TMD & TMV Series

2-Component

2-Component 

2-component machines make parts with two materials (e.g. hard and soft) or two colours, to reduce the labour content.  

Parallel barrels 

Tat Ming has developed two compact 2-component machines with parallel barrels, the TMD50-S and TMD110-S. Naturally, they make small parts or parts with few cavities. The barrel separations are 200 mm and 400 mm respectively. 

Moulds for the parallel barrels are low cost as smaller mould bases could be used.  If parts could be laid out to fit 200 mm barrel separation, one mould could be used. If the centre space is wasted for 400 mm barrel separation, find out if two moulds could save some cost. 

TME50-S has 50 tons of clamping force.

TME110-S has 110 tons of clamping force.

2-component moulds 

2-component moulds are designed according to transfer technologies. The technologies are rotary table, robot arm and indexing cores. Transfer technologies are ways to take the parts from the first injection to the other side for the second injection.

Rotary table 

Rotary table is a part of a 2-component injection moulding machine using this technology. The core halves of the moulds are mounted on the rotary table, which in turn is mounted on the moveable platen of the injection moulding machine. 

In the above picture, one of two moulds is mounted on the rotary table.

Rotary table explained 

Refer to the diagram below. In the first shot after starting up the machine, only A is injected by barrel 1. The mould opens, the rotary table turns 180°, then the mould closes for the second injection by barrels 1 and 2. Note that barrel 2 moulds B over A. At the same time, barrel 1 moulds another A. 

When the mould opens again, the 2-component part is ejected from the barrel 2 side. This is repeated in each subsequent mould open. 

Note that the two barrels are at the centre lines of the two moulds.  

Robot transfer 

Refer to the diagram below. The transfer of the part from bottom core to top core could be done by a robot arm if the part has no undercut. 5-gallon bottle cap with liner is an example. The robot arm first removes the completed part before transferring the bottom part. 

The process is slower than rotary table due to the additional parts removal and insertion. Especially in multi-cavity moulds, removal and insertion could go wrong, reducing the production rate. 

Indexing cores 

Refer to the diagram below. After the top injection, the mould is opened, the cores indexes (advances in the ejection direction), turns 180° and then retracts. When the mould is closed, material from the bottom barrel is injected into the space between the part on the rotated core and the cavity.

A mechanism on the 2-component injection moulding machine indexes, rotates and to retracts the cores. It is simpler than the rotary table. 

A mould made using this technology costs more than moulds made for rotary table. 2-component tooth brush handles are an example. When the second injection goes into the cores and the cavities, the mould is better made using this technology.

Vertical barrel 

The TMV series adds a vertical barrel to our TME series to provide the second component. Space saving is its advantage, but a high ceiling is needed.

90° horizontal barrel 

The secondary barrel could be bigger if placed horizontally at the opposite side of the operator. It is therefore 90° to the primary barrel. We offer secondary barrels from our MA23 and TME50 models. The primary barrel and the clamping unit come from the TME series. 

In the diagram below, the primary barrel is at the centre of the fixed platen. The secondary barrel can be vertical or 90° horizontal. Note how the melt channels of both moulds turn 90° at least once which is not needed for parallel barrels.

Core-back 

The core-back technology is the simplest way to make space for the second component. An application is the soft material on the clips of cloth hangers. Not all 2-component moulds could be made using core-back technology. 

No rotary table nor indexing core mechanism is needed. In the diagram below, the core moves forward before the injection by barrel 2. It moves back before the injection by barrel 1. The core pull mechanism is used to move the core back and forth. Core pull is an option on an injection moulding machine.

Note that the two injections do not happen at the same time. Furthermore, the mould does not open between the two injections.

Piggy-back barrel 

The secondary injection unit rides piggy back on top of the primary barrel. The advantage of this design is the two nozzles could be very close to each other. The nozzle separation is 150 mm in the machine below. 

Like the previous two designs, existing TME models are used to provide the primary barrel and clamping unit. 

Summary 

Configurations of the secondary barrel compared 

Transfer technologies compared 

Marble appearance 

The technology that gives marble appearance on parts have been around for a long time. A standard injection moulding machine with a short screw is used so the material of one colour and master batch of a different colour are not mixed very well. 

Tat Ming has the knowhow. 

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