Manufacturing Plastic Gears

If it works, let me know. I'll do the same. I know it works for some products, like I've seen it in small household grinders.

My first job out of tech school, TSTC Waco, manufacturing and engineering technologies/machinist, back in '90 was as shop lead for a plastics fab company. As a result of that experience I have seen many applications where plastic was substituted for metal - often as an upgrade!

Typical little toys and such use ABS, acetal butate something or another. They are brittle.

However it is well worth the research to see what the different material and process costs are if this is a wear component that might extend overall life or efficiency. At times converting a critical pair (gear pair) can be astounding. So, kudos there.

Nylon stock comes to mind for ease of machinibility, corrosion resistance and durability. An added bonus is often a reduction in vibration and dB output. There are 1000's of possibilities, fom HDPE (high dens polyethelyne) to highly expensive Vespel and Torlon (I believe these are both trademarked product names)

The thing is; do you need a gear to be machined, molded, or both? as far as processes go, this will be your big limiting factor as I see it.

I might be able to add a bit more specific comment with a tad more info.

charles

In my experience, plastic, or nylon gears can never compete with the strength, durability, strength, or reliability of metal.

The only advantages are; it's cheap, and light weight.

my experience suggests otherwise. application considered.

Rummel3 is very correct - I have use composite gears (a polymer blend with 38% fibre glass, Kevlar, carbon fibre and a Dupont special mix) and never had a failure. Some of the gears were used in extreme high torque applications. Think new advanced technology composites and start at the Dupont website. They have a great online reference data base. Good luck in your search and contact me if you have any questions. I have been designing and engineering high performance and special application high pressure gears for over 45 years (some even were made of iron wood !!!).

It is all application dependant.

The products mentioned here; from globalspec "suffer from outgassing problems at elevated temperatures, and are brittle at low temperatures"

Granted there may be some applications that plastic gears may be sufficient, however, in any harsh environment, or high torque, the plastic gear will be the first to fail. It changes its properties with the application of heat, so cannot sustain prolonged use.

Time to rant; I am tired having to repair poor and cheap design. I had a water pump with a plastic gear impeller. It could only operate for 20 minutes at a time without overheating and starting to bind. I've also had to replace the pump in my heavy duty washing machine at least 3 times. it was the only thing that ever failed. (plastic pump). This is not even high torque. The gears are only pushing against water, not another gear. Photocopiers fail regularly because of all its plastic parts. Put in metal parts, and it will last 10 X longer.

Besides the fact the plastic does not come close to the strength or reliability of metal, it is created from oil - a limited resource and it is environmentally unfriendly. Metal is the most recycled material on the planet.

sorry for your bad luck with photo-copies and laundry. Poor design does not equate to a sufficient argument where an intelligent design has been applied.

With remark to petroleum products and by-products: Last time I checked those steel mills didnt heat themselves through osmosis.

May we please discuss the beautiful abandoned and operating mine sites. Not the pretty little toxic dumps like in MT, CO, NV, or WY. Oh no, lets take a trip to South- America or Asia, where mining operations look much worse than the horrific eyesores we have locally.

I'm not knockin metal, but there are alternatives. Often significantly better ones. This thread is one such example. Application considered.

Maybe we should be more specific when we talk about plastics. As engineers, designers, and manufacturers we should know better than to lump all synthetic materials into one word "plastic". The word plastic means: capable of being molded or formed. I am with you 100% on the issue of making quality products. The company that made that washing machine impeller may have chosen to make it out of HD polyethylene which is of course going to wear out quickly and enable the manufacturer to sell more parts. They could have easily made it from polyurethane which would outlast the steel because of corrosion and outlast the aluminum because of both wear and corrosion.

The result of people having experiences like yours should train the public to choose quality over low price. That in turn should train the manufacturers to produce better quality. I am as frustrated as anyone about why this doesn't happen, but let's not blame plastics in general because products are of low quality. Let's blame designers who don't choose to use the right material for the application for whatever reason, and consumers for continuing to purchase junk just because they think the price is right.

100% Agree.

Unfortunately the majority of people can usually only afford cheap, regardless of how educated they are on quality.

