Frequently Asked Questions
We get lots of good questions regarding the products and services we provide. Most of them are repeat questions, so we have posted the most common ones here to help save your valuable time. Though we recommend that you take a look at most if not all of these, we have further arranged them into sections [ TECHNICAL ], [ COSTS ], and [OTHER ] to help you find what you are looking for more quickly. If you don't see your questions addressed, please contact us today and we will be happy to help you get the answers you need.
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[ TECHNICAL ]
How big of a part can I make with one of your machines? - or - How big of a machine do I need?
This is probably the most common question we get, the most difficult to answer, and probably THE most important aspect of injection molding that can be understood. The Molding Primer (a work in progress) will provide a much more detailed and helpful answer, and could save you both lots of time and money when understood well.
As for an attempt at a short answer here, the small commonly available benchtop machines that use a manual handle to inject might be able to produce a part with an area of 2 or maybe even 3 square inches, provided the resin used is fairly runny and/or the molded part doesn't have any long, thin features (like thin fins, walls or small diameter protrusions that extend very deep into the mold). A suitable part might be a small, fairly thick walled medallion or perhaps a key fob using a polypropylene (PP) plastic or a very limited selection of other resins. The problem with these machines is they just don't generate very much injection force and also can't produce very much clamp pressure. These forces are paramount to making good parts with a variety of resins or parts with fine detail. Unfortunately, few real world useful parts can be made with these limitations.
Machines with air injection will improve both the number of resins available for use and the depth and fine detail that the mold may have, as they can generate more injection pressure. The larger the air cylinder used to inject the plastic, the higher the injection pressure and the stronger the machine must be to hold the mold closed (clamp pressure). Hydraulic machines provide even greater forces. Each step up in size and strength allows for larger parts with more depth and detail, more resin choices and more clamp pressure to make it all work. Don't expect any small benchtop machine to make a car bumper. A good rule of thumb is buy as much machine as you can afford and make what parts you can with it. Just because a part will fit into the machines mold area, doesn't mean it can make the part. If you know you can't make your part with any machine you can afford, then save your money until you can afford what you need, or use it for something else entirely. Perhaps a much needed vacation?
Since injection molding is about as much of an art as it is a science, nothing but experience will provide the best answer. That's where we come in. We will be happy to look at your part and steer you in the right direction, even if it is away from us.
Why get an injection molding machine and not a 3D printer?
Heck, if you want a 3D printer, get one. Most everyone that comes to us these days, first tried a 3D printer. They are GREAT for what they do. If you need to make one of something (or lots of varying prototypes) or perhaps just a handful of parts to test demand, functionality or maybe even make a big part that would just be too expensive to injection mold, then 3D printing may be right for you. They are also great at making parts that simply can't be designed to work with injection molding (although in many cases, a good mold designer can probably find a way to do it). With that said, then why aren't manufactures using these things to make your cereal bowls, TV remotes, and tons of other consumer grade products. The reason is they understand what 3D printers are good at doing, and what they aren't.
3D printers are painfully slow, the parts they make leave lots to be desired in terms of fit and finish (often requiring lots of post processing), somewhat limited in the plastics that they can use and even more limited on the ones they can use well, and finally produce parts that are basically 100% "knit" together leaving stresses and weak points throughout the entire part.
Personally, I was first introduced to 3D printing over 20 years ago as we had some prototype parts made for "show and tell" for a company I was working for at the time. Although I had been familiar with the process for many years before that, those were the first 3D printed parts I had ever seen first hand. We had to be careful in using them as they didn't have the strength to bend like the final (injection molded) parts would be required to do. They were made on (at the time) very expensive machines that you can now buy today for a fraction of the cost and probably produce an even better part, but although costs have come down on 3D printers over a hundred fold and quality has improved substantially, much of the same issues still remain today. It's just the nature of the process.
The most ironic customer I have ever had was a company that wanted a mold and an injection molding machine to produce lots of plastic key fobs with their name and logo on them to give out to potential customers at trade shows and such. The irony was that the company specialized in 3D printing.....
What should I look for in a benchtop molding machine?
This answer gets a little lengthy (but probably still not long enough) but we will try to hit the high points.
