Quite an Unusual one

Hi,

i am still in the middle of my 1st build for a friend and here comes the second already :cool:

This would be a brainstorm so , help and ideas will be highly appreciated. In fact i depend on it :semi-twins:

Basically with some hard earned money from my day job and a bit profit from the other build i want to start slowly to build this machine.

If i succeed it will be my dream machine:sentimental:

Before some months i asked the same question at the zone, but did not get any help there. So i have done some preliminary research alone.


So here are the details:

1. What i would like to achieve:

-Now comes the crazy part.
If its possible i would like to have a very sturdy and rugged router table with work dimensions 700x700x200mm. At the same time i would like to be able to mount a pneumatic impact hammer and form metal sheets on it. I would like to form a wok-like shape circle with aproximately 53-60cm diameter to shape it from flat to 15cm deep. The metal is soft, mild sheet 1.2mm thick. Now i shape them manualy.

Dont ask me why, its another 200 page explanation, but i want to be able to make this sheet into form using impacts, not any other method. Not spinning, not waterforming and so on. This is 100 percent shure. No doubt here. So big or small impact hammer head mounted on air rammer moved by CNC.
The impact are known frequency of 700 to 1000 impacts per minute and the impact head size ideally will be from 10 to 25, 30 mm in diameter and should not coincide, so there is a minimum speed that should be maintained.
For that task the main goal is not accuracy but repeatability! means the metal is springy, and so and so, what matters is the final shape to be same all over again. As i do it by hand now, and do it well, i am quite capable of programming the hits afters certain experimenting so that is not an issue.

Can this be done? Yes, i have seen a document where 30cm dish is achieved using unsupported round rails and 10mm hammer head.

What i want to achieve is good repeatability with a machine that will not break after a year doing this all day. And if at the same time i can use it for Wood and aluminum routing will be perfect. As i dont have money for 2/ even for one now


Here is a video how it is done by hand by a guy/not me, i do it for now with normal hammer/. The 1.2mm sheet is quite ductile in fact, not as people could imagine. The goal CNC-ing the process is repeating the same shape over and over again, in other words eliminating variables.
the thumper the guy uses on the video is bigger by one size that what i will use. The weight will be 4kg. He uses 35mm head , i would be happy even with smaller as i would CNC it, not be in a rush i mean.

https://www.youtube.com/watch?featur...&v=VbR6fHoZrTQ





2. What i figured till now

I hope and i would like to be with moving gantry. Making a mill like, will be last resort.

Basically i have no problem with the general design. Big steel profile, sturdy table, double gantry as Johnathan build but with added 3rd rail somewhere higher as normal gantry for additional strength. Eventual Z box in the middle with 3 or even 4 No money will be saved for the sturdiness of the gantry and the table. Welded steel. I will design it so to resist a direct hit from a truck:topsy_turvy:

I said rails. Now here is where i need help.
After a lot of thought and checking specifications and so i came to 2 conclusions. There was a bit consideration for the price also.
I decided that my best bet will be HIWIN Roller guide square supported rails , medium to heavy preload, 30 size.

The other choice i meditated a lot , was a big SBR rails like 30-50 size with double Plain Frelon carriages which are not cheap. Same price as big Hiwin roller carriages.


Then the movement. Here i am lost. Ball screws possibly with 2 nuts each on every axis, also 2 ballscrews for x, 2 for y and 2 for Z. Driven by short belts and so.

I also contemplate the possibility to make a floating Z plate and dumpen it with adjustable bike suspension, to imitate the rebound of the human hand when doing the same process, that could further lower the stress on the rails.

I will start posting the current design and will need your help here :hysterical:

Also it would be interesting if there is a chance to make it a separate machine with some kind of cheap heavy duty stuff instead of expensive Hiwin roller motion.
moved by belts or so.

One thing to me is clear though. It should be moved by at least Closed Loop Steppers, which i thing will be best.

I pity the guys neighbours.

Have you considered a fixed gantry design?

You can get circular rails if you want to rotate the circle.

Quote:

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Originally Posted by ~andy

I pity the guys neighbours.

Have you considered a fixed gantry design?

