Sprocket middle prints


#1

Hello,

My first time using makerbot and sketchup. I am a student who is attempting to make a plastic sprocket for a hydraulic pump that is used in a thermal evaporator machine. I downloaded catalog sprocket plug-in and created my design, pictured below. Once it started printing, I noticed makerbot printed the middle also. I previously used subtract and thought the inside was gone, but the entire middle printed. I have used circles fine to remove the middle. I have tried intersecting and deleting but nothing is working. I heed an innertube shape with teeth on the both sides of circle. Any help is much appreciated as my last 3 hours have been without results. Thanks


#2

It’s not quite clear what you are after. Is it a “two teeth rings” sprocket that lacks a cilindrical hole in the middle? Or do you want to subtract the two wheels to create one wheel with teeth on both the outside and on the inner hole?


#3

Thank you for the response. I did do a bad job of explaining, and could only post 1 picture. Below is a picture of the desired outcome from my first attempt. There was a small layer at the bottom that printed the entire 1/4 inch of the sprocket. I chiseled it away but there must be an easier way for future reference, and also to allow a better fit for the inside.

Right now I am creating an inner ring and outer ring and trying to combine with a hollow circle. Thanks again.

Derek


#4

Design a larger sprocket (A) without hole.
Design the “hole” (B) (as in image, with teeth) as if it were a smaller sprocket. It is going be the void in the desired result.
Subtract B from A. This could be done bby intersecting them in the same context. Or with one of the ‘Solid’ tools in SketchUp Pro.

Both A and B need to have the same thickness.
And make sure that the result has only front (white by default) faces on the outside.


#5

Thank you. I think my problem was a misunderstanding of ‘grouping’. I finally finished it and am printing. I had to worst time interfacing two sprockets so what I did, a)small sprocket/small circle for inside teeth, b) large sprocket/large ring for outer teeth, c) hollow circle to match the two. A and B are both 1/4" thick with c being shy of that. I will update tomorrow on results as I am leaving it printing.


#6

The middle still printed. Here is a picture in makerbot before the print. The hole in the middle was printed so I had to chisel it away.


#7

My guess without seeing the actual model is either incorrect grouping or incorrect orientation of faces.
If the printer doesn’t know what is inside and outside it doesn’t know where not to print.


#8

do you know of a link with literature about this. I am searching and only finding examples with a shaft in the middle. Thank you


#9

No, sorry, I only have practical knowledge.
Look at the model in Sketchup in monochrome and make sure everything on the outside is white.
You are telling th printer this is outside and this is inside. So it knows what is solid and what is a hole.
Uploading the model will always give you better answers.


#10

sproket.skp (1.7 MB)

sprocketfinal.skp (1.5 MB)

If you want to look and can recommend anything it would be much appreciated. I am working no my masters in electrical engineering so im trying to get this stuff. Its a sproket for a hydraulic pump on equipment. First time 3d printing


#11

I Looked at both files. You have 3 groups where you only should have one.

You should intersect the three groups and delete all the edges inside the “skin” of the sprocket.
The result should be a single group (or component), a SketchUp solid group with only a skin. All front faces (white) should be on the outside.

‘Entity Info’ shows a volume for the one and only solid group that you wish to 3D-print.


#12

Looking at the model ‘Sprocket’ the reason it prints the middle is that the bottom face is continuous. It doesn’t have a hole.

As Wo3Dan points out the other model is all groups.
I’ve cleaned it up for you to see how it should be.
Also, are you aware that the inner toothed ring isn’t centered to the outer ring. Effectively you have created a cam not a sprocket.

Solid sprocket.skp (435.3 KB)


#13

Thank you both for your help and taking time to help a noob. Unfortunately my advisor is ■■■■ about things and does not like how the 3d print has small gaps where the teeth connect to the ring, so he advised I try a different program to see if the 3d printing improves, I am currently trying Inventor Professional, haven’t touch CAD in 14 years but there are some decent youtube videos that are helping me through. Do you think this issue of the gap could be due to grouping too?

I did notice that it was off center once I picked up the print this morning hahaha, I should have aligned before 3d. The main issue I run in with groupings is I need to twist the outside teeth 4 degrees and not the middle. So I need to make both 3d, make components to twist only the top surface, and then regroup, interface and trim.

I tried another sketchup print this morning, manually fixing the teeth and I did finally resolve the middle print to a degree where I could snap it off. But my advisor did not like the small gap as mentioned previous and the thickness of the teeth.

I will open your improved design for me and try re-centering and printing tomorrow when I am back at the lab. I really do appreciate you taking time to help me.

Another long night in college :frowning:


#14

a 4 degree twist is simple.
Just select the edges that form the teeth, rotate from the center and type 4 enter.


#15

What!!! that just blew my mind. I did not know you could select just the outer surface ring for angle measurement. I was selecting the entire surface. Thank you. Your 5 second video has been hours of frustration summarized. The more I think of it and look at examples, I think the gap problem must deal with the groupings because every gear I have seen printed looks clean.

The last thing I would need help with is the teeth thickness, I played around with pressure angle, but do you know of a way to manually set the values? I need 1/16" at the base and 1/32" at the tip of the teeth.

Thank you so much again. Your knowledge is awesome


#16

I have no problem donating to you through paypal if you fix this for your time.

Again, I am working on my masters in electrical engineering in solar cells. A hydraulic pump was misused and a plastic sprocket got badly crushed. Because most everyone is physics I got assigned this task. I wish my mechanical engineering roommate did not graduate. My advisor gave me the task Tuesday and wanted results Friday, but I am learning all this for the first time so he kind of understands on the delay. This is no where near an assignment, we just need to lift a heavy drum to do thin film depositions. If not, no worries, I need to figure this stuff out for future reference anyways


#17

Money doesn’t come into it, I’m no engineer and as such don’t quite understand what you need in terms of making the pressure values correctly.
However there is a plugin for making gears. It is quite old and isn’t designed to make them correctly for 3d Printing but you might be able to use it to make a correctly profiled gear. It would then need some cleanup/exploding etc to make it a solid for printing.

Have a look here and see if it is any use to you.


#18

The whole proces has been explained excellently by Box, even the advantage of SketchUp’s stickines regarding the geometry (you could only select the top ring of the outher teeth and rotate this selection by 4 degrees) and the plugin that helps designing the correct tooth wheel.
One question remains though. You keep mentioning a gap in previous design. What gap do you mean?

I found a little opening in the inner group but don’t think you ment that.


#19

Yes, both of you all have been more than helpful. Sorry, I am in a car now but the red indicates the gap. The printer does zig zag for the teeth, a few lines in a circle and the becomes thick. The few lines done in a circle dont stick to the teeth. There are little gaps that you can see through. I really think this has to do with grouping because of how the middle was printed too.

All this has been extremely helpful, but I must figure out a way to make the teeth slightly wider too on sketch up. Autdoesk has been trying to convert from 2d to 3d for 8 hours now :(. So I anticipate playing around with sketchup a little more once I am back in the lab.

Thanks again for all your help


#20

Many of your problems seem beyond me but I think it’s just not understanding the program.

You can select an edge and scale it to a specific size. You can draw a circle with the correct number of segments for the teeth and then adjust the size of the actual segments to be 1/16 or any other size you want. Then draw the few lines that make the tooth with the specific length of 1/32 at the tip, select that and make a radial array and you have the face of the toothed wheel…

With a few accurate dimensions it is a few minutes work to model.