Large Spa & Hot Tub Vacuum Formers

A spa shell fails when the machine cannot hold heat and pressure evenly across ten feet of sheet

Corners cool faster than centers, deep-draw sections thin out, and the defect is set long before the shell reaches quality control. Belovac builds large format vacuum forming machines for spa and hot tub manufacturing, including swim spas up to 10′ x 25′.

Swim spa shell formed on a Belovac large format machine.

• Pneumatic clamping with 300 foot pounds of pressure per linear foot
• Siemens PLC touch screen with timed, automated sequencing across 7 zones on the upper and lower oven banks
• Forms ABS, HIPS, KYDEX, acrylic, HDPE, polycarbonate and most other thermoplastics
• Custom-built in the USA at Belovac’s facility in Banning, California

Why spa makers buy a custom large format machine instead of standard equipment

Standard equipment is not built for swim spa scale. A machine rated for a 6-foot sheet will not safely run a 10-foot swim spa shell, whatever its heater specs say. A full swim spa can need a forming surface 8 to 10 feet across, with draw depths deep enough to shape jet pockets, seating contours and footwells in one pull.

• Size, heating zones and automation are matched to your shell and production level
• One custom shell a week or dual-station production, on the same design approach
• Belovac confirms clamp frame height and platen travel against your parts before you commit
• Financing through Univest Capital is available

Compared with injection molding, vacuum forming requires less capital investment, costs less in tooling, turns around faster, and keeps small production runs affordable, which suits custom spa product lines.

Belovac’s large format machinery is capable of forming other oversized thermoplastic components too, so depending on forming area and draw depth, one machine can serve other manufacturing applications. Vacuum forming machines range from small tabletop units to industrial machines, and Belovac’s large-format line sits at the industrial end.

The vacuum forming process turns a flat plastic sheet into a spa shell in a series of four stages

A flat plastic sheet is clamped in a frame and heated, bringing it to its forming temperature. With the optional lower oven bank, heat reaches both sides of the sheet. The platen then raises the mold into the softened sheet, and vacuum suction pulls the plastic tight against the mold surface. Cooling sets the shape while vacuum holds it, and the formed shell is cut from the sheet and trimmed. Acrylic is commonly used for spa shells, and many cast acrylic shells are backed with fiberglass and resin after forming. The same heating, molding and cooling sequence is used to create complex shapes such as seating, footwells and jet pockets.

Your options come down to configuration, not just machine size

Belovac tailors each machine. The table below shows the choices that change cost and output, including the ability of a dual-station machine to cool one mold while another heats. See custom large format vacuum forming machines for other configurations.

Option	What it changes	Fits when
Single station	One mold heats, forms and cools in sequence	One custom shell a week
Dual station	One mold cools while another heats	Production-level volume
Lower oven bank	Faster cycles and better heat saturation on thick gauge	Heavy-gauge acrylic and ABS
Manual single-zone PLC	Basic heat control	Simple, low-volume parts
Full-auto multi-zone PLC	Stored settings for multiple designs, repeatable setup	Several spa models in rotation

Dual-station and PLC options are described on the BV A-Class full-auto vacuum former page.

Five specs decide whether a machine fits your shell

Compare these on every spec sheet. If a machine lacks the zones, clamping force or vacuum for the shell, adjusting heat timing or cycle speed will not compensate. The defect is a hardware limit, not operator error. The spa and hot tub forming machine buyer’s guide covers each check.

• Independent heater zones, because flat panels and deep jet pockets need different heat at the same time
• Clamping pressure per linear foot, which keeps heavy sheet from slipping or sagging
• Sustained vacuum, not peak vacuum, so footwells and seats keep a continuous pull
• Forming area and draw depth for the full shell plus trim allowance
• Material compatibility across ABS, acrylic and KYDEX, which respond differently to heat ramp and cooling

Platen travel, not vacuum strength, sets the limit on draw depth

A machine with strong vacuum and short travel still bottoms out on a deep part, and reworking tooling after it is built is expensive. Two measurements need checking against your mold before tooling is built.

Platen travel

Travel sets the ceiling on how deep a part can be drawn. Vacuum capacity then decides how well the sheet seats at depth. Read why platen travel limits draw depth.

Clamp frame height

Frame clearance must exceed mold height, not just match it. A short frame is more prone to vacuum leaks at the clamp edge on longer pulls. See how deep draws affect clamp frame height.

Plug assist

Plug assist pre-stretches material before the platen reaches full travel, which protects wall thickness in seating and footwells.

Hot tub shells and swim spas need different machines

Draft angles matter more on swim spas because the part is heavy and the contact area is large. Read how swim spa shells are manufactured.

Most spa shell defects trace to heat, vacuum or mold design

Match the symptom to the cause before blaming the sheet. See common vacuum forming issues and fixes.

Defect	Cause and fix
Webbing	Tall molds, sharp corners, rapid vacuum. Round corners, add draft, slow the vacuum.
Bubbles or hazing	Residual moisture. Dry the sheet in an industrial drying oven before loading.
Uneven thickness	Use consistent sheet gauge, tune vacuum settings, add plug assist.
Warping or cracking	Uneven heat or cooling. Use controlled air or mist cooling and hold vacuum through initial cooling.

Floor space and production line layout are settled before you order

Spec sheet dimensions describe the machine at rest, not in production. Plan for:

• Sheet loading clearance and mold changeover space
• Overhead clearance for platen travel, heater bank position and any crane or hoist
• Utility access for power and compressed air
• Where the machine sits in the spa production line, from sheet loading through cooling, cutting and trimming of formed pieces, plus room for future capacity

Belovac’s team helps clients plan layout, clearance and utility needs during the buying process, and engineering and technical teams are available for equipment selection and maintenance. See floor space planning for large format equipment.

Common questions before requesting a quote