Need Help! Automatic feed / Speeds far too high??


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    Default Automatic feed / Speeds far too high??

    hi,

    I've been using BobCAD/CAM v25 for some time now and whilst I'm generally really pleased with it there's this one issue that's "nagging" me: Automatic Feeds & Speeds.

    Whilst the notion of an integrated materials based cutting feeds and speeds calculation is really amazing - the automatically calculated values are usually way off. - FAR TOO FAST.
    My CNC Mill (small 4 axis machine) has a max of 6000RPM and isn't too powerful (it's quite ok for what I need it and fits my budget quite nicely... as much as I'd like to have something like a DMG MORI, HAAS, NAKAMURA... or whatever - it'll be a while before I can afford any of that.

    I currently run a trial of G-Wizzard Calculator to get a handle on the feeds/speeds and I really like it - however it requires me to double-set up my tools (inside bobcad of course and GWiz...) also I'd prefer to use the in-built option for convenience.
    The speeds calculated by G-Wizzard Calc are usually "spot" on - with the few exceptions (like engraving, as this is something the low RPM of the machine really doesn't permit "nicely" but still needs to be done at times).

    Now I wonder - aside from manually adjusting all feeds and speeds table within bobcat/cam (tedious to do) is there anything that can be done??

    For example:

    Tool: Carbide Roughing cutter, 8mm diameter, 4 flutes
    Stock Material: D2 Tool Steel 1.2379, annealed.
    All measurments: METRIC, feeds are in MM/MIN

    Trying to do some pocketcutting - (18mm wide slot, 10mm deep 30mm long)
    Standard 2 Axis Pocketing operation

    Now BobCAD basically ignores whatever is going to be set for step-over, cutting depth, etc... but the calculated speeds and feeds are set to:
    RPM: 4376.761
    Cutting Feed Rate: 349.962
    Plunge Feed Rate: 175.203
    SMM: 110
    Feed per Tooth: 0.020
    Plunge Feed per Tooth: 0.010

    Now if I'd be running the program at that neither my machine, my tools nor the material will like it...


    However if I calculate the feed/speed values using G-Wizzard: (if the to not too agressive but not fully conservative (there's a slider, at 2.0))
    Cut Depth: 4mm, Width: 8mm (full width (at least for the first cut) after that I'd to partial step overs of course).

    RPM: 2411
    Feed (mm/min): 274.5
    Plunge: 68.6
    SMM: 61
    Chipload (mm/tooth) 0.0285

    These values I can actually run with... although I'd probably slow it down a notch... but it's working.
    If I set G-Wizzard on "conservative" it would generate values a good bit too slow, jfyi.


    Any idea what's causing the "huge" difference to the BobCAD generated values?
    Any easy way to solve this inside bobcad?

    thanks!

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    Have you tried setting up your materials cut speeds by making your own Type of Material and Cut feed Rate. I think you could probably do it here.

    Milling Tools/Default/Stock Material Library

    Attached Thumbnails Attached Thumbnails Automatic feed / Speeds far too high??-feed-speed-jpg  


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    Quote Originally Posted by RAF. View Post
    Have you tried setting up your materials cut speeds by making your own Type of Material and Cut feed Rate. I think you could probably do it here.

    Milling Tools/Default/Stock Material Library
    thanks...

    I'm well aware of the stock material library... but I was hoping for some way to "correct" a bunch of them without having to go through each of the needed ones manually...
    I'd be spending the better part of a day matching and recalculating those I need.
    Also I was wondering why BobCAM's cutting data is so off ... even the SMM suggested by material specs / most tool specs gives lower values.
    Can this be some error in the conversion from inches to the metric system?



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    Although I enter my own speeds and feeds,can you list some examples with the details of some that are way off ? There are so many factors the can alter recommended data.
    I know some of the drilling on some materials are way out of line,but what else?
    Personally,from experience,I usually can get close,then dial it in no problems.But with all the variables,you cannot expect an app. to be spot on.G-Wizard is good.Machinist Toolbox is what BoB uses.It is not as detailed.You can purchase the "full"app. from BoB,which gives more functionality.
    Best advice I can give is use your overides to dial in,then edit program.There just no substitute for experience.Like I mentioned,just so many variables.I would just as soon all the speed/feed boxes were empty when doing cam.

    Last edited by jrmach; 01-13-2014 at 08:24 PM.


