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  • Awesome job! Please be willing to share your knowledge about things with the group.

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    • Hi Preso

      All the techie details about the transformer and controls would also be lovely. I am especially interested in how you kept the transformer out of saturation. That's the bit which gave me problems.

      Cheers
      Roger

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      • Originally posted by rcaffin View Post
        Hi Preso

        All the techie details about the transformer and controls would also be lovely. I am especially interested in how you kept the transformer out of saturation. That's the bit which gave me problems.

        Cheers
        Roger
        Saturation? Or are you talking about excessive current?
        Location: Helsinki, Finland, Europe

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        • Not sure what is meant by saturation. I just rewound the secondary with two turns of heavy gauge automotive battery cable and it works fine. I was working on a circuit diagram for how I wired in the digital timer relay, the low voltage circuit and the solid state relay. I will need to get it finished and post it with the rest of the data.
          Regards,
          Preso

          Comment


          • Saturation occurs when the input waveform causes the core to become fully magnetized before it reaches its peak voltage causing distortion in the output waveform. Also know as overdriving the transformer.
            Kevin

            More tools than sense.

            Comment


            • Originally posted by KJ1I View Post
              Saturation occurs when the input waveform causes the core to become fully magnetized before it reaches its peak voltage causing distortion in the output waveform. Also know as overdriving the transformer.
              More applicable to audio amplifiers and such.
              Distortion is not really problem on a spot welder

              Problem would be the huge input current in case that you saturate the transformer. But its not normally much of a problem with EI-core transformers, toroids can be more problematic.
              Location: Helsinki, Finland, Europe

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              • Hey guys,
                I did some reading on saturation myself. From what I read, saturation is not an issue when the secondary winding as working in a purely resistive load. It can occur when the secondary has been rectified into a DC load but that's about as far as my brain will stretch. I have completed a circuit diagram for the welder I built. The digital timer relay and socket are fairly cheap. Around AU$24 including shipping. I used an illuminated mains switch for my project and it was connected to the 24V DC power supply. The lamp was rated at 12V but it seems to be happy running at the higher voltage. It may fail early?
                Here is the circuit:

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                • Come on guys, start a new thread with this. This isn't a discussion forum.

                  Pete
                  1973 SB 10K .
                  BenchMaster mill.

                  Comment


                  • When the steel core of a transformer reaches saturation, the inductance changes radically. Then you can get huge current spikes which can take out fuses and cause other excitements. Bad news.

                    The amusing bit is that the better the quality of the transformer, the BIGGER the hazard. A really cheaply made E/I core tranny (like in a microwave?) is much safer than a good toroid here. Of course, what you really want is a tranny with an adjustable air gap, like on an old-fashioned arc welder with that big screw-in knob. That is one of the few cases where a large adjustment knob really does do something important.

                    Did you strip out the secondary winding first, before adding the battery cable winding?

                    Cheers
                    Roger

                    Comment


                    • Home built vertical head for Denbigh Milling Machine

                      Hi,
                      Here is another project I built back in 2013. I purchased a Denbigh mill which came with a vertical milling head. However, by the time I fitted a collet chuck and a vice on the table there was only about 50mm of useable Z travel left. The problem was that the vertical spindle was mounted on the axis of the horizontal arbor and there were no spur gears to raise the height of the drive above the arbor. I decided to provide the drive to the spindle independently by means of a 3 phase motor with a toothed belt drive controlled by a variable speed drive. The whole unit is mounted on the over arm and locked to the front of the column with a single bolt. It's not the most rigid setup but at least I was able to machine tall workpieces although I don't have a lot of Y axis travel. It's sufficient for the sort of work I do at present but I struggle to get enough torque for slitting saws and heavy cuts with an inserted tooth high rake facing cutter. I am thinking of fitting a 3:1 helical drive gearbox or something like a Dore Westbury reduction gearbox to give me a bit more torque. All the castings are aluminium and I was positively at the limit of my foundry experience when I did them. The main spindle casting was cored mainly because my biggest flask was just short of the volume I would need to pour the casting without the core. Even with the core I got some shrinkage. The spindle is supported by two cone bearings and fitted with lip seals. The spindle is MT3 and machined from a single piece of 4140 steel but not hardened and tempered.
                      The nameplate is shop made and chemically etched in brass. I powder coated in red and then sanded off the high spots before powder coating in clear. I like fitting nameplates to work that I do because it makes the work look a bit more authentic and I just like the look of those vintage nameplates. Unfortunately, contemporary workshop equipment looks a bit, well, crap with foil or vinyl stickers. It just doesn't scream out quality does it. I can remove the vertical head but it is heavy and I have fitted a shop made winch to the back of the mill which lifts the head via a draw bolt through the hollow spindle and a pulley fitted to the portal frame above the mill. I am old, I have lower back issues and I don't need to go back to hospital for more spinal surgery so I thought it prudent to use some mechanical assistance to get by. Having said that, I often press on with some jury rigged vertical machining process to get a job done rather than to reset with the horizontal arbor to do some proper metal hogging.
                      Regards,
                      Preso

                      Comment


                      • Preso;
                        super work. Again.

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                        • Preso;
                          Your work has a very commercial (not homemade) look to it, good job! Maybe some separate threads on these projects, like the brass nameplate?

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                          • I am planning to do a Youtube video on how to make the brass nameplates. I am making a steampunk-ish nixie tube clock and I have designed a retro looking Soviet era nameplate for it.
                            Regards, Preso

                            Comment


                            • Originally posted by Preso View Post
                              There are also four videos on Youtube detailing how I model the 3D printed parts for casting patterns, some stuff about powder coating, assembly of the machined castings, etc etc.

                              I am impressed by your fabs. Now I am subscriber #19 to your YouTube channel. As a subscriber, I will make unreasonable demands for more content more often, utter ignorant criticisms about your machine shop and video editing techniques, and compare you unfairly to the Stars of YouTube Shop content creation.

                              So, when is your next video coming out? It's been 10 minutes and I haven't seen a new video yet. HUH???

                              Comment


                              • Originally posted by Dan_the_Chemist View Post
                                I am impressed by your fabs. Now I am subscriber #19 to your YouTube channel. As a subscriber, I will make unreasonable demands for more content more often, utter ignorant criticisms about your machine shop and video editing techniques, and compare you unfairly to the Stars of YouTube Shop content creation.

                                So, when is your next video coming out? It's been 10 minutes and I haven't seen a new video yet. HUH???
                                Don't worry. I'm all over it like a rash!
                                Regards,
                                Preso

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