Quite an Unusual one

[Boyan Silyavski]

Other than the obvious fact it will need to be strongly built then I don't think it will be difficult make this work with but from what I see for it to work properly then you need the tool 90deg to the steel has it domes.? Affectively you need 5 Axis. . . . This would rule out Z axis like Jonathan's box design.

The overall angle of the shell/ the wok/ is 27 to 30 degrees from horizontal. meaning 53cm diameter and 14cm depth. That leads to 2 things:
1. A special hammer head with the desired angle to achieve the final result
2.As you say, more axis.
I calculated that for a 10-12mm diameter hammer head with specially designed angle it would not be a problem to form the shell. Thats how i saw they did it in on document. Though the impact frequency is unknown to me. Needless to say the shell will be greased or oiled so the head to be able to slip-stretch the sheet properly.

My approach for dual purpose machine would be to build a Sturdy gantry with something like 200x100x10.

Thats exactly my initial design intent

Then either have two separate Y axis one on each side each with own rails, screws, motors and Z axis or build a single double sided Y axis with Z axis on each side. My preference would probably be shared has it keeps cost and weight of gantry down but I would have rails on both sides.

Thats new idea to me, very grateful.

Then the Rear Y axis would have heavy duty Z axis with short stroke and attached to that would be a stepper driven Rotary table which striker mounts onto creating the 4th axis. This would enable you to keep the striker 90deg to metal at any dome depth.

I have thought of this but not sure if this is in my ability to design.Without mistakes, i mean.

Next To hold the Metal and create the 5th Axis I would build a sturdy fixture on a Rotating table driven by stepper. Few ways this could done.? Either using standard rotary table driven by stepper and bolting Sturdy metal holding fixture onto it. . . .OR. . . . Make a Diy rotary table from an Old car or truck clutch Fly wheel and plates and bearings. Base plate would have bearing attached to it on it's perimeter and the fly wheel would sit on them and rotate on central spindle. It would be driven by stepper directly from the fly wheel ring gear. . . . . This table assembly would be removable from the main bed.

I have to dig deeper about the clutch design then. I have contemplated something similar. Find a truck tire with the axle, fix it on a fixture 15degree inclined/half of the desired angle and made 2 axis only Y and Z. And rotate the tire by belt.
Believe it or not i could not find a tyre with axle here in Spain, for cheap from some scrapyard.

I have thought also of cutting 2 rings, similar to the rings i have for manual sinking, but at the outside cut with AT belt tooth/laser cut. Then flange them and lay them on a table where a lot of bearings are mounted in a circular pattern. The type of heavy load that are big balls only. I dont know the name in English.
But the thing will jump and i dont know how to fix it not to jump around.

Now strictly speaking this wouldn't be 5 Axis has you'll only ever be using 3 Axis at same time. So you could make so it shares the same drives and just swap motor connections or fit Switching system to swap over. (would need powering down drives first)
It would go like this.!! . . Locate tool on centre of metal disc and park gantry and Y axis. These would now not move again so can unplug or switch to drive both rotary tables. Then swap or switch over front Z axis to rear Z axis.

Thats ok for me.

But i don't understand in fact- what will i gain with the 4 rails on the gantry and 2 Z axis ? If i go with heavy duty preloaded roller guides i could use them at the same time for CNC and the impact hammer. if they f"""k i will just change them. or you mean to be able to do 2 things without swapping spindle with hammer? if just for avoiding swapping, then an over-sized Y could do the same job and park one of the Z out of the way.

Should be some Food for thought there.??

I will analyze and implement.

So Dean, my Big questions are:

Will Hiwin RGH 30 HA stand up to the task?

Will ballscrews with 2 nuts each stand up to the task and especially on Z, where additional vibrational creep has to be dealt with? Z with 2 ballscrews and 4 nuts should stand , yes? Ok, not forever, but at least for a time.

What size ballscrews on each axis? the normal speedy ones? 1605 and 1610 respectively?

[~andy]

Out of interest, how are you planning to monitor the affect of the hammer?

[Boyan Silyavski]

I would buy a rail package and Abb robot -----The 7th Axis is the table/carriage and carries the Robot to the Fixture -Numatic hammer on the head of the robot giving 6 axis control ?

I am saving for Bentley, so can not afford that one.

Out of interest, how are you planning to monitor the affect of the hammer?

To sink a shell is an art of itself. The idea is ideal shape with thicknesses distributed exactly where you want them, and its not linear. Repeating the result when hammering by hand is not possible, its difficult also to form a precise smooth shape .

Actually i am stretching the metal in a special way, not simply hammering it down. Every pass is different and the goal is to stretch and distribute the thickness where you want it without warping the sheet. As the sheet warps irreparably when not hammered properly. Ok, somewhat repairable, but with heat treating only. And it introduces other problems that have to be dealt with at further moment.

So implementing my hammering technique pass by pass will program it. Until i eliminate material variables, yes cold rolled steel is not so perfect as it sounds.

