[Jewelry making - Article 01172] - Re: [Orchid] CNC Wax Masters

[Jeffrey Everett]

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>      have a question for those doing CADCAM wax master patterns, How
>     much finishing do the patterns you send to your customers require,
>     Reason I'm asking is I have been getting masters that still are
>     showing tool marks on the back, some still have a significant
>     degree of flash in inside cuts, and nearly all look as though the
>     outside edges were filed with a checkering file!. The lines appear
>     to be about 60 to 75 lines per inch and have a depth of around .010
>     to perhaps as much as .020 IN. These are most noticeable on rounded
>     or areas that have a radius. 

    A pattern should have very little need for finishing other than
    light sanding and polishing. It sounds like the machine operator is
    using very coarse settings typically used in roughing passes. When
    milling wax, all roughing steps may be eliminated and only finishing
    toolpaths used. Finishing toolpaths typically have much smaller
    step-over distances (more passes) and can produce very smooth
    surfaces. The cutting tool used should be appropriate to the surface
    being machined i.e., curved or very fine tools for curved surfaces,
    flat tool for flat surfaces, etc. 

>     Is this type of tool marking inherent to parts machined with a mill
>     that uses steppers, or could this be solved by using a faster
>     spindle speed and a slower rate of travel? Or would it take a
>     different tool size accompanied by a difference in travel lineal
>     travel, do to the size of the tool serrations on the edges, to me
>     it seems as though a very small end mill is being used. 

    This type of tool marking is more a result of using step-over
    distances that are relatively large, and possibly using a cutting
    tool not appropriate for the desired surface. The difference between
    steppers and servos is most likely not an issue here. The issue at
    hand is possibly related to the inexperience of the machine operator
    in producing smooth wax patterns. 

    If a very small endmill is being used, then very small step-over
    distances are required if cutting curved surfaces. 

>     Some straight edges are reasonably free from the edge serrations
>     which lead me to believe that the X-Y steppers are not quite
>     working to insure a smooth arc. Or that the Tool is being pushed
>     too fast, 

    Possible but very unlikely. Even an inexpensive machine tool like
    the MaxNC is capable of producing smooth surfaces if the machine is
    work well and appropriate working parameters are used. I've seen
    stepper motor mills produce surfaces completely void of tool marks. 

>     I am doing quite a few castings for my client who is the one
>     actually paying for the originals, and I have broken several trying
>     to clean up flash and areas that were supposed to be cut all the
>     way through but weren't. 

    There shouldn't be any flashing. A jewelry wax pattern should be
    produced within certain specifications; rough surface finish and
    flashing are unacceptable. 

>     Fortunately until last Sunday all of the broken waxes were easy to
>     repair and I was able to fix and clean them up. Sunday I broke one
>     through a very detailed area and am not able to fix it, SO guess
>     what I get to eat. The originals are done on Ferris Green which
>     would seem to be a good material since it usually cuts and scrapes
>     pretty clean, so I just want to find out whether these (rough
>     waxes) are customary or is this just a case of operator error of
>     trying to hurry, I realize that tool marks can be a problem because
>     I used to work for Northrop aviation and spent many many shift
>     hours in front of Bridgeport and Lagun Milling machines, but back
>     then NC was just in it's infancy and I've had no real NC or CNC
>     experience so I'm not really sure of the limitations of a table top
>     system. 

    Ferris green is a good wax, no problem there. You haven't mentioned
    the machine being used to produce the waxes, but I doubt the machine
    is the problem here. Tabletop systems range in price from about $2K
    to $100K with most in the $10K to $20K range. The limitations of the
    very low end systems relate largely to accuracy and speed, but even
    the very lowest end system should be producing useable waxes.
    Operator inexperience is most likely the issue here. 

>     I have been studying EMC and G code and have collected some great
>     software but I don't know whether to start doing the CADCAM my own
>     self or keep swearing at the person doing the waxes I'm having
>     trouble with. 

    CAD/CAM is an area of specialization and requires a substantial
    investment of both time and money. More simply, if your vendor will
    not produce a quality of wax that works well for you, maybe it's time
    to find another vendor. 

>     I have managed to get MASTERCAM 9, JewelCad, and two other top
>     shelf programs, I've been looking at Sherline mills, but they only
>     work with Linux and EMC I'm used to Linux, but I really don't have
>     the time to write the code, and keep up my production, I'd rather
>     let the software do it. Does someone know if I can get a control
>     card and box that operates on a Windows platform and is it possible
>     to convert a Sherline to servos instead of steppers or are steppers
>     even the root of the problem? I'm hoping that I can if necessary
>     find an inexpensive milling machine that will work with the
>     software that I have accumulated, that's why I'm really curious
>     about a Sherline, that and the availability of a 4th axis not to
>     mention the initial price.

    OH boy... I'd dump any pirated software that are just taking up
    space on your hard drive and wasting your time (there's no way you're
    ever going to learn to use them all anyway) and buy one design
    program to begin with. I suggest Rhinoceros because it's affordable,
    and become a capable modeler. There is enough of a commitment
    required to learn Rhino well enough to use for jewelry work to keep
    you busy for a long time. You're FAR better off concentrating on just
    one capable program to begin with. Sorry if my frankness bothers you.
    Been there, done that... If you are truly serious in setting up a
    CAD/CAM system in-house, set a budget and fit the software and
    machine into that budget. Consider a package you can afford to
    lease-to-own. Probably your best low-end bet is the Taig mini-mill
    (www.microproto.com). It can be purchased with a 4th axis and control
    software/hardware for under $3000. DeskProto is a decent and
    inexpensive CAM program that has 4 axis capability. For about $5000,
    you can set up a useable and complete introductory system that will
    get you by Then you can dump the downloads. 

Jeffrey Everett


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