CNC Punch Progress… solenoids to raise head

CNC Punch Progress… solenoids to raise head
Just a quickie to let you know where I’m at with this CNC book puncher. Having got the now successful ‘punch through thick card’ aspect sorted, I had to be careful I didn’t add too much resistance to the forward punching motion such as with a return spring. The solution was quite simple, a solenoid to return the punch head to it’s start position, and then ‘hold’ that position (with the solenoid at that point operating on a lower current to reduce heat build up). However, typically in practice things never go to plan! It is quite common on treadle machines for the punch to stick in the card, hence quite a large spring is required. Conveniently at greater extensions (if I’ve remembered my A-level physics correctly!) this has a greater force, so retracting the cutter out of the card is no problem. However, with a solenoid of course, for force exerted in the armature by the coil is weaker at greater ‘extensions’, and so it is most inconvenient to have the grea-*test*-('") force required to retrieve the punch out of the card when the solenoid is at it’s weakest. I’ve tried two small ones at 48v (see -*test*-('") image below) which work at their most efficient at this point on the lever to get the best compromise between required force and effective distance of armature travel. It does limit the overall travel of the punch head of course, which might then affect the card cutting characteristics, as my initial -*test*-('")s seem to show this might be a problem (solenoids not effective over the full range of head travel if the punch is set up to rest at its highest from the card, therefore set to a working range the head momentum is bound to be affected).

Anyway, just to forewarn you when you next see photos of the machine with two large size solenoids on the back end if it comes to this, you’ll know why!!!

Nick Just my two-pennorth on the return solenoids: if you had a light return spring on the punch arm just to stop it falling down onto the card, you could then pulse the return solenoids when the main solenoids release. This would get out of the constant holding current situation you mention. I devised a simple pulsing relay circuit for use with castanets. It uses a relay and a capacitor to give a short duration pulse. If you like I could try and paste the diagram on this forum if I could work out how to do it. Bob

Great idea Bob; I wish I’d thought of that! I had considered the use of a solenoid and spring combination in order to build up extra force, but this was not what is required here, and I’m not sure the logic works! You idea does though… If I use a light return spring that, rather than one just for holding the punch head up, is capable of moving it from just above the card to the start position for the next punch, then the solenoid(s) just need provide the movement for retrieving the punch out of the card. As this occurs over a short distance, I can thus only need a small movement from the solenoid armature(s) which will therefore give me plenty of power for this operation with the armature(s) close to the coil and using the lever for mechanical advantage. As long as the length of punch travel is kept reasonable long the punch action has no problem making the perforation, so this light spring hopefully won’t affect the success of this – I’ll do some -*test*-('")ing and see how it goes. Might get away with just one magnet too! A pulsing circuit would be interesting Bob if you can remember how you did it! I could always use the punch up/down signal for this, but each time the solenoid(s) would be held high unnecessarily until the punch head is completely returned by the spring, and in any event if the head were to become stuck then this would leave the magnets on indefinitely until human intervention, so a short pulse interval separate to the head position data would be best. Who’d have thought automatically making perforated organ music would be so complicated! Still, it’s a very interesting and stimulating task, and one that has brought immense pleasure (combined with frustration!) so far, and also one that as a learning experience has greatly improved my engineering skills. I hope the real joy to come of sitting back and watching the finished machine not only work but provide a useful product for me will not be too far away! Thanks again, Nick

Hi every body, I just discovered this very interestins talking area! When I see all these solenoids on Nick's punching head, it reminds me many trials that I did a few years ago. I also built a punching machine suitable for cardboad, starting from Bob's booklet and software. Presentely, I built 2 of them. In both cases, the energy which drives the punch is given by little electric motors. And it work just fine. The good old principle on the sewing machine in fact... Some pictures ot a little machine are there: http://perso.orange.fr/orgue-de-barbarie/perforatrice_1.htm It works into up to 0.4 mm cardboard. A bigger one is here: http://perso.orange.fr/orgue-de-barbarie/une_nouvelle_perfo.htm . The punch drive comes from an electric screw driver and it runs into 1 mm thick cardboard. Unfortunately, for the moment all the comments are only in french. But there are many picture, drawings and videos. If it may give some ideas or new tracks... Pierre

Pierre - looks great !! I had thought about using a dot-matrix printer as the basis for a punching machine as well. Your web page translates very well - http://babelfish.altavista.com/babelfish/tr (AltaVista Babelfish), so I was able to read the text as well as the pictures. I thoroughly enjoyed reading the rest of your website as well - if you submit the URL of the top of your website to Babelfish (http://perso.orange.fr/orgue-de-barbarie), you can read the whole thing in English as the translator follows the links as well which was very cool !! Stephen.

That's very nice Stephen! Therefore, anybody is able to understand why some things are this way and not another one. All the site long, I tried to explain more than to present... Pierre

Many thanks for the link to your excellent website Pierre – your punching machines look great! I’ve got lots of studying of all that information to come. It’s the much thicker card I’m using that is causing all my design issues. I haven’t made much progress with the machine lately as my Chiappa rebuild has taken precedence, but I do have plans later in the Summer to complete the above machine but just for cutting round hole keyless book music up to 50kl, which the solenoids are quite capable of doing as things stand at the moment. I will next construct a mk2 keyed machine, this time of a completely different and novel design such that the cutting head will be very lightweight to move quickly across the card. The power for the punch will be coming from a special cam system off a motor, all mounted on the baseboard, and transferring power overhead to the punch such that the punch arm takes absolutely none of the punching load. This will allow the carriage to be fast in movement, yet span over twice the distance of the mk1 above, enabling me to cut over 100 key card music via this system. It’s a little on the ambitious side I know, and difficult to explain, but I’m at the drawing stage and am quite sure it will work, so I have faith they’ll both be punching away before too long. Anyway, I will keep you all posted on the progress, but don’t expect too much in the next few months as I’ve got plenty else on at the moment! Cheers for now, Nick

I understand very well the description of your future machine, since in Paris, one of our most famous organ music provider (Pierre Charial), uses such one. I guessed it was built by somebody from Belgium... It works exactely the way you say. A big motor and a cam system is on a base board, and the punching movement is "distributed" over the moving punching head. An amazingly little motor moves the very light head which only carries the punch an the matrix. The "brute" performances is not so high, since it take about 3 hours to punch a 27 tracks, 2 mn 30' piece of music. But impressively, it punches 6 piled 0.6 mm thick cardboards at the same time! Punch and matrix seems to be made of tungsten carbide... But this man is a professionnal and punches thousands books a year... From an amateur point of view more modest equipement may be sufficient. I have a couple of friends who got very interesting results, actionning the punch directly whith a little pneumatic jack, only powered by a little compressor picked on an old refrigerator. Not so smooth as my "sewing machine-like" system but it's highly reliable as well. Well, the topic is very wide and sure it may be covered by many different and efficient solutions... Pierre

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