Saturday, March 15, 2008

The Powder process...

I've had a lot of folks email me asking the difference in finishes for bicycles...how does powder coating differ from paint, are metallics possible with powder, what colors are available, and why is paint more expensive?

As I've been inundating y'all with pics of my paint booth construction, I thought I'd explain a bit about the powder process that I use, what it's strengths and weaknesses are, and what is possible in the world of powder today.

So, grab a cup of joe, and pull up a chair, and let's look at the process of powder coating a bicycle frame here at Groovy.
We begin by hand stripping the paint off of the existing frame and components, in this case, the shop demo Bigwheel. The primer I use is like concrete when you try to strip it off, super tough, so I do not relish this part of the process. Typically, there are portions that just will not come off, kinda like here in this pic...
The frame needs to be immaculately clean before any finish can be applied, both for quality of finish as well as durability. So, the next stop is the blast cabinet. The frame has to be totally closed up so that the abrasive material does not get inside the tubing, so all vent holes are taped over and water bottle bosses filled with bolts.
Here's a shot of the frame, fork, and bar all blasted and cleaned. All handling from this point on must be with gloves on so that the oils from your skin do not contaminate the base material. The abrasive blasting gives the finish a superior texture for mechanical adhesion.
Every thing gets wrapped in plastic and off to Chupp's powder coating we go. Vernon has a facility that has done many production runs of bicycle frames for large manufacturers as well as working for general industry. Vernon custom designed this facility and invested mucho bucks in the set up; the result is consistent finish quality and efficient operation.
We're going to start with Willy, Vernon's right hand man. Willy and I masked off the important aspects of the frame; the dropout faces, the steerer tube, the bottom bracket threads, the inside of the head tube, and the seat tube gets a expanding holder to hang from. All the parts get hung on a rail system that carries the pieces through the whole facility.
The next stop is the wash station. The parts enter a contained chamber that has high pressure wash fixtures that move parallel with the parts. The first application is a heated acid based solution that strips away all the oils and dirt from the parts, followed by two series of cleansing washes that leave the parts minty fresh.
Here's a shot of the acid solution tank...
and the two rinse tanks...
When the parts exit the wash station, everything gets a sealer coat to protect the base material and chemically prep the parts for the powder application.
Willy applies it to the parts using a simple pneumatic pressurized sprayer.
Then it's off to a heat chamber, to set the sealer and bake off all the moisture. The parts will stay for 20 minutes and the temperature varies dependant on the powder to be applied as some adhere better with the frame hot contrasted to warm to the touch.
Next up, it's off to the spray booth, where the rail carries the greatest static charge to help the parts attract and hold the powder. The gun also carries a variable charge that helps the powder attract to the frame.
The powder it's self will sit in a vibratory feed unit, gently shaking the powder in it's box allowing for it to be easily drawn up the tubing to the gun.
The powder comes in a variety of sizes...here's but one stack of stock that Vernon has available.
For this frame, we'll be using a metallic rootbeer with antique brown clear coat, it will give the white of the decals an aged look, kinda like document paper that has weathered and browned. I'm running some different material decals through the bake oven as well to test their capacity for the process.
Everybody, meet Freida...the chief applicator here at Chupps. The paint booth is a two step process, utilizing two filter walls. The powder is applied one side at a time, shooting toward the filter wall. The application is shockingly short, taking about 45 seconds. Quite the revelation, as a liquid paint job requires multiple application steps and loads of time.
The actual finish material is statically attracted to the base metal, but is very tenuous at this state. If you were to rub it at this time, it would simply come right off or smudge, leaving bare metal...one of the reasons the pieces are sprayed one side at a time, as the parts cannot rotate or be manipulated by hand.
Here are some shots now that everything is evenly covered. Notice the powder looks very grainy. As it is basically colored plastic dust, it will not take it's final shape until it is baked and melted, adhering to the base material's grain structure.
the parts move to a staging area waiting for oven time. One of the things that hits home is that this process has a lot of "hurry up and wait". Each part in sequence must complete it's time at each step and the stages reset for the next piece requirements.
The oven is set for a half cycle cure for these parts, as an antique brown clear will be applied overtop.
In the oven they go, and back out 15 minutes later...
Here's the first shots of the root beer powder fresh out of the oven. The grainy texture is gone, now replaced by the metallic gloss that is so much fun. The flash of the camera washed out the picture a bit, but you get the idea :)
Once the parts cool, the decals are applied and it is back to the spray booth for the antique brown clear.
Here's a close up look at the siphon tube that sits in the powder...
Parts are all sprayed and ready for the full cure bake cycle.
The final result...
You are going to have to wait ;) ... the final result will be a surprise. I can tell you this though, the finished product is very cool.
I'm waiting on some White Industries Eno Disc hubs to build the wheels, and then the big unveiling will happen.
Overall, powder offers an environmentally safe process, an incredible durable finish, and well over a thousand different colors that can often be matched to it's liquid brothers.
The finish is not as "show quality" as liquid paint and for the standard coater, the intense graphics are still unattainable. However, the price point for powder of this caliber is closer to most people's ability to commit.
Price for a standard powder job is $100.00, metallic or illusion colors bring $150.00.
So, what's next for Vernon's crew? It's a bike of another nature :)
Cheers,
rody

4 comments:

Anonymous said...

Rhodes - great post - interesting to see what is behind door number three. . .checkout the interview with "Dazza" over at Belgium Kneewarmers and let me know what you think.

CH

Chauncey Matthews said...

Hey Rody,
Thanks for the great post, I just had one of my frames pc'd for the first time and it's good to see my guy's setup was pretty close to your guy's. Although, he did coat the brake posts......
-Chauncey

Rody said...

Chauncey,

Gotta be proactive in educating your finisher...saves you a lot of time and effort :)

cheers,

rody

mark said...

most excellent post and photos on PC'in,,,,,,,enjoyed it immensely, well done
mark g, santaflagpolefe