Obviously to design something, first you should have your requirements,. then find the best product that meets your specifications. Too often I see designers start a design with a predetermined material in mind, in this case it is plastic or a derivitive.

A proper designer would know the strength, friction coeficcient, operating temperature, etc. and then look up the specifications of all known materials and pick the best.

How often I have cursed 'Value-Added Engineering'

As much as I detest the idea of planned obsolesence it does have some merrit. I have to replace my computer, inculding backup drives, printers, faxes, etc every 2-4 years just so I my software upgrades will function properly and so I can keep up with the competition. If those products were built to last 20 years I would not be able to afford them. I'm not sure I can afford them now. On the other hand there are brand names that I simply will no longer buy because the quality is so bad.

I have seen engineers fresh out of school follow the policy of looking up the very best material for a component and then specifiing it on a drawing. We end up calling that material "unobtainium". You either can't find it or can't afford it, or really don't want to work with it. The ability to find the balance between durability, workability, availability, and cost is the sign of a good engineer.

So you are trapped in the 'must have the latest computer and software.' hole

You deserve a rant....

Microsoft must love you.

My original commodore 128 system from the early 80s is still in use by a university student. It does everything necessary.It was certainly built to run 20 years. Try to find an old 486 computer running 'windows for workstations 3.1' and you will be amazed to find that it is faster then your current computer.

Except for the high quality of graphics in the latest games, there has been virtually no improvement in software over the last few years. They simply keep adding unnecessary software to hide their mistakes in programming.

must have latest software....give money to microsoft...hey this new software does not run on my computer... must get new computer....give money to microsoft.......must have latest software....give money to microsoft...hey this new software does not run on my computer... must get new computer....give money to microsoft.......must have latest software....give money to microsoft...hey this new software does not run on my computer... must get new computer....give money to microsoft.......must have latest software....give money to microsoft...hey this new software does not run on my computer... must get new computer....give money to microsoft.......

Microsoft programmers priorities

1. lets see how bad we can make a program, so we can sell upgrades. keep us in business forever. (addiction like cigarettes.)
2. must make computer users dumb so they are dependant on programmers
3. program must be so large, and waste so much memory that no computer except the latest can hold it.
4. program must have so many useless instructions,. no computer is fast enough
5. must do the same as other programs, just look different
6. must remove functionality, so they can buy separately what they got with the earlier program for free

Microsoft hardware priorities

1. make new computer that are bigger and faster
2. when the laws of physics says it cannot go faster...lie
3. use commodore technology such as multiple processors in parallel to pretend it is a faster serial computer. no one can compete.
4. use slow hard drives to keep hard drive industry in business, when we know bubble memory made hard drives obsolete in the 70s
5. must be upgradeable - so you can charge more money even though you will not provide upgrades and change the architecture with the next version.
6. must not be too far ahead of the software.
7. must make the computer user dependant on programmers

Microsoft sales rep motto 'bigger and faster is better' priorities

1. make consumers dumb
2. sell sell sell software
3. sell sell sell hardware
4. buy competition
5. sell sell sell software
6. sell sell sell hardware
7. buy competition
8. sell sell sell software
9. sell sell sell hardware
10. buy competition
11. sell sell sell software
12. sell sell sell hardware

I would like to see this rant elswhere... more accurately EVERYWHERE. I am one of those consumers who is still gnawing his hand off at the idea of Microsoft bondage and doesn't feel able to do anything about it.

More rant please. Extra "spittin' mad sauce". Mmmmmm..rant is GOOD!

You begin the rant, I'll go up a third and we can rant in harmony.

