hespj
01-03-2008, 12:32 PM
Here's what's kept me busy for the past month, a pair of MDF patterns for a hydro turbine casing. The patterns are going to a foundry where moulds for rotation moulding the turbine casings will be made. The patterns each measure about 6' x 4'9" x 15" (1740x1425x380mm). I've put a 12" plate square in the pic for scale.
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1577
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1578
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1579
Although I've got a 12" Z I obviously couldn't machine these in one piece. I cut shapes out of 1" and 3/4" MDF glued these together into four slabs (for each side), machined these slabs, and then glued them together. Actually, after machining the third slab I glued the fourth thin [3"] slab on top of it whilst still in the Shopbot, and then machined the 4th slab. Doing this allows machining a thicker part - my longest cutter is 5", so cuts six layers of MDF (4 1/2"), and needs 5" clearance minimum above the workpiece - say 10 1/4" total depth. Adding a 3" thick slab on top makes 7 1/2" total depth, and this top piece needs a 3 1/2" long cutter, and needs, say, 3 3/4" clearance. 7 1/2" + 3 3/4" = 11 1/4". You can see why the logistics of how to actually cut the parts took some time before I even started cutting.
It's taken most of Dec and a few days of Jan to do (not Sunday's or Christmas Day), with somebody helping with assembly. It's taken about 20 sheets of MDF. I have a very large scrap MDF pile.
John
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1577
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1578
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1579
Although I've got a 12" Z I obviously couldn't machine these in one piece. I cut shapes out of 1" and 3/4" MDF glued these together into four slabs (for each side), machined these slabs, and then glued them together. Actually, after machining the third slab I glued the fourth thin [3"] slab on top of it whilst still in the Shopbot, and then machined the 4th slab. Doing this allows machining a thicker part - my longest cutter is 5", so cuts six layers of MDF (4 1/2"), and needs 5" clearance minimum above the workpiece - say 10 1/4" total depth. Adding a 3" thick slab on top makes 7 1/2" total depth, and this top piece needs a 3 1/2" long cutter, and needs, say, 3 3/4" clearance. 7 1/2" + 3 3/4" = 11 1/4". You can see why the logistics of how to actually cut the parts took some time before I even started cutting.
It's taken most of Dec and a few days of Jan to do (not Sunday's or Christmas Day), with somebody helping with assembly. It's taken about 20 sheets of MDF. I have a very large scrap MDF pile.
John