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Talking About Welding Equipment and Techniques

Hi there. I’m Nina. Welcome to my website about welding. The process of welding together metal takes a lot more than a hot iron and some metal wire. There are many different machines and practices people use to carefully and skillfully weld together metal. With the right techniques, you can create truly beautiful welds that hold up to the test of time. The strong metal welds are often stronger than the two metal pieces they join together. I would like to use this site to talk about the different types of welding equipment, techniques and safety gear used for this exciting industry. Thanks for visiting.

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Talking About Welding Equipment and Techniques

Reduce Downtime Due To Cleaning Out Injection Molds When Switching Colors

by Matias Keranen

If you run a plastic injection molding company that offers custom-molded products, switching from one color to another is a necessary cost of doing business. Customers want parts that are different colors, and they won't want parts that are contaminated with different colors. Thus, you'll need to completely clean out your injection molds of one color before casting otherwise identical products that are a different color. Any plastic that's left over in a mold could melt into your new pieces and ruin them. Here are three tips to help you efficiently switch between colors.

Clean Out Molds with Hot Plastic

To get old plastic out of a mold, you can cast a few products with plastic that's the new color you want. For instance, if you were making dark blue products but now need light pink ones, you can make a few casts with light pink plastic. The light pink plastic will melt any blue plastic that remains in the injection mold, and there will soon be no more blue plastic left. You'll be all set to start making light pink products.

Until all the blue plastic is melted away, your light pink ones will be tinted blue. They might come out purple, since red and blue make purple. This plastic isn't wasted, though, because you can reuse it in darker colored casts, such as ones done for black products. A little blue and pink dye won't be noticeable in black products, because the black will overpower the lighter colors.

Use Extra Hot Plastic When Cleaning Molds

When using plastic to clean out molds, you should use extra hot plastic. Heating the plastic up beyond its usual temperature will melt any plastic in your mold more quickly, so you'll have to spend less time casting products that will be contaminated with the former color.

As Michael Sepe details, casting products at hotter temperatures can impact their quality. Specifically, in his tests, casting products at hotter temperatures reduced the final products molecular weight and, as a result, their impact resistance.

Because the products produced from these clean-out casts won't be sold as-is, however, you can safely use a higher temperature. The plastic will be either discarded, or reincorporated into a darker color and recast. If they're discarded, their impact resistance doesn't matter. If they're mixed with a darker color and recast, you can recast them at a lower temperature so that they have the proper molecular weight and impact resistance.

Reduce Your Shot Size When Cleaning Molds

While using extra hot plastic in an injection mold will clean out the mold itself well, a single shot may not get all of the old plastic off of the nozzle that directs plastic into the mold. To ensure all old plastic is melted off of the nozzle, you'll need to shoot newly colored, extremely hot plastic out of it several times.

You can increase how many times your injection mold's nozzle opens and closes in a single casting by reducing the shot size. Set it so that filling the mold one time requires four shots of plastic rather than just one, for instance, and you'll increase the number of times your nozzle is opening and closing by fourfold. By the time the mold itself is cleaned out, the nozzle will be cleaned off too.

Switching colors will take time, but you can reduce how long it takes with these three tips. They'll help you spend less time cleaning out old colored plastic -- and more time casting sellable products. If you're regularly switching colors, these simple steps could significantly improve your company's output.