Welding for nut welding|The welding electrode is SMK

Projection welding

Projection welding is resistance welding. A projection is provided on a welding part of base material, the welding current flows through the projection intensively to perform pressure bonding and heating simultaneously.
To energize the projection provided on base material intensively, it is possible to conduct excellent welding. Even if the plate thickness of welding base material is different, it is possible to increase current density by small current, and a nugget (A molten-clotted part occurring in a welded part in lap resistance welding) is formed certainly.

Examples of projection welding

Nut projection welding

Ring projection welding

Nut types

1. Square nut
2. Hexagon pilot nut
3. Round nut
4. Collared hexagon nut
5. T-type nut
6. Cap nut

Clearance hole of upper tip for nut welding

A clearance hole of upper tip is provided, and a breakage of a guide pin and the problem of a spark are remarkably decreased.

SMK products with clearance hole

1. Upper cap tip

2. Upper straight tip

3. Inverse-welding prevention cap tip

4. Missing-part prevention cap tip

Inverse-Welding Prevention Tip, Missing-Part Prevention Tip

Inverse-Welding Prevention Tip

Product

Normal welding

Inverse welding ※Feet of the nut welded to the stainless-steel ring.

How to choose the proper Inverse-Welding Prevention Tip (for square nut)

φd must be approx. 1 mm shorter than A.
If A is 11 mm, φd must be 10 mm.

How to choose the proper Inverse-Welding Prevention Tip (or hex nut)

φd must be approx. 1 mm shorter than A.

If A is 12 mm, φd must be 11 mm.
※Unsuitable for pilot nut.

Missing-Part Prevention Tip

Product

Normal welding

Inverse welding ※No electricity flows.

Welded without a nut. ※No electricity flows.

How to choose the proper Missing-Part Prevention Tip (for square nut)

φd must be approx. 1 mm shorter than A.

If A is 11 mm, φd must be 10 mm.

Examples of combination of Lower Electrodes for Nut Welding

Air & spring type

Lower electrode set for nut welding ＞

Air type

Guide pin for nut welding, Air cap for nut welding Selecting method (SMK recommendation)

Selecting method for square nut and hexagon nut

The hole diameter of an Air cap is equal to the lower hole diameter of a work piece.
Outside diameter of Guide pin

In case of 3S(KCF)Air pin
Please choose a 0.1～0.2mm smaller one than a Air cap hole diameter.
(Lower hole diameter of a work piece)

In case of ceramic based Guide pin
(G Guide pin, Siliguide pin, Aluguide pin)
Please choose a 0.1～0.2mm smaller one than a Aircap hole diameter.
(Lower hole diameter of a work piece)

G-guide pin Aluguide pin 3S air pin for nut welding

Example

In case of 3S(KCF)Air pin with M6 nut (Lower hole diameter of a work pieceφ7)

In case of ceramic based Guide pin with M6 nut（Lower hole diameter of a work pieceφ7)

Weld nut welding condition list

Hexagon nut

Square nut

※Please use this list as a guide. Please test welding condition carefully in advance. Because it changes due to a work piece, a welding machine, and a tip shape of electrode tip.