How do I Draw These Grooves & Toolpath Them?

[SobtzakEngineeringTechnologies]

Hello,

I'm in need of some assistance on this part.  Below is a picture of an older large bushing.  The grooves on the inner surface were mangled.  They are for grease.  I need to make some new bushing from a piece of brass tube with thick wall.  The problem I'm having is how do I add the grooves on the ID in a sinusoidal pattern as it goes around the inner perimeter?  I'm assuming it will be a sweep function or something like that but not sure how to set it up.

Also, once drawn, I'm not sure how to toolpath it.  Looking at using a boring bar with a tip or a lollipop endmil.

Any help is greatly appreciated!

[TheCADWhisperer]

@SobtzakEngineeringTechnologies 

Can you File>Export your *.f3d file of your attempt to model the geometry to your local drive and then Attach it here to a Reply?

[etfrench]

Start with two sketches.  Use the first sketch to create the bushing.  Draw a diagonal line in the second sketch.  Use that line to Split Face (Surface tab) the inner face of the bushing. Use that as the path for a pipe command to cut the bushing body.  Mirror that to create the pseudo sine wave.  

[SobtzakEngineeringTechnologies]

 TheCADWhisperer - I''ve attached my file.  Its just a simple cylinder at this point.

etfrench - Let me try to do this.  I've never used the Surface functions or pipe command.

[SobtzakEngineeringTechnologies]

Ok, I got a couple grooves based on your feedback.  Thx.  The original also had a horizontal groove running through the middle of the bushing.  I tried to add it in the same manner but it failed when I tried to create the 'pipe'.  Any suggestions?  I've attached my updated file.

 

[etfrench]

There are several ways to create the horizontal groove.

1. Just draw a circle on a plane at the height you want the groove.  Use the pipe tool to create a new body. Combine/Cut that body from the bushing.
2. Use the torus tool to create a torus. Combine/Cut it from the bushing.
3. Draw a circle with the diameter of the groove (on the vertical plane, not horizontal).  Use the Sweep command to create the groove.

[HughesTooling]

@SobtzakEngineeringTechnologies Have you put any thought into what sort of tool you'll use the machine these grooves? If you're going to try milling them you probably will not be able to use a lollipop cutter because the depth would be too shallow so you'll need to use a T shaped cutter like the image below.

Trouble is this will create an odd shape when cutting at angles. Also you will need to use a trace toolpath that will need to be the centre line of the cutter. You should be able to model something if you create a cylinder offset from the bore by the radius of the cutter minus the depth of the slot. Think you'll also need to create a sketch with the lead in and out because trace doesn't have any horizontal lead options.

Looking at the Trace toolpath it does have options for cutter compensation so you either need a path at the full depth or you can use centre line with compensation off.

Mark

[SobtzakEngineeringTechnologies]

etfrench - thanks for the options.  I had some trouble when I did it with the pipe command and wasn't sure if I was on the right track.  I'll take a look at it again!

HughsTooling - Mark.  You hit the exact next issue!!  I've been looking for a tool to cut these and how to CAM it!  I have the same concerns you have, a I haven't seen a lollipop cutter that can go deep enough and I couldn't find anything else.  WHAT IS THAT CUTTER CALLED??  It will make the diagonal sections wider but might be my only option.  I'll try to do centerline cut.

[etfrench]

Cutting tool holder is easy enough to make.  Round stock to fit in a boring head with two holes drilled in it.  One for a carbide cutter and one for a set screw to hold it in place.

Carbide engraving bits are easy to reshape with diamond lapping plates.

[HughesTooling]

@etfrench How are you going to get the correct path? Are there CNCs with cycles for this, you'd also need the CNC to feed the boring head out. I know there are dedicated machines for cutting these groves with cutters like you show maybe some CNC lathes could do it as well?

@SobtzakEngineeringTechnologies The cutter is listed under groove milling cutter here.

Mark

[etfrench]

One could also use a right angle cutting frame.  Here's one I built for my rose engine:

It's driven with a round poly belt and a motor suspended above it.  You could also use a dremel type tool to drive it.

I haven't tried to create a toolpath like this, but asking in the Manufacturing forum may get the answer.

[SobtzakEngineeringTechnologies]

All, I appreciate the feedback.  I've been able to create an initial toolpath with the trace function.  Biggest problem I see is something HughesTooling eluded to which is with a groove cutter, the more vertical portions of the grooves will be wider.  This is not an issue with a lollipop endmill but I haven't found one that will give me the depth of cut I need.  I'm adjusting to a 0.25in diameter and need to get as deep as I can. 

etfrench - that's a unique solution.  Not sure I want to take on that much work just to cut a few pieces.  I may move post over to manufacturing forum as recommended now that I figured out (from you all) how to draw the part!

Thx

[HughesTooling]

Found this on YouTube.

https://www.youtube.com/watch?app=desktop&v=TJH2q5ylJXM&t=0s