When it comes to injection molding for parts, the overall size, heart volume, and designer parts will determine if one layout is better than another layout. Since options for injection molding tools come in multiple layouts, we’re going to discuss the three most important in this article. Those are single cavity, family, and multi-cavity tools. Let’s dive in deep, so we can better understand which option is best for your business. 


#1 Single Cavity Tool

Single cavity means in each shot of plastic, the tool produces one individual part. This type of tooling is the fastest to make, but the unit part pricing is the most expensive. 


#2 Multi Cavity Tool

In a multi-cavity tool, each shot of plastic produces multiple quantities of the same part. Since there are more cavities to make than a single cavity tool, the tooling lead time is longer and the tooling is more expensive than a single cavity tool. But the benefit is being able to have a faster part production rate and a lower unit part pricing.


#3 Family Tooling

Lastly, we have family tools. Different parts of one assembly are put together or family into the same tool. Many times a family tool is the preferred option over a single cavity tool, as the tool price of the family tool is less than the individual tools of that part. The advantage of a family tool is you can have tooling price to be a little bit less than a single cavity tool. You can also have lower production costs because you’re combining all the parts into one tool and you can run all those parts on one injection molding press. One limiting factor is parts in the family tool need to be the same material and similarly shaped and size, so that the tooling is balanced. There are options to plug or shut off one or more cavities, but this sometimes can compromise the part’s precision and quality.


Secondary operations for injection molding are the most critical to your assembly function and your product’s overall cosmetic appearance. We are going to show you the main types of secondary operations and how best to design them and manage them.


– Heat Staking –

Heat staking inserts are installed by pressing the insert into a mounting hole with a thermal press to melt the plastic surrounding the insert. The majority of the time they are threaded or neural to get better strength the screw assembly. There are three important management tips with each state the inserts. Firstly, if the MOQ is lower or the tooling time is faster have discussions prior and be open to using equivalents. Secondly, since the inserts are installed by melting into the plastic. The tolerances from the processors tend to be relatively open. If they needed tolerance of the depth and the position of the insert needs to be tighter than 0.3 mm, best to have discussions prior on how to have that achieved. Lastly, best to determine the pullout force needed for these inserts so QC can be properly performed.


– Painting –

Painting parts is a secondary operation that may help with overall, cosmetics, UV resistance, wear, and chemical resistance. Before starting painting, determined the color and provide either a Pantone or RAL number and determine the color tolerance in a Delta e number. Decide if the overspray is acceptable or not, if not provided a drawing showing surfaces that need to be masked. For the painting process, ask if the parts are going to be painted in the painting booth and if the booth is environmentally controlled from the outside air. The ionizing guns help aid the paint adherence. For QC considerations, determines the simple alcohol or scotch tape test is sufficient.


– Screen & Pad Printing –

Screen and pad printing is a secondary operation used to apply logos or writing onto the plastic parts. Firstly, it’s important to provide a one-to-one size scale Adobe Illustrator file for the printed graphic, as that’s needed to make the screen or the rubber pad. Secondly, provide 2d drawings, given the location of tolerances of the print. If the location tolerances are greater than 0.3 mm, again highlight and discuss before kicking the project off. Automatic printing machines are more consistent for aesthetics and location than manually applying the printing. Determine if a simple alcohol or scotch tape test is sufficient for checking the adherence and communicate that with your factory.


And that’s all for the Injection Moulding Tool & Secondary Operations Introduction!