What types of plastics can the Model-S inject?

Because there are so many different variations of plastics on the market, this question is not simply answered. For each "type" of plastic (e.g. PS, PE, PP, ABS, etc.) there are often hundreds if not thousands of different "grades" to choose from that can vary widely in their processing requirements. Some grades of a particular type of plastic may be designed to melt at a lower temperature, and others at a higher temperature. Some grades may be formulated to flow very easily, and others not so easily. Some grades may have chemical additives or fillers mixed in with the plastic to modify its properties, and others won't. To make it even more complicated, sometimes two different types of plastics are blended together to create a COPOLYMER that has the combined properties of both plastics. Thermoplastic resin manufacturers are constantly coming out with new plastic grades and copolymer combinations, and then discontinuing the ones that don’t sell well. Our machines are designed for mixing and injecting thermoplastic materials, but not thermosets. Thermoplastics re-melt when you heat them, thermosets don’t.

When choosing a particular thermoplastic, one important consideration is to make sure the temperature necessary to process it is within the capability of the machine (i.e. 600 F max.). Another important consideration is its melt flow rating (MFR). Plastic grades with a higher MFR usually work best in our hand-operated machines because less injection force (or torque, when mixing) is required to make them flow. Additionally, determining what MFR is necessary for your application will also depend on the size and shape of the part you are injecting. In other words, one particular plastic grade may flow well enough to inject a small part with simple geometry, but not flow well enough to completely fill the mold cavity of a larger part with many intricate pathways.

The positive thing about having so many choices, is if one particular resin grade doesn’t work well, you can often find an alternative grade that produces better results. For example, it’s not uncommon for thermoplastic resin manufacturers to offer several grades that are substantially similar to each other, except for a having different MFR. A good website to find and compare the properties (processing temp, melt flow, etc.) of nearly every thermoplastic resin grade on the market is www.matweb.com.

What materials / polymers can I mix with the Model-M Mixing device?

Because there is such a wide variety of colorants, fillers and additives on the market, available in many different forms (e.g. powders, liquids, pellets, etc.) we cannot make any sort of generic statement of what is suitable. Successfully mixing a colorant, filler or additive in with a molten polymer will also depend on the polymer itself. If you try mixing materials together that are inherently incompatible with each other, our mixing device will do nothing to change that incompatibility. It’s also important to keep in mind that whatever you mix must also be capable of being injected. For example, although you might be able to successfully mix a thermoplastic polymer with a filler material comprising long fibers, that resulting mixture could still clog the nozzle orifice of the Model-S injection molder when trying to inject it. So, the process limitations of both the Model-M mixing device and the Model-S Injection Molder must be taken into consideration when deciding what materials to mix together.

Notwithstanding the above caveats, we have mixed various types of colorants in various forms (powdered, liquid and pellet),  as well as fillers and chemical additives, all with excellent results.We have also mixed different types of polymers together also with excellent results. We have also conducted some limited experiments mixing nanomaterials in with various polymers, and at least so far those results also appear to be excellent, although we do not have a SEM to analyze the mixed samples on a nano scale.

The Mix-Molder ® System is a new product, and our experimentation is ongoing. As our knowledge base increases and we get feedback from our customers, we plan to offer additional guidance/ recommendations and helpful hints related to the mixing of various materials and polymers.

We believe our Model-M will ultimately be regarded as the device of choice for mixing molten polymers on a laboratory scale, because of its simplicity, compact size, ease of use, and employment of an innovative helical blade mixing element that creates exceptional laminar and chaotic flow within the melt chamber, which is typically not achievable with conventional screw type mixers and augers.

Do I need an overhead mixer or is the hand mixing tool sufficient?

A hand mixing tool comes included with the Model-M device.

The hand mixing tool is ideal for stirring a molten polymer before injecting it. Stirring ensures the entire melt in the barrel is at a uniform temperature, and also reduces the time it takes for the polymer to completely melt, which decreases the chance of degradation for heat sensitive polymers. An evenly melted polymer is also easier to inject.

The hand tool often works well for mixing powdered and liquid colorants into the polymer, because they can usually be distributed throughout the polymer matrix easily, without extensive mixing.

