Constraints, CPlanes, GD&T's

I’m curious to understand the difference between the R8 ‘new stuff’ of ‘auto plane’ and the regular ‘cplane to object’ approach.

I’ve decided that Cplanes are in fact crucial to the whole parametric ideologies. And I intend to focus on them a fair amount.

I believe that no matter the part type, the “Cplanes” should be exploited as much as other parametric programs do.

Pretty much any part file should contain an intuitive interface to the XY, XZ, YZ planes – as well as an assortment of auxiliary types and of course any custom type.

Yes, Rhino has ‘named cplanes’ etc, but the key here is intuitive access to such a GUI.

I am interested in seeing how GH will empower me with said Cplane functionalities.

This is close to what I’m thinking, and similar to something I’ve seen before in GH:



Somem like this:

I’ve got a few projects that came across my desk recently, which might give me some motivation to learn more about GH. I’m going to try turning them into some examples for GD&T / Constraints testing. I’ll most likely be attempting to use GH for the parametrics and anything that will help.

The first one will be a rectangular type part. The other part I have on my list atm, is more of an angle-bracket type part. I might put them in separate threads.

For the rectangular part this is literally all they gave me to work with fml lol:

not even sure which holes should be countersunk, so will update later :smiling_face_with_tear:

I’ll be doing updates over time, to demonstrate how things are going.

My theories behind dimensional / geometric – constraints – is mostly based on principles of degrees of freedom in design intent / features n’ such. I’ll be focusing on the ‘constraints’ principles. The GD&T portion is more of a tangential detail in this regard.

I’ll be using GH to learn as I go and see what I can do with it for these demonstration purposes.

Finally finished the GH primer :sweat_smile:

For the sake of time I might just do this all manually the old fashioned way and just dream about doing it via constraints, and add constraint style stuff later, cause the boss might get mad if I take too long on this :rofl:

Initial file prep:
rectangular_plate.3dm (2.9 MB)

I’ll add more developed versions later.

I’m mostly sharing this job to make it more interesting for me :sweat_smile: and also to provide real world example for what I’d like to use ‘constraint’ style technology for – until a good constraint-UI exist, it will mostly be theory and prototyping.

From the initial setup you can see the rectangular prism looking object appears to be real close to the dimensions of 3"x6"x0.75".

The problem here is I don’t know exactly what the design intent is or even the tolerances. However, it would be nice to be able to still setup the whole job in a manner where those 3 simple dimensions can be adjusted at any time via 3 simple inputs, to be whatever they need to be and automatically adjust. Hence, dimensional and geometric constraints.

For now I will just use the dimensions shown in my first screen shot, cause that’s what the silly thing measures via my digital calipers. And without the customer telling me what they want, I can only guess.

Apparently this thing will interface with a Fanuc M-16iB series robot, so I’ll try to upload the bad GD&T data I got for that in a minute.

I’m not even sure this will suffice. I might have to measure the robot directly or find better drawings lol. I’m not sure what they mean by h7 or H7

So far I used some midline references, offsets, and mirroring. Of course there’s many ways to constrain geometries n’ such. Basically used one 11/32" circle and mirrored it twice, then wirecut.

I will have to figure out the countersink angle later (similar previous job was 90 deg) and decide on some type of cone shape there.

similar prev job with diff dimensions, just checking countersink reference.

Using metric units referenced in an inch unit file should be fun :joy:

Would be nice if the hidden lines were dashed a little better. :neutral_face: Oddly the print looks bettter than it did on screen …

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What’s GD&T

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Geometric Dimensioning and Tolerancing


Exactly :sandwich: :smile:
Geometries Dimensions and Tolerances :smiley: Just that stuff you’re supposed ta put on your layouts to tell ppl how to make something :upside_down_face:

The tolerances are important cause it tells the manufacturer how much to charge you to make it :joy:

At least they know when parts are good or bad, cause anything out of spec is not good haha.

The mistake some designers make is thinking manufacturers can achieve perfection 0.00000" .

Without indicating the allotted tolerances, you leave interpretation out the window. You could end up with “slop” or end up with a huge bill invoice for “rocket parts”, when they should’ve just been “trinkets”.

Constraints will be my main focus on these latest projects I’m obligated to work on. I think Degrees Of Freedom (DOF) is the foundation of ‘constraints’.

