Color Dosing for Blow Molding
Blow molding is our second largest application after injection molding — bottles, containers, jerrycans and PET preforms. Batch sizes are larger and the value per part is lower than in injection molding, which is exactly why a per-tonne saving carries further here.
The problem with pre-blending
- Pigment and resin have different particle sizes and bulk densities, so a pre-blended batch separates again while it is conveyed to the machine
- What arrives at the start of a run and what arrives at the end are not carrying the same pigment load — the color fades batch by batch
- Pigment left on conveying lines and in the hopper is carry-off: paid for, never moulded
- On lines that dry the resin first, pigment added before drying is driven off and redeposited in the dryer
What dosing at the throat changes
- The unit sits on the machine throat, so pigment meets resin after conveying and after drying — there is no distance left for it to separate over
- Dry the resin only, then dose and mix inside the hopper — the sequence, not just the equipment, is what fixes the fade
- Fully enclosed dosing, so pigment does not drift onto a neighbouring line running clear or light-colored product
- Recipes held on the unit and recalled, so a color is reproduced rather than re-weighed
A PET preform plant that bought three times
A PET preform works in Wuhan started with one trial unit and now runs 75 machines on MegaColor, ordered across three purchases. What they changed was the sequence: they stopped coloring before drying, and moved to drying the resin alone and dosing into the hopper afterwards. That ended both the pigment carry-off during conveying and the batch-by-batch fade.
Blending operators went from 12 to 3. Scrap on their worst colors had run as high as 21%, and after the change the line effectively stopped producing color-related scrap.
We run blow molding ourselves
Our parent company, Zhejiang Sunup, is a plastics processor in its own right. Its floor in Huangyan runs 70 injection molding machines and 20 blow molding machines, every one of them fed by a MegaColor dosing unit. Customers who visit are walked through that floor and are welcome to bring a colorimeter and measure the parts themselves.
That is also why blow molding is not a brochure claim for us: the machines were proven on our own production before they were sold as suitable for yours.
Which model for which line
Resin temperature and throughput per machine decide the model.
| Your line | Model | Throughput |
|---|---|---|
| PE / PP bottles and containers | ICOLOR5 Standard | 50–70 kg/h |
| PET preforms and other high-temperature resins | Same model, high-temperature configuration — see model codes | 50–70 kg/h |
| Two powders dosed together | ICOLOR5 Dual-Powder | 50–70 kg/h |
| Resin plus regrind or filler | ICOLOR5 Dual-Material | 50–70 kg/h |
| More than 70 kg/h per machine | Large-Capacity | Higher throughput |
Our measured consistency figures were taken under injection molding conditions. Blow molding draws material differently, and we do not extrapolate one to the other. Send us the resin and the pigment from your own line — we test on your material and the numbers you get are yours. There is no charge for this step.
Get the data on your own material
Send us the resin and the pigment you run. We test on your material and settle the model once there is data.
Lead time, shipping terms and export documentation are confirmed per order.