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Thread: Encoder advantages/disadvantages

  1. #1

    Encoder advantages/disadvantages

    So I've been trying to make a decision between a ULS Versalaser and Epilog Legend 36EXT and while they both seem like good machines, I was wondering if I could get some technical clarity on the advantages/disadvantages of the different systems they use to position/move the laser. From what i've read, the VersaLaser uses a stepper motor which doesn't require an encoder, while the Epilog uses a linear encoder and servos. I work for an architecture firm and the cutter will primarily be used for precision work necessitating clean and accurate cuts........If you guys could let me know if there is a tangible difference between the accuracy of the two machines, what type of maitenance each system requires (we will primarily be cutting basswood), and maybe some examples of experiences with both machines, that would be great! Thank you.
    Last edited by Vince Cimo; 08-24-2007 at 12:37 PM.

  2. #2
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    Vince,

    I believe you'll find the greater accuracy with the servo motor systems. They rely on "feedbeck" for positioning accuracy via an encoder strip (Epilog). If the strip gets dirty however~fuzzballs/dust bunnies, you'll have the privilege of experiencing VERY erratic positioning behavior with the machine Stepper motors don't have this "problem" as degrees of angle are part of their "gearing". Servos are quieter, steppers are cheaper......I have both systems in my machines and they perform well enough for me


    Bruce
    Epilog TT 35W, 2 LMI SE225CV's
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  3. #3
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    Vince,

    I would have both systems cut a series of circles Small, medium, large. This should answer your questions between both systems. Look for the nub.

    You will no what I mean when you see it.

  4. #4
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    I just posted this on another topic the other day. Having an Epilog Helix in my office for 8 months, and now a brand new Universal PLS system installed last Friday, I can tell you that there is no different in encoder vs. stepper motor quality. In fact, the quality of cut on the Universal is as good or better than the cut on the Epilog. Not sure if that's a function of the driver, the beam, or what, but the quality is equal to or better.

    If you plan on doing modeling, one feature that's on the Universal that's not on the Epilog that you'll probably use a ton would be Vector Marking. On the Epilog, unless I'm mistaken, you have two modes, Vector (cutting out), and Raster (marking). With the Universal, you have 3- Vector, Vector Marking, and Rastering.

    If you were to raster patterns on an object, such as the lines on a ruler (or scale as I've always been taught to call it), you could vector mark those lines a lot faster than rastering them. It's a very powerful feature and I think you'll find for the work you'll be doing, it might be a "must have" feature.

    I'm new to the Universal, and I haven't had much time behind the wheel, as my mother had surgery this week, so my time has been limited. But, in the short time I have had it, I can say that there's no comparison when it comes to quality of machine and driver combination. It's way ahead of the Epilog.

    Also, the focus method on the Universal is more like a proper CNC machine, where as you set the machine to itself and then just put in material thickness, rather than the old CNC rational of setting the machine up to every single part. You can, of course, manually focus to each part if you wish, but there's no need. I haven't manually or automatically focused one job yet. You just put the material on the table, tell it that it's "X" thick, and hit the go button. No need to focus on that particular thickness because the machine knows where it is. I might be completely wrong on this description, but I'll give it a shot- on the Epilog, the machine has no idea where the Z-Axis is located. On the Universal, the machine knows exactly where the Z-Axis is located therefore, you can do things like just put in material thickness. It takes where it knows the table is and adjusts for where the material is. You could switch material thickness 100 times in a day and never once have to focus the machine.

    I could be completely wrong, but that's what it appears to be happening to me.

    Just my two cents.
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    Quote Originally Posted by Scott Shepherd View Post

    ....

    If you plan on doing modeling, one feature that's on the Universal that's not on the Epilog that you'll probably use a ton would be Vector Marking. On the Epilog, unless I'm mistaken, you have two modes, Vector (cutting out), and Raster (marking). With the Universal, you have 3- Vector, Vector Marking, and Rastering.

    If you were to raster patterns on an object, such as the lines on a ruler (or scale as I've always been taught to call it), you could vector mark those lines a lot faster than rastering them. It's a very powerful feature and I think you'll find for the work you'll be doing, it might be a "must have" feature.
    It is available on the Epilog, but is called color mapping. See the tutorial about architectural modeling at http://www.epiloglaser.com/tl_vector_color_mapping.htm. I've been using the technique with the LaserBuzz projects.
    Epilog 40W Mini24, Corel X6 (64-bit)


  7. #7
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    Good call Ed- as I said, I could be mistaken, and I was. Thanks for correcting me. Now that you linked to that page, I recall reading the article when I first got the Helix.
    Trotec Speedy 300 75W Universal PLS4.60 with Rotary Attachment
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  8. #8
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    Quote Originally Posted by Scott Shepherd View Post
    Good call Ed- as I said, I could be mistaken, and I was. Thanks for correcting me...
    Talk is cheap. Send me $100!
    Epilog 40W Mini24, Corel X6 (64-bit)


  9. #9
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    How about a 100 Lira?
    Trotec Speedy 300 75W Universal PLS4.60 with Rotary Attachment
    HP Designjet L26500 61" Wide Format Latex Printer
    ShopBot 48" x 96" CNC Router, Ricoh Dye Sublimation Printer
    Summa S140-T 48" Vinyl Plotter, Xenetech XOT 13 x 13 Rotary Engraver, Corel X5, Adobe Creative Cloud

    Real name Steve but that name was taken on the forum. Used Middle name. Call me Steve or Scott, doesn't matter.

