Heat Forming Solid Surface Countertops: A Matched Control Panel and Silicone Heater Mats
Bending solid surface sheet into a curved countertop edge, a radius wall or a cove calls for one thing above all: heat that's even, controlled and repeatable. Too cold and the sheet cracks or whitens in the bend. Too hot and it can blister. A fabricator came to us wanting simpler heating control boxes. Here's how we built that system.
The problem
The fabricator heats solid surface sheet on flexible silicone heater mats, then forms it. Their existing control boxes were large and hard to store. Their wish list:
- Heat three mats of very different sizes from one controller. The sizes they listed were 6 x 12 in, 12 x 48 in and 15 x 96 in.
- Keep the controls as simple as possible: on/off, a setpoint and a temperature readout. No data logging, no ramp/soak profiles.
- Ideally, be able to run on either 120V or 240V shop power.
- A small footprint that fits on a shelf or mounts on a rolling cart.
They also asked, reasonably, whether each mat really needed its own controller, or whether one setpoint could run all of them.
What temperature are we holding?
Published solid surface guidance puts the sheet forming range at about 275–325 °F (135–165 °C). The Corian thermoforming guide adds that the sheet shouldn't be allowed to exceed 350 °F, and that the part should stay restrained in the form until it cools to about 180 °F. SolidSurface.com notes that forming too cold can crack and whiten the material, and forming too hot can blister, whiten or crack it. (Sources are listed below. Always follow the fabrication guide for the specific brand and color of sheet you're forming, because some colors want the low end of the range.)
That window is too narrow for "roughly warm". Each mat needs its own temperature measurement and a controller acting on it.
The approach: one zone per mat
We kept the operator's side simple and put the complexity where it belongs, inside the panel.
Why not one controller for all three mats? A 6 x 12 in mat and a 15 x 96 in mat don't heat up at the same rate or lose heat at the same rate. With one controller reading one thermocouple, only the mat with the sensor is really controlled. The others overshoot or lag. Giving each mat its own thermocouple and controller solves that, and the operator can still set all three zones to the same temperature. It stays "one setpoint" in practice, just enforced per mat.
Why two versions instead of one box with two plugs? A resistance heater is built for one voltage. Put a 120V mat on 240V and it tries to draw about four times its rated power. Put a 240V mat on 120V and you get about a quarter of the heat. Since the mats are matched to the supply anyway, we offered the panel in two versions:
- 120V version: 3 zones, 20A main, up to about 750 W per zone. It runs on standard shop power, so it can be used in the shop and out in the field.
- 240V version: 3 zones, for larger or higher-wattage mats. With more power available, mats warm up faster, which suits a fixed shop setup.
What's in the panel
Both versions share the same layout:
- One Watlow EZ-ZONE PM temperature controller per zone, giving PID control with a clear setpoint and process readout on the door.
- An individual Control Power on/off switch per zone, so unused mats can simply be switched off.
- Solid-state relay switching and a DIN-rail circuit breaker for each zone. SSRs switch the heater quietly and without contact wear, which suits the frequent cycling of PID control.
- Heater twist-lock receptacles and thermocouple jacks on the bottom of the enclosure, labeled Zone 1 to Zone 3, so mats plug straight in.
- A power cord and plug, in a grey steel wall-mount enclosure with a hinged door.
The panel is built by an outside panel shop and shipped to Entherm. We then connect the customer's actual heater mats, test the complete system, and ship the panel and mats together.
The heater mats
The mats are flexible silicone rubber heaters, each with a built-in Type J thermocouple and an approximately 120 in (10 ft) cordset. They're made to order in custom widths, lengths, voltages and watt densities. Two sizes from recent quotes show the range:
- 10 x 65 in, 120V, 750 W: about 1.15 W/sq in.
- 20 x 65 in, 240V, 1200 W: about 0.92 W/sq in.
Those modest watt densities suit a job where even heat across a wide sheet matters more than speed. We size mats to the customer's forms, not to a catalog.
The result
The fabricator gets a compact panel anyone on the shop floor can run: switch on a zone, set the temperature, watch the readout. The panel and mats arrive as a tested set, so setup is plug-and-play, and one supplier stands behind both.
Request a quote
Forming solid surface, acrylic or another thermoplastic sheet with silicone heater mats? Tell us your mat sizes, your available voltage and how many zones you need, and we'll match a panel and heaters to your setup.
Email sales@entherm.com or call 1-877-368-4376.
Sources: SolidSurface.com, "Thermoforming" (forming temperature table and notes for Corian): https://www.solidsurface.com/working-with-solid-surface/thermoforming · Corian Solid Surface Fabrication/Installation Fundamentals, Thermoforming (K-25297): https://www.corian.com/sites/corian.com/IMG/pdf/k-25297-thermoforming.pdf