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Thread: CAMaster Stinger 1 or ShopSabre 23

  1. #31
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    Todd, my guess is you are dealing with the new sales guy at SS. I do not know him so I should not say this, but he kind of reminds me like a used car salesman for some reason. I dealt with Brandon at SS and I bet Mark did too. Brandon is a very good salesman. Answers questions, and is good at getting back to you. They are in their new shop now, and I suspect things have changed a bit as a result.

  2. #32
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    Todd...
    Sorry, I made the assumption that since you were looking at CAMaster machines, you had looked over that "FAQ" section. There have been over 20K views of that thread, around 12 guys may have listened.

    I agree, the ballscrew vs. rack & pinion usually makes no difference to me. On small (< 3' lengths) tables I prefer screws because it lowers costs to the customer, especially at higher reduction ratios and since I only sell to experienced users that know exactly what they need and have found that no OEM provides that combo in a small format machine, they prefer that additional cutting power over a published speed rating.

    What does make a difference is: what is the final drive ratio? How many motor turns per inch of travel? Most commonly used R & P will use 1.25 to 2.75 revs per inch. Most ballscrews will be 2.5 to 6. Motor rpms are limited. Torque is fixed. Performance, which should be the mix of torque and speed, will be a product of those numbers. Few if any know those numbers. And it may not matter if the machine does the job they want it to.

    Most experienced users find that they don't care about the mfgr provided numbers, because they are just like paint on fishing lures: Made to catch fishermen, not fish. What's important is: does it catch fish? Only use will prove that. Same for CNC. How does it cut? At what speed can it cut in my material and hold a given tolerance?

    The one number most small CNC (machine size not mfgr size) do not offer is: "Our machine will cut (xxx) material, using a 1/4" bit at 1/4" depth at (X) inches per minute and hold (.00X") tolerance. This is easily tested on any machine using 6" squares and 6" diameter circles and measured with a digital caliper. It is the one item that can provide the most info to any experienced user. That spec is what divides small machines into their price classes. The numbers would surprise many.

    Someone mentioned a machine I am using as a long term demo project. It is an inexpensive import that inspection shows has good machining but poor assembly and low "plumb, square, level" measurements. Good parts, but poor assembly. A few hours of machining later and that machine, with NEMA34 closed loop steppers and Centroid control will outperform both you mention at a lower price. Add WinCNC and it will outperform both at a higher price. WinCNC and Centroid are so far advanced over all the other DIY controls that it is hard to explain. And I do have speed/tolerance data for my customers.

    I really feel that the "Find a machine that you like from a mfgr you can trust" is the best advice you can get. If in fact you really get involved with this craft, and once you have a few years experience, like most, you will upgrade. If you buy from the same company, you did well on your first pick. If not, you are 50/50. Better than most. A 500 batting average will keep you in the bigs.
    Gary Campbell
    CNC Replacement & Upgrade Controllers
    Custom 9012 Centroid ATC

  3. #33
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    It's interesting to hear how you define performance.

    I think my involvement in the craft will be strictly as a hobbyist user. I have no desire to build my own CNC because I have too many other projects. If I factored in how much I value my time to do those, it couldn't pay off for me.

    So I'll defer to experts like you and Camaster and ShopSabre and ShopBot, to design and build the machines. I will learn enough to make an educated purchase, but then I plan on learning to use it on my projects (and the ones my wife is waiting on 🙂 )

    Now I have to learn about spindle power and how to buy enough but not too much for the machine, steppers and loops, and controllers.

  4. #34
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    Quote Originally Posted by todd werner View Post
    Now I have to learn about spindle power and how to buy enough but not too much for the machine, steppers and loops, and controllers.
    More is better when it comes to spindle power. I went with the 1.7kw (2.28hp) and have had no regrets with it. It has never bogged or complained. I was told that the 1.0kw was a little underpowered for routing and more suited for engraving. The 3.0kw would’ve been nice but it seemed like overkill for my needs and was an additional $500.
    Please help support the Creek.