You can get circular rails if you want to rotate the circle.

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You should pity my neighbors too. Thats why i rented a house in the countryside. Cause its hours and hours.

I have considered. Unfortunately i live in a rented house. If i have to move a half tone machine just changing house, it would be quite difficult. Also the build could become quite expensive with moving tables and so.

Also here is how i think. If the rails can support such a job, then they will be ok for moving gantry if the gantry is extremely rigid.

I have considered round THK rails but that could lead to other problems, like reinforcing the rings where the sheet is mounted.
Now the rings are meant to be integrated in the table bed. I mean the sheet would be bolted around round hole in the table bed with 12x M10 screws.


The basic idea for the table bed made from 100x100 steel profile:

Attachment 10240Attachment 10241

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.

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

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.

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.

Should be some Food for thought there.??

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 ?

Quote:

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Originally Posted by JAZZCNC

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.

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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.

Quote:

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Originally Posted by JAZZCNC

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

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Thats exactly my initial design intent

Quote:

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Originally Posted by JAZZCNC

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.

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Thats new idea to me, very grateful.

Quote:

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Originally Posted by JAZZCNC

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.

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

Quote:

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Originally Posted by JAZZCNC

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.

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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.

Quote:

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Originally Posted by JAZZCNC

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.

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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.

Quote:

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Originally Posted by JAZZCNC

Should be some Food for thought there.??

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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?

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

Quote:

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Originally Posted by Ulsterman

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 ?

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

Quote:

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Originally Posted by ~andy

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

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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:toot:

Quote:

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Originally Posted by silyavski

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.

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

Quote:

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Originally Posted by silyavski

So Dean, my Big questions are:

Will Hiwin RGH 30 HA stand up to the task?

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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.

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.

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

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

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

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

Attachment 10257

I am more and more inclined to make a special machine for the purpose. Anyways still contemplating it.

Nevertheless i have to start buying. So i decided to go backwards. The spindle first.

Need some help with the choice:

Now the big question is 3kw or 2.2kw spindle? I am more inclined to the 3kw. As a brand name inverter will be expensive this size, i am looking into the chinese vfds. Are they reliable enough, Dean mentioned somewhere that now they make them good. Should i know how to distinguish them or what? I see some have aluminum backs some not.

I recently bought a 2.2kW spindle + VFD from Chai (ebay: linearmotionbearings2008) as part of a larger order. I've not had a chance to fire it up yet but it came well packaged and all appears to be in order. The price came out to be a few pounds more than the cheapest I could find but I found a number of very bad reviews for the cheapest seller (things not turning up, etc). From what I've read the spindles are normally ok, they all claim Japanese / German bearings but it's luck if they are. The standard VFD's are also normally ok but they seem to vary in quality more although I think the quality has improved a lot in recent years, it seems they either last for ever or go pop in the first few weeks.

Guys, i have to start sooner this build as everyday i change my mind.:joker:

Now here is the deal. i have decided to make the machine with working area 1200 x 2500 and at the same time make it fast and rigid. Till now the problem was limited space and problems in moving the machine.
Now the funny part. I bought yesterday a towbar and am looking to buy a suitable platform trailer, so i will mount directly the machine on the trailer :hysterical:
I did not want to cut myself short just because i could note move it from home to home. So its decided.

I will definitely go with the Johnathan design of a gantry just make it suit my needs and abilities. maybe even add one more beam at one side like a standart gantry, as Dean suggested somewhere.

So here is where i need help:
When the machine was small it was clear that 1605 screw for the z and 1610 for X and Z.

Now some options for the gantry:
1. make it from 2 100x100x4 = whole gantry below 50kg

2. make it from 3 100x100x3 / 2soldered together/ - 1m=9kg, so whole gantry will be ~ 65 kg

3. make it from 3 100x100x7 = whole gantry 80-90kg

-So, the big question is how to move the gantry at 2600mm length?
-What screws, what motors?
-Servo maybe ? I know nothing about servo, can you point me to good money wise servo for the long axis?
-What drive relation 1:1 , 1:2, 1:3
-unfortunately i can not machine rotating ballnut. Could somebody help me here? any other options?


