Injection Molding Questions from a customer standpoint

11 Aug.,2025

 

Injection Molding Questions from a customer standpoint

There isn't an injection molding subforum, so hopefully this will work.

My wife wants to develop a household item that would be best suited to manufacture via injection molding, so I'm working on the preliminary stuff.

I've contacted a few shops and have received one quote so far. The quote received was from a more "PROTO"type shop it seems with a significant web interface. I'm not going to name names though. The quote I received seemed to be significantly higher than expected, especially for the mold making. Am I missing something as far as the quality the mold needs to be? There are three different parts and I was quoted $5k for a mold for a part that is less than 4"x3"x.5". I can't really say what the parts is, but we'll say it is shaped like a hook from a clothes hanger. I haven't received a quote back yet from what I feel would be a more down to earth IM shop, so I have no comparison.

Does anyone here do a lot of mold making and can tell me if this is a reasonable price?

Are there any representatives for IM shops here on PM that I can talk to about quotes?

Thanks.

Jay
$5k isn't much but it really depends on what you are getting, and what you want. Aluminum molds are my favorite, both to make and run. Are all three parts moldable? If so can they all be put in the same mold, ie be made from the same plastic?
My original intention was to have all 3 pieces in the same mold to where they would break apart by the end user for final assembly. The outfit said they can't do it that way, which strikes me as odd, but it has more to do with the way they quote electronically.

Sent from my HTC One using Tapatalk the price of 5k is normal,maybe even a tad cheap,yes even for one part. as long as the parts are somewhat similar in size and height,and of course, same plastic, they can all go in one mold. but be careful what you get. some hack shops make garbage molds that flash (leaks at Parting Line), have poor cooling lines, and crappy steel that wont survive long in the Mold Press. the range between a cheesy mold and high quality mold is far apart. (used to make plastic inj. molds for 20 years) Jay,

Welcome to the world of product development. (insert half a smiley) Yes, it can cost 10,000's of dollars to get even a simple-cheap-and-cheerful product ready for production. Ask me about my $400 prototype sheet metal brackets (estimated production cost in modest volume: well under $2). Tooling is expensive, and you pay for it all right up front before you ever know you'll make any sales.

$5,000 does not sound terribly high for a mold, although another shop probably can quote it lower based on your rough description of the part complexity. Doesn't do you any good in this instance, but that same $5,000 would probably buy you a more complex part at the same vendor. If you are hinting at the same PROTO vendor everyone here is familiar with, you get some intangibles, namely that the mold will definitely work with the injection machines. Being in the middle between independent mold makers and molders can be an aggravating situation. For what it's worth, between 3 molds; the one given already, one for a part that is 1"x2"x1/2" and one that is 16"x8"x1/2", the total mold price was about $23,000. The per part price seemed high at about $6 for the three parts at units. This is probably not going to happen. It's a unique enough product that it might be able to sell for $7-8 but after shipping and packaging, I'm already upside down. And I refuse to go overseas for something like this.

Edit: the per part price was after the mold cost. So the first would cost $23-30 each. Volume is EVERYTHING. At 10,000 parts it might be just $2 a set, at 100,000 it could be $0.75 a set. At a million you'd probably be shocked at how low it would go.

Another thing to remember. It is VERY easy to design an expensive to mold part, and often quite difficult to design one cheap to mold. I would approach other vendors and see if any of them can recommend changes to get the price where you need it. Those "get your prototype done FAST' outfits sell speed, not price. Lots of considerations developing a molded part; mold design dictates both cycle time and post molding handling,packing, etc. Plus, while I realize you only want to test the waters, but parts is only one shift, if that. That is going to incur a set-up charge, for sure. We don't do custom molding, but if someone places a rush order that makes us pull a mold to hang another, we add four hours just for set-up, then setting up the job we pulled again. Sounds like because of different part sizes you have three molds, which may be happiest in three different size presses, so THREE set-ups.

The old traditional way to approach this is to talk to a custom molder, not the toolmaker. The molder will offer guidance as to what material the mold should be (aluminium, P-20 pre hard, or fully hardened tool steel) gating (sprue direct to part, cheap, but expensive to have someone de-gate each part, conventional runner and tab gates, or a hot tip) and mold bases (many molders use at least some Master Unit Die sets, which save part of the cost of the mold base) but not all molders use the same size. Once you get a molder to agree to run the job, they will contract with a toolshop that can do the tooling, and get it right.

Which brings up the point... unless you have some familiarity with injection molding, don't even think of building your own. There are all sorts of nuances that only become evident upon test shooting, and you get charged by the hour plus set-ups for the press time for test shots.

