Blight's CNC lathe

[daconfusion]

Over the past 3 days I have spent some time drawing up the new tailstock and support system. Looks good actually, but it seems like this will turn out to be quite a big project too.

Biggest part is probably to make a new spindle, but it doesn't have to come first.

Made a quick render of the current design. It's not a complete model, so there are a lot of things missing. Lots of bolt holes and other stuff.

Are you going to add fillets? There are a few stress raisers, the ones that support the rails may be a concern.

[The Blight]

Fillets where? I think you will have to elaborate, because I don't think I understand what you are suggesting.

[daconfusion]

It may not be worth it, but your FEA could show you the value added versus mass:

I was thinking about fillets on the block that has the two white screws attached on the left side.

It looks like it has plenty of reaction force support with three of those rails or screws, but I do not know what kind of cyclic loading the machine sees.

Great work by the way.

[The Blight]

Not really worth it I think. Takes more time to machine away excess material. Added mass = better vibration dampening too.

Fillets to the top chamfering?

I can't really add fillets to the bottom, as all these blocks are bolted together.

Cutting loads are upwards to the 2 support rails and the tail stock, and if the load is cyclic, it would mean that the machine is vibrating, and thats not good. Should be an even load during cutting. At least thats what I hope. This machine is not made to hog away material, so I can just ease it back if there is need.

I have been thinking about doing a full simulation of this, but I'm too lazy at the moment. Lots of other stuff to work on.

Also found out that I had not tightened the bolts between the back and bottom plate, so thats why it was vibrating while doing a cut-off on steel last time.

Thanks for the suggestions, and please tell me if I haven't understood you correctly. Would have been nice with a "sketch up" feature on the forum.

[daconfusion]

I am new to CNC machines or work machines in general.

Can you please explain where the primary loads will be applied, and in what direction?






For example, if the primary load (blue arrow) would cause the red resulting moment. I think the blue arrow could be represented at a "centroid" created by the three reacting screws.

I was thinking about you eliminating the sharp corners circled in red. The one on the left would not be serious if the load is applied as assumed. Honestly I dont think it would affect the circle on the right either. Not sure of the radius that would be adequate.


Red would be the fillets around the bearing blocks above.

Either way, you would not be removing material, but adding. Changing the mass should change the assembly's natural frequency, not sure how much damping would be added.

Thanks for entertaining my thoughts.

[daconfusion]

Wait...are those top blocks bolted on?

Doh!

Nevermind that is pointless then.

[The Blight]

The load on the tool is as marked with the blue arrow.

The load the spindle sees, as marked in red, is also correct = the rails will start twisting the other direction. There will also be some load upwards (both rails bending up).

As long as I can bring the frequency down far enough, I wont have to worry too much about it. I doubt it though, as most of the machine is made of sheets.

Yep, bolted on had to laugh at that comment though!

Great suggestions, and things to consider. When I made this, I didn't really have the tools to do any calculations, so it was all done by speculations. I'm trying to correct some of the silly mistakes now with the new design.