So now i am a bit confused between 2 options, make a sturdy beast 1250x1250 or make a sturdy beast 1250x2500 with your help. I mean an exemplary sturdy beast for the generations to come:beer:

If you are going to put this in a trailer you'll need to make sure you add some way so you can jack it up on sturdy legs. If it's resting on the trailer wheels I think the machine will probably shake itself to bits.

Quote:

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Originally Posted by Wobblycogs

If you are going to put this in a trailer you'll need to make sure you add some way so you can jack it up on sturdy legs. If it's resting on the trailer wheels I think the machine will probably shake itself to bits.

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I agree with you. i will take off the wheels and hard mount the trailer to the floor, and the machine will be hard mounted on the trailer. The trailer idea is to use it only when i change rented houses. Will not drive it around :pirate:

Hi there. Almost finishing my design.

Basically i decided to go Big.

I designed quite an unusual gantry and Z with the main idea of eliminating as much overhang as possible, light as possible and easy to build as possible.

Another thing is that affected by Jonathan's build i could not help but contemplate an extreme machine with 3rd gantry beam. See picture 6. I believe Jazz sugested something similar, if i am not wrong.


The gantry would be driven by rotating nuts/2510 ball screw/ if Jonathan or somebody is kind enough to make them for me, i know free time is an issue there.

The gantry design as tested by me will have less than 0.01 flex and bend /twist/ and will weight 2 beams -40kg +Z weight or 55kg+Z weight if triple.

For the moment i am very inclined to invest in the Leadshine hybrid 220V AC drives, though maybe i will start with Geckos as i have them. Depends what would cost me for rails and ballscrews for 1250x2500. Still have not decided. But if i make it only 1250x1250, definetly the 3 beam design and the AC drives.


What worries me most is the bed, as i dont have money for 20mmm alu bed. I am contemplating how to make a strong cheap bed with strong channels.



Now please tell me what do you think? My main idea is to build something exceptional if possible, cheap as possible where possible :pirate:, and as simple as possible, so when i share the plans it could easily be repeated by other people.

PS. The Z design is just a sketch, is not finished, will be lightened and i will try to move the ball screw further to the center without messing with the spindle. Another point is that now the plan is for 100mm diameter spindle, as i assume most people would choose for such a machine.

Attachment 10937Attachment 10938Attachment 10939Attachment 10940Attachment 10941Attachment 10942

I've also thinking about what to do for a bed with t-slots. My first thought was, like you, 20mm aluminium and machine channels into it. Then I saw the price of the piece of aluminium I'd need! It's probably the route I'll end up taking though as it's fairly simple.

The alternative option (which I've not priced up yet) is to get some aluminium profile, lay that on the bed so that it's very close to flat and then take a thin surfacing cut. You can then use the built in t-slots. Not sure how much cheaper that will be in the long run though. If you can get away with using regular or even thin walled profile I suspect it would be cheaper.

I've just about finished buying all the parts for my machine, cheap and simple are not available options :highly_amused:

Quote:

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Originally Posted by Wobblycogs

I've also thinking about what to do for a bed with t-slots. My first thought was, like you, 20mm aluminium and machine channels into it. Then I saw the price of the piece of aluminium I'd need! It's probably the route I'll end up taking though as it's fairly simple.

The alternative option (which I've not priced up yet) is to get some aluminium profile, lay that on the bed so that it's very close to flat and then take a thin surfacing cut. You can then use the built in t-slots. Not sure how much cheaper that will be in the long run though. If you can get away with using regular or even thin walled profile I suspect it would be cheaper.

I've just about finished buying all the parts for my machine, cheap and simple are not available options :highly_amused:

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The DIYer biggest problem is that we never know what exactly the machine would be for, so we want it as multi functional as possible. At least that's me.

For now the best i thought of would be to do the bed in the following manner:

Most of it Plywood with nuts covered by expanded PVC sheet 10mm, covered by another sacrificial sheet of the same material. The area near me/ the first square meter/, made with the thick alu channel extrusion + sacrificial PVC, or all same but holes left for a toolplate that can be bolted over all directly to the supporting beams. Or the first square meter made from square bars, cut and bolted so that emulate tool plate. Even if not perfect, they will be strong to bolt to and the plastic over them will be resurfaced. I even think that that type of machine could scratch steel, so i could resurface them directly.