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  5. #35
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    Like Bruce, I selected the 1.7kw spindle for my machine and expect it will do just fine with the kind of things I'll likely be cutting, which will be both hobby and some business focused work.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  6. #36
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    I am 100% sure the 1.7Kw would be enough for me. Everything I'm reading says in many ways even the 1Kw is more capable than a router, and I would I'd be OK with a router.

    So really I'm reading about motors and such and wondering if I'd be better off with a 1.7Kw and the stock motors, versus looking into a motor upgrade with the 1KW spindle.

    If I understand what I'm reading, with a stepper motor, there's a risk they slip and lose position if there's too much resistance. So I'm trying to figure out if a motor with more torque is less likely to slip, or if it's just faster or less likely to get stuck. I'm going to ask the two companies if there are any options to upgrade to a closed loop or hybrid stepper system. https://www.motioncontroltips.com/op...motor-systems/
    I don't want a bigger model, the two I'm comparing are really close to the perfect size for what I want to do and where I'm putting it. I just don't want to feel any need to upgrade for as long as possible and I see a lot of hybrid or closed loop stepper systems being discussed, and they do come in NEMA 23 sizes.
    Last edited by todd werner; 03-11-2018 at 3:58 PM.

  7. #37
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    Todd, maybe you're over thinking this because "what you're going to do" with the machine is going to dictate whether or not things like heavier motors will pay off. If you're not going to be driving the machine hard, then heavier motors just add cost. Of the three or so CNC brands you're potentially looking at, the setups they build in as standard seem to be pretty appropriate for the size machine you're considering. I personally feel that a spindle is worthy for a variety of reasons, but "beefing up" other things might not matter. As you note, there's a lot of "techie talk" about various motors, etc., but you really have to ask yourself if that's relevant to your situation for a small machine to enjoy in your shop. Remember, you said you originally were considering one of the very nice kit machines, rather than these much heavier units. Honestly, this almost really comes down to "what color do you like?" relative to what manufacturer makes you feel the most comfortable.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  8. #38
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    Todd...
    I read that page you linked to and will tell you that even tho it is sprinkled with some facts it is mostly marketing hype intended on selling their higher priced motors and drives. Closed loop steppers are not servos. Anyone that is selling steppers and uses the term servo is B.S.ing you. If you have a stepper motor, lets say 400 ozin (holding torque @ zero rpm) rated and you put an encoder on it you gain ZERO torque, and by extension ZERO acceleration. You only gain the ability to have the machine alarm out (similar to an estop event) if the actual position is more encoder counts away from the commanded position than the "alarm setting". When/if the load reduces far enough an encoder equipped stepper will force its way back into its position.

    Torque is like lever "power" around a fulcrum. It is the ability to accelerate a load. Power is the ability to keep a load moving. Torque is required to get your gantry up to speed and what keeps it from losing position when the bit hits a rock hard knot. The faster a stepper moves the less the torque becomes, until it reaches a certain rpm then it falls to near nothing. In your world you will have to keep the load on your bit under that which would cause you to lose steps. This is true if you have a closed loop system with a minor error and an alarm, or a standard stepper that moved off course and just kept cutting on an erroneous path. Either way your part is shot.

    I don't know if either of those models have a closed loop option, but if they do and you purchase it, you will still have to learn to keep loads appropriate. "S"ome companies that used a lot of closed loop have spread a lot of propaganda regarding them. They electronically neuter the settings in the drive so that a complete stall or some number of inches for some number of seconds are the alarm settings. So you could lose position by an inch and cut for 30 minutes and not gain position back until a retract was programmed.

    FYI: Those same companies that use verbiage like your linked page for the DIY crowd, market the same motors and drives to mfgr's by saying closed loop allows them to use smaller, cheaper motors, (for a number of reasons) and reduce costs. In other words they tell the story to each that they want to hear.
    Gary Campbell
    CNC Replacement & Upgrade Controllers
    Custom 9012 Centroid ATC

  9. #39
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    Properly designed and installed a stepper motor system is fine, there are thousands of older milling machines that had stepper motor CNC and worked fine. Even today they are used on a lot of routers, laser engravers and 3D printers, you name it. Servos with encoders are better and faster, but unless your running production do you need that speed?

