CNC Shark Forum

Thanks for posting this. Your solution is very pure and simple, the mark of a great design.
A great alternative to a costly 4th Axis.

Since you have a fixed ratio between the y travel and degrees that the workpiece turns, you should be able to calculate steps per degree and use true rotary axis software to drive this. ( as well as "wrapping" a linear file.)

Outstanding work. I feel the best feature of the Shark is the user group, and you folks remind me of that almost every day.

Bob,
You have just given a good example of "teaching me how to use this thing".
Thank you.
Now I'm waiting for the wrapping tutorial.
Bob

When drilling the center holes in the ends of the work piece, I use this simple centering fixture.
Be careful if you use these files, I kept changing designs as I machined the fixture.
At least it will give you a rough idea of what I did. Bob

Bob,

Very nice novel idea.
The only issue i see with this is of course you have to have it the 20 inch piece in there even if you are doing a small piece. The other might be an issue from having the the rack gearing on the bottom. If you have a lot of shaving coming off your cut it could clog the track. You could either put it upside down on the top of the gear (not as easy) or you can put a constant air on the track to prevent contamination by the shavings. (you can also enclose the ends)
Keep us posted how it works.
Thanks

Tim

Bob

Do you know the pitch diameter of the gear?

I calculated by using measurements to be 2.39" pitch diameter and 7.51 circumference.
With the rack I measured .2453 between teeth and calculated using this measurement that you would need to travel 7.35" with a complete revolution of the gear.

So I would assume if you were machining a 2.5 diameter .050 deep you would have a 1/1 ratio on the Y axis dimensions. You said that x axis was not affected.

So, If you were machining a 1.25 diameter you would have a 1/2 ratio and would have to double the y axis dimensions.

Does that make sense?

Bob

Tim Owens wrote:Bob,

Very nice novel idea.
The only issue i see with this is of course you have to have it the 20 inch piece in there even if you are doing a small piece. The other might be an issue from having the the rack gearing on the bottom. If you have a lot of shaving coming off your cut it could clog the track. You could either put it upside down on the top of the gear (not as easy) or you can put a constant air on the track to prevent contamination by the shavings. (you can also enclose the ends)
Keep us posted how it works.
Thanks

Tim

Hi Tim,
I agree with you that this device has limitations. However, it provides a good starting point for those of us who want to get an introduction to 4th axis work. When the limitations of this machine start to hinder creativity, it will be time to look for a more versatile solution. And, I know that you are developing an excellent answer to these limitations with your 4th axis at Next Wave.
Thank you for your helpful suggestions.
Bob

BobA wrote:Bob

Do you know the pitch diameter of the gear?

I calculated by using measurements to be 2.39" pitch diameter and 7.51 circumference.
With the rack I measured .2453 between teeth and calculated using this measurement that you would need to travel 7.35" with a complete revolution of the gear.

So I would assume if you were machining a 2.5 diameter .050 deep you would have a 1/1 ratio on the Y axis dimensions. You said that x axis was not affected.

So, If you were machining a 1.25 diameter you would have a 1/2 ratio and would have to double the y axis dimensions.

Does that make sense?

Bob

Bob,
All this thinking is making my head hurt. You sound right...I arrived at my ratio by comparing circumfrences. A little trial and error also helps. When I was designing the machine, I knew that the different diameters would need to be taken into consideration. I estimated the change needed in Y and tried a sample. The second sample worked as planned.
With your experience, you will probably get it in one.
Bob

Thank you Bob.You really put your talents in this .Great job.Thanks.

You're welcome.
Has anyone tried this contraption yet?
Bob

I thought you did Bob Ha Ha Ha

Its on my list of things to do, but the list is long and distinguished

Roger