AC Resistance Welding vs CD Welding: Which Is Right for Battery Tabs, Wire Mesh and Filtration?
Quick answer: Choose CD (capacitive discharge) welding for battery tabs, electronics, permanent jewelry and any spot weld next to heat-sensitive material. Its 1–10 millisecond pulse finishes before heat spreads. Choose AC resistance welding for wire mesh, filter baskets, hermetic seams and foil. Its continuous current can run through a roller electrode to create a true seam, and it can be dialled down for fine wire that a CD pulse would burn through. Most shops need one or the other; manufacturers doing both kinds of work need both machines.
Table of Contents
- The two resistance welding technologies explained
- How CD welding works
- How AC resistance welding works
- Head-to-head comparison
- Where CD welding wins
- Where AC welding wins
- Welding wire mesh and filtration components
- How to specify a mesh or filtration welding system
- The Sunstone lineup: which machine for which job
- Choose CD if / Choose AC if
- Frequently asked questions
The two resistance welding technologies explained
Both AC resistance welding and CD welding create joints by passing electrical current through metal at the weld interface. Resistance at the contact point generates heat, and the metal fuses under electrode pressure. That's where the similarity ends.
CD welding stores energy in capacitors and releases it in a millisecond burst. AC welding draws power from a transformer continuously for as long as the weld is active. That difference in energy delivery determines which applications each technology handles well, and using the wrong one produces consistently poor results.
How CD (capacitive discharge) welding works
Energy storage and release
A CD welder charges a bank of capacitors to a set level between welds. When triggered, the stored charge discharges through the electrodes in a single controlled pulse lasting roughly 1–10 milliseconds, far shorter than any transformer-based process.
The operator sets the energy per weld in joules. Because each pulse comes from a pre-charged capacitor bank rather than live mains power, it delivers the same energy regardless of mains voltage fluctuations, which is where CD's weld-to-weld consistency comes from. Our what is a CD spot welder guide covers the mechanism in detail.
Pulse shape and dual pulse
A CD pulse is a single high-peak event that decays as the capacitors empty. Its shape depends on the capacitor bank and circuit inductance. Advanced systems such as Sunstone's CD line with Tru-Fire Technology control the discharge electronically to improve consistency at very low joule settings.
Dual-pulse CD systems fire two sequential pulses: the first conditions the interface surface, the second completes the fusion. This is the professional configuration for battery tab welding, where surface oxide variation is a major source of inconsistent welds.
Best applications
- Battery tab welding (18650, 21700, pouch cell tabs): the short pulse keeps heat away from the cell
- Electronics: fine wire termination, thermocouple assembly, component leads
- Permanent jewelry: jump ring fusion in fine precious metal chain
- Precision spot welding on thin, heat-sensitive materials
- R&D and prototyping: quick setup and repeatable results across many materials
How AC resistance welding works
Continuous energy delivery
AC resistance welding uses a transformer to step mains voltage down to a high-current, low-voltage output. Current flows continuously for the length of the weld, which is measured in line-frequency cycles rather than a single pulse: a 5-cycle weld at 60 Hz lasts about 83 milliseconds, a 10-cycle weld about 167 milliseconds. Sunstone AC resistance welders can be set as short as 1/100 second for fine control at the low end.
That continuous delivery is not a limitation. It is exactly what makes AC suited to seam and mesh work.
Seam welding capability
By maintaining current through a rolling electrode (such as Sunstone's EL-Roll) as it travels along the part, AC welding creates a continuous seam: an unbroken fusion line. CD welding, with one discharge per trigger, can only produce a row of overlapping spots. For hermetic seals, filter seams and mesh panels, AC is the correct technology.
