fits between those two?  Any of 'em > the distance between the closest point to line.  See above.

If I give you a radius, where does that fit from this point to a tangent point on this line?    THERE YOU GO!  That's the right one

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I can't imagine that any CAD/CAM system can give you what you're asking for, as you're not giving complete information.  

[Jake L]

37 minutes ago, Aaron Eberhard said:

You need 2 pieces of information to create a tangent arc. If you have those two pieces of information, you can calculate the missing 3rd, right?

There's a critical piece of missing information to solving this, which is either the tangent point (on the bottom line) or the radius.    Without specifying those two, there's an effectively infinite amount of possible answers.

Thanks for the reply!

Wanna make sure I understand this statement correctly. You're saying the original question does not have enough information to solve. This is because to create an arc tangent to a line, you must specify the tangent point. The tangent point cannot be derived for the bottom line without the radius, and the radius cannot be derived from the given info (a line and a point on the line).

But don't I disprove this in the video I posted? Like you said, I derived the radius from the given information. Mastercam should be able to do the same thing I did in the background.... right?

1 hour ago, Aaron Eberhard said:

Unfortunately, unless you have a specific reason for choosing the centerpoint you did (i.e., it's called out by the print to find the bisecting angle between these two features and create the radius centered off of that?) it's just really a random point in space that confirmation bias makes look more likely to be correct

I disagree with this statement. The reason I chose the centerpoint I did was because of the original question. I want an arc tangent to the endpoint of the angled line. Only one arc exists that has this characteristic and is also tangent to the bottom line. 

It's entirely possible I'm misunderstanding something here, so please correct me if I am. With that said, I think we all agree Mastercam is not capable of solving the original question "easily".

 

After thinking about Aarons response and writing this reply, I realize I have the capability to attempt to write a chook to solve this issue. I should have time tomorrow night to dig into this. Maybe I'll be another victim of Aaron's signature (love that signature BTW), maybe I'll make something that works. Either way I'll be back with an update.

Another huge thanks for all the replies. Seems like it's been mostly machine-control or mill-turn related questions on eMC recently, was nice to get a CAD discussion going.

 

[Aaron Eberhard]

8 hours ago, Jake L said:

I feel like there must be a function to do this but I can't find it.

I have 2D wireframe (shown light blue) and I want to create the green arc as shown.

Currently I use "Circle Edge Point" set to "2 Points tangent" and adjust the the arc radius until I get something close. But there must be a way to get the exact arc right?

Not sure it matters but I'm in MC2024 TIA

 

 

28 minutes ago, Jake L said:

Thanks for the reply!

Wanna make sure I understand this statement correctly. You're saying the original question does not have enough information to solve. This is because to create an arc tangent to a line, you must specify the tangent point. The tangent point cannot be derived for the bottom line without the radius, and the radius cannot be derived from the given info (a line and a point on the line).

But don't I disprove this in the video I posted? Like you said, I derived the radius from the given information. Mastercam should be able to do the same thing I did in the background.... right?

I disagree with this statement. The reason I chose the centerpoint I did was because of the original question. I want an arc tangent to the endpoint of the angled line. Only one arc exists that has this characteristic and is also tangent to the bottom line. 

It's entirely possible I'm misunderstanding something here, so please correct me if I am. With that said, I think we all agree Mastercam is not capable of solving the original question "easily".

 

After thinking about Aarons response and writing this reply, I realize I have the capability to attempt to write a chook to solve this issue. I should have time tomorrow night to dig into this. Maybe I'll be another victim of Aaron's signature (love that signature BTW), maybe I'll make something that works. Either way I'll be back with an update.

Another huge thanks for all the replies. Seems like it's been mostly machine-control or mill-turn related questions on eMC recently, was nice to get a CAD discussion going.

 

 

Sorry if I used too many words Correct that Mastercam doesn't (to my knowledge) have a way to create an arc from two tangent lines and a single contact point. 

