Re: Automatic Tool Path Generation
From: PnRMolds@aol.com
Date: Tue Feb 03 1998 - 16:56:35 EET
Hmmmm... Some interesting points of view here on this topic. I must say
first that I agree with Mark Bannister..
STL files have terrible resolution! Use the
original geometry data if at all possible. I must tell you as an injection
molder and mold builder STL files are the bain of my existence.
I would certainly prefer to work with the original part data before any STL
file. While it is not disputed that the accuracy of the STL file may be
increased, this step itself makes working with the part more cumbersome. In
addition no matter how much you increase the accuracy, the STL model will
still not be a very good representation of the of the part. Consider that you
will end up approximating ("posted" NC code sent to NC machine) an
approximation (generated tool path) of an approximation (STL file) of the
original part. If you are planning on NC machining an RP part to improve the
accuracy I would question the use of the STL file vs. the original part data -
even if it has been translated through IGES, VDA, STEP etc.
Of course if you are working on a Cray perhaps you can run your approximations
until they approach infiinity..... ;-)
Personally I have been in the mold making end of this biz for about 10 years.
In that time I have seen dramatic improvements in the quality of imported data
files which for us arrive in IGES format unless the customer is working in
Pro/Engineer or Cimatron -what we utilize for tool path generation. Over the
last few years I have seen VERY FEW problems with IGES files including those
with complete (trimmed) surface and wireframe data. I am not saying that we
do not see anomalies but in general things have improved a great deal in this
regard.
See below.....
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In a message dated 98-02-03 07:10:58 EST, it was written:
<< Subj: Re: Automatic Tool Path Generation
Date: 98-02-03 07:10:58 EST
From: info@spline.nl (Delft Spline Systems)
Sender: owner-rp-ml@bart.lpt.fi
To: rp-ml@bart.lpt.fi ('RPML')
Brent Stucker asked:
>I have heard about software packages that use STL files to generate tool
>paths automatically. Is anyone familiar with commercially available
software
>that can be used for that purpose?
>
Mark Bannister replied:
> AlphaCam
Bert VandenBerg wrote:
> Delcam's PowerMill/CopyCad programs
> Cimitron's CAM systems
> VERO's VisiCAM
> Tebis AG's Tebis 3.0
> MatraDataVision CAD/CAM system
Hi Brent,
So sorry (not quite) to send the following self-promotion to this
list, however, you did ask for it.
All the above CAM packages can indeed do the job that you require.
However, they are aimed at professional toolmakers (CAM specialists),
not at (rapid) prototype builders. This means that they include many
milling parameters that must be set, and that they are quite expensive.
The advantage is that they offer many possibilities, the disadvantage that
much training is needed. In any case no automatic toolpath generation.
While some of this is true, in my opinion this can be a misleading statment.
The comment above seems to suggest a complicated routine requiring tons of
experience is needed to use such CAM applications. I do have a fair amount of
experience in modeling but virtually none in tool pathing. However, I spent a
few hours by myself on a seat of Cimatron and was able to figure it our all by
my lonesome even though I have had no training in NC programming and am not a
mold maker or CAM specialist in any way. As far as setting parameters is
concerned, Cimatron has the functionality to store tool path "templates" for
future use. Thereby parameters can be recycled time after time without the
repetitive task of changing the parameters maually everytime. Even so, since
every toolmaker/programmer that I have seen has their own ideas ot speeds and
feeds for cutting tools I would consider having control over the machining
paramters to be a requirement.
As far as the cost goes... ten times $1500 is not as high as it can get but
it seems to me that you still get what you pay for. Note that I will be
downloading the DeskProto demo.
In the final analysis.. I would like to know how things turn out.
As far as we know our DeskProto software is the only package that
does indeed offer (almost) automatich toolpath generation based on STL
geometry. The almost indicates that some user interaction is needed:
you have to enter the tool to be used and the distance between the
toolpaths (which is in fact the accuracy). The rest is done automatically.
Price of the software is ca USD 1,500.00 where the above packages
will cost about ten times as much.
Please download a demo-version from our Web-Site and test the software
with your own STL files.
Mark Bannister also wrote:
> Again as has been mentioned many times here before, STL files have
> terrible resolution!
The resolution in most cases is not the problem as it can be freely
chosen. The big advantage of STL is the data-transmission without
any problems. This in contrast to other formats like IGES. Because
of this oven some professional injection mould toolmakers do indeed
use STL.
Best Regards,
Lex Lennings.
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Delft Spline Systems, The Netherlands.
We offer DeskProto: affordable Rapid Prototyping using CNC milling
mailto:info@spline.nl
website:http://www.spline.nl >>
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Best Regards to all,
Ron Ptaszek
P&R Precision, Inc. - InjectionMolds.com
T: 810-254-6720
Direct Email: Ron@InjectionMolds.com
http://InjectionMolds.com
and coming soon....
http://Prototyping.com
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