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RE: DStV again[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: DStV again
- From: "Conrad Harrison" <sch.tectonic(--nospam--at)bigpond.com>
- Date: Fri, 18 Apr 2008 15:07:48 +0930
Seems like you have a good approach to the situation.
In manufacturing the general approach is to use wood, re-useable machining wax, or low melting point metal alloys to test that CNC machine code produces the correct dimension and geometry. If surface finish is important, then a prototype with the real material is produced.
The fabricator can therefore make a low cost prototype with re-useable materials and check against the drawings supplied.
The Peddinghaus website also suggested that its machines have video display units which show the part shape produced by the DStV file. It didn’t mention if dimension and geometry were shown, in any case it pays to make a prototype first. That maybe a problem if the DStV contains quantity to produce.
I’m not sure of the limitations of DStV files, but if they are part descriptions then they are not necessarily suitable in their raw form for sending direct to tooling. The other reasons for making prototypes is to check setup of the work piece and cutting tool travel paths. If the work piece is in the wrong place then holes will be in the wrong place: or the cutting tool will be snapped as it hits hard material when meant to be traveling through free space.
Size of cutting tools is also important. With a pen plotter , the pen is centred on the line to be drawn, an experienced drafter working on a drawing board will allow for pen thickness, drawing to either side of the layout lines: making sure objects don’t get larger and holes don’t get smaller. With a 100mm diameter cutting tool this is even more important. The tool path for a 25mm diameter cutting tool will not be the same as for a 100mm diameter tool. Change the tool size and the CNC machine code needs to change. Consider the different paths between using a 10mm diameter tool to cut a 10mm slotted hole, and using the same 10mm tool to cut a 20mm slotted hole. Only the fabricator knows what tooling they have available and are going to use.
With no thought may be possible to get say 5 parts from a steel plate, with some thought may get 10 parts from the same size plate. If a part needs to be cut from plate then folded into an angle, then it cannot be produced by one machine. If a standard steel angle is to be drilled and cut, then it could be processed by one machine: but the location of the work piece will be critical.
Put simply the fabricator has some process design to do, and decisions to make, and should not rely on part descriptions in DStV files.
So disclaiming the reliability of the DStV files as you do is the way to go.
B.Tech (mfg & mech), MIIE, gradTIEAust
- DStV again
- From: G Vishwanath
- DStV again
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