3D printing an engine frame?

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RM-MN

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p.s. I managed to make my Ring gear. I had to create a "new body" first, then start the involute gear operation, then pad it.
Then I made a disc, and substracted the gear from the disc. There is an option external gear true/false. (I hope that makes internal gears).
How to test a ring gear? I think for what we do it is sufficient to just mount two of the small gears in the correct distance on some fixture and rotate the ring gear on them.
I just noticed that I spent hours to design a sprocket in another CAD thing, and that Freecad now has a macro for it.
You are correct in your thought that FreeCAD has a switch for making internal/external gears. My first time making a gear came out as an internal when I intended external and it took a while to discover that switch at which point it turned into an external.
 

timo_gross

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Hello,

I am confused, partially because I am also very new (once again) to Freecad, I understand the difficulties to edit an imported stl or whatever foreign file.
But if I open two files .FCStd I got the bodies on the left model tree in the combo view. These files I am able to save, close open at a later stage and edit them again by for example changing the sprocket pitch from 1/2 inch to 3/16 inch. That what I ment with original file.
freecad.jpg
The screenshot shows the minisprocket and a random rectangle block. I saved them separately and then put them back into the same file. Now I can still manipulate both of them.

Greetings
 

timo_gross

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1st result of todays experiment:K1600_P1000971.JPG

The picture shows gears in module 1 (roughly 24 DP for size comparison). White gear PLA, came just out of the printer (still warm) 60 teeth internal. Made with Freecad without tweak. Export *.stl and sent to printer.
Small metal left, I bought from the gear lady for small fee. Right metal gear I hobbed on the hobby milling machine. They work reasonably accetable together.
Not ZF made for F1 :cool:, but good enough for a plastic toy.

2nd result of todays part two of the experimentK1600_P1000972.JPG

Picture shows modul 0.5 gears. ( comparison 48 dp). The brass ring gear is a tedious procedure the white pla gear works sort of almost, actually I am impressed that it is not completely unusable. the small gear is shop made from brass rod.

Verdict: I guess module 1 is already quite small for a 0.4 mm Nozzle with a hobby level FDM printer.

Greetings Timo
 

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An Engineer nearby (sadly now in the workshop in the sky) made a ring gear by casting Mazak around a change wheel from his lathe. He said the change wheel stayed in the part while he set-it up and machined the ring gear in the lathe, then with some "careful beating" he drove the change wheel out of the ring gear without distorting the ring gear. The finished part was on his Hyper-cycloidal engine using a ring gear instead of a crank. Ran very smoothly! (left hand of the engines in the photo - with the chair as background).
PICT0020.JPG

I like your "new technology" method as well.
K2
 

timo_gross

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I like your "new technology" method as well.
K2
I do not like the printed gears that much. Metal ones just are "more real". The brass ring gear was made with my "poor mans slotting head" changing the milling spindle with the slotter attachment, mounting a manual dividing head. Then slot one gap at a time.
 
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Fair comment Timo. From my experience a majority of "traditional" Engineers pooh-pooed the introduction of "plastic" intake manifolds, thermostat housings, throttle bodies, etc, as they thought they would lead to high warranty costs due to poor durability. However history has proven the correct use of plastics in such applications as most cars have them as cost effective parts that keep products competitive and available to the budgets of many. I am sure that rubber tyres were laughed at by the wooden-wheel makers... just as steel was inferior to bronze for swords for hundreds of years. But in the right application, appropriately designed plastic parts are "right". I agree that brass is prettier for visible "classic" designs. And all to often, to copy a part in the "wrong" material will lead to early life failures. IMHO Plastic gears should be used in designs appropriate to the hardness, wear and friction properties, tensile and compressive strengths of the plastic. Not simply copies of designs that are suited to brass, steel or other material. And consideration of the temperature, lubrication, impact loading, speed etc. is necessary.
A friend sold his "Mini-mill" because it was full of nylon gears, and his milling, to correct feeds and speeds for the torque of the motor, materials, etc., simply could not take the duty he needed from the machine. But it had been fine when drilling previous models, that didn't have any milling. The gears were Mazak on earlier versions, but obviously just copied in nylon, and failed as expected, on the version he could buy.
Cheers!
K2
 

a41capt

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I thought that attempting an almost 100% model steam (compressed air) engine from FDM printed parts would be an interesting challenge. I have yet to print the ring and spur gears for Elmer’s #5 geared engine (life gets in the way occasionally), but the emergency gear printed from PLA + for my mini mill functioned fine until a replacement could be shipped. Granted, it was only used for light cuts, knowing it wasn’t as strong as the original nylon gear, but the teeth showed almost no signs of wear.

I figured for a small model that wouldn’t see much stress, PLA printed gears on this application would be fine, and a new challenge to a newbie 3D print guy like me!

John W
 

awake

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Good grief - I go away on a little trip (just 3500 miles of driving), and before I even get half-way through, y'all have jumped way ahead on this project! Well done, all. I will try to contribute when I get to a place with better internet - it's been very spotty up to now.
 

krypto

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While I agree that from a craftsman standpoint a nice brass gear is superior, especially for a highly detailed scale engine, it's certainly handy to easily produce plastic gears for testing as material is expensive and shop time is scarce.

Looks like the .3mm nozzle and new profile worked better than I expected!

gear1.jpg


The gear teeth are much better formed than my previous example and I think this is possibly a working gear set. It takes forever, but from trying some other non-practical prints with this setup the printer is producing the most detailed work I've seen in 4 years of ownership.

gear2.jpg


A dime for scale.

gear3.jpg


So far the drilled-out .2mm to .3mm nozzles are working great so I might just keep making them as I need them. I don't think I need many as I mostly do practical prints like bins and such.
 

a41capt

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After reading some things and watching a video about print strength, I’ve begun printing 4 layer perimeters and top/bottom layers. I’m finding that infill isn’t nearly as important as outer wall strength when it comes to resisting lateral forces. Maybe that’s why my simple PLA gear replacement for my mini mill worked as well as it did.

John W
 
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