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  1. #1
    Hi,

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

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

    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

    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.







    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

    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

    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.
    Last edited by Boyan Silyavski; 26-09-2013 at 04:29 PM.

  2. #2
    I pity the guys neighbours.

    Have you considered a fixed gantry design?

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

  3. #3
    Quote Originally Posted by ~andy View Post
    I pity the guys neighbours.

    Have you considered a fixed gantry design?

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

    Click image for larger version. 

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    Last edited by Boyan Silyavski; 26-09-2013 at 07:07 PM.

  4. #4
    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.??

  5. #5
    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 ?

  6. #6
    Quote Originally Posted by JAZZCNC View Post
    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.

    Quote Originally Posted by JAZZCNC View Post
    My approach for dual purpose machine would be to build a Sturdy gantry with something like 200x100x10.
    Thats exactly my initial design intent

    Quote Originally Posted by JAZZCNC View Post
    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.

    Quote Originally Posted by JAZZCNC View Post
    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.

    Quote Originally Posted by JAZZCNC View Post
    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.

    Quote Originally Posted by JAZZCNC View Post
    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.

    Quote Originally Posted by JAZZCNC View Post
    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?

  7. #7
    Out of interest, how are you planning to monitor the affect of the hammer?

  8. #8
    Quote Originally Posted by Ulsterman View Post
    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.

    Quote Originally Posted by ~andy View Post
    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
    Last edited by Boyan Silyavski; 26-09-2013 at 09:07 PM.

  9. #9
    Quote Originally Posted by silyavski View Post
    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




    Quote Originally Posted by silyavski View Post
    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.

  10. #10
    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.

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