Dennis As others have said, the prices you have are not out of the realm of possibility. It's hard to tell without seeing the parts whether they could be all run in the same tool if they are being made out of the same type of plastic. We do prototyping and mold building as well and our first step in the developement process is to 3D print the said new product. We have a SLA printer and it allows us to make accurate changes to sizes for fit. When we're happy with fit and function we will build an aluminum tool for injection molding. We have had aluminum molds last several hundred thousand cycles which is enough to determine how big a seller your product is going to be. Should a multi cavity, high production quality mold be needed to keep up with demand, you should have time to get it going before the aluminum prototype gives up the ghost. We are a captive molder (we only develope our own products,no outside work) but if I can help you with advise I will. Good luck! The developement process can be daunting. We are working on a product now that has been in the works for going on 2 years and we are still in the prototype mold phase.
That is a good deal for a high-quality mold by an American tool maker.

You can probably get it made for half that if you go to the bad place.

And if you go to the "bad place" you better have the machinery and tooling (nevermind the expertise) to rework the runner/nozzles/shut off faces/etc when the mould won't shoot properly. $5k is very cheap for an injection mould. Someone with zero experience thinks the price is high, surprise surprise. Some people just have the default mentality that every price they see is "high".
I went back and read "RC Mechanics" post, nowhere do I see any writings justifying your vicious reply.

"Someone with zero experience thinks the price is high, surprise surprise. Some people just have the default mentality that every price they see is "high"."

Vicious reply? I replied to a generalization that was intended to encompass me. If you don't think that was justifiable, move along. There were 10 other replies to my question telling me what I found is what to expect and I thanked them. You didn't notice that did you?

My understanding of how molds are made and priced was unclear, which is why I asked. We're all manufacturers here, so I looked at the mold making process of taking a negative of my part and machining that cavity into two chunks of aluminum. An hour of CAM and a couple hours of machining does not justify $5k to me. So there has to be more right? Or are mold makers doubling and tripling their cost because they can?

Common Custom Injection Molding Questions and Answers

Injection molding is a versatile and precise process, making it ideal for OEMs that rely on complex, highly engineered plastic parts for high-performance applications such as medical devices or automotive engine components.

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Given the importance of these injection-molded parts — and the potential far-reaching impact of part defect or failure — selecting a custom injection molding partner must be a carefully considered decision. As a result, OEMs must ask the right questions to gain insights and assurances to help them make the best strategic choice.

Often, these questions revolve around project-related design, materials, process optimization, quality assurance, testing, etc., and the injection molder’s engineers are usually best suited to answer.

As the trusted custom injection molder for OEMs in a range of industries, Kaysun engineering professionals routinely field the frequently asked questions we’ve compiled and answered here.

1. Which plastic should I use for my application?

Material selection is uniquely application-driven since characteristics and factors such as mechanical properties, performance requirements, tooling needs, operating environment, regulatory standards, and price all come into play. Approving a tentative plastic or suggesting a “good fit” based solely on specs and a print would be a disservice to manufacturers and the injection-molded parts. Kaysun is committed to being an injection molding partner that comes alongside OEMs to guide discussions and choices to match design, materials, and goals.

2. Can I substitute plastics?

There are often opportunities to substitute materials for various reasons, but it’s typically not a simple swap-out. Mechanical properties, thermal performance, chemical compatibility, aesthetics, potential tooling changes, processing differences (cycle times, weight, etc.), dimensional stability, secondary operations, compliance considerations, and cost may all be impacted. The expertise of an injection molder is critical in weighing advantages and disadvantages before deciding. Kaysun’s specially trained engineers and our 10 master molders offer analysis on plastics behaviors, mold flow, and potential barriers to success that may not otherwise be readily apparent.

3. Should tooling be made from aluminum or steel?

Steel tooling was once an expensive and time-consuming option that made the comparative speed and cost-effectiveness of creating aluminum tooling an attractive alternative in certain situations. Over the years, manufacturing advancements made cutting steel as efficient as machining aluminum, and steel quickly became the tooling material of choice. Steel provides the closest match to actual production conditions during tooling design and testing, along with better structural integrity and consistent molding repeatability to ensure tight tolerances and complex geometries are maintained to top-quality standards.

The choice really isn’t either/or. Selecting the proper grade of molding tool steel is essential to achieve the desired project outcomes. It influences how plastics behave during molding, which could impact cycle times, part criteria, production volume, and overall cost and maintenance.

4. Can tooling design be modified after the build is complete?

Technically, tooling design can be changed at any point in production. However, where the tooling change falls in the process can be both challenging and costly. Depending on the scope of the changes and status of qualification, Kaysun may be able to offer in-house adjustments to existing tooling to mitigate outsourcing expenses and minimize downtime while accomplishing the goal.

