Defining machinable parts from a monolithic end product

greenions · Apr 30, 2019

Hi Experts,

I am very new to CNC machining and have never done any hands on machining. I prefer to let experts handle the job and I can focus on describing what I want from the end product.

I wish design a metal only product (preferably stainless steel). I have attached a 3D view of the product along with the dimensions. I have also attached engineering drawings (top, front and side views).

I am guessing machining the monolithic model in one shot is either going to be impossible or will end up being too expensive. I need some help in figuring how to define smaller machinable parts so that it is cheaper to build the overall product. The end product should be very close to the monolithic construction as much as possible in terms of strength and stiffness.

What are my options?

To give you a little bit more context, the end product is supposed to rest on another steel disk (through needle thrust bearings) and rotate on a vertical axis freely. Note that precision is important for me and hence I prefer not to go toward injection molding route.

I would appreciate if somebody can point me to the right way of building the overall product.

Milland · Apr 30, 2019

From what I see, you don't need "how to make", you need "what to make". Right now you don't have even a sensible mechanical concept, let alone design drawings.

Sincere advice - find a local mechanical engineer. You may ultimately have a good idea/concept, but you need someone actually skilled in the art of engineering (or at least mechanical design) to help you realize it.

Good luck, let us know how it goes.

Hazzert · Apr 30, 2019

Is the other piece a “desk”? Because your monolith is going to weigh north of 110 pounds.

Vancbiker · Apr 30, 2019

Looks a lot like the beginnings of a telescope mount......

adama · May 1, 2019

If you keep the same thickness its real easy to laser cut and bend that bit!

Toolroomguy · May 1, 2019

greenions said:
I have also attached engineering drawings (top, front and side views).

I would appreciate if somebody can point me to the right way of building the overall product.

Those are not engineering drawings. Google GD&T.

I suggest looking for a suitable part that is already produced, unless you have thousands of dollars for custom workpieces.

Finegrain · May 1, 2019

adama said:
If you keep the same thickness its real easy to laser cut and bend that bit!

2" thick?

Regards.

Mike

Toolroomguy · May 1, 2019

Finegrain said:
2" thick?

Regards.

Mike

I saw that and wondered if it was supposed to be mm.

Since it was designed,and not just what we refer to as a cartoon in my shop, we should be able to look at his spec for max deflection on the base and the working load calculations.

To need 2" stainless steel it must be a mount for a navel gun.

Tichy · May 1, 2019

It's 2 or 3 tempi depending on whether you have a suitable radius mill. Speaking about using a 3-axis mill tho. With a 4 axis mill doable in 1. You haven't given us any technical drawing at all.

Don't understand the jibes about the size tho.

DMF_TomB · May 1, 2019

greenions said:
Hi Experts,

I am very new to CNC machining and have never done any hands on machining. I prefer to let experts handle the job and I can focus on describing what I want from the end product.

I wish design a metal only product (preferably stainless steel). I have attached a 3D view of the product along with the dimensions. I have also attached engineering drawings (top, front and side views).

I am guessing machining the monolithic model in one shot is either going to be impossible or will end up being too expensive. I need some help in figuring how to define smaller machinable parts so that it is cheaper to build the overall product. The end product should be very close to the monolithic construction as much as possible in terms of strength and stiffness.

What are my options?

To give you a little bit more context, the end product is supposed to rest on another steel disk (through needle thrust bearings) and rotate on a vertical axis freely. Note that precision is important for me and hence I prefer not to go toward injection molding route.

I would appreciate if somebody can point me to the right way of building the overall product.

.
having castings made is a common method to get the rough shape of a finished parts and after 5 or 10% machined off you did not waste a lot of metal. that is a 1000lb piece of metal where 900lbs is machined into chips is just wasteful and expensive.

Tichy · May 1, 2019

He hasn't even told us how many he wants to make. Maybe it's just one.

I'd ask the question if it's really vital that this be just one solid part or if can consist of three parts screwed together.

cameraman · May 1, 2019

Although some prefer monoliths …

movies_2001_a_space_odyssey_desktop_1920x1080_wallpaper-240678[1].jpg

Really since the Neolithic period (5000 BC -ish ) , I'm more of fan of Trilithons …

___________________________________________________________________________________________________

@OP It's called engineering... Where physics meets practical requirements.

