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Thread: PRSalpha BT48 buddy vs PRSalpha 48

  1. #1
    Join Date
    Feb 2009
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    , Seattle WA
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    Default PRSalpha BT48 buddy vs PRSalpha 48

    Hi everyone, we have been looking into purchasing a shop bot for some time now. We are a business that plans on machining mainly aluminum and copper plate. Thickness's ranging from .020 to possibly up to a half inch. Most of our work will be machining .125 or less. We have been looking into the buddy because we can use the power stick which we may use in the future. This is opposed to a fix table (PRSalpha 48) that limits our options. Our debate here is what is going to get the job done for us with the highest accuracy. The Buddy or the PRSalpha 48? We want to mainly stress that accuracy is a high priority and which ever table can best deliver that accuracy will be our favored choice. We want to use the 5HP single phase columbo spindle to machine our parts. Please let us know what will best fit out needs, the power stick is absolutely expendable if accuracy is compromised.

    Thank you!

  2. #2
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    Jan 2004
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    What kind of accuracy do you need? I would say the x and y of both machines should function with the same accuracy, but the z using the powerstick would require greater care. A lot of it depends on how good of a machinist you are.

  3. #3
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    Do you own one or both of these machines or is this your opinion? Take the operator out of the equation 100%, I'm purely comparing machine to machine. Which one would be better for strictly metal or are they truly equal in accuracy and speed?

  4. #4
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    elaborate more please on "the Z axis would require better care", I don't want to invest thousands and have to baby a machine, while i could of went with a different model and less headache if you know what i mean! Thanks Erik Get back to me!

  5. #5
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    Apr 2008
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    New Bern, NC
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    I have a BT 32 with the original aluminum moving table and a Power Stick. I use the Power Stick for cutting out wood furniture pieces and it performs well. However, I do not believe the Power Stick would be as accurate as a solid table for high accuracy machining. A new Buddy only comes with a Power Stick, so I would look to a solid table machine for what you are talking about. Just my humble opinion....joe

  6. #6
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    Nov 2007
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    Vankleek Hill, ON
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    J: My first thoughts are that if you're looking to hold 0.0005 or better all day like a HAAS mill, then you're best to buy a HAAS.

    That said, the Buddy is built with the same superstructure components as the bigger machines so logic suggests that the most most rigid of all the Shopbots will be the BT32, whether standard or a Alpha because of it's shorter spans.

    Beyond that, I believe it's been suggested on this forum that a spindle has better bearings in it than a router. Being that the application you're describing is what amounts to very large envelope milling machine.

    I'd want to find a spindle that's proven to work well at lower RPMs because of the broad range of mills/cutters and related knowledge base available to machinists. You'll need to think about how to get around flooding (chuckle) but then aluminum moves heat away a lot better than steel so that's in your favour.

    Again, from the good advise I've read here, not all spindles are what they're cracked up to be in the sub 3000 rpm range. Ceramic bearings, if available, are designed for high speed applications but are more precise at all speeds so again, the tolerances you want to hold are what's most important in choosing a Shopbot or a large CNC mill.

    I've looked into this topic as well, but I'm certainly no expert; I've simply amused myself with a few metal lathes and a bit of basic milling.

    It was with this kind of flexibility in mind that I bought my BT-32 Standard Buddy. My plan remains to upgrade it to a spindle, and have a "good" machine shop add an extra set of V-groove rollers on the Y and Z axes and have them mount two more tracks (4 in all) to the X axis for the moving aluminum table to run on. Obviously, much care will be needed in the alignment, hence the need for a "good" shop.

    I would then surface my aluminum table with a fly cutter in both the X and Y axes.

    My very limited knowledge and experience suggests to me that assuming the job is done right this is as far as I could hope to go in turning my Buddy into a large format milling machine that could handle the non-ferrous, soft metals, plastics and woods.

    In this case please consider that my two cents on this are perhaps only worth just that so you'd best get solid advise from some of the other fellows who actually know. In that case, I'll not be at all offended if they tell me not to quit my day job because I'll be learning too :-)

    What's holding me up at the moment (besides an unheated garage) is that I'm giving serious thought to moving up to a BT-48 and having a 48" X 48" foamed aluminum or honeycomb table made up (with a 1/4" +/- solid alum. skin laminated on top and machined flat. This would keep the weight down enough, hopefully, that the stock steppers would have the torque needed to prevent problems when cutting shapes.

    At this point, I will caution you that my wife is shouting in the background, "Don't listen, I'm working on having him committed"! She's hoping some of the guys that know will fire away! Me too actually :-)

  7. #7
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    Jan 2004
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    On the new version of the Buddy, as Joseph said, only comes with the powerstick. Yes I have a BT48 standard with the old style aluminum table. I used to own a 4x8 old PRT. As you move farther and farther out from the center of the Powerstick you are moving father out from the most stable portion of the table, thus getting into more and more chance of z variation. On my buddy the whole table is supported by v rollers. I would say for your application the fixed table would be most accurate. I would call shopbot however since the shopbot is more designed as a wood cutting machine as far as I know. The reason I ask what kind of accuracy you will need is because +/-0.005 is average for the shopbot...I usually see somewhere between that and +/- 0.008". So I'm sure you can do better with care of set up...as with any cnc.

  8. #8
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    Feb 2009
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    I think i will go with one of the alpha's with a fixed table. Ill post over in there section and see what they say. I'm thinkin a 48x48 because then i wont have to shear the width of my aluminum sheets (because they come 48" wide) just the length.

  9. #9
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    With the 48" table and an additional stand or table to hold up the cut off, you could cut your 4x8 sheets of aluminum in half using the bot. Wiht some registration trickery, you could cut 4x8 sheets on the bot if you had to do so.

    Just some thoughs.

    /RB

  10. #10
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    i like that idea R ball, i never thought of that.

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