5. Who owns the part design? Tooling?

Ownership typically depends on the arrangement agreed to between the injection molder and customer. Kaysun has non-disclosure agreements in place with all customers to protect intellectual property. Proprietary information and processes, part design, and tooling are and remain the property of the OEM.

6. What experience do your engineers have with scientific molding, DfM, and mold fill analysis?

Kaysun engineers have extensive training and proven experience in scientific molding, Design for Manufacturability (DfM), and mold fill analysis. Expertly applying these predictive principles and processes translate to more efficient injection molding.

DfM focuses on part design optimization and defect prevention through examining part geometry, wall thickness, draft angles, and material flow early in the design process. Should challenges arise they can be corrected at the point of least time and monetary impact. Likewise, affirming that a design is manufacturable early on prevents costly redesigns and delays.

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Simulation tools such as mold fill analysis provide valuable insights into the behavior of materials during injection molding. They help engineers visualize how plastic flows through tooling, finding potential defects such as sink marks, and making adjustments to optimize the design before tooling is made. Kaysun engineers depend on mold fill analysis and other advanced simulation software to refine part designs and molding processes — resulting in lower development time and costs without compromising quality outcomes.

7. Do you offer value-added services?

Molders that offer value-added services (aka, secondary operations) play an important role in supply chain management and delivering cost efficiencies for OEMs in need of welding, heat staking, machining, assembly, etc. Kaysun's vertically integrated services are customized to specific project needs, and provide competitive advantages in consistent product quality, timely production, limited risk exposure, and enhanced reliability.

8. How is automation incorporated into your molding process?

Automation is increasingly important in injection molding to improve efficiency, consistency, and safety. At Kaysun, we use a variety of automated systems, and nearly all of our machines include robotics for part removal, insert loading, and secondary operations such as assembly or inspection. Automation allows us to maintain consistent cycle times and cooling times, manage quality, and improve overall throughput, which is especially beneficial for high-volume production runs.

9. How old are your presses? What does maintenance and replacement look like?

Presses are the workhorses of injection molding. How a molder invests in and maintains presses could signal their approach to leaning into challenging projects and innovative solutions. Annually, Kaysun replaces two or three molding machines that are nearing the end of their operational life, and also adds two or three new machines to increase capacity. This regular best practice helps prevent equipment-related downtime and also ensures production is supported by a fleet of state-of-the-art machinery and technologies.

10. What process controls are in place for quality assurance?

The precision and reliability required of complex applications means injection molding quality control held to the same exacting standards. Kaysun is committed to cross-functional, collaborative teamwork and implementation of rigorous quality control. In-process monitoring using RJG technology, dimensional inspections, and in-depth statistical analysis of tight tolerances is supported by our in-house Quality Lab. Quality technicians conduct comprehensive testing on samples at intervals of 3 times per shift to ensure all parts conform to specifications.

11. How do you manage part defects and nonconformities?

Automated inspections using RJG technology continuously scan for defects. Should a suspect cycle arise, robots extract the nonconforming parts for further engineering evaluation and correction. Should dimensional nonconformity occur, engineers backtrack to the last known good inspection to analyze data from that point forward to find and correct errant dimensions that caused departure from specifications.

12. What sustainability initiatives have you implemented to reduce your corporate carbon footprint?

Creating a more sustainable workplace can be challenging for manufacturers, but Kaysun is up to the challenge. With the support of our internal Green Team, we have several initiatives that focus on reducing our carbon footprint.

Since injection molding consumes a lot of energy, finding ways to conserve it is a primary goal. Installing our Central Material Handling System saves 1.5 million kilowatt hours per year. We also committed to plastic-waste-to-energy conversion in partnership with renewable fuel and power producer Convergen Energy, diverting more than 2.7 million pounds of plastic waste from landfills and helping our local utility company reduce greenhouse gas emissions by 40%.

LED lighting, installation of a more efficient tool chiller system, and other facility upgrades also contribute to helping Kaysun be responsible stewards — a goal recently recognized by receiving a Focus on Energy Energy Efficiency Excellence Award and a grant to fund future conservation efforts.

Understanding the intricacies of injection molding is essential for any manufacturer looking to partner with an injection molder that can consistently produce high-quality plastic parts. By addressing these frequently asked questions, we hope you gained valuable insights into how Kaysun can help you achieve your injection molding goals.

Have more questions? Great! Reach out to the Kaysun team any time. We’re here and happy to help.

If you have more questions or would like to discuss your project in detail, feel free to reach out to our team of experts. We’re here to help you succeed!

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