3d milled parts

[richclay]

Hello

I'm new to cnc machining and wondered if someone here could give me an educated guess as to how long the milling would take on shapes like the ones in the photo if they were 3d contour milled from both sides to a point where I could then tumble the parts to get the final surface smooth?


The parts will be approx' 10" long and made from aluminium.

Kind regards

Rich

[awerby]

A big mill with a fast spindle will be a lot quicker than a small one with a slow spindle. Aluminum also doesn't tumble-finish particularly well. Sculpture tools like this are usually made in wood (boxwood is best) - why aluminum? If you're looking to mass-produce these, CNC milling them one at a time isn't a particularly economical way to go. Use the CNC process to make masters, then cast from those to make your actual aluminum parts - that will go a lot faster, and the time it takes to do each original part will matter less.

Andrew Werby
www.computersculpture.com

[Cruiser]

You leave too many variables to calculate a time. Since time changes would be a direct relation to the type of holding device for each operation and the overlaps involved with the programed surface finish results expected, as well as the size and quality of the tool and its subsequent speed and feed rate etc. etc. etc..........

[richclay]

Hi Andrew

thanks for your reply, I'd be looking at milling them in multiples from sheet. Aluminium is quick to mill, fairly lightweight, and easy to get hold of. You're right about boxwood being the ideal but genuine boxwood only comes in logs of no wider than 6" diameter, once you move out from the centre this obviously gets a smaller and so even less efficient, it's also extremely expensive, difficult to get hold of and cracks during drying.

Do you have an idea how quickly a large vmc might contour one part, if it had say an 8000 rpm spindle?

[richclay]

Hi Don

thanks for your reply, the quality of the milled finish would depend on what I could reasonably get away with before tumbling them to produce a smooth rounded end result, the tumbled finish is the one that's going to be seen. I have seen the finish tumbled aluminium has and it's good enough for what I have planned. I'm not looking for a time accurate to the second, and I'm not asking about work holding, just an educated guess on the amount of actual cutting time for one side of the part.

[Algirdas]

actual cutting time with 8000rpm will take 56 hours at least.
It's not proper to mill these parts. Make mold and manual finish after. Pressing is also good. Plastic or natural compound - the best. Hand carving much easier if You don't need mass production.

[richclay]

Hi Algirdas

I don't believe it would take 56 hours to mill the contours on that part.

I am aware that I could make molds and have them cast, or that I could hand carve them but there are reasons why I have chosen not to take those routes.

[aucran]

What about using a 4axis machine? Just leave a bit of stock on both ends that can be cut off with a band saw and buffed out, since these are going to be tumbled anyways.

At least that way you save the 2nd set up.

You would need to be pretty light on your cuts though, they look thin in areas and even made out of AL they would be easy to bend and break.

Not sure on time though

[richclay]

Hi Aucran

Thanks for your reply, it's nice to get one from someone who is trying to be genuinely helpful. I think a 4th axis setup wouldn't be as efficient as machining them from a sheet.

I'm really just interested in responses to the original question.

[pontiacg5]

Your looking at several separate cycles, your not just going to cut shapes like that out of a sheet on a 3 axis mill without turning the work. I would guess that Algirdas guess is pretty close. You would have to make all sorts of fixtures to hold the work too, since it would be odd sizes after the first program.

Gah, thinking about it makes my head hurt. It would be 10X better from bar stock on a 4th axis and 100X better cast.

[diyengineer]

Originally Posted by richclay Hello I'm new to cnc machining and wondered if someone here could give me an educated guess as to how long the milling would take on shapes like the ones in the photo if they were 3d contour milled from both sides to a point where I could then tumble the parts to get the final surface smooth? The parts will be approx' 10" long and made from aluminium. Kind regards Rich

Cast them.
http://www.foundry101.com/search.htm

[richclay]

ok my mistake, apologies to Algirdas, I thought he was just taking the micky. I figured I'd be able to just get some cam software and 3d contour mill from each side, I thought there would be some experimentation as to how long they'd need to be tumbled for to get rid of any ridges from the cutter.