Building a Heat-Shrink Tunnel

[widgitmaster]

Building a Heat-Shrink Tunnel

Because I sell many items on eBay, I do a lot of packing & shipping. It would be to my advantage to have a shrink wrap system, to make my sales look professional! Now that I have a machine shop in my garage (due to spontaneous CNC fever), it is reasonable that I can make my own system!
Due to the high cost of new equipment, I have entertained the idea of building a heat shrink tunnel to my specifications. First off, it needs a 10" wide conveyor belt. The belt can be speed controlled or fixed, but items moving too slow under the heat lamps could ignite!

Features:

Surround heat on 4 sides.
Shrink wrap cutter / sealer.
4 infrared replaceable tubes.
Adjustable speed conveyor up to 10 ft. per minute.
Adjustable temperature controllers for upper and lower heaters.
Casters for maneuverability.
Application: Electronics parts, hardware, etc.

Any Ideas regarding the design of this type of gizmo?
Eric

[mxtras]

I would suggest using lightweight extrusions like 80/20 for the basic structures because with this kind of thing, it is not something I would likely sit down and design 100% - I would design the basics, but more than half of the work would be designed on the fly and the extrusion stuff is easier to attach stuff to.

I seems like a pretty straight forward thing to build. Concentrate on the most critical element of it in earnest - heat control. I would suggest making the mounts for the heaters very adjustable and choose an adjustable heat source - like maybe IR heaters.

What areas do you feel are going to be the most difficult?

Scott

[widgitmaster]

Because I have 30 years experience in machine tooling, I think my main concerns would be the thermal controls! Building things like framework are a piece of cake for me, I would probably use 2024 ground jig plate and some square schedule 80 tubing for legs. (I like overkill)
While googling around, I noticed one manufacturer used a glass filled nylon belt, that alone sounds challenging! Would not have expected that to be flexible!
Eric

[Evodyne]

I've seen pallet wrappers that had a section of conveyor that could rotate. When a pallet ran onto this section the conveyor would stop and this section would spin. Plastic shrink wrap film on a roll stood vertically next to this section. An arm would pull the end over and somehow get it to catch to the boxes on the pallet. The rotation would wrap it all up. After X turns a hot wire cut the film and the arm retracted. A squirrel cage blower with heating elements turned on and, via ductwork, blew a stream of hot air up and down the height of the boxes. These were still spinning and this shrunk the whole package nice and tight. The conveyor section would stop spinning lined up with the rest on the conveyor, the blower would shut off, the conveyor would restart, and the wrapped pallet would move off while an unwrapped one moved on. It seemed the blowing air did a lot more that heaters alone would, and it was easy to control. You may be able to incoporate some of these ideas. Good luck!

Evodyne

[2muchstuff]

I'm at work and don't have time to go into detail. Check this out http://shrinkwrap.net

[lurch]

I helped a friend step up his tshirt printing business to silkscreen from heatpress. The biggest cost obstacle a decent heat tunnel to heat the plastic in the ink to 318F around its melt point, so it would fix to the fabric. We built our first oven with 2x4s, PVC rollers, screen wire, and some quartz shop heaters from Lowes. After initial testing we added a heat shield in the hottest area under the heater elements, and enclosed it with cardboard, adding an old oven range fume hood for exhaust out the top. We fiddled with the coverage of the infeed and outfeed openings until we had a stable temperature for a piece of fabric traveling on the conveyor belt above 320F. It's still in use with a few upgrades, plywood sides, a longer infeed conveyor section, and better ducting to exhaust fumes to the outdoors. Also the wiring in the heaters had to be upgraded to something with better shielding. That was two years ago, It cost around $250.00 to build and with about a $100.00 in upgrades it still serves today several hours a day, four days a week. Though YMMV..... It's certainly doable. For such a small volume I would suggest a recirculating blower on the inside, and sheet metal walls. If you want to be safe use properly shielded wiring, or adapt a shround to seperate the hot zones from the wiring. Keep it simple, above all. And work safely....

[2muchstuff]

I used to work in a hobby shop where we used to shrinkwrap models and other stuff. The shrinkwrap machine was pretty simple as things go. On the right, a pair of rollers to hold the roll of shrinkwrap and a plate to separate the folded over wrap. In the middle, a welded bar setup to hold an L-shaped nichrome wire that cut the wrap. Separating the wire from the bar was an insulator and the wire was covered with a heat resistant type of tape. The heat/power to the wire was controlled by a variable ceramic wire wound resistor wired directly to line voltage hidden underneath. The bar was spring loaded so that when you let go of it, it would sping back up. On the left side was a metal box with heavy plastic drapes on either side to hold the heat in. On top of the box was a fitting to accept a heat gun. Under the fitting was a diffuser plate in side the box. Inside the box was a black rubber belt attached to a variable speed motor/gearbox for the conveyer. On the front was the on/off switch, belt speed control knob and a cord going to the heat gun. The heat gun was one of those red ones with a squirrel cage blower and a black wooden handle. Heat was controlled by adjusting the damper on the side. Overall dimentions were about 24" deep, 5' long and 15" high. As you pushed down on the bar, a switch would close suppling power to the wire. You would pull on the item slightly with the bar down until the plastic wrap melted together/cut and then pull it away. We rarely used the box with the conveyer because it was faster to used just the gun and we got better finished product.

[ViperTX]

If you are just trying to cause shrink wrap to shrink then any hot air source....like a blow dryer will work.....if you're looking at blister pack then that's another story.

[2muchstuff]

Yes, any hot air source will do. Back then there wasn't hair dryers like we have now. But there were times we would use the thing for 12 hours a day non stop for weeks on end.