Yep, I was going off of the original problem (at the top of this reply).   What I'm saying is your second reply where you added the video gave the crucial constraint, at that point you've completed the puzzle.

I'm guessing you'll be able to chook it fairly easily now that you've figured out how to do it.   It probably hasn't come up enough for someone at CNC to take a look at it, because how often is this scenario encountered? 

 

[Jake L]

23 minutes ago, Aaron Eberhard said:

Sorry if I used too many words Correct that Mastercam doesn't (to my knowledge) have a way to create an arc from two tangent lines and a single contact point. 

Yep, I was going off of the original problem (at the top of this reply).   What I'm saying is your second reply where you added the video gave the crucial constraint, at that point you've completed the puzzle.

I'm guessing you'll be able to chook it fairly easily now that you've figured out how to do it.   It probably hasn't come up enough for someone at CNC to take a look at it, because how often is this scenario encountered? 

Sorry, misinterpretation on my end. You weren't finding an issue with the original question, you were providing a more in depth explanation to the provided solution.

Thank you sir, this is much appreciated. 

 

[Newbeeee™]

15 hours ago, cruzila said:

Mastercam does not have the ability to make these constraints in this manner

 

You learn something new every day!!!!

Every day is a school day!!!!

[gcode]

22 hours ago, Jake L said:

Here's a video showing another workaround to get the arc I want. 

Dropbox - Create Arc Workaround Example

Way back in ancient times in my high school drafting class we solved hundreds of geometric problems like this,

using a T-square, scale, protractor and a compass. At the time I wondered what the point was, yet 53 years later, here we are.

My old drafting teacher was a strict taskmaster and would be supremely disappointed in me for forgetting the ancient ways.  

[Kalibre]

18 hours ago, Aaron Eberhard said:

You need 2 pieces of information to create a tangent arc. If you have those two pieces of information, you can calculate the missing 3rd, right?

There's a critical piece of missing information to solving this, which is either the tangent point (on the bottom line) or the radius.    Without specifying those two, there's an effectively infinite amount of possible answers.

But the distance from the intersection to the tangent point have to be equal for both lines, always. We've got that for the angled line, it's all that's needed.

Jake: A "tangent - 2 entities - thru point" type option would save you a few clicks, but your doing it right geometry wise with the "line bisect" method. 

 

[gcode]

26 minutes ago, Kalibre said:

Jake: A "tangent - 2 entities - thru point" type option would save you a few clicks, b

I tried this 3 times and got 3 different answers, none of which were correct.

Parametric modelers, Catia, SolidWorks and NX all got the same answer as did Jake's old school geometry solution.

 

[bird2010]

As long as Mastercam corrects the calculation result to the correct value....
Mastercam will be faster than SW NX Catia...

If arc tangent-arc dynamics.... Adding a tangent option can handle this type of graphics more efficiently

[Kalibre]

1 hour ago, gcode said:

I tried this 3 times and got 3 different answers, none of which were correct.

Parametric modelers, Catia, SolidWorks and NX all got the same answer as did Jake's old school geometry solution.

 

I mean if MCAM implemented a proper one. We're in agreement here.

[Newbeeee™]

6 hours ago, gcode said:

Way back in ancient times in my high school drafting class we solved hundreds of geometric problems like this,

using a T-square, scale, protractor and a compass. At the time I wondered what the point was, yet 53 years later, here we are.

My old drafting teacher was a strict taskmaster and would be supremely disappointed in me for forgetting the ancient ways.  

You missed the bit then where he said "Listen up G, in 53 years time you'll thank me for this NOW PAY ATTENTION"

 

[gcode]

11 minutes ago, Newbeeee™ said:

You missed the bit then where he said "Listen up G, in 53 years time you'll thank me for this NOW PAY ATTENTION"

 

I liked that drafting class and at one point even looked at going to a tech college and making it a career.