After some thinking, calculating and so on, i believe i have the perfect compromise. Meaning- 1250x2500x200, very simple but robust Z, Z and gantry and bearings that will support the impact hammer. yes, i am still into the metal sheet forming idea. Atr least i would like to be able to try, without breaking the machine.

Basically with the design i achieved a 100mm/3kw/ spindle to have least possible overhang- the bit center from the gantry at ~ 80mm only. The spindle will be packed in aluminum rectangular of a kind. For the impact hammer a shell with the same dimension will be fashioned, so they could be easily interchanged.

I wanted roller blocks on the gantry and everywhere, but will be extremely expensive, and as i am not completely sure for the metal forming success, i decided on 2 roller rails +4 blocks on the Z and all else Hiwin 20 HG. For the sake of vibration and overbuilding i decided to put everywhere else 3 bearing blocks instead of 2. That will make everything rigid enough to withstand continuous vibration and at the end 4 blocks more from china will cost me only 150 euros more, which is irrelevant if the experiment succeeds or fails. having in mind that one roller blocks costs 100eu and 1 meter rail is double the HGR 20 rail price.

The roller blocks and rails for the gantry i found used for 150eu with shipping, so its a good deal.


Now the ball screw on the Z. Obviously with this extremely low overhang there is no place to fit the ball screw. So i fit it aside when i discarded the idea of third profile on the gantry, due to weight. So for the sake of vibrations of the impact hammer, i decided to fit 2 ballscrews. I believe even with one will work if not the hammer. As they are extremely cheap, i want just to be sure and overbuild here

What i want to say that if i had not made any big error, this design is quite sweet looking for a sturdy DIY machine.Take away the 3rd bearing blocks and the second ballscrews from the design/ due to the impact hammer/ and here you have quite simple but sturdy Z with only 80mm overhang to center of router bit from gantry. I am happy.

Any critique will be appreciated. Its not finished but i wanted to share.

PS. Dont worry for the holes placement and assembly, its under control :-) . Some minor changes will be made to the design so everything can fit in place without problems.


Attachment 10986Attachment 10987Attachment 10988Attachment 10989Attachment 10990

Silyavski, I'm liking the Z design but I worry the whole thing will shake to pieces once the hammer gets going.

Quote:

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Originally Posted by EddyCurrent

Silyavski, I'm liking the Z design but I worry the whole thing will shake to pieces once the hammer gets going.

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I really hope it would work. If you knew how much time, money, effort, sacrifice and Love went to that project, you will understand why i will take the risque.

If interested look here at this dissertation . I know it by heart of course, but from page 53 onward is the interesting stuff. On page 55 you can see what machine they used and later the tool and the result. I mean if they did it like this, i should be able to do it even better with mine.

I know you want a machine to do everything but I was thinking about this cheap 2 axis idea.
Hammer mounted in a steel frame, the hammer can pivot.
A linear actuator connected to the top of the hammer can pivot it to the required angle.
The base rotates under the hammer.

Attachment 10991

This is not the one I would use but is just an example
http://www.ebay.co.uk/itm/18-STROKE-...p2054897.l4275

Quote:

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Originally Posted by EddyCurrent

I know you want a machine to do everything but I was thinking about this cheap 2 axis idea.
Hammer mounted in a steel frame, the hammer can pivot.
A linear actuator connected to the top of the hammer can pivot it to the required angle.
The base rotates under the hammer.

Attachment 10991

This is not the one I would use but is just an example
18" STROKE LINEAR ACTUATOR | eBay

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Eddy,
Thanks!
This is a very fresh idea. I would say the best idea till now.
It still will have to have Z and rotating axis. But this great idea eliminates the gantry and bearings blocks there. It will be best to use screw jack servo motor or similar instead the actuator.

I see a lot of +++:
Only 2 cheap big bearings will support the Z, where the hammer is, the enclosed structure will be more rigid and so on....