I remember being taught that DOF should basically be 0 when things are fully constrained. And depending on how designs are driven, 0 DOF might not always be the goal, but is the basic idea.

Somem like this:

Boss got mad at me today for having too many questions, not understanding the design intent, and not having their designs done, and not having the robot running parts, so I had to kibosh the parametric stuff for now. :sweat_smile:

I got two questions on my mind still about the design I have to come up with out of thin air, and still have to add the tolerances, material type (6061 Al), etc:

Woulda been nice to receive a drawing close to something like this from the get go. But guess it’s too much to ask. :sweat_smile: Always fun when clients want magic to happen and us to read their minds.

The final question on my mind is what the potential quotes might be for the price a machine shop would charge to make a part like this, so I might reach out to get some quotes, as I’m curious if another shop could do this cheaper and faster than my self. Will be fun to get some quotes.

If I had to hold 5 place decimals I’d probably charge you a million bucks. :smile:

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ikr :sweat_smile:
Here’s an updated version with tolerances added:

I still have to add the countersinks, and maybe surface callouts. And I am just guessing on the tolerances since the ‘boss’ didn’t give me any lol. Not sure how you can read their minds when they’re not even thinking of a number :joy:

So, basically the plate will have 0.511" of distance, plus the 10mm for the silly robot (0.39"+0.511"=0.901"… 22.9mm) estimated length, which means I’ll need to check mcmaster for some examples of each pitch and decide on some fasteners. I will probably just buy a box of each and just use 90 deg heads.

Looks like mcmaster only giving me a thread pitch of 1mm under some standard parameters, so guess I’ll have to wait till monday to see n’ reverse-engineer the pitch off the silly robot. For now I’ll use 1mm as example.

Not sure what this feature is called lol:

Their draftsman must’ve been using solidwrks … haha jk

Funny way to model threads haha:

Oh well I can fix it later…

Just realized I don’t have some of the dims for the hole locations.

Almost a fully workable print:

There’s definitely room for improvement in terms of Rhino’s interface relative to dimensioning and placement. The placement of diameter and radial dimensions is still very frustrating in Rhino.

History breaking is silly. Dimensions should simply be parametric.

That’s a fit tolerance H for holes h for shafts.

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That’s good to know. I appreciate the knowledge. :beers:

I’m working on a new print. I’ve been wondering about this anomaly, and today I’m remembering seeing this before.

vector vs raster:

Someday I hope to have better control over the hidden line characteristics. And it would be nice if we could add ‘centerlines’ similar to how we can add ‘centermarks’, but with more control options.

weird print anomaly:

current state of file:

rectangular_plate.3dm (8.4 MB)

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Tried print to pdf to mitigate the issue, but seems to still have the anomaly. It would be great if the user had more control.

looks like no difference between 300dpi and 150dpi – at first glance, but later I think it helped…

print preview:

print result:
rectangular_plate_150dpi.pdf (197.8 KB)

Hmm, this looks like it might suffice:

Now, I’ll have to try printing the pdf to the printer :joy: :sweat_smile:

Looks like the print came out as it looks in the pdf. I wish Rhino would print this from the get go.

Decided to research what already exists in the market for ‘Fanuc M-16iB series robot Tooling Adaptors and Flanges EOAT’, thought this looked interesting:

Would be fun to buy an off-the-shelf-part like that and send the customer the tracking number :joy:

They want to use this silly bracketry too: McMaster-Carr

Could model it with constraints but, for now I’ll just download it :smiling_face_with_tear:

Customer wanted 11/32" holes. I’m changing it to 8mm :yawning_face:

This other part will be derived out of this material:

I need to reduce this 5.75" dim down to 4". Actually based on how the silly draftsman dimensioned it, I would have to make that particular dim 4"-.25" so 3.75" lol

For now I’ll just wirecut it and moreface haha

driven dimensions would be cool though

Teknic does a beautiful job with their GD&T’s

bout ta download their stp model which is awesome :sunglasses:

Now I got to figure out how the customer wants the next part designed :joy:

Wish they would just give me the design intent and .3dm’s so I wouldn’t have to read their minds :sob:

Next I’ll have to make the mastercam files and create setup sheets. Eventually machine some one-off prototypes and hope the customer gets what they think they wanted lol.