Cleaning of Injection Molding Tools I Dry Ice Blasting I Processing Hack

Hello and welcome to a new processing hack blog post, in particular on how to clean you injection mold in an optimal way. 

Dry ice cleaning (Dry ice blasting) is an efficient, non-abrasive method for cleaning injection molding tools that allows for faster cleaning cycles and reduced production downtime. The process involves propelling solid carbon dioxide (CO2) pellets at a high speed toward the mold surface, which removes contaminants through a combination of kinetic energy, thermal shock, and gas expansion (sublimation). 

Key Benefits

Minimal Downtime: Molds can be cleaned in-place (in-situ) and at their operating temperature, eliminating the need for cooling, disassembly, reassembly, and reheating. This can reduce cleaning times by up to 75% or more.

Non-Abrasive: Dry ice is a soft medium that sublimates into a gas upon impact, so it does not damage or erode delicate mold surfaces, intricate details, or critical tolerances (Class A-D finishes). This helps prolong the lifespan of valuable tooling.

No Secondary Waste: Because the dry ice turns directly into CO2 gas, there is no water, chemicals, or blasting media residue left behind. The only cleanup required is the removed contaminant itself, which can often be simply swept or vacuumed away.

Improved Product Quality: Cleaning molds more frequently and effectively ensures consistent venting and cavity shape, which helps prevent defects like flash, short shots, and splay, leading to lower scrap rates and higher part quality.

Environmentally Friendly and Safe: The process reduces or eliminates the need for harsh chemical solvents, improving workplace safety and environmental compliance. The CO2 used is often a reclaimed byproduct from other industrial processes.

Cleans Complex Geometries: The process can reach into hard-to-access areas, crevices, and fine vents that are difficult to clean with manual methods or other media. 

Apart from dry ice cleaning, there are three more cleaning technologies which can be utilized. I have listed them in Table 1. 

Table 1: Comparison of injection tool cleaning technologies. 

How It Works

The cleaning action is based on three main principles: 

• Kinetic Effect: High-velocity dry ice pellets physically impact and dislodge contaminants.
• Thermal Shock: The extreme cold temperature of the dry ice (-78.5°C or -109.3°F) causes the surface residue to shrink and become brittle, breaking its bond with the warmer mold substrate.
• Gas Expansion: Upon impact, the dry ice pellets instantly sublimate (turn into gas). This rapid expansion of CO2 volume creates microscopic "mini-explosions" that lift and carry the dirt particles away from the surface. 

Implementation

Manufacturers can either invest in their own portable dry ice blasting equipment (machines and a supply of dry ice and compressed air are needed) or utilize third-party contract cleaning services. Leading equipment manufacturers like Cold Jet offer a range of machines and accessories tailored for delicate to more aggressive cleaning applications. 

Thanks for reading & #findoutaboutplastics

Greetings,

Herwig 

Literature: 

[1] https://blog.coldjet.com/dry-ice-blasting-vs.-alternative-cleaning-methods

[2] https://www.findoutaboutplastics.com/2016/12/optimizing-your-injection-moulding.html