How to Make a Star Rolling Machine
by Vic Chaney
Want to roll your own stars? This is how to make a star rolling machine. I have read about using a Harbor Freight cement mixer, but they are kind of pricey and rather big. Where would I put it? This rolling machine is inexpensive, easy to make, and easy to store.
Figure 1 - Side View of the Entire Project
Figure 2 - Front View of the Drum
This uses parts mostly from Amazon.com and Home Depot.
- Flange coupling connector
- Aluminum project enclosure 4.33x2.01x1.5
- Aluminum Electronics minibox 7x5x3
- 12V DC gear motor 62 RPM
- 12V 5A DC power supply
- White Bucket, 5 gal HDPE
- Casters, rigid (2)
- Push button
- (optional) gun tap, 6-32
- (optional) gun tap 4-40
- aluminum plate, 4' circle 1/8inch thick
- electrical cord and plug
- electric cord strain reliefs (3)
- aluminum tape
- plywood, 1/2" thick
- (6) 6-32 x 1/2" stainless steel FHMS: bucket plate
- (4) 4-40 x 1/4" machine screws: flange coupling
- (8) #6 x 1/2" flat head sheet metal screws (casters)
- (3) #8 x 1/2" sheet metal screws: mount motor box
- (4) M3 5mm machine screws: mount motor in box
The rolling container is a "food safe" bucket, which is made of HDPE and has a rounded junction between bottom and sides to avoid trapping chemicals. It is resistant to solvents like acetone and denatured alcohol. A speed control allows different speeds to be used, which is important for different stages of the rolling process. It will handle 4 to 6 pounds of stars at a time. It can store in a small space. (Figure 1 is the entire project on side view, Figure 2 is a front view.)
Figure 3 - The Bucket With a Line Drawn For Cutting It
I started with the bucket (figure 3) and cut it to 8 5/8" in height with a saber saw. An inch or two taller and it might handle even more stars but would also make reaching into it to add star comp a little more difficult. It definitely needs all the heavy rims at the top removed.
Figure 4 - A Drawing of the Project With Dimensions (see bottom of article for PDF copy)
Figure 5 - A Drawing of the Project Without Dimensions (see bottom of article for PDF copy)
A stand is made from 1/2" thick plywood. The drawing with dimensions shows the pieces (figure 4). A drawing without dimensions is at figure 5 for clarity.
Figure 6 - The wood stand pieces cut and dadoed
The side pieces are cut from rectangles, orange color on the drawing. Perpendicular lines are drawn on them from the bottom, measurements are made to where the cuts intersect, and then lines can be drawn and cut for the cross pieces that hold the parts. I cut it with a saber saw. Figure 6 shows the cut pieces. The cross pieces are dadoed for more strength and rigidity, glued, and nailed. You could likely do almost as well without the dados and just butt jointing, gluing, and nailing. I like the strength and sturdiness of the dado joinery. After the pieces are glued, the top motor support and the sides where they meet the caster table are trimmed to blend into the adjacent pieces.
Figure 7 - Inside the Motor Enclosure
The motor is enclosed in a metal project enclosure. (Figure 7) The enclosure is closed tightly and grounded, to prevent possibility of sparks from inside the motor getting near flammable chemicals. The third ground wire from the electrical cord is connected to the motor enclosure, as well as the power supply enclosure. The motor wire goes out of the box through a strain relief to protect the connections inside, and to further protect against flammable dust getting into the motor area, where there are possibly small sparks generated inside the motor. A makeshift strain relief can be made with a zip tie twice around the cord, plastic electrical tape, and a grommet. A piece of thin plastic goes under the bottom of the motor box where a recessed area would keep the box from sitting square on its support.
The bucket has a strip of aluminum tape for the wheels to ride on to prevent static electricity from building up (Figure 1). Another strip of metal tape goes from this aluminum tape to the plate connecting the bottom of the bucket, so there is a path to ground for reduction of static electricity buildup. Is this necessary? Maybe not, but when dealing with energetic chemicals it is a simple step that makes it all safer. I used copper tape, removing the adhesive with acetone from under it at the end. Then sandwich it between the ends of the aluminum tape circling the bucket for a better electrical connection. A layer of clear plastic tape keeps it in place. I used copper because I had some strips with adhesive, but a strip of the aluminum tape could be cut and used in the same way. The other end of the connecting tape goes under the aluminum plate attaching the bucket. When I ran the rolling machine without the metal tapes, I could brush my fingers on the dry bucket and feel the static levitating the hairs on my arm. With the process using wet chemicals the static may not be a big issue without the metal tapes, but again safety is a priority.
