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  • Casting a thing of the past ?

    Or just easier to produce patterns for short runs?

    Playing about today using Solid edge to get a .stl model of a hypothetical crankcase then move it into Vectric's Cut3D program to generate the code.

    Direct link here but 5.6meg download

    http://www.stevenson-engineers.co.uk.../crankcase.wmv

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    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.




  • #2
    Like watching grass grow.

    I bet it was more fun doing it.

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    • #3
      Sir John, forgive my lack of knowledge, but how does one hold that part to the table? I presume it's got 4 tabs in the corners, no? When the cut out toolpath is run, then how is the part held?

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      • #4
        That's just a demo. Either the part isn't designed to be actually made, or they're going to make it out of a deeper block than the finished part.

        Casting is still very much alive and well, as many of those toolpaths take hours (or days, in some cases) to run. Can't exactly make 100 parts a week if it takes you 30 hours to machine. What you're seeing is appropriate for prototype and similar work, where several zeros attached to the end of a quote is not an inhibition. It's also appropriate for making patterns and cores, ironically.

        Edit:

        Here's a cool video of a part like that getting made.

        http://youtube.com/watch?v=pPCrTYwp2UY

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        • #5
          Originally posted by toastydeath
          Casting is still very much alive and well, as many of those toolpaths take hours (or days, in some cases) to run.
          There's a neat How It's Made episode where they're making aluminum engine blocks, and it's all castings. But these aren't your GrandPa's castings: nearly everything on the line, from pouring the sand to tamping, to coring the sprue holes, is done robotically. There's not a human in sight, even for quality control, which is done with image recognition.

          There was another slick casting episode about making pulleys. The casting sand is used for a mold, a set of pulleys are cast (these were cast iron), the sand casting is shredded and the pulleys separated, and the sand is immediately recycled for the next set of castings.
          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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          • #6
            Originally posted by toastydeath
            That's just a demo. Either the part isn't designed to be actually made, or they're going to make it out of a deeper block than the finished part.

            Casting is still very much alive and well, as many of those toolpaths take hours (or days, in some cases) to run. Can't exactly make 100 parts a week if it takes you 30 hours to machine. What you're seeing is appropriate for prototype and similar work, where several zeros attached to the end of a quote is not an inhibition. It's also appropriate for making patterns and cores, ironically.

            Edit:

            Here's a cool video of a part like that getting made.

            http://youtube.com/watch?v=pPCrTYwp2UY
            I agree casting is alive and well. Unless the customer wants billet machined, LOL.

            I would let the CNC cut a pattern oversized with shrink and warp factors added. Have that cast and let a cnc finnish cut the whole thing in lets say 4 minutes VS 10 minutes with all the roughing passes needed. Some guys may want to work thier machine to death and make chips for the chip conveyor, myself I want to make parts that are done quick if thats my bread and butter.

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            • #7
              As TD has said it's just a demo but it will be cut to go on the example board that we take to the shows, probably cut two, one as the rough waterline part with the first tool and the finished item with the ball nose cutter.
              It will be held with a couple of screws tapped in from underneath on a sacrificial plate so it can go all round to machine the shape out. The inside on the finished engine would be machined out later to accept the crank so that material where the screws fit is not needed.

              Probably run this tonight after work whilst I'm having tea, just waiting for a parcel of cutters to arrive.

              True you don't want to make 100's of these with these time restraints but a one off for the pattern is still well in on time compared to conventional pattern making.

              For a prototype it's still quicker given the same time to make the pattern, travel to the foundry, leave it to be cast, travel back etc but the whole job is more for interest than use. We are always looking for examples that would take a lot of making by manual methods to work with.

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              Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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              • #8
                Im afraid this is just another indication of the march of progress in that in the olden days machining most shapes from the solid could not be done!

                As a one off for a look see machining from solid is ok but not in the workplace where even traditional casting has given over to lost wax casting processes by reasons of complexity.

                Still nice to watch it being machined!

                Peter
                I have tools I don't know how to use!!

                Comment


                • #9
                  John

                  I think that you're onto a good thing for non cored parts -and a bike crankcase is a great example. I can think of others where I've had to import timing case castings from Australia and, because they're "3rd generation" castings (ie made from a pattern that was copied from a part), the critical dimensions are slightly out and a lot of compromise is needed in the subsequent machining. It would be much easier to go your way if you have the machinery and associated software skills.

