Help with CAD and small brass gear

[The Extractor]

Hi all, I have a customer needing some small brass gears. He brought me a 3D printed carbon fiber gear that needs to be machined from brass and a usb drive with an STL file of the part.
I have a Bridgeport Ez Trak in the shop. What program will work best for me to dimension the gear so I can program it on the mill?
Or does anyone have a CAM program with the correct post processor for the Ez Trak?
Any help is appreciated!

 

[len_1962]

ask the guy if he created the STL file from a solid Model from and CAD software and then ask them to make you a DWG or DXF to use.
If he downloaded the STL for a website maybe the site has a dimensioned 2D download???
but big thing is asking them the right questions so they can help you get the data you need to help them. Most just think that a this is all easy like the big red staples button!

 

[The Extractor]

Its a bit of a complicated story so I cant really do that. Its his customer's 80 year old uncle that made the file so not really feasible.
I think the uncle drew and 3D printed it. I don't know if he drew it or used some sort of scanner.
I guess what I need is to convert it to a format autocad can import.

Agreed on asking the right questions!
I relate it to everyone thinking its as easy a microwave.

 

[implmex]

Hi The Extractor:
You need that gear profile if you want to CNC mill that part.
And it has to be the correct profile.
The DP needs to be correct.
The pressure angle needs to be correct.
The involute profile needs to be correct.

An STL file will not do it...you need a CAD file format your CAM system can follow to generate your toolpath.
A DXF file will probably work just fine.

So somebody needs to make that file if you cannot get it from the customer.
Is it going to be you?
Do you have the CAD tools you need to do that?

If you do not, your Prototrak is not going to help you very much.
So you need to do it the old fashioned way:
If you think the 3D printed gear has a good enough tooth profile on it somewhere around its periphery, make yourself a fly cutter by hand grinding it from an HSS blank and fitting it to the 3D printed gear with a Dremel a backlight and a magnifier so you can see what you're doing.
Bolt the 3D printed gear onto your brass blank and mount the whole works on a dividing head or a rotary table standing up.
Whisker out the tooth spaces on the brass gear until you just touch the printed gear with your cutter.
Mark the 3D printed gear with a Sharpie so you can see when you just touch it with the flycutter.

Doing it this way allows you to circumvent the whole CADCAM thing...you don't need to care what DP or PA or involute profile is, but you will have a correspondingly crappy gear (by gear standards).
But if it works, who cares!

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[no704]

How many? 3D print them in PLA and cast them.

 

[bob]

I would tell the guy to go to Boston Gear

 

[nihilistic]

Reverse engineering can be fun but time intensive. You could take a photocopy/scan of the gear and import the picture to autocad. Draw up the necessary geometry as best you can and machine from that.

 

[The Extractor]

Thank you everyone.
I do not have a cam system, so I may try and hand program it. sigh.
I got it converted to a dxf so I can import it into autcad and trace it so I can make a drawing to program from.
I may just bag the CAD stuff and hand make one as implmex suggested.
Boston gear is a good suggestion.
Thanks for the help so far everyone!

 

[crickets]

It is possible to convert an STL file to DXF in FreeCAD. If there is any interest, I can write up the sequence of operations later in this thread.

 

[The Extractor]

Boston gear said no.

 

[kenton]

You should be able to program 1 tooth profile and either copy, rotate or use a subprogram to rotate the profile around the center.

 

[Conrad Hoffman]

If it's a simple gear, I think I've used this in the past- https://geargenerator.com/#200,200,...0,0,0,0,0,2,0,60,5,12,20,0,1,0,0,0,0,0,3,-515

I'd be hesitant to trust somebody else's file unless I knew exactly how they came up with it.

 

[Strostkovy]

An stl file is fine for a gear if sufficiently detailed. I often export STL cross sections to DXFs in sketchup, but solidworks can save an STL as a STP file if that works.
Not all gears need to be absolutely perfect. Slip rolls have atrocious gear fit, for example. Some gears only connect hand operated controls. I'd just take the DXF and fillet the intersections. I don't think I would take a job for a single gear with no cam software though.