Here is the hole, and it only has a little to do with Microsoft. My niche in machining is that I often machine parts that have complex surfaces and shapes. In the 70's I would have carved a pattern and run the job on a tracer or a 3D pantograph. Doing these jobs with CNC takes less than a tenth of the time with much better finishing which reduces or eliminates hand finishing. There is there have been amazing imporvements in machining technology especially in the last 10 years. In this country with our high cost of labor the only way to compete is to make use of the technology and eliminate as much of the labor intensive aspects of production as possible. HSM (high speed machning) is one of the best thnigs to happen in the industry in 20 years but it requires the blending of machine tool design, cutter design and materials, processing speed, and CAD/CAM software. In order to generate the CNC programs to take advantage of the software I have to have computers that can do the job. There are PC based CNC controls that use DOS and as you say can run very fast but they are not in a 486 and they will not run the programming software. I have a Pentium III collecting dust because it simply can't keep up. I have a CNC machine that has a 486 built in in parallel with the control. It handles the file storage, and the drip feed function just fine. However I have had 5 experts look at it ( I am not a computer geek, iI just use them ) and not one could figure out a way to install a USB port which would save me a lot of time. Am I in a computer and software hole? You bet. When I bought my latest computer it had a graphics card that was supposed to be great for games. I don't play games. I didn't work with my CAD/CAM system. I had to replace it. AAAAGGGGGGG!

It seems as though we might be identifying a market niche. A niche in which end-user specific control and application machines computers are built around customer specs.?

Low cost on the front end with profit margins generated from bi-annual service upgrades. A fluid or dynamic system for each clients needs?

a niche, yes, if you mean monopoly!

You said "and not one could figure out a way to install a USB port which would save me a lot of time"

Why install a USB port when an inexpensive adapter will allow USB to be used in any other type of port?

As for unobtanium.

I agree. you must define best with cost in consideration. Overkill is just bad business. The standard for good engineering depending on the application is 20% over the maximum requirement.

I disagree with planned obsolescence. You will lose business if your product fails as soon as the warranty expires. The North American auto industry is second to imports because of planned obsolescence.

Been there and done that.. I have a background in special application gear design - what type of gear are you looking at.. What is the power - electric or pneumatic drive. What is the size and tooth configuration - straight gear, planetary gear, bevel gear or what.. Need tooth count and pitch angle if known,, I know of several aerospace type composite materials that would fit your requirements. NOT plastic - composite - plastic is cheap and brittle.. Send me some info and I would be happy to assist you.

ata@stny.rr.com / Ken

Nylon and Delrin are good plastic gear materials providing that the torque applied to them is not excessive for the plastic. They are available with different fillers that effect strength, friction, wear, etc.. In low torque applications plastic gears can be good because of the wear characteristics and reduced friction. They are obviously not as strong as steel or bronze gears but may out wear aluminum or brass gears. Another plastic gear material that is not as well known is Turcite. It is a hard thermoplastic with friction characteristics that make it even more slipery than teflon. You can find more info on Turcite at Boedeker.com, or search turcite Shamban Plastics.

If you decide to mold plastic gears be sure to get good consultation on the mold design, particularly in relation to shrink factor. If the mold is not designed correctly to compensate for the material shrinage you can end up with gears that do not run concentric ot that do not mesh properly.

I personally love the sound of straight cut steel gears, only from a hot rod guys perspective though....

They will take torque but not shock. Constant running at high torque don't kill they fast. It the sudden start and stop that snap the teeth off.

Pineapple

"what are the common material in plastic gear manufacturing? is the material can compete with metal?i am focusing in replacing the gear material in gear pump usage..thank you"

There is an application where plastics will do the job as well if not better that other materials when all factors are considered. OTOH various metals, and alloys, similarly have the places where they can rule supremel One gear pump could be best with plastic and the next with metal. There no one material fits all applications.

A simple question requiring a simple answer. The Bard of Avalon would have summed all this up as "Much Ado About Nothing." TMI.

And in addition to the properly selected and designed plastic gears we have added steel gears.

Not the only candidates for gear manufacturing materials. Must also include Cast Iron,
"Zamac" alloy of zinc, aluminum and magnesium, wood as used in old clocks and grist mills.

Perhaps others can add more materials to the list.

As I don't see any further comments from the original "Guest" - I have to assume he doesn't have an interest anymore in the "Plastic" gears. I have enjoyed all the comments regarding the gears and there is a multitude of materials for and type of gears in use today. As new technology arrives - new materials to address the issues will also arrive. If the "Original Guest" has any more questions I would love to hear them - especially what he is trying to use them for..

Typically, nylon (PA66 or PA46) is used along with Acetal (POM). Sometimes teflon (PTFE) is used for additional lubrication.

Parts can be machined from stock shapes or injection molded.