                  A friend of mine bought a Speedway Jap crankcase, cast in Scandanavia I think and machined in the Czech republic. Even then they weren't cheap. I wonder how yours would compare.

                  Charles

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                  • #10
                    John, have you tried any lost foam/wax patterns with Cut-3D?
                    I have Vcarve and I'm well impressed. Does Cut3D allow independent axis scaling for shrinkage etc?
                    Just got my head together
                    now my body's falling apart

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                    • #11
                      Charles,
                      I know what you mean only too well.
                      Recently I was given a water jacket housing that had the holes and counterbore clearly marked on the casting, I was asked to drill and counterbore them and face the main face up which I did.

                      Later this was returned with a gasket and I had to slot the 4 outer holes as this casting was taken off an original and no allowance was made for shrinkage. This was on an old Alvis and there must be many of the old clubs out there having the same problems.

                      Swarf,
                      Yes Cut 3D will make allowances.

                      This is the original setup screen for that crankcase.



                      Just above the picture of the car model is a ticked window which reads , "Lock XYZ ratio"

                      In this picture I have unclicked it and changed X from 77.99mm to 120.0mm



                      So it is possible to draw an accurate model and have two files, one that produces the pattern with shrinkage and one that will machine the part to original size.

                      So far this is as far as I have got as my bag of cutters didn't get delivered today.



                      .
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                      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                      Comment


                      • #12
                        As an amature I need to ask....

                        say you have the measure ments for a copy and had to make the real thing to original size, which is about 1/8" larger.

                        Could you use a smaller ball end mill say from 7/16 to 3/8 to compensate?

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                        • #13
                          OK John.
                          To do this on a decent scale (not in production speed terms but simply to be able to make real engine parts rather than model parts) what's the best approach to getting a reasonable machine .
                          Is it refurb a Bridgy Interact and add Mach 3 or would you start somewhere else. What sort of sterling cost is it to get set up with a machine, software and associated kit?

                          Comment


                          • #14
                            Charles,
                            It all depends on size of part. Guessing what you want it for then I'd say go as big as you can.
                            Pays off in getting rigidity and also, daft as it sounds it's cheaper.

                            A Bridgy BOSS 1 to 5 is an easy way to go, quite a few of them about, usually broken as the electronics were crap. They go from free to about £900.
                            Just looked on ebay but there are not listed but a good idea of what is available is this one for 500 notes.

                            http://cgi.ebay.co.uk/Supermax-CNC-m...mZ190225326059

                            That will get you a CNC built machine as opposed to a conversion with ballscrews,motors, mounts and pressure oiling etc.

                            The electronics can be dumped except for the cabinet and transformer.
                            You then need and all in UK pounds.
                            3 drivers @ £70 each
                            Power cap at £25
                            Handfull of assorted electronic bits at say £25
                            Breakout board at £50
                            Computer, usually for free or a few quid.
                            Mach license at £80

                            You may or may not have to budget for an invertor to get use of the spindle motor or for use on single phase

                            That will get you a running machine.

                            3D CAD software to get the file, Alibre Express is free and can do the parts you need, Solid Edge, Solid works and Rhino do educational copies if you can get on a scheme for about £200 a pop.

                            Cut 3D costs £160

                            Add to this is fixtures and tooling as needed for the jobs so it's not too great an outlay if you do it yourself.

                            The alternative is to buy new, either the Sieg or the Tormach if it will fit your budget and size restraints.

                            .
                            .

                            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                            • #15
                              You machine those, and you'll have 70% + of the weight of the blank in expensive chips......

                              Someone once told me that the milling machine was invented purely as a matter of necessity because casting or forging alone wasn't good enough. Mills are too expensive to use unless there is absolutely no alternative. He had a point.

                              how come that fancy expensive simulator gizzie produces a part looking so coarse and crude? Can't it interpolate and smooth out the layers (I know it can)? Looks like a really poor quality "grown" part. Maybe no problem for the proto?
                              1601

                              Keep eye on ball.
                              Hashim Khan

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