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How to switch from 3D printing to injection molding

3D printing has been an awesome way of creating products in recent years. We, as a company, used 3D printers to create prototypes from time to time. However, like any other current technology, 3D printing also has limits if your goal changes over time. For example, if you want to make more parts in the same amount of time, you need to add more printers to your printer fleet. Unfortunately, that may not be possible or feasible all the time.

APSX LLC received new customers from the 3D printing industry specifically for this main reason. These customers converted their production process into plastic injection molding. The roadmap from 3D printing to injection molding is pretty straightforward.

1 – The 3D drawing of the part

As a 3D printing business, you already have your part designed in a 3D environment (CAD). Sometimes a 3D printable part can not be a good candidate for injection molding. You can easily revise the features of the part so that it is compatible with injection molding. Some typical 3D file formats are STEP and IGES files. You can use Fusion 360 or Solidworks software or similar for that purpose.

2 – The 3D drawing of the mold

The next step in this process is to create the mold for injection molding in a 3D environment (CAD). You need to subtract the part from the mold surface to create the cavity on the mold. Now you can think about how you will make the mold in the next step. APSX LLC has 3D files for the standard size blank mold on its website. You can download it whenever you are ready to try this.

3 – Making the mold

Once you have the g-code out of the 3D software, you have the options (CAM):

a. 3D printing the mold: You can use high-quality (not PLA) 3D printer material that can withstand some level of clamping force and heat. The other good characteristic of the mold material is its high conductivity. That makes the mold cool down easily. The mold size can be a full-size mold or an insert type.

APSX 3D printed molds

APSX LLC successfully tested sample 3D printed molds from the 3D printer companies such as OriginStratasysMarkForgedFormlabsElegoo and Asiga.

b. CNC milling the mold on a high melt plastic block: If you want your milling process to be forgiving and easier, you can mill plastic material such as polycarbonate or other translucent material. That would also allow you to see how the injected material flows inside the mold. Follow the link here to watch.

APSX polycarbonate mold

c. CNC milling the mold on an aluminum block: The ultimate goal would be to mill the mold on an aluminum block. APSX SPYDER CNC machine is a good choice since it was designed with that purpose in mind.

Once you switch from 3D printing to injection molding, you will see its benefits in fully functional plastic parts, lower cost per piece, and much shorter production times. These are the essentials for a growing business to meet its increasing demand.

Please get in touch with us to receive more information about APSX-PIM and SPYDER CNC.

APSX-PIM Updates
This is where you can find the updates on the APSX-PIM injection molding machine.
Three advantages and cautions about injection molding

ADVANTAGES FOR INJECTION MOLDING

 

1 - Low scrap rates

Relative to traditional manufacturing processes like CNC machining which cut away substantial percentages of an original plastic block or sheet, scrap rates are so low. Note: waste plastic from injection molding manufacturing typically comes consistently from four areas: the sprue, the runners, the gate locations, and any overflow material called “flashing”.

2 – Repeat-ability and Accuracy
The second part you produce is going to be practically identical to the first one. This is a wonderful characteristic when trying to produce brand consistency and part reliability in production. Plastic injection molding is such a precise method that the finished product to be very precise. In fact, accuracy is typically within 0.005 inches.

3 – Wide range of material selection
Most polymers may be used for injection molding, including all thermoplastics, some thermosets, and some elastomers. One cool benefit of plastic injection molding is that fillers can be added to components during processing, reducing the density of the liquid plastic while adding enhanced strength to the finished part. Plastic injection molding is an ideal process for industries or products where parts need to be strong. This allows product designers to choose from a vast selection of materials so they can choose exactly the right properties for the injection molded parts they need.

CAUTIONS FOR INJECTION MOLDING

Upfront costs tend to be very high due to design, testing, and tooling requirements. If you are going to produce parts in high volumes you want to make sure you get the design right the first time. That is more complicated than you might think. Getting the design right includes:
-Initial prototype development is typically completed on a 3D printer and often in a different material (such as ABS plastic) than the final part will be constructed in
-Designing an injection mold tool for an initial production round
-Refining any and all details in the injection mold tool prior to mass-production in an injection mold manufacturing plant.
 
1 - High tooling costs and long lead times
Tooling is a huge project and only one phase of the entire injection molding process. Before you can produce an injection molded part you first have to design and prototype a part (probably via CNC or 3D printing), then you have to design and prototype a mold tool that can produce replicas of the part in volume. As you can imagine, all of the iteration required to get the tool correct prior to mass production requires both time and money.

2 - Difficult to make changes on tool
If you want to add plastic to the part you can always make the tool cavity larger by cutting away steel or aluminum. But if you are trying to take away plastic you need to decrease the size of the tool cavity by adding aluminum or metal to it.