Best applications
- Wire mesh and screen welding: fusing intersections across a mesh in a single seam pass
- Continuous seams: hermetic package seals, filter body seams, pouch cell perimeter seals
- Foil welding: very thin foil where sustained, controllable current fuses without burn-through
- Filter baskets and strainer bodies: mesh-to-frame joins and longitudinal seams
- Stainless insulation blanket fabrication for industrial applications
Head-to-head comparison
| Factor | CD welding | AC resistance welding |
|---|---|---|
| Energy delivery | Single 1–10 ms capacitor pulse | Continuous transformer current, timed in line cycles |
| Heat input | Very low; minimal heat-affected zone | Moderate and sustained; larger heat-affected zone |
| Weld types | Spot only | Spot, roll-spot and continuous seam |
| Typical materials | Nickel, gold, silver, platinum, most ferrous metals; copper needs high-joule systems | Thin steel, stainless, nickel alloys in sheet, foil and mesh form, roughly 0.05–1.2 mm |
| Best for | Battery tabs, electronics, jewelry, R&D | Mesh, filtration, hermetic seams, foil |
| Price | About $500 entry to $2,000+ professional dual-pulse | Professional manufacturing tier; quoted by configuration |
Heat input and material sensitivity
CD's millisecond pulse deposits energy at the interface and ends before significant heat conducts into the surrounding material, which is why it suits lithium cells, PCB components and set stones in jewelry. AC's sustained energy produces a larger heat-affected zone, but for mesh intersections, seams and foil that sustained energy is exactly what the joint needs.
Speed and throughput
Each CD weld takes milliseconds, so single-spot work is fast. But a mesh grid with hundreds of intersections means hundreds of trigger presses and repositioning. AC is slower per spot, yet its seam mode welds every intersection along a pass, which is dramatically faster for mesh and seam production.
Ease of setup
CD setup is a joule setting calibrated on scrap. The Sunstone Wave AC uses digital energy control on a 10-inch color touchscreen that displays parameters as a live waveform, so operators can see how each adjustment changes the weld, which matters when managing complex seam profiles.
Where CD welding wins
Battery tab and pack assembly
CD welding is the industry standard for 18650, 21700 and pouch cell tab welding because the weld completes before meaningful heat reaches the cell. AC's sustained current is not appropriate for spot welding tabs directly to cylindrical cell terminals. Dual-pulse CD systems such as the Sunstone CD200DP and CD400DP add a conditioning pulse that evens out nickel oxide variation across a full pack build. See our battery tab welding guide for settings and technique.
Electronics and precision micro welding
Thermocouple assembly, fine wire termination, sensor leads and component joining all benefit from CD's minimal heat-affected zone. Adjacent solder joints and heat-sensitive components stay near ambient temperature through a correctly set CD weld.
Prototyping and R&D
CD's wide material compatibility and one-trigger-per-weld operation make it the flexible workhorse for labs where materials change frequently. A new material means a calibration on scrap, not a machine reconfiguration.
Where AC welding wins
Wire mesh and screen
Fusing every intersection across a mesh grid is one of AC's most distinctive applications. A roller electrode in seam mode traverses the panel and welds each crossing with consistent current in one pass. A CD welder spot-welding each intersection would take many times longer and produce less consistent results.
Foil and pouch cell sealing
Very thin foil, around 0.05 mm, needs sustained, controllable energy; CD's high peak current makes burn-through more likely at these thicknesses. Sealing the perimeter of a lithium pouch cell casing is a seam application for AC, while welding the tabs is a CD job. A pouch cell maker can legitimately need both machines.
Filter baskets and hermetic seals
AC seam welders build filter bodies, attach mesh screen to strainer baskets, and seal seams. Welding the mesh to the frame and sealing the basket seam on one machine, with different electrodes, streamlines production.
Welding wire mesh and filtration components
Most people discover resistance welding through battery tabs, so their first machine is a CD welder. Based on the calls our team fields, the most common mismatch we see is a buyer who already owns a good CD welder and discovers it can't do their mesh or filter work. Here is why, and what the application actually needs.
Fine wire needs less energy than a CD pulse delivers
Filtration mesh is typically stainless steel, Monel or nickel alloy wire from about 0.05 mm to 0.5 mm in diameter. The mass at each crossing is tiny. A CD pulse sized for 0.15 mm nickel strip carries far more energy than two crossing 0.1 mm wires can absorb, so the wire burns instead of fusing, and fine mesh often needs less energy than the practical minimum of many CD systems. AC's continuously controllable current, with weld times down to 1/100 second, can be dialled to fuse an intersection without burning through.
