Pressure Vacuum Casting Impregnation Rig

Discussion in 'Castings, finishing/ repair/ and patina's' started by Al2O3, Sep 10, 2017.

  1. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Trying to decide if my views are a couple decades out of date and the world has moved on or that's a healthy bit of salesmanship......Ok, thought it over and I'm going with the latter and standing by my view and previous statements about it being a matter of economics as to whether post processing such as impregnation makes more sense than the degree of metal quality control.

    As a contract manufacturer, the value proposition to the customer always seems to come down the balance of price, quality, and delivery. You can readily find two of the three but getting the third one comes hard and in a competitive world, perfection is the enemy of good enough. He's selling quality. The question is at what price? He starts off his discussion by saying they specialize. There ya-go. Even 20-30 years ago rotary degassing and grain modifiers were the norm for castings that were critically stressed or required very dense metal. The mold material you use (he say's Petrobond), how much re-melt versus virgin ingot you allow, the level of investment in molten metal management & equipment and monitoring, how many alloys you're going to offer and manage.....etc. It all goes into the price/quality equation.

    I have no doubt they make good castings that have better than average metal and machining properties, but also suspect he isn't always successful selling that at their price. Statements such as machines like billit, calling impregnation a salvage operation......it's just salesmanship. Their castings won't have billet mechanical properties and whether you call it post processing or a salvage operation is really just a matter of a value engineering decision if it gets the job done.

    All that said, in commercial foundries there are many similar trade-offs in choice of metal alloys and casting processes. Some alloys have much better as-cast mechanical properties without heat treating but can't equal the strength of the solution/precipitation treated alloys. For a given metal quality a permanent mold will always produce a better part than various methods of bonded sand as long as your production volumes can support the tooling expense.....horses for courses.

    For my home based casting endeavors it starts with the source of metal. I'd love to have certified ingot but recycled automotive castings are good enough for 95%+ of what I'll do but you never really know what you have as far as alloy. My initial water necks were remelted many times completely recycling the parts, sprue, and cup stock, and were never degassed because I didn't have a lance. That is one of the best ways to introduce metal contamination and porosity. His fuel pump casting example was a junk casting and even with the above mine didn't exhibit that kind of visible porosity. He should also get a new display sample of that part with the large surface defects at 3:45 LoL.

    All that said, he could sell for me. Think I'll give'm a call. :)

    Best,
    Kelly
     
    Last edited: Feb 27, 2018
  2. Tobho Mott

    Tobho Mott Silver Banner Member

    I've never cast anything that needed to hold pressure or even hold water, so I don't worry too much about vacuum impregnation or degassing my aluminum. But if one of mine came out swiss cheese looking like the "most other foundries think this is perfectly acceptable" example at 1:24, it would be going back in the pot for sure...

    He did have some very nice looking castings to show off though; I kept hoping he'd show us more about how they degas their stuff. I didn't even notice that defect at 3:45 until you pointed it out, lol...

    Jeff
     
  3. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    At 1:13 that appears to be a rotary degasser being extracted from a holding furnace. There are at least two other holding furnaces in the picture and they may be the same or other alloys. The electrical box above the holding furnace on the left may be for H2 monitoring/measurement. The holding furnaces are actually a bit on the smallish side for a production foundry but again depends upon what scale of production you specialize. The rest of what can be seen in the foundry operation parts of the video looks pretty much to be standard fare for a small to mid size commercial foundry. Pitty, they are becoming an extinct species in the US and most production these days are in the so-called low cost economies.

    Best,
    Kelly
     
  4. DavidF

    DavidF Administrator Staff Member Banner Member

    He is using A-356, much nicer machining than plain old 356
     
  5. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Agreed, but like I said, nothing new there and both versions of the alloy have been available forever.......just a matter of $/lb.

    Best,
    Kelly
     

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