Figure 8 - Inside the Power Supply Enclosure
The wire goes out of the motor to another aluminum box holding the power supply. (Figure 8) The cord is long enough so that the power supply box can be set on the ground. This puts even more distance between the motor and its power source and gets that part of the electricity farther from the flammable powders. Again, the third ground wire is connected to the box. A push on/push-off button turns it all on, and then it can be activated with your foot. I drilled holes for ventilation, but on a 90°F hot day neither aluminum box got even warm to the touch, so I think the ventilation holes are not needed. I salvaged a power cord from computer equipment. A circuit diagram is in Figure 9.
Figure 9 - A Drawing of the Electrical Circuit Diagram (see bottom of article for PDF copy)
The motor connects to the base of the bucket by a flange coupling connector with setscrews coupling to the shaft, and a circular aluminum plate. (Figure 10) Four 4-40 machine screws connect the coupler to the 1/8" piece of sheet aluminum by threads in the aluminum. A full-sized drawing of this aluminum plate is at AlBottomPlate.pdf, so you can print it, cut it out, glue it to the plate with rubber cement, and it will help you cut out the plate and find where to drill the holes. The aluminum is connected to the underside of the bucket with stainless steel 6-32 flat head machine screws, also threaded into the aluminum plate. Stainless steel is needed here because the heads are inside the bucket, and this avoids possible sparks from hitting the screws. The heads are sealed down with silicone to waterproof the inside of the bucket for easier cleaning.
Figure 10 - A Close-Up of the Back Plate and Connection to the Motor
An alternative to threading the holes in the aluminum plate is to< use nuts. The screws from the coupling connector should start from the bucket side with flat heads, and then put the nuts on at the coupling connector. Tip: if you use a tap to thread the holes use a "gun-tap", which has two flutes and pushes the filings forward past the end of the tap. Drill the proper sized hole, chuck the tap into your variable-speed electric drill, add a little oil to the tap, and run the tap into the hole. Then reverse the drill and run it back out again. It takes only seconds per hole. These taps only work for through-holes, and not blind-end holes.
The bucket can be removed by loosening the setscrews holding the coupler to the motor, but I find it easier to leave it attached and just pick up the whole thing to dump out the stars or to clean it. It doesn’t weigh much, so you can hold the bottom edge of the bucket against the wheels with one hand, and pick up the back of the plywood base with the other hand for easy management of the bucket.
The bucket rides on fixed casters to bear the weight of the bucket. The dimensioned drawing (figure 3) shows where I put them, but I found the location by finding a good location by trial and error, taping them down, and then marking that location. I used #6 flat head sheet metal screws. My bucket turns true to the rotation of the shaft, but the bottom of the bucket is not perfectly flat, and it is possible you may want to add some shims under the plate to get it to turn true. Run the motor with the bucket pointing straight up and see if the bucket wobbles at all. If it wobbles, some shims may be needed.
If you are right-handed, you may find that a clockwise rotation of the drum is easiest. Then the stars are more on the left side of the drum, and your right hand can reach in and sprinkle comp onto the stars. The direction of the rotation can be changed by reversing the motor wires where they connect to the speed control.
A Video of the Star Roller in Use
The video shows some stars being rolled. These are firefly stars and are about 1/2 inch in diameter. There are about 3/4 pound of stars here, which will become bigger after adding the primer. I started the stars with ground corn cob pet bedding. It consists of pieces of corn cob about 1/8 inch in diameter. Wet them with distilled water, blot off excess moisture with a paper towel, and start rolling and adding the dry star composition alternating with spraying distilled water. Use denatured alcohol if you are using red gum as the binder. It takes about 10 grams of corn cob to make one pound of finished 1/2 inch stars. The roller is also useful for adding primer layers to screen-sliced or cut stars. I have used two pounds (finished) of stars in the bucket, with enough room for twice or three times this amount in this situation. If the bucket is cut off a little taller, it could hold more but would make access to sprinkling chemicals more difficult, and it seems to hold plenty as it is.
I hope you find this useful to you. Of course, I offer no guarantees on the use of this, but I find it works nicely and have made a point of making it safe. It cost me less than $100, but I had some of the materials and fasteners already. The parts list shows the harder to find parts.
PDF file copies of the diagrams in this article: