Frequently asked questions and answers. If your question isn’t answered here please use the support options in the section below.
PPolyamide can be processed with up to 35 % of mid-sized glass fibres without any problems. Glass spheres and short glass fibres can be processed with up to 50 % in volume.
For the choice of the distance (L) we provide you with a spreadsheet in the support section. You can read about the distances depending on the type of Exaflow gate inserts and materials there. In special cases please get in touch with our application engineers.
An open jet formation can be prevent by following parameters:
- Use of a higher gate insert diameter
- Install dead-end recess
- Graduated injection profile (reduce injection speed)
- Increase mass temperature
- Increase screw back pressure
- Increase tool temperature around the area of the injection point
For the production of mouldings with a thin wall thickness we recommend our Miniflow ( without head). If a 100 % sunk gate must be warranted it’s possible to grind down the head of our standard Exaflow up to 0.4 mm (please attend our application examples).
Terpolymeres can be processed without any problems, however the gate diameter and the distance between gate and ejector should be designed as big as possible.
LCP’s can be processed without any problems, however the cold runner cross section and the gate cross section should be as small as possible since the material “lives by the shearing”.
Polyolefins tend to thread forming (during the demoulding process), thus during the injection moulding of flat components an impact wall around the area of the head should be installed (please attend our application examples).
The dead-end recess has several influences on the injection process:
- Decrease of shearing
- Reduction of pressure loss (up to 33 % in the injection region)
- Improves the laminar flow
- Prevents open jet formations due to improved laminar flow and the flow front gets an unsymmetrical velocity profile which results in a spin that makes the flow front attach to the interior wall of the moulding during the ejection process and brakes the following molten mass.
The cross-section of the gate depends on the processed materials, shot weight and the proportion of flow path and wall thickness. (please look at the spreadsheet in our support section). The recommended distance between gate and ejection can’t be adhered. In general, Exaflow recommends a full-round cold runner cross-section. If the recommended distance can’t be adhered we recommend a half-round cold runner cross-section to ensure the necessary deflection.
A trapezoidal shaped cold runner distributor is possible in general, but due to the result of it’s geometry it’s the most constrained variant of a cold runner. For an unproblematic demoulding process a long distance between gate and ejector should be picked.
The choice of size for the cold runner cross-section in general is a compromise. On the one hand a small cold runner is wanted to reduce the sprue leftovers and on the other hand the cross section should be as large as possible to reduce the shear of the moulding as much as possible (except for LCP).
Problems usually occur with high-viscosity materials (PC, PMMA, ABS). Solution:
- Graduated injection profile (fills the gate region slowly)
- Increase cylinder temperature, increase back pressure
- Increase tool temperature
- Increase gate diameter
- Inject the moulded part at a different spot
Processing thermoplastic elastomeres is possible without any problems. However you should focus, in coherence with the shore hardness, the design of the cold runner connection. You can find assistance for this in the support section.
It’s possible to process PC-ABS blends without any problems. You should keep the same installation conditions as for pure PC processing.