What Is a 6 Head Welding Machine?

A 6 head welding machine is a CNC welding system built to weld multiple corners and joints of a PVCu window or door frame in a single automated cycle. Instead of welding one corner at a time, a 6 head machine positions six welding heads around the frame at once, typically covering all four corners plus a central transom, so the whole frame is fused in one pass.

For fabricators, this means less handling, fewer setups, and far more consistent welds across every frame that leaves the factory.

How a 6 Head Welding Machine Works

A 6 head CNC welder clamps the cut PVCu profiles into position, then brings all six heads together to mill, heat, and fuse the joints simultaneously. Because every corner and transom is welded in the same cycle, under the same conditions, the finished frame has uniform strength and appearance from joint to joint.

The process typically runs through several automated stages:

• Profile clamping and alignment
• High speed milling of the weld faces
• Simultaneous heating and fusion at all six points
• Compression and cooling
• Release of the finished, welded frame

Because the machine handles four corners and a mid rail transom together, output increases significantly compared with single or twin head welders, while a single operator can run the whole cycle.

Standard Welding vs Seamless Welding

Most CNC welders leave a small bead or seam of melted material at each corner, which then has to be cleaned or “corner cleaned” by hand or with a separate machine before the frame is ready to glaze. This adds a labour step and introduces room for inconsistency.

A seamless welding machine removes that step entirely. The corner is welded, fused, and finished in one operation, with no visible weld bead and no need for corner cleaning afterwards. The result is a frame with a continuous, uniform surface and a noticeably sharper finish, straight off the machine.

Seamless 6 head and 8 head welding technology, built by Graf Synergy, is exclusive to Haffner in the UK fenestration industry. That means UK fabricators looking for true seamless welding at this scale currently have one route to it.

Haffner’s 6 Head and 8 Head Seamless Welding Machines

Haffner supplies two Graf Synergy machines built around this seamless welding process, and between them they cover most high output PVCu fabrication needs.

SL6-FF EVO RS, 6 Head CNC Welding Machine

The SL6-FF EVO RS is the natural evolution of Graf Synergy’s 4 head SL4-FF EVO. Its six heads weld all four corners of a PVCu frame plus one transom in a single operation, with no cleaning or retouching required afterwards.

Key points:

• Seamless welding with no corner cleaning step
• Welds 4 corners and 1 transom in one cycle
• Handles white, foiled, and aluminium clad profiles
• Works with non weldable inserts such as fibreglass, aluminium, or resin reinforcement
• One operator required, reducing labour while increasing output
• Active Welding System checks tolerances before welding begins

SL8-FF TR, 8 Head CNC Welding Machine

The SL8-FF TR takes the same seamless principle further. Its eight heads weld all four corners plus two transoms simultaneously, making it the choice for fabricators running higher volumes or more complex frame designs with multiple mid rails.

Key points:

• Seamless welding, patented by Graf Synergy, with no reworking needed
• Welds 4 corners and 2 transoms in one cycle
• Same versatility as the SL6, covering white, foiled, and aluminium clad profiles
• Built for manufacturers looking to scale output without compromising weld quality
• Reduced footprint relative to the number of joints welded per cycle

6 Head vs 8 Head: Which One Fits Your Production Line?

Both machines use the same seamless welding technology and the same underlying Graf Synergy platform, so the decision usually comes down to frame design and volume rather than weld quality.

• Choose the SL6-FF EVO RS if your production is mainly standard frames with a single transom, and you want to move from a corner cleaning workflow to seamless welding with a smaller footprint.
• Choose the SL8-FF TR if you regularly fabricate frames with two transoms, or you need to push output further while keeping every weld seamless.

Why Fabricators Are Moving to 6 and 8 Head Seamless Welding

For a UK window and door fabricator, the case for a 6 or 8 head seamless welder usually comes down to three things:

• Consistency: every frame comes off the machine with the same finish, rather than depending on how well each corner was cleaned by hand.
• Labour: removing the corner cleaning stage entirely frees up staff and cuts a step out of the production line.
• Output: welding multiple corners and transoms at once, in one cycle, increases throughput without adding operators.

Want to see seamless 6 head or 8 head welding in action? Get in touch with Haffner to book a demonstration and find the right machine for your production line.

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