3 - Uniform wall thickness requirement
While there are no wall thickness restrictions, the goal is usually to choose the thinnest wall possible. Thinner walls use less material which reduces cost and take less time to cool, reducing cycle time. Keeping walls from being too thick is important to prevent inconsistencies in the cooling process resulting in defects like sink marks. A good rule of thumb is to keep walls less than or equal to 4mm thick. The thicker the walls the more material you will use, the longer the cycle time will be and the higher the cost per part will be. Conversely, if wall thickness is any thinner than 1mm or so you might experience trouble filling the mold tool. Designers can compensate for this potentiality by using a material with a higher melt flow index like Nylon which is often suitable for walls as thin as 0.5mm.

4 - Financial Considerations
Entry Cost: Preparing a product for injection molded manufacturing requires a large initial investment.
Production Quantity: Determine the number of parts produced at which injection molding becomes the most cost effective and the number of parts produced at which break even on investment

5 - Design Considerations
Part Design: You want to design the part from day one with injection molding in mind. Simplifying geometry and minimizing the number of parts early on will pay dividends down the road.
Tool Design: Make sure to design the mold tool to prevent defects during production.
The main enemy of any injection molded plastic part is stress. When a plastic resin is melted in preparation for molding, the molecular bonds are temporarily broken due to the heat and force. As the molecules are pushed through each feature, they are forced to bend, turn and distort to form the shape of the part. As the material cools and the molecular bonds re-link the resin into its rigid form, these stresses are in effect locked into the part. Part stresses can cause warpage, sink marks, cracking, premature failure and other problems. You should design your parts with as much consideration for stress reduction as possible. Some ways to do this are by adding smooth transitions between features and using rounds and fillets in possible high stress areas.
The gate type and location selection are also an important factor for proper mold design. Place gates at the heaviest cross section to allow for part packing and minimize voids & sink. Be sure that stress from the gate is in an area that will not affect part function or aesthetics. Gates vary in size and shape depending upon the type of plastic being molded and the size of the part. Large parts will require larger gates to provide a bigger flow of resin to shorten the mold time. Small gates have a better appearance but take longer time to mold or may need to have higher pressure to fill correctly.

6 - Production Considerations
Cycle Time: Small changes can make a big difference and cutting a few seconds from your cycle
Assembly: Design your part to minimize assembly.
Science of mold making

*There is not a "single" mold that can be used for injecting molding for "all" plastic materials. Because each plastic has its own chemical, mechanical and thermal characteristics. Therefore, each mold is unique for the material intended to be used. The gate, runner and draft angle may differ from material to material. 


We work with the following companies on mold making for the APX-PIM Injection Machine.
Polyject - Brian Thibeault - 603-882-6570 - brian.thibeault@polyject.com

Please ask for a quote from Protomold, ICOmold or XcentricMold for finished plastic parts for your own design and get their feedback for your design to see if it even can be molded at all or not. Then please get back to us with your specific mold related questions so that we can reply to your questions intelligently.

Traditionally injection molds have been expensive to manufacture. Molds are typically constructed from hardened steel, pre-hardened steel, aluminum, and/or beryllium-copper alloy. Today, aluminum molds cost substantially less than steel injection molded parts. When higher grade aluminum such as QC-7 and QC-10 aircraft aluminum is used and machined with modern computerized equipment, they can be economical for molding hundreds of thousands of parts. Aluminum molds also offer quick turnaround and faster cycles because of better heat dissipation. It can also be coated for wear resistance to fiberglass reinforced materials. Today's Mold companies use CNC machining and Electrical Discharge Machining (EDM) in the mold manufacturing processes.

Molds consist of two primary halves, injection molds (A plate) and ejector molds (B plate). First, plastic resin enters the mold through a sprue in the injection mold. The sprue bushing is to seal tightly against the nozzle of the injection barrel of the molding machine in order to allow molten plastic to flow from the barrel into the mold, also known as cavity. The sprue bushing directs the molten plastic to the cavity images through channels that are machined into the faces of the A and B plates. These channels allow plastic to run along them, so they are referred to as runners. The amount of resin required to fill the sprue, runner and cavities of a mold is called a shot.
To properly release the part when the mold opens, the side walls of the mold are tapered in the direction that the mold opens. This tapering is referred to as "draft in the line of draw". The draft required for mold release is primarily dependent on the depth of the cavity. Injection molds are usually designed so that the molded part remains securely on the ejector side of the mold when it opens, and draws the runner and the sprue out of the other side along with the parts. The part then falls freely when ejected from the ejector side. 2-3 degrees draft is required for mold-ability of the parts. The angle should be large enough to allow to eject the part out of the mold. The corners should NOT be too sharp. Otherwise sink marks may occur.

More complex plastic parts are formed using more complex injection molds. These may have sections called slides, that move into a cavity perpendicular to the draw direction, to form overhanging or undercut part features. Some injection molds allow previously injection molded parts to be re-inserted to allow a new plastic layer to form around the first part. This is often referred to as overmolding.

Injection molds can produce several copies of the same parts in a single "shot". The number of "impressions" in the mold of that part is often incorrectly referred to as cavitation. A tool with one impression will often be called a single cavity mold. A custom mold with 2 or more cavities of the same parts will likely be referred to as multiple cavity (family) molds. When you design a mold for more than one parts (multi-cavity), the part distribution should be so balanced that each part is placed at equal distance to the sprue. That allows the mold flow smooth and consistent.
Injection molding can create injection molded parts with complex geometry that many other processes cannot. There are a few precautions when designing something that will be made using this process to reduce the risk of weak spots. First, streamline your product or keep the thickness relatively uniform. Second, try not cramming too many details into one part may cause visual defects in show surfaces or the inability to fill some of the details without sacrificing others.