First thing, please allow us to help you with your search. We have seen and even owned most every benchtop molding machine that has ever been manufactured. If we haven't owned it, it's probably because we've either built one like it somewhere down the line, and/or we can now see the problems with designs from the start. We've pretty much seen it all. We truly enjoy working with customers who are interested in injection molding and will be happy to help you, even if you don't buy from us.
Like 3D printers, benchtop molding machines have their own limitations. It is important to understand these so you can get the right machine for you. Large commercial floor model machines are typically rated in mold and shot size, mold clamp tonnage, and injection pressure. Also important are the plastics the machine can process long term (due to compatibility issues between the plastics and the machine's barrel and screw materials). These considerations are just as important in the benchtop molding world, but unfortunately aren't typically addressed, often because those interested in benchtop machines are new to the world of injection molding and simply don't know to ask.
A machine you are considering will certainly require enough plastic to produce the part in one shot ( we recommend a rated shot size around 1.5 - 2 times the part size for a benchtop machine), enough injection pressure to push the plastic into even the most difficult to reach parts of the mold, and the clamp tonnage to hold your mold closed during the process. What those required specifications end up being depends entirely on the size and characteristics of your part and require some experience in evaluating (that's where we can help). Once you know the specifications that you need, if the machine that you are considering doesn't provide this type of information, then you probably need to look elsewhere. --- Oh, and just for those that may not know. You CANNOT inject multiple times into a mold (well in almost all cases, probably including yours) to try to get more shot size out of a machine. And while we're at it, turning up the heat DOESN'T (to a great extent) allow you to get the plastic to push deeper into the mold with a machine that can't deliver enough injection pressure. It just simply causes quality problems with the part and degradation to the plastic ---.
Other things to consider in benchtop machines, is safety, and ease of use. The smaller hand operated machines commonly found on the market today can only produce injection pressures of around 2000 psi at best (though they won't mention that) machines who's designs allow the plunger to contact the melted plastic can be messy and a little more difficult to use. However, if your budget is tight, your part is small and simple enough and your volumes are low enough that you feel that you can deal with such issues, then you may want to consider such a machine for the time being. We sell such machines in our rebuilt machine section often with capabilities equal to or better and at prices that will beat the new ones found on the market today.
Just remember. "You get what you pay for". Almost everyone has heard of this mantra and it applies to benchtop molding machines as well. But with that said, the best machine is one that meets your needs, while providing you the best value. That doesn't always mean the lowest cost or the most expensive machine either. We have spent a great deal of time in finding a design that provides the most bang for your buck. Our Proto-Ject machines offer the best value available today in a safe, powerful, lightweight and easy to use machine. Let us know if we can assist in finding the right machine for you.
Why should I consider a benchtop machine that injects at least twice the plastic I need for my part?
Along the same lines of the "How big of a machine do I need" question from above, this particular question doesn't come up as often as it should because most buyers are unaware of this need until they are either told to consider it or until they have purchased a machine too small for their needs. The reasoning is simple. Most all benchtop molding machines are of the plunger type. Because of this, some plastic gets injected into the mold and some works it's way up thru the unmelted pellets higher in the barrel (heating chamber), pushing out the air and helping to melt the cold pellets for the next shot. This is good, and helps to keep the melt air free and flowing uninterrupted so that shots can be made at a fast pace. Most machines are rated at the MAXIMUM plastic that is possible to shoot in one shot (Manning Innovations machines included). Although such a feat is possible (it requires packing the cylinder), completely exhausting the melted plastic form the machine will SEVERELY impact the frequency and quality of the shots to follow. We recommend a machine to have a shot sise ratio of 1.5 - 2 times the part weight for the best experience.
Are benchtop machines messy or difficult to use?
Some are messy and some aren't. Some are difficult to use and some aren't. The ones that are messy are automatically more difficult to use from that aspect alone.
So how do you know which is which? The smaller machines where the filling funnel is heated can get quite messy as the plastic melts outside the barrel (melt chamber) and sticks to the funnel and plunger and will require cleaning often (a difficult and messy process). It also often requires the user to occasionally apply a non-stick coating to the plunger to keep it from pulling the plastic back out of the barrel (this is a bigger problem with some plastics more than others).
Our ProtoJect machines maintain a cold layer of plastic pellets between the melted plastic and the plunger. This eliminates this problem completely and makes these a joy to use. Even more expensive benchtop machines don't provide this feature.
What size and type air compressor do I need for an air injected molding machine?
