Ashbrook Engineering

Critical to Quality! You may have never heard of this phrase, but it is essential in every proven process and assembly. One great example of this is Americas favorite burger, the Big Mac! Go to our site to read more in depth of how we use CTQs on the daily.

https://www.designwithashbrook.com/blog-3-1/establishing-critical-to-quality-ctq-specifications-for-your-product-and-assembly

lot of inventors start by building their first prototype themselves — and that’s often the right move. But at some point, you’ll face a decision: keep learning everything on your own, or bring in a team to help get your design ready for production.

This post walks through when to stay hands-on, and when hiring a product design team can save time, money, and frustration.

If you’re moving from CAD to manufacturing, a second set of expert eyes can make all the difference.

🔗 Link in bio to read the full blog
🎁 We offer 4 hours of free design time to inventors getting started

Unlock the power of precision manufacturing! Discover the 5 major metal forming techniques that shape everything from car parts to kitchen tools. Whether it’s forging, rolling, extrusion, drawing, or stamping — these processes are the backbone of modern industry.

Have you ever wondered what goes into designing a machined part?

Here are common design mistakes that can drive up costs, and drive down efficiency.

Product Spotlight: CanStache

We’re happy to announce our friends over at have launched! Visit their page to purchase CanStache packs on amazon, WalMart, and other retailers.

We are lucky enough to have helped the Can Stache team bring their vision to life, and look forward to seeing how far they take their business.

Have you ever wondered where some of the marks seen on products we use every day come from?

In most situations these marks are known as "witness lines". Witness lines occur on injection molded parts when plastic flows over a mold section where two or more parts of the mold meet.

Pictured in this post is a CD storage container base showing 8 witness lines from ejector pins. These witness lines created by the molds ejector pins are exaggerated from standard witness lines. These 8 locations receive high force from the molds ejection system to remove the part from the mold.

If a part is not fully cooled before ejection, or the ejector pins are improperly sized, it is possible for the ejection system to damage the part, or leave excessive marking on the parts surface.

Improper part design can also create a need for excessive ejection force, which can lead to part damage during production.

Be sure to check out our recent blog post to learn more about this parts design and manufacturing!

We published a new blog on our website this week. This blog outlines part one of the design elements employed in this CD storage case. Give it a read and let us know your thoughts! Part two coming soon.

On slide two of this post is the underside of the storage case base. Circled in orange are the three gate locations used to fill this part. Circled in blue are weld lines formed at the locations the flow fronts from the three gates intersect.

Weld lines occur when plastic flow fronts collide with one another, and cannot move along the length of the part before cooling.

If multiple gate locations are required to fill a part, potential weld line locations must be identified and analyzed. It is best to minimize weld lines on locations of a part that will undergo mechanical stresses. In this exact case, the weld lines also create a cosmetic blemish. Luckily this part is not subjected to much mechanical stress, so this should not affect the structural integrity of the part in the field.

This weeks design review will focus on identifying another injection molding gate location/type and mold type.

This tape roll has a gate vestige (orange) located close to its edge. This edge of the part happens to be the parting line (plane where mold halves open from) - Outlined in blue.

If we zoom in, it appears that the runner was sheared off from the part at the gate. This leads us to assume that the part utilizes what is known as a tunnel gate.

The main advantage of a tunnel gate is that when the mold is opened, the part is sheared from the runner system at the gate - In other words, the part is automatically separated from its runner system and requires less human operation than manual degating (cost savings!).

Tunnel gates certainly serve a purpose, but come with the drawbacks of being limited to certain material types, and being difficult to repair in the event of an issue.

The design of a tunnel gate will allow the plastic to "tunnel" through the steel of a two plate cold runner mold, providing access to gate locations otherwise unusable on a mold of this style. On a traditional two plate cold runner mold, gating is only possible along the parting line of the mold.

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When designing any part, a common challenge is striking a balance between aesthetic quality and ease of manufacturing. When parts feature design aspects that cannot easily be ejected from basic injection molds (known as "undercuts"), the molds get more complex and costly.

On slide 1, circled in orange, we see what are known as "witness lines". These visible features occur in injection molded parts where plastic flows over a joint of two or more steel mold parts. The blue circle outlines where plastic is injected into the mold.

In this exact situation, these witness lines are likely formed from moving mold parts commonly referred to as "lifters". The lifters are required to allow this part to be ejected from its mold. With the current part geometry (seen on slide 2), the retainer arm tabs of this part would be stuck in the mold without a special ejection mechanism to allow the part to be freed.

To remove this undercut, the aesthetic quality of the part face would be impacted by creating a hole for a "pass through core". This pass through core would allow the part to be ejected easier, at the expense of a perfectly flat part face.

Welcome to the first Ashbrook Engineering design analysis post! The aim of these posts will be to share a bit about what our design process entails. Each week we will be breaking down design elements of different parts and assemblies.

These posts will be released in conjunction with full part analysis blogs on our website. These blogs will feature part analyses in far greater detail than our posts.

This week, we'll outline some basic design elements of a tape dispenser housing. This tape dispenser housing was manufactured via injection molding of polystyrene. Polystyrene is a great material choice for this application, because it optically clear, readily available, and cost effective.

On slide two, we see a close up of both the recycling code (6 = polystyrene), and gate vestige. The gate vestige (circled in blue) indicates where the plastic was injected into the mold to form the part. Notice how the gate vestige is hidden in the recycling code emblem. This a is quite a smart way to hide an unattractive feature on an otherwise attractive part!

We hope this post format will be informative and useful. Look forwards to next weeks post for a deeper dive into this part design. Read the full blog post in our bio, and drop any questions you may have regarding this part in the comments.