Butr if you mean literally, the answer is with 37db ear protection

[JAZZCNC]

But i don't understand in fact- what will i gain with the 4 rails on the gantry and 2 Z axis ? If i go with heavy duty preloaded roller guides i could use them at the same time for CNC and the impact hammer. if they f"""k i will just change them. or you mean to be able to do 2 things without swapping spindle with hammer? if just for avoiding swapping, then an over-sized Y could do the same job and park one of the Z out of the way.

Yes was just to avoid swapping but if you have room for extra wide Y axis that would work OK

So Dean, my Big questions are:

Will Hiwin RGH 30 HA stand up to the task?

Yes easily. 30mm bearings are massive things and can handle large loads.

Will ballscrews with 2 nuts each stand up to the task and especially on Z, where additional vibrational creep has to be dealt with? Z with 2 ballscrews and 4 nuts should stand , yes? Ok, not forever, but at least for a time.

What size ballscrews on each axis? the normal speedy ones? 1605 and 1610 respectively?[/QUOTE]

Don't think 2 nuts would matter or help in this instance has reducing backlash isn't required.
Regards Z axis then Obviously two screws will take more punishment than one but single screw would just means changing sooner and less complicated.!

Yes standard screw pitch and either 16 or 20mm should be fine.

[Wobblycogs]

Please take what I say with a pinch of salt as I'm new to this but I can't help feeling that if you are doing this on a regular basis you'd be better off building a dedicated machine for it. By starting with a regular CNC design you seem to need to provide five axes (6 if you have a rotating attachment on the bed).

The machine I'm thinking of is arranged like a lathe but with tail stock replaced with a three axis hammer. The tail stock would move in and out and the hammer up and down as well as swivel to ensure the hammering is always 90deg to the work piece.

[John McNamara]

Hi Silyavski

Would a support under the hammer help?

Effectively an anvil that could be formed against. Ideally different anvils for forming groves or depressions of a certain shape.

This would also mean you could work rectangular or other shapes as well.

The anvil moves in unison with the top hammer so it should not be too difficult to incorporate it. (Although being able to rotate the anvil and the head in unison would be an advantage)

Have you seen this video?

Ford unveils new CNC prototyping process for metal parts | Manufacturers Monthly

Regards
John

[Ulsterman]

Metal spinning and Flow forming lathe DENN model ZENN 80 CNC - YouTube
Have you considered flow forming ?------A lot of Automotive parts done this way now

The other option is the Robot because you don't need 7 axis with rail but only 6 -Part on the fixture and hammer on the Robot --2nd hand they are not so expensive now especially if single channel

[John McNamara]

I guess the question is this machine a special purpose machine that has only one task making dished circular parts, or is it to be more general purpose?

Is the reason that only hammering will work, not flow forming as in Ulsterman's post or the Ford Link I posted, because of the sound qualities of the finished object when struck?

I guess the hammering introduces stresses that cause various resonance effects as in symbols.

Regards
John

[Boyan Silyavski]

Hi guys,

Thanks for the interest and the help.

Let me answer some questions:

1. Please don't forget its a DIY machine and i don't have a machine shop, though can use some services where necessary. Also i don't have the budget for robots, CNC machining centers and so on. I am into making that musical instrument, but still learning, so as i am not a successful maker yet, the main purpose of the machine will be to sink the shells so i am not tired after 4 hours of precise manual sinking and so i have time to learn to tune it, which is much more difficult task.

2. 2 in 1?
I have a small belt driven CNC and i need bigger machine urgently. I am still thinking that if the machine is well designed, it can be a 2 purpose machine. Lets say 25% normal CNC and 75% special purpose.

3. What you call Flow forming is Supported ISF/incremental sheet forming/ . Unfortunately i aim for introducing particular stress in the material which can be achieved only with hammering. You guessed right that it affects dramatically the later capabilities of the musical instrument.

In fact support head bellow or a fixed form is not needed. They use this type of ISF for achieving precision and faster programming time. I dont care for that, as i know what i am doing and will take the material springiness in count, that's what they want to eliminate using the anvil.

That examples are another reason that i believe i could go without 5 or 6 axis. The air hammer will 1/2 ISF and 1/2 introduce stress meanwhile, carefully adjusting the pass depth and the pass pattern. With a properly designed tool head.


4. But lets look at the 5 or 6 axis design. I have no idea about these. What CAD and CAM? Now i use Aspire and mach3. I think they can not support this type of machining?

Also can somebody point me to a good DIY design of additional axis? I saw only 2000$ axis as the cheapest in the net

5.My worries about Z backslash are based on that the vibrating hammer will f///k the ball screw if let oscillate meanwhile back-slashing


6. So HIWIN 30 roller bearings. Do we rule out totally the Frelon SBR like supported plain bearings? Why they are not widely used on DIY CNC? They support a lot of load, are fast, self cleaning and support oscillating vibrations

7.And what about an rotary 4rth axis which rotates the mounted shell left and right only 15+15 degrees? Then always the head will be 90 degrees to the shell And the Z could be normal. I am talking something like my manual sinking stand? Driven by motor at the shafts