Proto-Ject Machines : The type and size of air compressor used with our new Proto-Ject machines depends on the machine model and if it is fitted with Air Saving Technology (AST). This feature allows a machine to use as much as 70% less air than a machine without the feature.
[ Proto-Ject 150 ] You will need to select a compressor capable of delivering at least 5.0 SCFM of air at 90 psi and must also be capable of delivering a maximum pressure of 150 psi to the injection molding machine. Typically this means that the compressor may need to have a maximum tank pressure of 175+ psi so that it does not drop below 150 psi on the output line when cycling between its low (on) and high (off) cycle pressures. We also recommend a minimum tank size of 15 gallons and 20-30 gallons is even better to minimize how often the compressor must start. This is especially important if you expect frequent injecting cycles. Though you may not always require such high air pressure, having extra pressure will pay off on more demanding projects. There are a few 110-120VAC air compressors available at the time of this writing that are capable of delivering this amount of volume and pressure. We have had good experience with these two compressors. (1) The Dewalt 15 gal, 225 psi, 1.6 Hp air compressor is available in a vertical and horizontal configuration and is capable of delivering 5.0 SCFM @90psi. (2) The Husky 20 or 30 gal, 175 psi, 1.7 Hp air compressor available from Home Depot. The DeWalt will deliver higher pressures than the Huskies but is somewhat louder (in our experience). Of course jumping up to a 220-240VAC compressor won't ever hurt if you have the capability. Just remember to look for the 175+ psi.
[ Proto-Ject 300 ] For this model you might can get by with a 110-120VAC compressor (see ones recommended above) if you expect to only be making a few shots an hour (perhaps 10-15) and have the Air Saving Technology (AST) feature, but for more frequent injection cycles, you will definitely require a 220-240VAC compressor capable of delivering a minimum of 10 SCFM @90 psi with a maximum tank pressure of 175+ psi. There are a multitude of suitable compressors on the market that can meet this requirement. Just select one that has a good customer satisfaction score.
[ Smaller Rebuilt Air Powered Injection Molders ] Most of the smaller (not Proto-Ject) air powered benchtop molding machines we offer can operate on most any 110-120VAC air compressor. It is recommended that you get one that is quiet and has a tank size of 10gal or larger to minimize cycle starts. Max pressure can be closer to 125-150psi on these as most of the smaller machines don't require pressures much higher than this.
[ COSTS ]
How much does a machine cost?
Because machines come is many styles and sizes and configurations, it is difficult to be specific with prices. However, we sometimes have small used machines as low as around $500 with most rebuilt machines starting around $1,000. New Proto-Ject machines start around $6,000 and with some specialty built machines going well over $10,000+. We will work hard to help you find the most machine for your money to meet your part manufacturing goals. We will explain the benefits and weaknesses of virtually every type of benchtop machine on the market and help you find what you need (even if it is not sold by us).
How much does a mold cost?
Of course, an injection molding machine is of little value without a mold. Unfortunately, custom mold costs very wildly based on the part you are making. Form, fit and finish are what determine the costs of building a mold and we can often help you to design your part to make it more easily mold-able, eject-able and with reduced production costs. We have made many simple custom molds over the years for as little as a few hundred dollars, but most custom molds that work with our larger machines usually start around $1,000. We do offer small practice molds starting at around $75 each. These make various household and toy type items and help teach the basics of injection molding. The costs can be kept low on these because they are very simple and are produced in larger quantities. Molds are also available for quality labs that are used in material testing. These types of molds are usually priced well below $500. Contact us today and let us give you a quote on your custom mold.
How much does it cost for MI to make my parts?
If you decide that purchasing a machine is not right for you, you can let us produce your parts. The beginning of the process is the making of the mold. The costs associated with that will be similar to the "How much does a mold cost" answer above. However there will likely be a lower cost to the mold if a specified minimum quantity of parts is produced for the customer with the first order. Also, the mold remains the property of Manning Innovations until such time as you purchase the mold outright at an additional cost. This cost is typically around 25% of the original mold cost plus shipping. Contact us to discuss a plan to make your custom part(s).
[ OTHER ]
How long before I get my parts?
For a new part, you can usually expect parts shipped within 10-20 days from time of paid order, but it will depend upon workload at the time of order and the complexity of the mold being built. Reorders will usually ship within 7-10 days depending upon workload.