For sheet metal design engineer position interviewer ask questions on sheet metal design and manufacturing. To crack sheet-metal design engineer interview a good understanding of basic fundamentals of sheetmetal design will be helpful.
In this article we will discuss common sheetmetal interview questions. You can also contribute your experience by writing interview questions in comment section. We will try to add those questions in this article as well.
What is the standard bending inside radius during sheet metal fabrication?
For hard materials (e.g. CRCA and stainless steel) minimum inside radius is 0.7 times of sheet thickness and for soft material (e.g. Aluminium) minimum inside radius is equal to sheet thickness.
What is the minimum Flange Length in Sheet-Metal Bend?
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 Hole/Slot distance from Edge?
Minimum Distance = 3 X Sheet Thickness + R (Inside Bend Radius)
What do you understand by bending allowance in sheet metal fabrication? How to calculation bending allowance?
When sheet-Metal parts are bend, metal is deformed plastically to change its shape.
After bending total length e.g. (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?
There is a direct relationship between k-factor and y-factor:
What are the surface finish operations on sheet metal parts?
Following are commonly used surface finish operations on sheet-metal parts:
- Pre-Treatment : Phosphate Conversion Coating, Chromate Conversion Coating, Derusting, Descaling
- Powder Coating
- Plating: Zn Plating/Galvanising, Tin plating, Silver plating
What are the design parameters need to be considered while selecting material for sheet metal parts?
Following are the parameters need to 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 the strength of the sheet metal parts?
Reinforcement techniques are used in sheet metal parts to increase sheetmetal strength in a localized section.
- Bending: Bending in direction 90 degree to load applied, hem bend
- Forming tools: sheet-metal rib, louver, lance & Tab
What do you understand by a press tool 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 do you understand by stamping operation?
Stamping is a process of giving desired shape to sheet-metal parts using press tool.
Blanking, punching, pressing, piercing, bending and forming operations are done with stamping dies.
What are various 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 sheet-metal assembly operations?
Depending on the product application sheet-metal assembly operations are finalized. Below we have given some of commonly used assembly operations.
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
Where dowel pins are used?
Dowel Pins are used to align two or more sheetmetal parts during assembly.
What are 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.
During the interview for the sheetmetal industry, interviewer asks questions on sheetmetal manufacturing process, k-factor, material section, finish operations and product verification and validation tests.
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