Void (internal vacuum void)
Internal cavity in a thick section of the part; the outer surface may look perfect.
Symptoms
- Bubble or void in the cross-section
- Bubble inside a transparent part
- Low part weight, reduced strength
Tip: Cutting a section from a thick part helps to tell a void from moisture bubbles (with moisture, the bubbles are distributed irregularly).
Order of solutions
- Check the moisture of the material; dry it if necessary
- Increase the holding pressure and time
- Raise the mold temperature somewhat
- Enlarge the gate or move it closer to the thick section
- Make the section thinner or core it out
Likely causes
Process setting
- Holding ends too early or pressure too low
- Mold too cold (the surface solidifies too early)
- Metering insufficient
- Moisture in the material (steam bubbles)
Mold
- Gate too small, freezes early
Part design
- Section too thick
Was this information helpful? If you notice anything missing or wrong, please .
Related articles
Çökme izi ve iç boşluk: kalın bölge, nervür ve tutma
Aynı sorunun iki yüzü: yüzeyde çukur ya da içeride boşluk. Nedenlerini ayıran ipuçları ve tasarımdaki kalıcı çözüm.
MalzemeHammadde kurutma rehberi: hangi malzeme neden ve nasıl kurutulur?
PA, PC, PET ve ABS'de nem; gümüş çizgiden mukavemet kaybına kadar. Temsili kurutma değerleri ve dikkat edilecekler.
Other defects
Short shot (incomplete fill)
The cavity does not fill completely; the farthest or thinnest area of the part stays incomplete.
Flash
Plastic escapes through the parting line or around the ejector pins.
Sink mark
A dent on the surface opposite a thick section; the surface is drawn inwards.
Weld line (knit line)
A line and a weak zone where two melt fronts meet.