Very small parts are becoming more and more common in the plastics industry, as the functional elements of various components become ever smaller. Microinjection units are used both in micro system technology and multi-component molding.
A Demanding Injection Unit Technology
More is expected from microinjection units. Besides using special microinjection technology molds, microinjection units should be able to process a whole spectrum of materials. Tasks for microinjection technology:
- minimal shot weight
- Short residence times
- minimal melt work
- High degree of dosing precision
- Excellent melt homogeneity
- Excellent response and control of the injection movement
- Ability to process the whole spectrum of materials
- High repeatability for all processes
The Process Determines the Design
Ferromatik Milacron offers two different designs, depending on your needs:
- Two stage injection unit with an extruder and injection plunger
- Fully electric injection unit with 14 mm screw.
With the 2-stage injection unit an 18 mm extruder screw (L/D = 15) is used. The feed zone depth of the screw can accept and process standard sized granulate. In order to reduce residence times the land width has been enlarged. The melted material is introduced into the injection plunger cylinder via a ball non-return valve (The ball non-return valve is located between the extruder and injection plunger cylinder). The material flows around the plunger via a path within the cylinder, and the plunger is forced back by the melt pressure during plasticizing. The injection is done with a plunger based on the piston injection principle. In order to achieve optimal shot weight, three plunger diameters are available (7 mm, 9mm and 11 mm). Because of the arrangement of extruder and injection plunger, we work according to “first in-first out”. This reduces the thermal loading on the molding material. The screw and the plunger injection movements are hydraulically driven.
The fully electric injection unit with 14 mm screw combines the precision of an electro-mechanical injection movement with the homogenous melt processing of the conventional screw plasticizing and a reduced residence time, afforded by the small screw diameter. The screw diameter cannot be reduced further due to the limitations of the strength. The repeatability and flexibility of this injection unit is excellent. The optimizing feed area ensures reliable feed of standard granulates with a diameter of three to three and a half millimeters. The danger of a screw breakage is eliminated by the robust screw design and the use of an electrical torque lock-out.
A Solid Foundation
While hydraulic drive technology for the 2-stage injection unit with an extruder is only available with the
K-TEC series, the fully electric injection unit with 14 mm screw can be used with all machine series (MAXIMA, ELEKTRA and K-TEC) , especially for multi-component technology. The injection unit of the fully electric ELEKTRA evolution machine series, for example, allows manufacturers to meet the high standards required for the production of minute parts for medical technology applications. In addition, the fully electric injection unit with 14 mm screw can be retrofitted with a stand alone control system (also for machines from other manufacturers). Our applications team can advise you on the best machine configuration for your production needs.
