How to transition efficiently

Transitioning from one material to the next is common, necessary practice. We have illustrated an inconvenient issue and the recommended steps to transition more efficiently.

Table of Contents

Transition Windows

Incomplete Transitioning

Recommended Solution

Transition Windows

A transition window is the temperature range in which one material's operating temperature overlaps with the other. If the transition happens outside of this window, there is a high risk of degradation, burn, and potentially a clog. 

To transition safely and effectively, it is important to: 

• transition in the correct, and safe temperature window.
• wait for at least 15 minutes (estimated residency time of any material in the barrel at 5RPM).
• follow our recommended solution below.
• inspect the output regularly and confirm visually that only one material is being extruded. 

Figure 1. Standard Purge from/to PLA

Incomplete Transition

The following illustration gives a good account of what is happening unseen inside the Hopper when transitioning. This can happen also happen with purging materials, powder, shredded or even pre-compounded material. 

Figure 2.

Text:
1. When pouring material B on top of material A,
2. depending on the weight, size, or shape of both materials,
3. vibration may cause uneven distribution
4. resulting in an incomplete transition.

As illustrated, the main issue comes from the distribution and dispersion of the particles based on their separate characteristics. To avoid this, let's have a look at the method 3devo staff uses to transition effectively. 

Recommended transition process

The simple solution is to avoid mixing materials in the Hopper. Though this has to be done with care.

Figure 3.

Text:
1. Wait for material A to pass through.
2. When little of material A is visible, pour small amount of material B.
DO NOT let barrel run empty!
3. Wait for visible evidence of complete transition, 
4. and when ONLY material A is visible around screw, continue. 
DO NOT let barrel run empty!

To summarize, if we wait until there's only very little of material A is left, we limit the chance of any backflow, or unwanted mixing.