Introduction: Grow Bucket Laser Cut Acrylic Heat Shield
If you have an indoor bucket grow setup (AKA Space Bucket), you may find the need regulate the temperature of your plant independently from the heat of your lights. These instructions are for an acrylic friction-fit heat shield (no glue required) to thermally separate your lights from your plant while allowing light through.
I have included my cut files, but *buckets are not the same* so if you want a nice exact friction fit I recommend following the measurement instructions to make exactly the right size shield.
Glass heat shields are quite common in the Space Bucket community, and people report them to be 'cool to the touch'. Ekrof's tomato plant (bucket build here) has been trained to grow against the glass, as it was starting to outgrow the bucket, and the shield prevented it from being burnt.
However, the glass is expensive and hard to get cut into a circle, so this tutorial uses acrylic. The temperature of my acrylic heat shield seems stable at 28 degrees Celsius (ambient temperature is 22-23C). My light chamber is outfitted with four 32W CFL bulbs (Family Med brand) a USB fan (Stylepie Summer Fruits fan) for exhaust and extra holes for passive intake. Ekrof recommends having active intake over my set up because blowing air on the lights helps cool them down.
- 12x12 inch piece of clear acrylic ($10), 3/16 to 1/4 inch thick
I used 3/16 inch thick but 1/4 is fine too. Too thin runs the risk of warping under the heat of the lights. DO NOT use the kind that people use for windows as these are likely to block UV light. You want just the plain stuff, and it doesn't matter if it's extruded or cast acrylic. I got mine from TAP Plastics from the scrap bin, and I got it on a Friday when scrap is 50% off, so it only cost me $5 for two.
- Laser cutter that can cut through the acrylic
Getting access to acrylic sheet and a laser cutter sounds hard, but I've lived in Toronto, New York, and San Francisco, and these things were accessible in all three cities. Ask the maker space or hackerspace that hosts the laser cutter - you will likely be required to go through some sort of safety training before being able to use it. You may also be able to convince a kind maker space member to help you cut your acrylic for you.
Toronto: Plastic from Plastic World (http://plasticworld.ca/), laser cutter at HackLab (https://hacklab.to/)
New York: Plastic from Canal Plastics (http://canalplastic.com/), laser cutter at NYC Resistor (http://www.nycresistor.com/)
San Francisco: Plastic from TAP Plastics (http://www.tapplastics.com/), laser cutter at Noisebridge (https://www.noisebridge.net//)
I haven't used the laser cutter in Toronto, but I've bought plastic at all the places listed and used the laser cutter at NYC Resistor and Noisebridge.
Step 1: Measure the Bucket
For the light mounts, I use the top half of a five gallon bucket. I have picked up over 150 five buckets from local bakeries (if you're in San Francisco, check out the list here: https://growbucket.life/faq) and found that there are TWO sizes of five gallon buckets, which I encounter in equal proportion. The first size has a 11.75 inch interior rim diameter while the second smaller size has a 10.75 inch interior diameter. If you come across the second size, make sure you ask your source for lids as it is hard to find a place to buy the smaller lids. In the photo, the bigger size is on the left and the smaller size on the right.
To decide how big you need to cut your circle, you need three dimensions of the top half of a 5 gallon bucket
1. Top inner rim diameter
2. Bottom inner rim diameter
3. Kerf of the laser cutter on this material
The kerf is the amount of material that the laser obliterates. You want to account for the kerf so that your piece will be perfectly sized. To measure the kerf, I recommend cutting out a test piece of acrylic, and then measuring the size of the piece you cut out, and the size of the hole. The difference is twice the kerf.
For a friction fit of your heat shield at a height close to the bottom of the bucket, the diameter of circle in your cut file should be:
(top diameter - bottom diameter)/3 + bottom diameter + kerf
Imagine that you are constructing a circle to fit perfectly at height 2/3 down your bucket top. The actual circle will likely sit a bit lower when it is pushed into place, due to give in the plastic.
Step 2: Cut Your Heat Shield
When I put my acrylic in the laser cutter, I like to remove the film on the top side and leave the film on the bottom side, so the acrylic isn't scratched by the laser bed. Don't forget to remove the bottom film afterwards.
Included here are cut files for my smaller and bigger rimmed buckets. My measurements were as follows.
Smaller 10.75 inch rim bucket
Top inner diameter: 29cm
Bottom inner diameter: 26.9cm
Bigger 11.75 inch rim bucket
Top inner diameter: 26.6
Bottom inner diameter: 25.2
The kerf for my laser cutter on this material was 0.3 mm.
Step 3: Install Your Shield
To install the shield, take out everything in the bucket above where the shield should go (lights and fan in my case). Put the shield in the bucket and carefully use your fingers to push the shield into place. It should be able to stay perfectly in place with friction. Be careful not to turn the shield sideways or else it will come out the other end of the bucket.
Your grow bucket should be designed so that in the light chamber there is ventilation. In my case it's active exhaust (the fan on top) and passive intake through holes.
Hope this helps and post a picture if you make one!
For more of my grow bucket stuff, check out https://growbucket.life/ and https://medium.com/grow-bucket-life-project-kickst...
I also highly recommend joining the Space Bucket community!