×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Profile of Coplanar Mating Surfaces

Profile of Coplanar Mating Surfaces

Profile of Coplanar Mating Surfaces

(OP)
Hello! I have 3 identical parts (see attached image), which need to be intimately mated using a clamp.

ALL mating round surfaces must be in contact WITHOUT any gaps once the 3 parts are clamped. Before clamping, a very small gap can be tolerated (0.002") and thanks to clamping forces we expect to close the gaps. Note that if profile is used on these 7-inch tall parts, some of the round surfaces could be on their max side or min side, so some will be in contact and some will not until they are clamped.

QUESTIONS:

1) What is the best way to dimension the 3 faces on each side of the part for machining?
2) Should the RIGHT faces (3X) be PERPENDICULAR to the part floor to minimize tilting with PROFILE as additional control (w/ or w/o continuous feature?) ?
3) Should the LEFT faces (3X) be PARALLEL to RIGHT faces?

Thank you!

RE: Profile of Coplanar Mating Surfaces

koorookoo,

Is the base of each piece mating with the floor? Is this critical?

Why do the faces need to mate accurately? Is this structural, or do you need a thermal or electrical contact?

--
JHG

RE: Profile of Coplanar Mating Surfaces

(OP)
The base will be bolted down as well (bolts and details are not shown in the diagram). So, somewhat might have an impact on the above mating surfaces.

Also, the face need to be in contact for vibration (i.e., structural) reasons. If they are in contact, the parts would be more stable as they'd be considered to have a wider base, as opposed to individually, where they'd wobble.

Thanks,

RE: Profile of Coplanar Mating Surfaces

koorookoo,

You need to think your design through quite a bit. I don't think this is a drafting problem.

If your pieces are rigid and you are straining them .002" on assembly, you may be imposing high stresses, at assembly. To get around this, you may need to specify ultra-tight tolerances. Any stresses in service will be added to your assembly stresses.

Consider using side plates to connect your pieces. This will be flexible at assembly time, and it will be rigid when you clamp the bolts down.

--
JHG

RE: Profile of Coplanar Mating Surfaces

(OP)
Thank you drawoh, your advice is well taken into consideration. However, we would still like to know, as originally asked, if all's acceptable structurally, how would one dimension the part?

Profile and perpendicular for one side and what about the other faces? Parallel or profile to first faces?

Thank you again.

RE: Profile of Coplanar Mating Surfaces

Profile can control perpendicularity, so only profile is required. Since the faces on each side are otherwise independent, independent profile tolerances can be applied on each side to the faces; there is no reason to chain the tolerance build-up from one side to the other. Each individual face (6 per part) will need a refinement, such as flatness.

Your original goal is going to be difficult to realize. You need a strain analysis to determine if the parts will deform enough to close the gaps.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources