Semi-Pro Spot Welder (for 18650 battery, 21700, etc...)

by Collins_Tuong

💡 Why Get This Design? This design is perfect for 3D printer builders, and hands-on makers who want a reliable and professional-looking spot welder built at workshop/home. If you've ever built a 3D printer, upgraded a Creality, or assembled a CNC frame — this project will feel natural to you. It’s also ideal for people who love functional DIY builds that not only work well, but look sharp on the workbench. Unlike many random wood-plank welders, this one is engineered for precision, alignment, and sturdiness — and feels like a real machine. ⚠️ Warning – Electrical Safety This project runs on AC 220V, and working with high current involves serious risks. You should only attempt this if you have basic electrical knowledge and know how to handle power electronics. Improper wiring can lead to shock, fire, or component failure — so, as always: Safety First! 🧰 What You Need Before Printing Here's the full list of components required to build the machine: 🔌 1. Microwave Transformer (MOT) Sourced from a used microwave oven My build used a 1200W Electrolux MOT Core size: 95mm x 65mm x 80mm Primary coil removed and replaced with AWG 000 (3/0) copper wire (~10.4mm diameter) Wound 3 turns, resulting in ~3.3V output 🧱 2. Insulation Base Plate I used 15mm thick PVC You can also use wood, plastic, or any insulating material available This plate isolates the transformer from the metal frame 🔩 3. Mechanical Parts (Mostly from 3D Printer Hardware) 4× Smooth rods: ⌀8mm × 190mm 6× LM8UU linear bearings 1× Aluminum extrusion: 4020, length 100mm 2× Heatblock clones (E3D V6 MK3 style) 2× Cast corner brackets: for 2020 profile, or 1 for 4020 4× RC car suspension springs (90–100mm length) I used cheap Tamiya 1/10 scale shocks 1× Reprap mechanical endstop switch (or equivalent) Screws: M3, M5, M6 + nuts & washers 🧲 4. Electrical Contacts & Wiring 1× Copper rod for welding tips: CuCrZr (C18150) or CuCr (C18200) – RWMA Class 2 Diameter: ⌀3mm Length: 10mm, or 2× rods of 40–50mm 2× Flexible