Seams and hermetic seals need continuous fusion
A filter basket seam, a pouch cell perimeter or a mesh-to-frame join has to be fused along its whole length. A row of CD spots, however dense, leaves unwelded metal between spots, which under pressure or vacuum is a leak path. A continuous AC seam with a roller electrode produces a genuinely hermetic joint when set up correctly.
Common mesh and filtration applications
- Filter baskets and strainer bodies: hydraulic, chemical processing, water treatment and HVAC filters, assembled by welding mesh to frames and sealing formed mesh cylinders.
- Wire screen and mesh panels: air filtration, liquid straining, security screens and grating, with every intersection welded by a roller in seam mode.
- Pouch cell and foil sealing: perimeter seals on foil-laminate casings and other foil work around 0.05–0.1 mm.
- Medical and pharmaceutical filtration: suction filters, IV line filters and device housings that need hermetic welds and documented, repeatable parameters. Stored weld schedules support that documentation.
- Food-grade filtration: 304 and 316L stainless strainers, cones and inline housings, where a smooth continuous seam avoids the crevices between spot welds that can trap product and bacteria.
Electrode selection
Match the tip to the wire. For very fine wire (0.05–0.1 mm), a pointed or small-radius tip concentrates current at the intersection; for heavier wire (0.3–0.5 mm), a flat tip spreads energy across the larger contact. Copper alloy electrodes (RWMA Class 2) are the standard for most stainless mesh; tungsten tips are used where electrode life or erosion is a concern. Roller electrodes are matched to the mesh's wire pitch, since roller diameter and width change current distribution along the seam.
Fixturing and cooling
Mesh weld quality depends on consistent electrode contact. Production work needs fixturing that holds the mesh flat on a rigid backing so every crossing is in contact before current flows. Circumferential basket seams benefit from rotation fixtures that keep travel speed and electrode angle constant. Long seams at high duty cycles need a water-cooled handpiece (Sunstone's PG3W) and a recirculating chiller; heat building in the cables otherwise degrades insulation and current consistency.
How to specify a mesh or filtration welding system
Wire diameter and material
| Wire diameter | Energy requirement |
|---|---|
| Very fine, 0.05–0.1 mm | Lowest energy and shortest weld times; most sensitive to over-delivery, so fine low-end control is essential |
| Standard filtration, 0.1–0.3 mm | Mid-range settings |
| Heavier mesh and screen, 0.3–0.5 mm | Higher energy and longer weld time; more tolerant of variation |
Material matters too. Stainless steel's high electrical resistivity (roughly 700–750 nΩ·m for 304 and 316) means it heats efficiently under resistance welding current, without the very high peak currents copper needs. Monel and Inconel alloys behave differently again and need their own parameter development.
Weld pitch and seam length
Weld pitch, the spacing between welds or roll-spot cycles, sets how densely intersections are fused. Structural mesh needs tight pitch; filtration mesh needs enough fusion to hold without distorting the aperture that sets flow. Seam length drives cooling: short seams in normal volumes rarely need it, while long seams at high duty cycles benefit from a water-cooled configuration.
Production volume
- Prototyping and small batches: a Wave AC with a handpiece and manual seam traversal, with the operator controlling travel speed.
- Medium production: more consistent fixturing, possibly semi-automated traversal, water cooling if seam length requires it, and stored schedules for fast changeover between parts.
- High volume: Sunstone offers semi-automated configurations for the Wave AC; talk to us about integration before specifying.
The Sunstone lineup: which machine for which job
CD line for battery, electronics and jewelry work
- Zapp / Zapp Plus 2: permanent jewelry, fine jewelry repair, entry battery tab welding
- Orion mPulse / mPulse PRO: professional permanent jewelry and precision spot welding with Tru-Fire Technology
- CD200DP: professional dual-pulse battery tab welding, up to 200 J with independent conditioning and fusion pulses
- CD400DP: high-power battery welding and copper tab capability, up to 400 J
For the full CD range, see our Sunstone CD spot welder review and best battery spot welders guide.
