Estimating Machine Time

Any estimates on how long it will take a 3 axis mill to complete an AR lower receiver from a forged billet block of 7075-T6? Would spindle speed above 12K RPM increase production? 5 axis mill? Can you use more than one rotary in the machine setup? Any "tombstones" already available for this purpose?

45 Bravo said:

Any estimates on how long it will take a 3 axis mill to complete an AR lower receiver from a forged billet block of 7075-T6?

Click to expand...

There are a lot of variables involved in that question, what machine, how many are you making, the skill of the person writing the programs and running the machine, etc

45 Bravo said:

Would spindle speed above 12K RPM increase production?

Click to expand...

yes

45 Bravo said:

5 axis mill?

Click to expand...

???

45 Bravo said:

Can you use more than one rotary in the machine setup?

Click to expand...

Yes but you have to pay for all those additional axis and have the skill to use them.

45 Bravo said:

Any "tombstones" already available for this purpose?

Click to expand...

I honestly don't know off the top of my head but if you plan on making enough to justify a new machine you will probably want to make your own optimized for your process. If you are only making one or two the you have way more money than I do to be looking for commercial solutions.

We made them one at a time in about 35 mins using a 10k VMC with a 5c rotary.

I think 45 minutes on a 3 axis mill. From bar stock. Not including broaching
Don


Sent from my iPhone using Tapatalk Pro

45 Bravo said:

Any estimates on how long it will take a 3 axis mill to complete an AR lower receiver from a forged billet block of 7075-T6?

Click to expand...

this would really be dependent on the machine, how you program and hold it. We have made these in the past ( before my time ) and I was told it took about 40 minutes a piece to machine, and then secondary operations like broaching the mag well.

45 Bravo said:

5 axis mill?

Click to expand...

I would not see a 5 axis resulting in a faster turn

45 Bravo said:

Any "tombstones" already available for this purpose?

Click to expand...

I would guess not a standard for holding AR receivers. You may be able to use a standard generic, but a purpose built would provide better flexibility for your purpose. We make custom tombstones and pallet fixtures for our customers all the time . A custom for this would not be a problem.

As you can tell I am not a machinist. I have been throwing this idea around for awhile. Small to medium production of lower receivers, say 50 per 24hrs. Googled and YouTubed a good bit already but wanted to ask some questions. Have been looking at the Haas VF4SS which has a 12K spindle speed, upgrade to 15k available. Is this big enough to accommodate? Fast enough spindle? Necessary?

Currently throwing out ideas with the guys about work piece setup and holding. One of which would require only two evolution's. Evolution 1 would secure via the left and right of the receiver via a vice. Machine the top of the receiver, buffer tube extension, cut the trigger well and cut/broach the magazine well, cut bolt catch slot and whatever else is deemed accessible. Evolution 2 would secure the receiver upside down and from the inside of the magazine well, trigger well and bolt catch slot via a delrin or other plastic mold, possibly spring loaded for tension. Could possibly mill the take down and pivot pin locations in evolution 1 so that pins could be inserted to assist in work piece retention in evolution 2. Would this secure the work piece enough to finish it? I am seeing that to make this work in only 2 setups evolution 2 would have to be done with a rotary table or rotary mill head.

Correct me if I am wrong but a Hass VF4SS is a vertical mill. A tombstone is typically ran on a horizontal mill. You would be looking for a fixturing plate for multiple piece on a vertical. Similar concept but less flexibility.

at 50 per 24 hours are you running three shifts or multiple machines ?

cstrickland said:

Correct me if I am wrong but a Hass VF4SS is a vertical mill. A tombstone is typically ran on a horizontal mill. You would be looking for a fixturing plate for multiple piece on a vertical. Similar concept but less flexibility.

at 50 per 24 hours are you running three shifts or multiple machines ?

Click to expand...

I see where you went there. Makes complete sense about the tombstone. This is a one machine idea that is still in concept phase. Determining what a machine like this could do in a 24hr period could help me determine if and how to market this and at what scale.

First, consider why you want to do this. If it's for the love of the endeavor, then more power to you. If it's to make money, well, it's kind of a flooded market; you'd better have an angle. Don't forget the licensing requirements, inspection, finishing, packaging, marketing, shipping, etc., which will eat up your margin.

A 5 axis will save a bit of time if done right, as you can do it in fewer setups, but you might get more throughput out of two machines of half the price, especially if the fixturing is well though out.

the mag well is a time eater that and some of the trigger pocket
need a long em with a fair amount of stick out
really need to broach or wire edm the mag well.
done right with 4 axis indexing you can do it with just 3 set ups.

2 speedos and a cat40 with 4th axis