i4 Inverter Resistance Spot Welder
Designed to handle the toughest metals
I4 Smart welder

The i4 Inverter Resistance Spot Welder is designed to handle the difficult to weld materials such as boron steels and Advanced High Strength Steels (AHSS). These new metals are rapidly becoming the material of choice among car manufacturers. The i4 includes an OEM programmable feature with detailed repair illustrations and customized weld programs.


Double-Acting Spot Gun

New innovative Spot Gun from ProSpot features double-acting cylinder, wide-spreading electrodes and self-aligning electrodes. 

Extension Arms

The Pro Spot i4 comes with a variety of extension arms to accommodate and welding job situation.

Single-Sided Welding

10 different Single-Sided welding applications give you the power and versatility to complete any job.

Control Panel

The i4 features a large 4″x6″ monitor capable of displaying instructions and OEM repair procedures. 

i4 Software

The i4 Software is stored on an upgradable flash card. We consistently release the latest and newest repair procedures and features to keep you up to date. 

i4 Combi: Built-in MIG Welder

The i4 features an easy upgrade to include a PR-155 MIG welder. It can be installed later as an upgrade or ordered with the MIG welder built-in from the factory. 

i4 Overhead Installation

The Pro Spot i4 is available in an overhead ceiling-mounted version. The ceiling-mounted version hangs from the ceiling at 20′ bracket spacing giving you extra floor space and accessibility.  


Push one button to open electrodes wide, then push the other button to close electrodes and weld. Pro Spot’s PS-500 Spot Gun System features electrode pressure over 600 Lb. with all extension arm sizes.


Changing the arms on our weld guns is quick and easy.

The i4 comes standard with several different types of weld arm extensions (508mm U-Arm, C-Arm, Wheelhouse Arm) and others are available upon request, so that you can tackle any welding problem with as much ease and accuracy as possible.


The i4 is capable of handling a variety of single-sided welding needs, including washer, nut & bolt, nail, rivet and stitch.


The i4 features a clean, ergonomic interface layout with the power switch and electrode pressure knobs all set in a convenient and straight forward manner. It also has a large 4×6″ monitor capable of displaying images and OEM repair procedures.

  1. Power Switch
  2. 3 Phase Power Indication Lights
  3. Electrode Pressure Gauge
  4. Electrode Pressure Control Knob
  5. Display Screen


Cooling system for i4:

The i4 is both water cooled and air cooled. The air cooling starts when the temp reach 42c and shuts off automatically at 37c. Welding can remain while air cooling is on.

The water cooling is loop based system that cools the transformer weld cables and spot gun. While the water cooling is running the welder can operate as normal.

The reason for the two cooling system is that Pro Spot found it being most efficient and will extend the duty cycle of the welder.


  • The i4‘s software is easily upgraded with a removable Flash Card as new data and information become available. The latest i4 software features over 3,000 GM OEM repair screens including Dodge, Toyota, Lexus, Volvo, and more.

  • The i4 data log feature is an easy way to manage weld history, quality of welds and power applied to each weld. Detailed information is stored in an excel file stored on a removable USB flash drive.

  • Weld-Bonding program for your advanced steel applications. Current is controlled via stored parameters. Amperage Feedback Display: Shows the exact amount of current being used by the welder for each weld.

  • Access over 3,000 OEM Repair Screens (including: GM, Toyota, Lexus, Volvo, Dodge and More!) as well as general welder help and maintenance on-board.



The i4 package can include a MIG welder as an option. It can also be installed later as an upgrade. This feature allows the convenience of STRSW and MIG welding in one unit.

Mig Features
  • 220V 1-phase ready to use
  • Binzel connector: quick-connect all-in-one adapter
  • Ideal for collision repair welding


The i4 has an overhead installation option. With the overhead option, the welder hangs from a track system that can cover up to 14 bays.

Overhead Features
  • All the features of a portable i4 welder. ( Optional MIG welder included. )
  • Convenient overhead mounting system.
  • No cables, air hoses or equipment on the floor.
  • Always connected, ready to weld.
  • Stores out of the way when not in use.
  • Moves easily around the shop.
  • Saves valuable shop floor space.


Input Voltage:

  • 3 phase
  • 208 – 240V 50/60HZ
  • 400 – 420V 50/60HZ
  • 460 – 480V 50/60HZ

Welding Amperage:

  • 12500A max (3-phase)

Weld Cable Length:

  • 2.5m (8′)

Electrode Pressure:

  • 7 bars (90 PSI) – 280 DaN (616Lb)

Cooling System:

  • Air (2 fans), Compressed air (weld gun and weld cables)
  • Water cooling (inverter, transformer, welding gun)


  • i4 Upgradable Software Platform


  • IP21

Shipping Weight:

  • 169 kg (373 lb)

Patents (3):

  • no. 5,239,155
  • no. 6,706,990
  • no. 6,539,770

How Can We Help?

Have more questions?

Our customer service team are ready for your questions.