Tolerance Study for Almirah

Tushar Zala : - 171173119146

Devarsh Kaka : - 171173119507

Kaivalya Kavi : - 171173119030

• Problem Statement:
• As per the assembly sequence, It is possible that Door of the Almirah cannot fit properly with casing of the Almirah while assembling the door with the casing.�So, for this problem we will perform Tolerance study. This study will provide us actual problem with product.

• Assembly Sequence: �Hinge is bolted with casing and support hinge is bolted with Door.�So Casing Hinge will be assemble with Door Support Hinge.��Approach: Here, answering the problem statement we will be perform two study between the casing Hinges and Door Support Hinges.
• Worst case gap between mounting surface of between Casing Hinge and Door Support Hinge.
• Axial Variation and Acceptable Criteria between Casing Hinge and Door Support Hinge.

Casing Hinge

Door Support Hinge

1. Worst case gap between mounting surface of between Casing Hinge and Door Support Hinge.

• In this tolerance study we will be finding out worst case gap between Mounting Surface of Casing Hinge and Door Support Hinge. As per nominal CAD Condition this gap is 0.25 mm as shown in below image.
• From this study we will come to know that at worst case condition is there will be any problem with Door Support Hinge and Casing Hinge during the assembly in vertical Direction.

Nominal Cad Clearance = 0.25 mm

Worst Case Gap = 0.25 mm

PNT A

PNT B

PNT A: On the surface of Casing Hinge.

PNT B: On the Surface of the Door Support Hinge.

​

Target: To Find worst case gap between PNT A & B

Approach: Worst case gap between mounting surface of between Casing Hinge and Door Support Hinge.

Worst Case Gap ?

PNT A

PNT B

A

B

C

D

PNT A: On the surface of Casing Hinge.

PNT B: On the Surface of the Door Support Hinge.

​

Target: To Find worst case gap between PNT A & B

Loop Diagram: To find worst case gap between mounting surface of between Casing Hinge and Door Support Hinge.

Tolerance Stack Report: To find worst case gap between mounting surface of between Casing Hinge and Door Support Hinge.

Result:

So as per worst case, Tolerance variation is ±1.20 mm due to which Maximum Clearance possibility is of 1.45 mm whereas Maximum Interference Possibility of 0.95 mm between mounting surface of between Casing Hinge and Door Support Hinge in vertical direction

Suggestions: To avoid Interference at worst case between mounting surface of between Casing Hinge and Door Support Hinge.

Suggestions:

For avoiding interference at worst case we need to decease to total Tolerance or we need to increase nominal CAD Clearance. So here are two suggestion as per design point of view.

1. Define surface to surface Dimension for Door Support Hinge: This will reduce Tolerance variation by reducing tolerance two major Contributor i.e. ‘C’ & ‘D’. So resulting Tolerance Variation will be 0.75 mm (0.25 mm + 0.25 mm + 0.25 mm) from 1.20 mm.
2. Also we need to decrease the length of Casing Hinge up to 59.25 mm from 59.75 mm.

​

So with these two suggestions, at worst case interference possibility will be neglected.

X.XX ±X.XX

Worst Case Gap ?

PNT A

PNT B

A

PNT A: On the surface of Casing Hinge.

PNT B: On the Surface of the Door Support Hinge.

​

Target: To Find worst case gap between PNT A & B

Loop Diagram: To find worst case gap between mounting surface of between Casing Hinge and Door Support Hinge.

B

Suggested

Tolerance Stack Report: To find worst case gap between mounting surface of between Casing Hinge and Door Support Hinge.

Result after Suggestions:

So as per Suggestions at worst case, Tolerance variation is ±0.75 mm due to which Maximum Clearance possibility is of 1.45 mm whereas Maximum Interference Possibility is 0.00 mm between mounting surface of between Casing Hinge and Door Support Hinge in vertical direction

Suggested

2. Axial Variation and Acceptable Criteria between Casing Hinge and Door Support Hinge.

• In this tolerance study we will be finding out Axial variation & Acceptable criteria between Casing Hinge and Door Support Hinge. Where
• Axial variation: It is maximum possible variation possibility between Casing Hinge Hole Axis to Door Support Hinge Axis considering other hinges are perfectly aligned.
• Acceptable Criteria: It is Float at MMC condition between Casing Hinge and Door Support Hinge. This MMC Float will accommodate axial variation between Casing Hinge and Door Support Hinge.

​

• So at the end of the study, for no fitment issue of the assembly, Axial variation between Casing Hinge and Door Support Hinge should be equal to the Acceptable criteria.

Axial variation= ?

PNT A

PNT B

PNT A: On the surface of Casing Hinge.

PNT B: On the Surface of the Door Support Hinge.

​

Target: To Find axial variation between PNT A & B

Approach: Axial Variation and Acceptable Criteria between Casing Hinge and Door Support Hinge.

Door Support Hinge Axis

Casing Hinge Axis

Acceptable Criteria

Acceptable Criteria: Axial Variation and Acceptable Criteria between Casing Hinge and Door Support Hinge.

Acceptable Criteria

Acceptable Criteria 1:

= {(MMC of Hole 1 – MMC of Shaft 1) + (MMC of Hole 2 – MMC Shaft 2)}

= {(2.30 -2.00 ) + (2.80 – 2.00)} / 2

= {(0.30) + (0.80)}/2

= ±0.55 mm

So acceptable criteria for the Assembly of Casing Hinge & Door Support hinge is ±0.55 mm

• So if for no Fitment issue, Axial Variation should be less than or equal to this acceptable Criteria i.e. ±0.55 mm.

Loop Diagram: To find Axial Variation and Acceptable Criteria between Casing Hinge and Door Support Hinge.

Clarification of “B”

A

Datum A

Casing Hinge

B

Datum A

Casing Hinge

B

Assembly Float1

(Not Considered as used for Adjustability)

E

Datum A

Casing Hinge

D

F

G

Clarification of “C & D”

Datum A

Casing Hinge

D

Assembly Float 2

(Not Considered as used for Adjustability)

Enlarged View

Enlarged View

Aligned Side

C

Tolerance Stack Report: Axial Variation and Acceptable Criteria between Casing Hinge and Door Support Hinge.

Result:

So per tolerance study, at worst case Axial variation is ±2.10 mm between axis of Casing Hinge and Door Support Hinge.

Conclusion.

Result:

So per tolerance study, at worst case Axial variation is ±2.10mm between axis of Casing Hinge and Door Support Hinge, whereas our acceptable criteria is ±0.55mm,

Thus in this case there will be fitment issue with the existing design.

​

To avoid fitment issue, below are the suggestions for design changes.

• We can provide slot in Door hinge support Bracket of Ø3.00 ± 0.2 X 6.5 mm
• This will increase our acceptable criteria from ±0.55mm to ±2.30mm
• Below is the calculation, with suggested dimension of the slot