# Union not working

**URL:** <https://discourse.shapr3d.com/t/union-not-working/23894>\
**Category:** Modeling Questions\
**Created:** [February 1, 2023, 11:05pm UTC](https://discourse.shapr3d.com/t/union-not-working/23894 "2023-02-01T23:05:29Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![derekstavis](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.shapr3d.com/derekstavis/32/8220_2.png) [@derekstavis](https://discourse.shapr3d.com/u/derekstavis)\
**Post date:** [February 1, 2023, 11:05pm UTC](https://discourse.shapr3d.com/t/union-not-working/23894/1 "2023-02-01T23:05:29Z")

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I often struggle with the Union tool, even though I believe I have done my steps in the right order. This an example of parts that will not union doesn’t matter what I do.

This is my sketch plane and all the lines that make up to this design:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/f/a/fa40152df5902f124ba90c2f90372993c9d0eff5.jpeg)

Every feature has been extruded by selecting the slices from the sketch and pulling/pushing up/down.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/f/a/fa6a469ff679c77af9623c2b3a4ff8f71554de6d.jpeg)

The outer and inner rings were the ones extruded first, then these 5 parts were extruded from the plane:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/a/3/a3a267079f1013228697716a180d15554fc16ff9.jpeg)

Trying to union either the 5 parts with the inner ring or with the outer ring does not yield a unique part:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/8/f/8fcf1e8c3d6ff2f3d2042e97e1121355845ce591.jpeg)

When I zoom in a lot, I can see that the arc is not perfect, and sometimes does not intersect the rings:

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/a/8/a89fa3407567ed5dc980bfc19c72303824c5896a.jpeg)

Even weirder: The sketch does not align with the extrusion anymore

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/3X/7/f/7f76287db12f32e695559c5b8096bec940934201.jpeg)

I have no idea why this happened, and I don’t think that the sketch or the order of steps here was wrong.

What is going on here? Is this a precision issue, a sketch issue, or what?

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<div class="post-metadata">

**Author:** ![Cjacob](https://avatars.discourse-cdn.com/v4/letter/c/51bf81/32.png) [@Cjacob](https://discourse.shapr3d.com/u/Cjacob)\
**Post date:** [February 1, 2023, 11:14pm UTC](https://discourse.shapr3d.com/t/union-not-working/23894/2 "2023-02-01T23:14:34Z")

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Hi,

Seen the same issue, try “overlapping” the two or more objects and then union. Would suggest doing a sample first, then try on your above design.