My dad was a petroleum engineer, working at the bleeding edge of modern tech. This was in 1971/72

and he told me it was a bad idea. He said there was this new tech coming and in 15 years there would 

be no drafting jobs. He was right too. By the late 80's AutoCad and it's kin had decimated the manual 

drafting industry. 

I'd have never made it as a draftsman anyway, My penmanship looks like a drunken chicken scribbling

in the barnyard dust.

 

[Jake L]

3 minutes ago, gcode said:

I liked that drafting class and at one point even looked at going to a tech college and making it a career.

Being young, I've always thought it would be fun to go back to the time before CAD/CAM, but only for a couple days. I have a feeling I would get sick of it pretty fast.

 

[#Rekd™]

Back in high school we had an old German welding/ drafting teacher, much like G-Code describes (drill Sargent/ taskmaster). He would make students cry. I still remember everything he taught us (well I think I remember!!!).

Yes drafting with a T-Square and Vellum paper!

I had an employee retire after nearly 40 years, he didn't use computers.... he would make "quick sketches" (his description) that were nothing short of works of art. Everything neatly scaled, shaded and sectioned and dimensioned immaculately.  

[gcode]

12 minutes ago, #Rekd™ said:

old German welding/ drafting teacher

my drafting teacher made us memorize the factional tables from 0 to 1 by 1/64th

We achieved that, then he demanded 1/128th.

That knowledge really helped me in my early days as a up and coming machinist.

 

16 minutes ago, #Rekd™ said:

works of art. Everything neatly scaled, shaded and sectioned and dimensioned immaculately

I worked with a guy once who could do that in Mastercam V7 ( no solids)

He would design and draft up B/P's for fixtures and tooling that looked like they came

out of the Boeing engineering department.

[Newbeeee™]

37 minutes ago, gcode said:

I liked that drafting class and at one point even looked at going to a tech college and making it a career.

My dad was a petroleum engineer, working at the bleeding edge of modern tech. This was in 1971/72

and he told me it was a bad idea. He said there was this new tech coming and in 15 years there would 

be no drafting jobs. He was right too. By the late 80's AutoCad and it's kin had decimated the manual 

drafting industry. 

I'd have never made it as a draftsman anyway, My penmanship looks like a drunken chicken scribbling

in the barnyard dust.

 

Although my toolmaking apprenticeship, turned into Modelshop/R&D, that quickly turned into the DO at the age of 21. I was REALLY fortunate that my mentor agreed to take me under his wing - he told me "I don't think I can make a silk purse out of a sows ear, but I think I can make a sows ear purse out of you"

But we'd hit it off early during my apprenticeship - while work experience in the DO, he gave me my 1st job which was to copy an existing print. Mylar, 5H and 2H pencils, rule ("we don't call them rulers in here as the Queen of England has F'all to do with this job") square, protractor, compass and the most important thing eraser - and away I went.

The part was the base of an instrument which was square with the 4x corners turned off, and everything was about the C/L - and I thought I was doing okay when he said "that top right quadrant - tatty - have another go at it"....so the eraser got a hammering and 15 minutes later "that's good, but it shows up the bottom right quadrant - have another go at that"....so out with the eraser again and 15 minutes later rinse and repeat for the left hand side....  End of day I remember him saying "the cleaners will love you tonight - look at all that mess on the floor"

But yes, printing was my downfall - CAD was a godsend. There's 2x real arts to being a drafty from a "picture drawing " perspective  - neat printing, and the most important one having the initial visibility of first laying the job out in your head so you know you can then get all views and all dimensions on the sheet.

As with everything now, things change and it's a lost art - but we now have the other extreme where "everyone can use a computer", so everyone thinks they can be an "engineer"!

[gcode]

10 minutes ago, Newbeeee™ said:

"we don't call them rulers in here as the Queen of England has F'all to do with this job"

[cruzila]

Remember getting berated for using the eraser and not rolling the pencil well enough. I still have a drafting table, that thing is heavy!