It seems doable. I will start working on this design and definitely will bring it to life when i have the big CNC machine ready.

By the way i have my eyes on big THK steel slew ring roller bearings in ebay. For the shell mount rotation. Will dig deeper these days. They ask like 500eur for 60cm diameter bearing assembly which is incredibly cheap. Though the one that suits me seems not to have mounting holes for the actual ring. Will investigate further.


However the Big question for me here is - How i would control that thing? What software? This is quite unclear to me.

Just thinking very quickly about control, it may not be good enough for your requirement though. (trying to keep it cheap and simple)
Forget software.

The base would be a simple motor and gearbox
The screwjack would be simple motor operated.

The base would rotate at a constant speed.
At each full turn it will trigger a switch that will move the screwjack a small amount using a timer to run the motor.
2 limit switches will indicate when the hammer is at each end of it's travel.

OR

There will be one motor that drives everything.
The base and screwjack are connected by belts and pulleys to provide the correct speeds.

As the base rotates the hammer will slowly spiral into the centre.

OR

A VFD will control the screwjack
A simple motor will rotate the base

A tacho generator will be connected to the base so that it's output will be proportional to the rotation speed.
The output from the tacho will feed the reference (0 to 10v) of the VFD.
As the base rotates the hammer will move a small amount to spiral into the centre and if the base speed changes so will the screwjack speed.

Quote:

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Originally Posted by EddyCurrent

Just thinking very quickly about control, it may not be good enough for your requirement though. (trying to keep it cheap and simple)

The base would be a simple motor and gearbox
The screwjack would be simple motor operated.

The base would rotate at a constant speed.
At each full turn it will trigger a switch that will move the screwjack a small amount using a timer to run the motor.
2 limit switches will indicate when the hammer is at each end of it's travel.

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It should be programmable. There are certain moments that the hammer needs to spiral towards the center, otherwise waves of material rize due to accumulated tension and at a certain moment everything will wrap if not controlled.

Mach3 can do 2 axis so G code could control it and now I've seen the power of Mach3 Brains there's all kinds of things you could do.

The hammer is now mounted on a gimbal and can be made to work in a circular motion by moving the X and Y axes.

No need for a rotating base so it can be made cheap and strong.
Mach3 can operate the X and Y axes.

Attachment 10992

OR easier

A small X Y gantry mounted on top moves the end of the hammer so 50mm there would be maybe 300mm at the other end of the hammer.
Then Mach3 could be used in the normal way where you would use a 2D software to draw a reduced size pan with the required toolpaths.
A pneumatic proportional valve working on 0-10v (like a VFD) could be used to control air pressure to the hammer using M codes e,g, M3 to turn on the air
then for example S500 would tell the valve to deliver 5Bar, S200 = 2Bar , etc.
So the S codes could be put in the G code as required to change the hammer power.

Attachment 10993

Now back to reality. I need some help here please! With motor calculations. I read numerous threads here and at the zone, have done numerous calculations as far as i could but will shamelessly ask here again as i am stuck.Almost finished the drawings. The Z looks quite nice and now i am sure its possible, though some blocks will look like cheese due to the ridiculous hole placement:redface:

I though i had everything clear until yesterday i calculated the weights.

The Z weights 32kg and the gantry in total 120kg :black_eyed:

Part of the problem lies that i don't know what exactly i want:hysterical: as till now i have experience only with small weak machines.

1. I would like the gantry and the Z to be rigid as they are in the drawings
2. I would like the machine to be in the middle between resolution and speed. What i am not sure is what speeds i want/not rapids-cutting speed/. I will cut wood and aluminum on that machine. I chose 1610 to move the z left right and 2510 screw to move the gantry. I thought of 1:1, now i am thinking of 2:1, otherwise not only i am jumping in the so called "servo territory" but will have to jump in the "expensive big servo territory"

I have decided on the 3kw spindle. I am not sure but i believe i will be happy with sturdy heavy machine that could do 250IPM /6350mm per min/- cutting in wood at good if not full cutter depth. The weight should help with the depth and i assume with the aluminum finish. Aluminum i will be happy if i do it at flute diameter depth. It seems the machine will be sturdy enough for this, having in mind the very extremely low overhang with my design, enclosed frame spoindle and strong gantry +the quantity of bearings.

