After installing the aluminum heat plate cover I custom ordered from Trick Laser I noticed it took significantly longer to warm up the Onyx heated bed. The heat plate cover helps regulate the temperature more accurately by acting as a thermal buffer and aids in keeping the entire bed the same temperature. One downside to this approach is the additional power required to heat both the glass and the aluminum plate. The 12V PSU has problems with keeping the bed at any temperature above 80° C. One way to combat this is increasing the voltage going to the bed from 12 to 24V. In order to get the 24V the PSU needs to be upgraded. The default SeeMeCNC provided PSU is 12V.
I acquired a MeanWell 500W 24V AC/DC Power Supply w/ PFC, more than capable of handling the load required by the Onyx.
I wanted to power the Rambo controller via 12V. Running the board at 24V so the onboard mosfet could control the Onyx would put a significant strain on it. To do this while only using the 24V PSU a 24 to 12V step down unit is required. I used a standard 20A unit found on eBay or Amazon.
Since the Rambo would be running on 12 volts, controlling the 24 volt Onyx would require a Solid State Relay. I used the Crydom D1D40 1DC Series Solid State Relay 40A 32VDC Industrial Panel Mount from eBay. The heated bed wires coming from the Rambo are moved from the Onyx to the SSR. The SSR uses the 12V PID signal coming from the Rambo to control the power to the Onyx. I found polarity was important for the signal side of the SSR, negative needed to be on the “4” screw with positive on the “+3” screw. If I reversed the polarity the SSR would constantly stay on. SSRs output a significant amount of heat, especially when they are turning on and off rapidly due to the Rambo’s PID output. A heatsink was attached to the back of the SSR to ensure heat dissipation could occur efficiently. The positive end of the Onyx board was attached to the other end of the SSR, and the SSR was attached to the positive end of the 24V PSU. The negative end of the Onyx was attached directly to the 24V PSU.
The Rostock Max v2 is designed to house a standard ATX power supply used in desktops. Since the MeanWell 24V PSU is not ATX, some modifications needed to be made to the printer to attach the PSU. The SSR and 24V to 12V converter were mounted to the 24V PSU.
Initial tests saw significant improvement in the speed at which the Onyx heated up and in its ability to reach over 80° C with ease. It takes the glass and aluminum to catch up to the temperature of the bed, but it all managed to get to 100° C in under 5 minutes!
