Powder Coating the Sandbox Excavator

A few month ago I have writen an Instructable about how I build this metal sandbox excavator. If you haven't seen it so far, have a look at this instructable. At that time the result was still bare metal, which is not very suitable for a toy that will stand outside. Rain and moisture from the ground would let this thing rust to dust faster than I build it up.

This is why I had to protect the metal somehow. Since I have access to a powder coating setup I decided to use this process. It is very fast and (if you have the propper machines) also very clean way to coat metal parts. In this Instructable I will show you the steps how I got to the final result.

• Sandblaser (or grinder / sandpaper)
• Degreaser
• Powder coating setup
• Powder in your favorite color

As always the most important step is the preparation. To make the powder stick to the metal properly it is necesarry to get rid of the millscale and all the dirt from grinding and welding.

I used a sandblaster to do this, but an angle grinder or even sandpaper will work, too. Unfortuantly, I didn't make any pictures of the preparations. After sandblasting the parts, I used a blanket and degreaser to remove all the remaining dirt and dust from sandblasting.

Before I started with the powder coating, I switched on the oven which is needed to cure the parts afterwards. It needs some time to heat up to about 180°C.

Powder coating is a process where electrostaticly charged tiny particles of the coating material are sprayed on the workpiece. It is basically a pretty simple thing. You just hang your metal parts on an electrostatically charged hook and "shoot" it with the powder coating pistol. Since the particles are pulled towards the workpiece, you don't even have to be very accurate in aiming at the free spots on the workpiece.

For the colors I descided to go for the classical excavator colors. Black for the base and yellow for the arms.

When the powder is on the workpiece the tricky part of the process beginns. The electrostatic force that keeps the particles on the piece is not very strong after you remove the workpiece from the hook. You have to be very careful when you move the part into the oven. If you touch it or hit something during the way the powder will just fall of the piece. I had to redo a few parts because I was not careful enough...

When the parts make it to the oven without loosing the coating, the relaxing part beginns. In the first minutes I checked the surface temperature of the part a few times until it was close to 180°C (curing time and temperature are depending on the manufacturer specification which is printed on the package with the powder). When it reaches this temperature it is only necessary to wait for the specified duration. In may case 20 minutes. After that you can take the parts out of the oven and let them cool down.

When all the parts are powder coated and cooled down, it is time for the best part of any project -- The final assembly :-)

I screwed all the pieces back to where they belong and put some grease in the joints. Then I checked if the motion of the parts is still working as intended. To support the weight of the arms, I included a gas spring into the design which I remounted in its place.

As a final touch I added rubber grips for kid bicycles on the levers to make it a little more comfortable to play with. Finaly I added a wooden board as a seat (not in the pictures) and it was done.

This was the whole process of how I build the excavator. I hope you liked my instructable.