3. I thought of driving the Z with hybrid closed loop Leadshine Nema 23 3Nm, same the Z left right and 2x the same that move the gantry.

That was when i did not know about the actual weight.

Now the question is:
-do i make my machine smaller / which i would not like much, cause the money will be almost the same and missing eventual job on the long run could be very undesirable/

or

Keep it like this and figure how to drive it.


So definitely i need some help in this mess in order to evaluate options and make no mistake here.

The servos i am looking at are these: my friend Fred's BST store
He seems to have the lowest priced servos and drivers around and as i will buy the rails and screws from him, seems quite logical choice

Questions:
having in mind that i don't want to compromise one axis due to small savings of $ and ruin the integrity of the machine. Obviously on the long axis i will go with servos. And here BST store llloking at the prices of servos i am almost ready to fit servos on all axis, as they are almost the price of the Leadshine closed loops

1. The Z weight will stay the same. 10kg spindle + some aluminum, there is nothing more to do except lower the weight about 5-6kg which i believe is not worth it . That is clear. RM1605 screw . Should i stay with 3Nm leadshine Nema 23 closed loop motor 1:1, change the relation 2:1, or upgrade the motor to servo?
If servo, what reduction and how big the servo motor?

2. Z weight again same. RM1610 screw. Should i stay with 3Nm leadshine Nema 23 closed loop motor 1:1, change the relation 2:1, or upgrade the motor to servo? If servo, what reduction and how big the servo motor?

3. Gantry 120kg :black_eyed:, 2510, rotating ball nut both sides.
options i see:

- drive it with 2 servo motors, one each side. I am lost what power i need here. According to what i calculated if i am not mistaken could go with 2x 6N.M 1.8KW 3000RPM 110ST AC Servo Motor 110ST-M06030 + Matched Servo Driver / 310euro each . i am not sure though if the reduction here should be 2:1? Or if with 2:1 reduction i could go with smaller servos like the 4N.M 1.2KW 3000RPM 110ST AC Servo Motor 110ST-M04030 + Matched Servo Driver, where the price is 304euro, so as you see there is almost no price difference .

-drive it with 1 big motor and 25mm belt which i am almost sure i can fit to pass through the gantry beam
for a motor i believe the 130ST-M10025 servo motor and servo driver system 2.6KW 10Nm 2500rpm 10A / 375 euro/ would be ok. Again not sure if the ratio should be 2:1 as i assume.

4. Or i stay with closed loop steppers, but they arent cheap, i almost decided on servos.


5. I can not find what size in Nema are these servo motors so i could continue with the drawings, in fact no info on these cheap servos

PS. Found the documents at last for the servos PDF specs
it seems they are Xinje Servo drives and motors here PDF for the drives

Attachment 11053Attachment 11054Attachment 11055


What are your thoughts guys?? Please, don't be shy :redface: , tell me where i am wrong


here are some updated cheese drawings:

Attachment 11047Attachment 11048Attachment 11049Attachment 11050Attachment 11051Attachment 11052

Answers to questions:

1) Ballscrews give a very large mechanical advantage. You do not need to worry about the weight of the Z-axis so much. See here. You'll be fine with a generic 3Nm motor and 70V stepper driver. The closed loop ones are a good concept, but cost a huge amount more for little gain.

2) Don't use RM1610 - it doesn't gain anything.

3) I wouldn't go with the long belt idea, especially when using servos as servos work best when they are rigidly coupled to the load - i.e. without a long stretchy belt.

You may well be fine with two stepper motors - have you tried putting the values in this spreadsheet?

If using one servo, the formula you need is this:

Je=M*(L/(2*pi))^2

Je is the equivalent inertia, L is the pitch of the screw (so 0.005m with 1:2 ratio) and M is the mass of the gantry.