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    Quote Originally Posted by jrmach View Post
    Although I enter my own speeds and feeds,can you list some examples with the details of some that are way off ? There are so many factors the can alter recommended data.
    I know some of the drilling on some materials are way out of line,but what else?
    I'm no longer at the shop right now (it's after 2am right now - long day)... but in my initial post I gave an example of D2 Tool Steel... that one is for example really off for most operations.

    When I do the math with the spec sheets of the steel supplier and my tool data (TiAln micro-grain carbide rougher in that case)
    just the suggested RPM... bobcat is somewhere around 4300 RPM - whilst otherwise I'd get 2200-2800RPMs suggested.
    the SMM suggested by the steel's spec is 72... BobCAM has it at 110 (!)


    It's similarly off with Titanium Grade 5, O1 Tool Steel, Aluminium (some), ...

    Basically so far I don't think I had one single "success" with any material I chose with the recommended (BobCAM) feeds and speeds.
    Always had to manually calculate and adjust.

    I'm well aware that there are many parameters that are influencing the choice in cutting speeds... and I assume BobCAMs data is geared towards the more modern high speed machining centers with at least a CAT50 taper for tool holders and overall geared towards larger / sturdier machines.
    But the offset is quite large in the data I get.

    As mentioned when I use G-wizzard calculator set on a moderate level - I get near perfect feeds and speeds.
    It just would be nice if I wouldn't have to buy yet another piece of software and use it parallel to bobCam just for getting the speeds right... as there's already a material database found within Bobcam...



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    Here is the machinist toolbox data in inches.I see nothing far fetching.I will have to see what the metrics is bringing.Maybe a problem there.

    Attached Thumbnails Attached Thumbnails Automatic feed / Speeds far too high??-d2-jpg  
    Last edited by jrmach; 01-13-2014 at 09:16 PM.


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    You could check out fs wizard.The guy who wrote the software is on PM.His name is Zero Divide.Lots of posts about it.I have a free version.Has a lot of functionality,especially suited for HSM on tougher metals.

    Attached Thumbnails Attached Thumbnails Automatic feed / Speeds far too high??-fs-jpg  


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    If I were in your shoes I think I would consider it worth a day to set up the material library in order to have speeds/feeds I liked from then on. In my case I only had to set up aluminum and "soft steel" so it didn't take nearly that long but it is such a pleasure to never have to make adjustments. Your situation obviously requires a bigger up-front time investment but I think it would still be worth it. Are you really spending less time now setting custom values in every part while looking for a work around?



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    Quote Originally Posted by Ben S View Post
    If I were in your shoes I think I would consider it worth a day to set up the material library in order to have speeds/feeds I liked from then on. In my case I only had to set up aluminum and "soft steel" so it didn't take nearly that long but it is such a pleasure to never have to make adjustments. Your situation obviously requires a bigger up-front time investment but I think it would still be worth it. Are you really spending less time now setting custom values in every part while looking for a work around?
    Ben,

    thanks ...
    well No, of course you're right - I spend more time, overall to set it up time after time again.
    I work with half a dozen different tool steels, two types of Titanium, a bunch of Al-alloys, some plastics, composites, wood, a bunch of non-ferrous metals...
    Mostly I use full carbide tooling, some indexable carbide tooling and a small number of HSS tools (mostly reamers and two dove tail cutters).


    Well I was just hoping that there's a faster work around - a way to globally influence how BobCAM interprets the values in the Stock library... or something like that...
    But alas, I'll be using a software to calculate each material, at the time I'll be setting up a new job... will then store the successful values in BobCAM's stock library... and hopefully in a few month will have set all my standard materials up automatically.


    Also to jrmarch:
    thanks for the heads up on Zero Divides' software... I'll be giving it a try later today...



    thanks to everyone for the inputs!



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    at least on FS Wizard,if you have any questions,you can talk to the "man" that made the software.He also listens for suggestions.



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    Quote Originally Posted by jrmach View Post
    at least on FS Wizard,if you have any questions,you can talk to the "man" that made the software.He also listens for suggestions.
    well that too



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    I just downloaded the Android app. Very cool. I've been looking for something like it for a while. Thanks jrmach!

    Sent from my SCH-I535 using Tapatalk



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Automatic feed / Speeds far too high??
Automatic feed / Speeds far too high??