Old Microwave Oven UV Curing Enclosure

thingiverse

My son has just purchase a 3D Resin printer. This uses UV setting resin, not melting plastic filament like my printers. One accessory that is very handy is a UV curing enclosure used to finish setting the print. I my "treasures" was an old microwave oven. The old oven has the RF stuff removed, and gives a fine enclosure with timer, turntable and safety interlock. Old microwave ovens are often just tossed out, so the cost for this setup is pretty low. And I had a number of UV flashlights bought for another project that did not go ahead. So.... The power wires that went to the transformer now feed a plug pack. The plug pack is secured with a cable tie, and the spade terminals that went to the original power transformer fit the mains pins quite well. A length of Aluminum angle is the LED heat sink. It is mounted to shield the direct UV from the front. See the pictures for details of the mounting. Make sure there are no shorts to the heat sink. I used fiber washers under the M2.5 screw heads. 5 x high power UV LEDs are wired in series. A bit of heat sink grease is applied under each LED. The constant current power supply can be made up using an LM317 regulator. I actually used an LM337 as I have a bag of them. This current value is set to suit the LEDs used. Mine is nominally 600mA, but it turns out the plug pack I used is a bit low in voltage so it does not get quite there. EDIT!!! OOPS! Looking at this picture, I just realized the Tant caps are in backwards! I will have to fix that! Also, I now have a circuit. Note that the LM317 heat sink tab must be insulated. That is one reason I used the LM337 as the tab is the -Ve volts and in my design, as is the chassis. So, the LM337 can just be screwed down without insulation. The turntable plate and rollers were missing from this oven so I have made a small turntable to fit over the drive. A larger one with rollers will follow.