Molding trial
When filling new or unfamiliar injection molds for the first time, where shot size for that mold is unknown, an injection molding company technician/tool setter usually starts with a small shot weight and fills gradually until the mold is 95 to 99% full. Once this is achieved a small amount of holding pressure will be applied and holding time increased until gate freeze off (solidification time) has occurred on the injection molded part. Gate solidification time is an important as it determines cycle time, which itself is an important issue in the economics of the production process. Holding pressure is increased until the parts are free of sinks and part weight has been achieved. Once the parts are good enough and have passed any specific criteria, a setting sheet is produced for people to follow in the future.

Runner and Gate Design
The runner should be thick enough to carry high amount of plastics without early premature cool down. The gate should be thin enough to have a smooth plastic flow into the cavity.

Wall Thickness
Wall thickness and design determine if a part would have a sink or wrap after the injection molding or not. Uneven mold wall thickness is always a problem. Certain materials should also have a minimum thickness for a perfect mold-ability.

Here is the video series for Mold Making on Fusion 360:
Who needs a small injection molding machine?
Injection molding machines, also known as presses, consist of a material hopper, an injection ram or screw-type plunger, and a heating unit. The molds are clamped to the platen of the molding machine, where plastic is injected through the sprue orifice to create injection molds.
Today, electric presses are taking over the typical hydraulic injection molding machines. Companies who produce injection molds prefer them as they offer 80% less energy consumption and nearly 100% repeatability, by utilizing electric motors.

Among the list below, you will find that APSX-PIM reduces your injection molding costs no matter what.



Low Volume Manufacturing

If the part will not be consumed more than 200K pieces a year, the APSX-PIM is a perfect manufacturing machine for the part. In fact, manufacturers will sometimes dedicate an APSX-PIM to each part. Low initial investment cost and fully automated production settings for many types of plastics make it perfect solution for many low volume manufacturers such as medical device makers, aerospace and also custom plastic part manufacturers.



Engineering Prototype, Research and Development

R&D part requests suddenly can ruin a well-run daily production schedule. APSX-PIM offers an alternative. Its low cost makes it perfectly suited to one-off designs. APSX-PIM allows product development departments to keep a machine "at the ready", dedicated solely to R&D work. There are many benefits to this approach. The prototype turn-around time is quicker, the product designers gain a clearer understanding of the manufacturing process, and consequently the final design is easier to manufacture when the production model shows up in the job queue of the injection machine shop. Development with the use of a APSX-PIM is more efficient and eliminates the huge expense of typical conventional manufacturing processes, the expense all the way from an "idea" to production. It also allows a clear separation of the cost accounting of the daily conventional manufacturing processes from the costs of product development.



Bootstrap Entrepreneur
Establishing a new business is always a high-risk task. The high capital cost of mold design and injection molding is difficult to justify and often impossible to use finance without a proven business plan. APSX-PIM can get you started at very low cost. By using a APSX-PIM instead of a high volume and large size injection machine, your business would have significantly lower capitalization costs. This is a typical bootstrap technique: it gets you up and running and proves the plan. Once the business is established and the sales are demonstrated, it becomes much easier to justify an investment in equipment for larger volume.



Hobbyist / Engineer Alone
You may start a new business while keeping your day job. One of the problems of this is the difficulty in establishing relationships with local businesses when you have limited working hours. Your contractors will be unwilling to meet you on your time; they may not consider you to be an important customer. You may have trouble getting what you need when you need it. But if you can make your own prototypes, you will reduce your frustration and the time between your initial idea and final product. If you are just a general hobbyist, you’ll be more than pleased with the precision, repeatability and ease of use our machine provides for how little you’ve spent. There is nothing else on the market that comes close to APSX-PIM for the price!



Education
Before APSX-PIM, injection molding machinery for education was limited for students. Most machines on the market are too expensive and have difficult learning curves. Our machines demonstrate the theory and practice of real world production makes the best educational tool. That requires a machine capable of performing real industrial processes. With its precision and real world capability, APSX-PIM can offer your students a much greater understanding of the way things work using our easy-to-learn touch screen tablet PC and software. Typically trade and engineering schools will use our machine to teach students how to go from an “idea” to a 3D design with (Fusion 360), to a CNC mold with (APSX-CNC), to a real tangible part for production with (APSX-PIM) in just one day…amazing! This process is easily accomplishable in minimal time and only gets better the more you practice! In fact, here at APSX we design and put into production new parts for our products regularly using this same exact one day “idea” to “finished product” process!
Alternative ways to make small plastic parts
So you need a custom plastic part, but you don’t know how to get it made or how to make it yourself. Is it large or small? Should it be flexible or stiff? Is it round, square, or some other uncommon shape?