You shall carefully read job description before the start of every interview. Always ask yourself, what skill set interviewer is looking for? Try to gain those skills. In this article, we will discuss commonly asked sheetmetal interview questions and answers.
What is minimum inside bending radius for sheet metal fabrication?
For hard materials (for example CRCA and stainless steel), Minimum inside radius is 0.7 times of sheet thickness
For softer materials (for example Aluminium) minimum inside radius is equal to sheet thickness.
What is recommended minimum Flange Length for Sheet Metal Bending?
Minimum flange length shall be equal to 4 times of sheet thickness plus inside radius.
Minimum Flange length = 4 X T (sheet thickness) + R (Inside Bend Radius)
What is minimum recommended Hole/Slot distance from Edge?
Minimum Distance = 3 X Sheet Thickness + R (Inside Bend Radius)
What are the general Tolerance followed during sheet-metal Design?
ISO 2768-m is mostly used as default tolerance.
What is bending allowance and how to calculate it?
When sheet-Metal parts are bend, metal is deformed plastically to change its shape.
After bending total length (Length + Height) of sheetmetal part is not equal to Flat Length. This increase in overall length is known as bending allowance.
Flat Length = Length + Height – Bend Deduction
What is K-factor in sheet metal fabrication?
K-Factor is a constant factor, used to calculate the flat pattern using CAD software’s. Value of k-factor depends on material, Bend radius, sheet thickness and machines used.
Mathematically K-Factor is a ratio of position of neutral axis and sheet thickness.Value of K-factor is always less than 0.5
What is Y-Factor in Sheet metal?
Y-factor is similar to y factor. It is used to calculate flat pattern of sheetmetal parts:
What are sheet metal surface finish operations ?
Following are commonly used sheet metal surface finish operations:
- Pre-Treatment : Phosphate Conversion Coating, Chromate Conversion Coating, Derusting, Descaling
- Powder Coating
- Plating: Zn Plating/Galvanising, Tin plating, Silver plating
What are design parameters need to be considered for the selection of sheet metal material?
Following parameters are considered during material selection:
- Product IP-Rating
- Working Temperature
- Corrosion Resistance
- Required Part Strength
- Part Weight constraints
- Final Finish operation
- Part joining Methods (Riveting/Welding/Screw)
What are the reinforcement techniques used to improve strength of sheetmetal parts?
Reinforcement techniques are used to increase sheetmetal strength in localized section.
Various Reinforcement Techniques are:
- Bending: Bending in direction 90 degree to load applied, hem bend
- Forming tools: sheet-metal rib, louver, lance & Tab
What is a press tool and why it is used in sheetmetal ?
Press tools are used in hydraulic, pneumatic & mechanical presses to produce stamped sheet-metal parts.
Press tools can be classified based on operation: blanking, piercing, bending and forming.
What is the difference between progressive, compound & combination tools?
What is stamping operation?
Stamping is a process of shaping sheet-metal parts using press tool.
Blanking, punching, pressing, piercing, bending and forming operations are done with stamping dies.
What are various types of sheetmetal operations?
- Sheet metal Cutting operations: Punching, Piercing,Perforation, Cutting off, Parting off, Dinking, Trimming, Shaving, Shearing, Notching etc
- Material Removal Operations: Deburring, Grinding
- Sheetmetal Forming: Straight bend, Angle bend, Hem bend
- Material Joining Operations: Welding (Tig, MIG, GAS Welding), Riveting, Folding, Screws
- Final Finish Operations: Passivation, Chromate Conversion Coating, Plating, powder Coating
What are various sheet-metal assembly operations?
Depending on the product application sheet-metal assembly operations are finalized. Below some of commonly used assembly operations are given.
Sheet metal parts joining Techniques:
- Screws: self tapping screws, machine screws
- Welding : arc welding, TIG welding, MIG Welding
- Folding Techniques: Lap Joint, Hem Joint
- Press Fitting: PEM Inserts
Why dowel pins are used?
Dowel Pins are used to align two or more sheetmetal parts during assembly.
What is the effect of grain direction in sheet metal during bending operation?
Grain structure of sheet metal is aligned in rolling direction during cold rolling process. Bending in rolling direction in softer materials result in cracks. Therefore bending in the direction perpendicular to rolling direction is always preferred.
To sum up, in this article we discussed the interview questions related to sheet metal industry. As discussed above, Candidate should have knowledge of sheet metal manufacturing process, k-factor, material section, finish operations, product verification and validation tests to successfully crack interview.
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