Wave AC for mesh, filtration and seam work
The Sunstone Wave AC is Sunstone's current professional AC resistance welder:
- Output: up to 2,700 amperes
- Control: digital energy control on a 10-inch color touchscreen with live waveform display
- Modes: spot, roll-spot and continuous seam, plus dual pulse, multi-pulse and foil functions
- Schedules: 100+ stored weld configurations, with job chaining for multi-step sequences
- Electrodes: pointed electrodes for spot work; roller electrodes (EL-Roll) for seam work
For seam work, the Wave AC is paired with a handpiece built for guiding a roller electrode along a joint at consistent pressure and speed, such as Sunstone's PG2, or the water-cooled PG3W for long, high-duty-cycle seams. Confirm the exact bundle contents on the listing, since configurations vary. Our Sunstone Wave AC review covers the machine in depth, and our spot welder cost guide explains how AC and CD investments compare.
Choose CD if / Choose AC if
Choose CD welding if you weld battery tabs to cylindrical or pouch cells, join fine wires and components in electronics, do permanent jewelry, or need a flexible spot welder for R&D across many materials.
Choose AC resistance welding if you weld wire mesh or screen, build filter baskets or strainers, need hermetic seams, work with foil around 0.05 mm, or seal pouch cell casings.
Choose both if your production includes spot welds on heat-sensitive parts and continuous seams or mesh, such as a pouch cell manufacturer welding tabs and sealing casings.
Frequently asked questions
What is the difference between AC resistance welding and CD welding?
AC resistance welding draws continuous current from a mains transformer for the length of the weld. CD welding stores energy in capacitors and releases it in a single 1–10 millisecond pulse. AC can create continuous seam welds with roller electrodes; CD creates discrete spot welds. CD's shorter pulse produces a smaller heat-affected zone, which is why it's used for lithium battery tabs.
What machine do I need to weld wire mesh?
An AC resistance welder. Its continuous current can be controlled down to the low energy fine wire needs, and it can run in seam mode with a roller electrode to weld every intersection in one pass. A CD welder's pulse is poorly matched to fine wire and can't produce a continuous seam.
Can you spot weld wire mesh?
Yes. Individual intersections can be spot welded with an AC welder in spot mode. For panels where every intersection must be fused, continuous seam mode with a roller electrode is far more efficient than hundreds of individual welds.
Why can't I use a CD welder for mesh welding?
Two reasons. Fine wire often needs less energy than a CD system's practical minimum, so the pulse burns through instead of fusing. And CD produces one spot per trigger, so it can't make the continuous seam that filters and hermetic joints require.
Can AC resistance welding be used for battery tabs?
For sealing the perimeter of lithium pouch cell casings, yes; that's a standard AC seam application. For spot welding nickel strip tabs to cylindrical 18650 or 21700 terminals, no. That's a CD application, because the weld has to finish before heat reaches the cell.
What materials can be welded for filtration mesh?
Most commonly 304 and 316L stainless steel, plus Monel 400 for marine and highly corrosive environments, Inconel for high temperatures, and nickel alloy wire. Galvanized mesh can be welded but releases zinc fume, so it needs good ventilation.
What is the Sunstone Wave AC used for?
Continuous seam welding, foil welding, pouch cell sealing, wire mesh and screen welding, hermetic sealing and filter production. It delivers up to 2,700 amperes with digital energy control and a live waveform display, and stores 100+ weld schedules.
Does Sunstone make both AC and CD welders?
Yes. The CD line includes the Zapp and Zapp Plus 2, Orion mPulse and mPulse PRO, and the CD200DP and CD400DP. The AC line is anchored by the Wave AC. The two technologies serve different applications and aren't interchangeable.
Not sure whether your application needs CD, AC or both? Contact our team with your material, thickness and production volume, and we'll help you specify the right system.