An overhead mixer is generally recommended when mixing two different polymers together, or colorants that are in pellet form (i.e. masterbatch), or other types of fillers or difficult to mix materials, such as nanotubes. To get the best results for mixing these types of materials, a higher rotational speed of the mixing blade is often necessary and sometimes for an extended period of time, which is difficult to accomplish with the hand mixing tool.

If you plan to use an overhead mixer with the Model-M device, you will need a machine mixing tool (Item MMT-001-1), which is available for purchase separately. The removable mixing blade attached to the hand mixing tool will also fit the machine mixing tool.

What type of overhead mixer is suitable for use with the model-M device?

Our evaluation of different off-the-shelf overhead mixers is ongoing, and we will provide updated information as it becomes available. However, at this time we recommend the following characteristics for whatever overhead mixer you choose:

• HIGH TORQUE
• LOW SPEED CAPABILITY
• THROUGH SHAFT
• TORQUE DISPLAY
• RPM SPEED DISPLAY
• TORQUE OVERLOAD PROTECTION

For example, below are two off-the-shelf overhead mixer models we have successfully used in cooperation with our Model-M Mixing Device.

1. Caframo Model BDC-1850

2. Heidolph Model RZR 2102

Between the above 2 mixers, our choice would probably be the BDC-1850, because it’s substantially less expensive, and for us (at least so far) seems to perform just as well if not better than the RZR 2102. One advantage the RZR-2102 does have is a simultaneous display of the torque and RPM, whereas the BDC-1850 requires you to toggle between the two readouts.

Why are there different injection tube capacities available?

Both the Model-M and Model-S include a 16 cm3 capacity injection tube (a/k/a melt chamber or barrel). However, capacity change-over kits are available for purchase separately, allowing you to either increase or decrease that capacity.

Our CCK-003-1 change-over kit includes a larger capacity injection tube of 23 cm3.

Our CCK-001-1 change-over kit includes a smaller capacity injection tube of 10 cm3.

Not surprisingly, the advantage of using a larger capacity injection tube is the ability to make larger parts. However, one advantage of using a smaller capacity tube is increased injection force, because the downward pressure applied by the user is concentrated to a smaller surface area, resulting in an increased force per square inch. This would be particularly useful if the material you want to inject has a lower melt flow rating (MFR) or is otherwise difficult to inject. A smaller capacity tube may also be desirable when there is only a small amount of material available to inject, or if the material or the additive mixed into it is very expensive (e.g. nanotubes).

It only takes a few minutes to “change over” the Model-M and Model-S to a different capacity injection tube.

Is it difficult to clean the injection tube and other components?

No. To minimize polymer residue from sticking, the injection tube, funnel tray and injection nozzle are all polished and plated. The injection ram is Teflon coated. The helical mixing blade and components of the material stripping assembly are Teflon coated.

A cleaning tool kit (Item CTK-001-2) is also available for purchase separately. If there is any degraded polymer residue sticking to the inside walls of the injection tube, the cleaning tool can be inserted into the tube to easily remove it, which is much faster than purging out the residue by adding in new material.  

Also, since the injection tube is removable, it can simply be detached from the Model-M or Model-S, allowing you to easily look inside the tube to confirm all is clean.

If you should happen to get any sort of charred polymer residue stuck to the injection tube walls that cannot be cleaned out with the cleaning tool, the nozzle can then be easily detached from the tube, allowing you to insert a tubular brass wire brush to more aggressively clean out the tube.

There is a video posted on our VIDEOS page that demonstrates how to clean the injection tube using the cleaning tool.  

What is the largest mold size the Model-S Molder can accommodate?

The maximum mold dimensions according to our specifications are: 2.63" H x 4.00" W x 2.50" D (67mm H X 102mm W X 64 mm D).

The mold height is limited to 2.63” because the nozzle is positioned directly above it, but there is some flexibility to accommodate a larger mold width and depth.

The depth of 2.50" could be increased a little if you remove the 3/8" thick adjustable backing plate and then place the mold directly against the backwall of the machine frame. However, your mold would then need to be radiused at the bottom edge to match the (.75”) radius of the inside corner of the frame, where the vertical backwall meets the horizontal base.

The width of the mold could also extend past the 4.00" width of the machine if desired, however if it extends too far, you may need to attach c-clamps to the extended mold ends to help hold them tightly closed.

Where is the Mix-Molder ® System manufactured?

United States