Next find the inertia of the servo motor rotor (Jr), e.g. it says in the datasheet for 110ST-M04030 is 7.61kg-cm^2. You then need to find what 'inertia ratio' the motors will tolerate - typically it might be Je/Jr<5. So just use the above formula to calculate Je, divide it by Jr (7.61kg-cm^2) and if the result is less than 5 the motor is probably suitable.

e.g, M=120kg, L=0.5cm (1:2 ratio):
Je=120*(0.5/(2*pi))^2=0.76kg-cm^2

Je/Jr=0.76/7.61=0.1.
0.1 is much less than 5... so that servo is plenty big enough. Another way to look at it is rearrange the formula to find the mass a particular servo will drive, e.g:

M=Je/(L/(2*pi))^2
Je=Jr*5=7.61*5=38.05
M=38.05/(0.5/(2*pi))^2=6000kg(!)
Or if the ratio is 1:1, that's
M=38.05/(1/(2*pi))^2=1500kg
(So note the quadratic relationship - if you double the ratio the drive-able mass goes down by a factor of 4)

The rated speed of that motor is 3000rpm, so the gantry would go at 3000*0.01=30m/min with 1:1. You need to check the Je/Jr ratio - Je=Jr gets the most efficient energy transfer, but the drives do tolerate a mismatch so you need to find how much, as going with them equal generally results in an oversize motor. You should also include the inertia of the pulleys in the system - just work out their inertia (assuming cylinders is near enough) and add them to the Je value, remembering to take into account the drive ratio.

Either way, you can see that that servo is far bigger than you need... so I suggest you put the formulas in a spreadsheet and find which motor is best. Also try the stepper motor spreadsheet I linked to earlier, as I expect you'll find that there are suitable stepper motors available.

4) If you use stepper motors, and select the correct size motors, then they wont stall unless you crash the machine. The only time the closed loop servos help therefore, is if the machine crashes. For the same amount of money as the closed loop stepper you could get a much higher torque standard stepper motor and be certain that it wont stall.

I forgot to mention...I'm not keen on the placement of your Z-axis ballscrew. If a large force is applied parallel to Z, the axis will begin to skew (i.e. rotate in the Y-Z plane), due to the ballscrew placement being off center. The effect can be reduced by increasing the spacing of the Z-axis linear bearings, or go back to two ballscrews, or get the ballscrew closer to the center. That's why on the new machine I placed the ballscrew intersecting the Z-axis ram - it got it closer to central, but admittedly still not ideal.

Jonathan, good reply.

Hi,
my first helping post here but I was reading for quite some time...
silyavski
here is part of my excel spreadsheet that might be useful for you- - just type in your variables in green boxes and you should get all the date you need.
Attachment 11071
I do not guarantee correctness of the results but I'm fairly confident that they are correct.
It's slightly more complicated then most spreadsheets that I've seen here so if you have any questions ask here.

Quote:

---

Originally Posted by Bart

Hi,
my first helping post here but I was reading for quite some time...
silyavski
here is part of my excel spreadsheet that might be useful for you- - just type in your variables in green boxes and you should get all the date you need.
Attachment 11071
I do not guarantee correctness of the results but I'm fairly confident that they are correct.
It's slightly more complicated then most spreadsheets that I've seen here so if you have any questions ask here.

---

Thanks!
P[W] stands for calculated power per motor for X or for both motors?

Some updates:

Motors:
Thanks for the help! Now things are more clear there.

The main option i will go most possibly is 4 servos x 400w or 2x400w +2x750w.

Obviously from the calculations if 2:1 then 2x200w+2x400w will be sufficient, but as the price difference between 200w,400w and 750w is merely 5-10 euro, i dont see a reason why not going properly bigger.

The Hybrid stepper option i discarded due to price similar to servos.

DC Servos and motors from Leadshine are almost the price of AC servos and motors , so 220v seems a lot better choice

Steppers are still an option, except for the long axis that moves the gantry. However i would like the Z also to be closed loop, due to the vibrations. Plus the price of decent driver and motor and PSU is almost as the price of AC servo, hence the servo decision.