Without knowing the application … I.e. what is mounted to your alt-azimuth mount it is impossible to make any sensible recommendations.

Is it an optical system that has various vibration and accuracy requirements... Radar mount ? what kind of environment, (like laser cannon mounted on a war ship ) … Mechanical and shock requirements service life... Or is jib or crane arm mounted between the fork / yoke etc. Alignment of other bores and bearings being a critical factor + possibility of additional mechatronics and precision adjustments ?

Sure the thing can be broken down into a least 3 components and have a lot of weight removed and structure added.

What are the loads and geometries of the other assemblies …

Kinda weird to come onto a forum and ask for free design engineering ? For an application that is completely undefined ?

G00 Proto · May 1, 2019

I think the engineer must be confused and defined this in inches instead of millimeters. I have a hard time picturing many applications that would require a 2" wall thickness out of stainless steel (especially since he is considering injection molding as an alternative). If I am correct, and it is supposed to be millimeters, I would probably just machine the whole thing on a four axis mill in two ops.

If it actually is in Inches, this is one of the few time (maybe the first) that DMF-Tom could have some meaningful input

, because I would sure as heck cast that bad boy.

DMF_TomB · May 1, 2019

i often have had to make prototype parts. if its only one part then yes its often make from solid or welded pieces and machined.
.
obviously if going to mass produce a part is then designed for low cost manufacturing is a science in itself. castings, forgings, die casting, molding all are normally used cause if making 1000's of parts the individual cost is much lower. and many parts can be cheaper low carbon steel and then electroplated.
.
not unusual for a prototype part to easily cost over $1000. or even over $10,000. and a mass produced parts ends up being over 90% cheaper. its like a plastic part machined being $100. but once a mold is made a injection molded part can be only $0.10, its very common for many parts

adama · May 1, 2019

Finegrain said:
2" thick?

Regards.

Mike

Yeah its not very wide, i had not seen the 2" thickness, hence ignore the laser cut comment unless you have a BMF CO2 in the 9-10Kw range, but even then its not really a issue, looks a nice inside radius, would bend up with out too much difficulty, hell probably be pretty cheap - cost effective to even forge it if its really that big?

DMF_TomB · May 1, 2019

many engineers want every thing out of stainless steel and often i had to mention its easier and cheaper to make a prototype out of low carbon steel or aluminum and if and when the part is worn out or corroded we can then make a stainless part.
.
engineers wants to make a machine last 100's years when often the costs involved and company going bankrupt maybe better to make more temporary parts of lower cost and company stays in business longer. many a time it has to be explained no sense making a part to last over 20 years cause factory not going to be here that long. or at least most production lines have a 5 or 10 or 15 year life. not many are the same machines for over 20 years

HuFlungDung · May 1, 2019

Hazzert said:
Is the other piece a “desk”? Because your monolith is going to weigh north of 110 pounds.

More than that, maybe 500 lbs

It's probably for one of those public (pay per view) telescopes, which people are always walking off with, after they're so impressed by viewing something at 1X through a blurry mess of an optical system.

sfriedberg · May 1, 2019

If the thickness is supposed to be 2mm, rather than 2", it would be a no-brainer to call for uniform thickness, then make by cut and bend on a press. Not really a CNC process at all.

If the thickness is really supposed to be 2", it would be a lot saner to call for three pieces, welded or doweled+bolted together. And the pieces would be simple enough they don't really demand CNC machining.

Hazzert · May 1, 2019

HuFlungDung said:
More than that, maybe 500 lbs

I’m pretty confident in my estimate, the legs weigh about 15# ea and the base is 65#. I didn’t count the rads or the rounded edges of the legs but she’s a biggun.

Bending it from constant thickness material might be the easiest solution next to casting it. I’d be afraid to see how much those 18” legs would warp once freed from the rest of it.

michiganbuck · May 1, 2019

12" steel solid cube about 490+ pounds, A wood model/pattern then casting might be good for steel,aluminum,iron.

Guess you might even cast SS
Stainless Steel Investment Casting - 300 Series Precision Parts | Milwaukee Precision Casting, Inc.

*Making a wood model may prove the design works as intended.

QT Milland :[I really hope the OP takes my advice to find an engineer]

*That is very important not only to help with manufacturing but also for the best design.

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