Friday, October 17, 2014

A Square Deal (25)

Twenty-fifth post in an ongoing series.

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After submitting drawing to the foundry yesterday, today I found out they would like me to supply casting patterns for the leveler feet. These needed to be made with a taper or 'draft' so they could be pulled out of the sand readily, and to be made 1.5% oversize to allow for shrinkage. I spent a while this morning working in SketchUp to produce drawings of the piece I would need to make.

And then I got wind of a company that offered CNC machining services with a quick turnaround time - millitnow.com - I gave them a call and found out they had worked with bronze in the past so that was no problem for them. They did however want me to submit drawings as '3D solid models', however the best I could do with SketchUp, having the 'pro' version, was submit .dwg files and have them produce the 3D solid models. So I spent another couple of hours fiddling around with that and finally submitted some .dwg file to the company. I thought I should see how much they would charge for milling the exact pieces from billet vs the alternative, which involves shop time for me to make oversize wooden patterns for casting, sending them off, having the castings done and then finding a machine shop to clean up the castings and fit leveler screws. Unless the price from Mill it Now is whacked, I'm likely to go in that direction. Seems a lot more straightforward.

Dealing with mill it now and their desire that customers submit 3D models with which they can program their CNC machinery reminded me of my goal to move on from SketchUp. At this point I'm considering moving to either Solidworks or Rhino. Hard to decide at this point. I'll be looking to upgrade to a more powerful, purpose-built computer for CAD work too. I always get the feeling with computer stuff that if I wait another month there will be a cheaper model with more power available....

Okay, that didn't leave as much time for me at the shop today as I might have liked, however I did get a few things done. I moved the joinery along on the table top slab to start with. After that, I tackled the dust panels which are to be fitted between the pillow blocks. That entailed some final dimensioning and it seemed like a day to bring the Kiyohisa 'kamon' smoother out for some play:



A superb plane. Love the white steel, want to plane more wood now...drool.

Now, where was I?....

After fitting the dust panels to the pillow blocks and aprons, I decked the top edges of the panels down using the same plane - a bit of a balancing act and it went well:


All fitted - but hardly complete given what is yet to happen to these panels:


A closer look:



At the end of the day I fitted the side panels:


Good progress was also made with the drawer support rails, which are, well, at least 25% along the way on their somewhat complicated journey. Another day at the shop should see those fitted.

All for now - thanks for tuning in. Hope your weekend is full of (pick one):
  1. blissed-out relaxation and recuperation
  2. exciting challenges and stimulating diversions
On then, if you like, to post 26.

9 comments:

  1. CHRIS;
    Looking good! It is nice to see all the small details coming together! Can't wait for more joinery!
    J.T.

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    Replies
    1. J.T.

      most kind of you to comment, and I appreciate your enthusiasm. Don't worry, more joinery lies ahead!

      ~C

      Delete
  2. If you have to produce only four feet, you don't need a pattern that is able to resist to hundreds of uses.

    Producing patterns with a 3D printer might be a cheaper option.

    Otherwise, maybe, make a first pattern in plaster, make a mould with something like silicone and produce a few (4 + some extra ones) patterns in wax (or maybe in plaster if it is adequate for the foundry).

    Maybe I am wrong but I think that a wax pattern is less work for the foundry as they don't need to take the pattern out of the sand before pouring the bronze. There is also no need for "draft".


    Sylvain

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    Replies
    1. Sylvain,

      well, there will be 10 feet made, 5 for the side table and 5 larger ones for the coffee table.

      You make some good points about going the route of lost wax casting, which I have previously considered. I have a book on that process (Duhamel's "Bronze Casting Manual") which I've read through carefully, however, comparing approaches, it seems to be about the same amount of work for me, plus adds in the unfamiliarity of working with silicone molds and plaster. Even given a wax or plaster pattern which does not require any draft, there is still the matter of shrinkage and final machining to plan for which means the overall process is no simpler really. It might be cheaper, however the sand casting option was quite inexpensive already.

      I obtained that book on lost wax casting as I was originally planning to tackle this aspect of the project myself, however it means more time for me and the risk of experimenting, and the purchase of at least a modest amount of equipment, so I started to consider farming out this work.

      The CNC route appeals the most as it is more direct than the casting methods, and I have confidence that it will be within 0.005" of the design, with minimal work required afterwards. Any machining marks can be dealt with by me using files and/or abrasives, and subsequent machine shop work would be limited only to fitting the cap screw and circlip.

      I'll wait and see what the price is on the CNC option though before deciding which way to proceed though!

      I do appreciate your input and it helps me clarify direction giving me an opportunity to think over the issue again.

      ~C

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  3. Hey Chris,
    Excellent work and joinery in this piece. It looks like the Bubinga is finish planed, is that true? Really pretty grain and finish on what I can see so far. It looks like there is a little Chinese design in those cross pieces between the legs. I agree about the "superb plane". I have seen some that look like that one but not sure. Who is the blacksmith for that plane? I see a "150" on the main blade, does that mean the 150th one made? Thanks.

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    Replies
    1. David,

      thanks for your comment and questions.

      Some of the bubinga on the side table has been finish planed initially by super surfacer, though some has not. All will be finish planed when I'm done.

      The plane, as noted, is made by Kiyohisa, the trade name for the blacksmith named Watanabe Kiyoei. It is his 'kamon' model, which refers to any tool he makes with a special low-temperature 'yaki-modoshi' (tempering) process. He does that for some of his tools at 100˚, 135˚, and 150˚- mine was done at 150˚, hence the '150˚' stamp.

      The 'kamon' models are generally not sold outside of Japan, and in any case the waiting list for Kiyohisa tools is 18 months to 2 years now, just FYI.

      ~C

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  4. Thanks Chris. Yes, I have heard of Kiyohisa. That smith makes some darn nice chisels as well. So in Australia sells them and recommends them. Thanks for the excellent posts and the inspiring work!

    ReplyDelete
  5. Hi Chris,

    On the subject of CAD packages, I'm currently using Geomagic Design (formerly Alibre Design, before 3D Systems acquired Alibre). It's a fully parametric CAD suite like Solidworks (and unlike Rhino). Parametric CAD has its own learning curve, but there's immense delight in being able to whip up a new version of a design in just seconds by changing a couple of numbers. That said, CAD software isn't generally well suited to complex surface designs. There's a reason that jewelers gravitate to tools like Rhino over Solidworks (beyond just the price tag ;-).

    That said, the full Geomagic Design package includes a license to MOI (Moment of Inspiration, moi3d.com) as its surface design tool. This can be used much like Rhino, and will create standalone 3D models. These models can then be imported into Geomagic Design for incorporation into a traditional CAD model. E.g. I could produce a complex external decorative design of a part in MOI, but use traditional CAD modeling on the functional interior.

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    Replies
    1. John,

      very helpful input - thanks!

      I've been looking at software with parametric functions and it definitely has an appeal. While Rhino is not parametric, there is apparently a plug in which will give it parametric functionality - at a price of course. I'll check out Geomagic and see how it looks.

      ~C

      Delete

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