Another point there is i am starting to doubt about the cheap servos, so i am trying to get for the same price 4 x ACH750 Leadshine AC Servo motor drives + motors. Bargaining with Chinese people takes time :-)

The Z axis

The single screw design i am almost 99% sure will be without a problem. Hoewver i decided not to risque due to the impact hammer head and changed the design. Lost something of the beautiful simplicity and acquired annoying amount of pulleys and idlers, but i could not design it better for now. Best would be with 2 stepper motors on 1 drive, i know,not a very good idea, but works/my flimsy cnc is that way on the gantry without any problem, but is flimsy, not rigid like this design/
So, for now that's how it would be:

Attachment 11072Attachment 11073

Rotating ball nut
At the end i found somebody help me with making it. Jeff, from the forum, who happens to live very near, here in Spain. Wow, what a work shop and machines he has, especially compared to my garage.

Now as i decided on Servo, may be even will go with double ball nut/all over the machine also/. 1.450kg said Fred yesterday, weights the 2510 double nut. I wonder what the inertia will be, he he.

I thought of integrating it into the gantry, but at the end decided to fix it aside, due to the possibility to lower significantly the screw length+ avoiding an accidental hit of the gantry to the screw mount

Attachment 11074


Breakout board
-ESS and PMDX126 seems to be the first choice. What i don't like of this combo is the fact that i have to buy additional spindle control board

So i investigated quite a bit even looking at some second hand Galil motion boards on ebay.

Another good option seems the KFLOP. In fact it seemed ideal/8 axis they say +usb/ until i found that i have to know C+ and that half of its IO are 3v so i have to spend another 240$ for accompanying IO board.

What i need is very simple: cheap ethernet digital 8axis board :joker:

A question ?????
There is something i don't understand about boards and servos. Why all speak of the encoders to go in the BOB? Dont they go to the servo drive and the servo drive controls the closed loop? I read at Galil and KFLOP that the BOB closes the loop? Or am i mistaken?

Quote:

---

A question ?????
There is something i don't understand about boards and servos. Why all speak of the encoders to go in the BOB? Dont they go to the servo drive and the servo drive controls the closed loop? I read at Galil and KFLOP that the BOB closes the loop? Or am i mistaken?

---

I would always expect encoder feedback to go directly to the driver, you don't way any delay introduced, it should go directly to the summing junction that should also exist in the driver.
If feedback does go via the bob on any system, I would steer clear of it.

P [W]
Stands for maximum (instantaneous) mechanical power of a motor when going at full speed and utilizing full torque.
This wont happen in real life as with stepper motors you'll have a safety margin of 1/2 so you will get only half of that power from a stepper motor. It's also important to bear in mind that you will utilize half of this power only in two instances. First instance, when you're accelerating to full speed at full allowable acceleration during fraction of a sec just before reaching max speed. Second, when cutting at full speed with full allowable force. Otherwise you're using only fractions of that power.

Cutting a steel is done between 1 and 2 m/min so if your Vmax is 10 m/min than you will use only 10-20% of Pmax and only if the gantry had to be pushed with full allowable force which is unlikely to happen.

In a cell where you input a torque of motor it was required to input a combined torque of motors for given axis. Now you just input a torque of motor and number of motors.

I also see that you are interested in power of motors, so I've attached one more spreadsheet inside to calculate various mechanical powers of motor, as well as some information on power and current drawn from power supply - to help choose PS.

Attachment 11075

I don't know much about application of servo motors but from what i briefly read, the most important feature of a Servo Motors is a possibility to overload them up to 10 times which is not possible with stepper motors due to the nature of a driver.

If this overloading feature is possible than consider following.

For a 400 W servo motor that you've selected (assuming an overload factor of 5) you can get as much as 2000W for a fraction of a sec.
Now, if you open my spreadsheet (the new one) all the data there are for my design.
Equivalent Gantry Weight 290kg
Motors: 2x 1,5Nm -> maximum power of 150W per motor but steppers have to be used with some safety factor so as not to loose steps.

I've taken 1/2 so I'm Using only 75W of each motor. With that torque/power I can accelerate 290kg gantry to 10m/min (393 inches/min) in 55 mili sec. That's quite fast but with your servo and 2000W you will be able to accelerate it to the same speed in as little as 4,5 ms over a distance of 0,38 mm, ceteris paribus.

So what I want to say is: don't over-invest in motors.

Best regards