  10. #10
    Quote Originally Posted by Mike Mackenzie View Post
    Vince,

    I would have both systems cut a series of circles Small, medium, large. This should answer your questions between both systems. Look for the nub.

    You will no what I mean when you see it.
    I have a little nub on circles and at the end of almost all my completed cuts. It's not huge, but annoying, and mine are servos.
    Epilog Mini 24 45W/various other dangerous implements the wife has ok'd over the years

  11. #11
    I had a ULS for 8 trouble free years. I now have a Trotec with servos. As far as quality of cutting is concerned there's not a dimes worth of difference.

    As far as rastering is concerned the Trotec is quick.
    Mike Null

    St. Louis Laser, Inc.

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  12. #12
    I think the only difference you will see between the stepper and a servo in a laser is during rastering. The servos rock in speed, steppers lack the speed during rastering. You will not find much difference in vector cuts between servo and stepper. Good luck making the decision, it is a tough one to decide.
    Good problems in life...

    Kim

  13. #13
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    Quote Originally Posted by Kim Vellore View Post
    I think the only difference you will see between the stepper and a servo in a laser is during rastering. The servos rock in speed, steppers lack the speed during rastering.

    Kim

    I'd have to disagree with that. I took the same files I ran on a servo driven machine to a demo of the Universal with steppers and found that the time was actually less. Not by much, but it was less on all jobs. I run a certain type product, almost all rastered, very frequently. On the Servo system, the time was always in the 12-13 minute range and with the new system, it's constantly in the 10:30-11:30 range with better quality. It may be true in some machines, but not in the two machines asked about. I have both sitting right next to each other.
    Trotec Speedy 300 75W Universal PLS4.60 with Rotary Attachment
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    Real name Steve but that name was taken on the forum. Used Middle name. Call me Steve or Scott, doesn't matter.

  14. #14
    Scott

    The raster speed is identified by each manufacturer for each system. My machine runs servos and will raster substantially faster than any ULS machine. It rasters at 140 ips which is the reason I bought it.

    I think all manufacturers post their raster speed and it varies greatly, not all due the motors.
    Mike Null

    St. Louis Laser, Inc.

    Trotec Speedy 300 Newing Hall 350 Hot Stamping
    Woodworking shop CLTT and Laser Sublimation Sand Carving Graphtec CE5000-60
    Evolis Card Printer
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  15. #15
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    Mike, you have a Trotec, which wasn't questioned in the original thread, which I pointed out. If you are comparing the Epilog Helix and the PLS systems, then there is no difference in the Servo vs. Stepper debate. Well, there is a difference in this case, it could be shown that the quality of cut is better on the stepper system.

    I seriously doubt the speed/quality has anything to do with servo/stepper motors, but rather how all the pieces are tuned together.

    I have no doubt the Trotec is a faster machine, but it wasn't mentioned as a unit for comparison in the original post.

    If you have a servo system it doesn't mean anything. You can put a servo system on and then have a crappy motion system and what have you got? Or, you can have steppers with a superior motion system. What have you got? It's all about how it all comes together as one unit, not about one piece or the other. I think there are a couple of systems out there who pull it all together well and I think Trotec is one of them.

    I have much evidence of poor quality with a servo system. It's all documented, so I do have more than just my opinion in this case (between the two machines mentioned).

    I state my case because I think the debate between servo vs. stepper is a wasted debate. I think it's a red herring that takes the focus off of the real differences between machines. Just because one machine uses a servo doesn't make it better OR worse. It just makes it different. If it meets your application needs, then it doesn't matter one bit. I think part of the debate should shift from motors to motion systems and the quality of such.
    Last edited by Scott Shepherd; 08-26-2007 at 11:37 AM.
    Trotec Speedy 300 75W Universal PLS4.60 with Rotary Attachment
    HP Designjet L26500 61" Wide Format Latex Printer
    ShopBot 48" x 96" CNC Router, Ricoh Dye Sublimation Printer
    Summa S140-T 48" Vinyl Plotter, Xenetech XOT 13 x 13 Rotary Engraver, Corel X5, Adobe Creative Cloud

    Real name Steve but that name was taken on the forum. Used Middle name. Call me Steve or Scott, doesn't matter.

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