Machine Run Time

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ctwo
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Machine Run Time

Post by ctwo » Tue Jan 28, 2020 10:54 pm

I wanted to machine a custom coin 2" diameter in leaded steel, just like any common currency but larger. I use programs like scorch f-engrave v-carve or lazy cam. I'd be using 1/8" ball mill and a 60 degree D-bit with a 0.005" tip.

I am getting run time of 2 hrs roughing and finish of 1 hr. This is to feature depth of 15 thou and 5 thou passes. I felt like it was pushing it at 6 and 4 ipm with a top spindle speed of 3500.

That seems incredibly too long. Shouldn't something like that take 20 mins?

I looked up chip load for a 1/16" EM and saw a couple tenths. That results in a SFM of 54 and feed of 1.4 ipm, and much slower for the D-bit. It'd be all day. :|
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Re: Machine Run Time

Post by Harold_V » Wed Jan 29, 2020 4:31 am

You would be well served to talk with Doug Edwards, a reader of this board. He makes his living making dies (molds in which the waxes are made) for investment castings, and is extremely well acquainted with 3D machining. I think you'll discover that the time you are talking about isn't realistic. Cuts with small cutters demand fine feed rates, and equally fine stepover and depth of cut per pass. I have no doubt that some of the dies he's made took eight or more hours for the finish pass alone, and he has a spindle speed that exceeds yours by far. Perhaps he'll see this and comment. If not, perhaps you can contact him via PM and ask his opinion.

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ctwo
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Re: Machine Run Time

Post by ctwo » Wed Jan 29, 2020 10:15 am

The numbers come out as they do and I know most people doing this kind of work will be running a 50k RPM spindle. Even then I am getting 10 ipm. The work I see on youtube is hard to judge MT as there are cuts and time lapse, but I have a sense of machine speed on the real-time bits and they seem to move quicker than that.

For example, there seems to be quite a bit of real-time footage in this video, and that bit is moving...
https://www.youtube.com/watch?v=8t_t8Sp0fAg

This motorcycle took about 40 mins of machine time and did not break or wear out any bit, but does not have the detail I am wanting.
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Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

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Bill Shields
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Re: Machine Run Time

Post by Bill Shields » Wed Jan 29, 2020 11:41 am

with smaller tools, even 50K RPM is not enough and 20 minutes a very unrealistic number at the RPM available to you

if you are serious about this, you may want to look at a HF motor spindle that you can 'attach' to your existing machine with a dedicated tool attached.

THEN you can go to town
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ctwo
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Re: Machine Run Time

Post by ctwo » Thu Jan 30, 2020 10:38 am

That's is what I looking at a long while back and started building a high speed spindle and mound to the quill. I didn't like my build and the quill rocks a bit. Then I wanted a second high speed spindle and quill to mount to the back side of the ram (bport).

It all came down to costs and I don't really do enough of this, but there is also this reason for that.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

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Bill Shields
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Re: Machine Run Time

Post by Bill Shields » Thu Jan 30, 2020 11:29 am

maybe look around for a trashed plastic engraving machine (XYZ TRASHED) and rob the spindle from it.

I have also seen folks use air driven dental turbine units....you gotta go with light cuts but at 200,000 rpm....the feed rate adds up quickly...
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ctwo
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Re: Machine Run Time

Post by ctwo » Thu Jan 30, 2020 2:34 pm

Yeah there is this johnnyq90 YT channel and he made several tesla turbines and showed it driving a small drill bit. Takes a lot of air so I'd probably need a bigger compressor. Noise can be an issue which is one other reason I want to keep run times low. I just don't want to run that BP head at tilt so long, even though I rebuilt the whole thing.

I'm OK to run scratch engraving all day but it's not as nice and it's limited.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

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Bill Shields
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Re: Machine Run Time

Post by Bill Shields » Thu Jan 30, 2020 2:48 pm

in reality, the HF motorized spindles are quite the best way to go...but move over the $$$ a bit.

I have customers that cut 2mm internal threads all day with a carbide thread milling tools in TiVaAl alloy at 30,000 RPM + without batting an eye...but they are not quiet...

where there is a will there is a way...and if you cannot find the way then you really are not willing...giggle...
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ctwo
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Re: Machine Run Time

Post by ctwo » Thu Jan 30, 2020 9:11 pm

I live in a neighborhood that bans industrial equipment and my neighbor is a lawyer for one of the nation's leading universities. I've been exercising serious will in that regard, but I am also a cheap bastid...
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

Magicniner
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Re: Machine Run Time

Post by Magicniner » Sun Feb 02, 2020 12:32 pm

I built a pulley driven high speed spindle (30,000rpm) from an ER11 collet chuck on a 10mm straight shank and ran it from the main 7000rpm spindle of my machine with a pulley and round polyurethane belt. Once you grasp the concept it's not difficult to design something to suit any machine.

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