3D printing a gear box, I'm having some problems with the gears getting stuck.


by dennis_n
Tags: gear, gears, printing, stuck
dennis_n
dennis_n is offline
#1
Mar25-12, 08:40 PM
P: 3
I'm building a simple 20:1 gearbox prototype with 2 compound gears in a row connecting to a third small gear at the end. My goal is to multiply the rotational speed of the small gear.
They are all engaged on a straight line. But for some reason they get stuck most of the time.
I'm trying to figure out what the problem may be.
I had to make the shafts part of the base of the gearbox (cause my printer doesn't print support material, and I wouldn't be able to print a gear on top of a shaft), so each gear has a hole and it spins freely around the shaft. I don't know if that is less efficient than the shaft being part of the gear. I'm not an engineer to know those kinds of details.
I'm also wondering if all the gears being on a straight line, somehow causes them to lock in place most of the time.
I was hoping someone might have an idea.
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huntoon
huntoon is offline
#2
Mar25-12, 10:07 PM
P: 145
The shape of the gear is key for proper entrance and exit of teeth.

1. Have you tried grinding a chamfer into each tooth?

2. 3D prints are notoriously inaccurate. especially with low cost FDM machines. play with the feed rate of your plastic. Try to get the head a close to the part as possible. If possible heat the the build area while printing. This will make the deposition more uniform.

3. Try using the free gear template generator offered by Mattias Wandel at woodgears.ca: http://woodgears.ca/gear_cutting/template.html
OldEngr63
OldEngr63 is offline
#3
Mar26-12, 05:10 PM
P: 343
A caution about using Wandel's gear profiles. They are quite good enough for wooden gears, which is the purpose for which he markets his software, but I don't believe that they are true involutes, as far as I can tell. I have had some correspondence with him, and he is guarded about what he will reveal, but it appears that he has made some approximations that will result in something other than true involutes.

huntoon
huntoon is offline
#4
Mar26-12, 05:38 PM
P: 145

3D printing a gear box, I'm having some problems with the gears getting stuck.


Quote Quote by OldEngr63 View Post
A caution about using Wandel's gear profiles.... it appears that he has made some approximations that will result in something other than true involutes.
Good to know OldEngnr63....

You could always do it by hand, but Wandel's look better than the gear primitives found in most 3d software I have encountered. For a hobby project it's worth a shot.
johnmcrin
johnmcrin is offline
#5
Mar27-12, 11:57 AM
P: 1
The resulting gearbox has very little side to side movement. Usually you have to compensate for clearance and so doing will make an inefficient gear box whereby the gears move side to side a lot.

Regards
John
sticker printing


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