    I had a servo driven router before I had the one I just purchased and it was a pain in the butt. Most of the problem it was due to the people who designed and programmed the driver board and the software.

    PS Just read Gary's post and that was the issue with servo system I had. it would fault out all the time not due to a overload but the set up in the software. BUT the end user, me and a few others got blamed for everything under the sun!!
    Last edited by Bill George; 03-11-2018 at 10:12 AM.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  10. #40
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    Bill makes a good point. Even tho its related to load, the drives alarm setting uses an "encoder count error" to trigger an alarm event. Which triggers an output on the drive. Which triggers an input on the control system. The control system reacts in the manner that it has been programmed to. Take Bill's example above, the error count trigger was most likely set too low. Left alone most folks would set them in that manner. With the same result: a useless machine.

    1000 encoder counts per rev is pretty common on steppers. I will use the example of my Acorn project. 1000 encoder counts, set to 250 as the alarm threshold. On a 5mm pitch ballscrew which advances 5mm or .197" per rev the error is set at .197 / 4 = .049". Yup, ~50 thousandths. Set it any less than that and the drive will alarm out under acceleration. Depending on the motor torque and acceleration setting the actual position will often be 20, 30, 40 counts behind the commanded position and the same amount ahead during decel. And that is OK. Here's why:

    The drives will apply 100% of available torque once a loss of one native step is detected. Most of these motors have 200 native steps per rev. That's 5 encoder counts. so at 5 encoder counts drive power (amps) is increased until the count matches again. If you set it right, it's like cruise control on your car. Set at 60, come to an uphill section of road it presses on the gas, go down one it lets off. You wouldn't set the cruise to shut the car off if you were off by 1 or 2 mph would you? Besides, most of the time a non encoder equipped stepper looses position to the point where we hear the "ratchet" or slipping sound we have usually lost 3-400 steps or more. A 1/4 inch, an eighth at least. On the Acorn project using a step resolution of >8000 steps per inch and NEMA34 650 ozin steppers the acceleration can be set much higher in this case. Acceleration of 0 to 300 ipm (rapids) in .3 seconds. That's 1000 ipm/sec acceleration. Virtually unachievable with a NEMA23 stepper motor. So even if the bit hit a knot and got behind 249 counts, it would normally be back on position in a quarter second or alarm out.

    What you need to remember is that all these awesome features and the extra components and programming cost real money. When the mfgr offers them as an option, most customers buy the lower priced options. When they are standard, customers buy lower priced models. One major mfgr that offers both sells 10 to 1 open loop systems to closed. The consumer CNC market is 100% price, not feature driven. And they publish the specs consumers want. That's the way new CNC buyers want it. That's why I build for experienced users that know what they want and why. They don't run like the consumer grades, for the most part I try to eliminate the keyboard and mouse. And I wont sell a custom machine unless the purchaser agrees to a full day of training. My shop or his. Both cost real money. All the good stuff does.
    Last edited by Gary Campbell; 03-11-2018 at 11:37 AM.
    Gary Campbell
    CNC Replacement & Upgrade Controllers
    Custom 9012 Centroid ATC

  11. #41
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    I got the sense there was some marketing spin on that page, but even so, it sounds like a we'll set up closed loop with an alarm would potentially pause if a knot causes slipping, before the program ruins a job? Would such a system potentially let me re-zero and adjust my feed rate before the piece is ruined?

    A lot of what I plan to work on will be a multi-step project that I'll have hours and hours invested in. It might be worth it having a safety on those jobs where I won't lose a sheet of plywood, but will lose a 9 piece glued up neck blank with carbon fiber reinforcements. Because I know I'll be annoyed enough when I destroy my plywood.

    I do realize that it's far more likely a project will be destroyed because of user error on my part, and I'll make every effort to minimize that occurrence too. My nature is usually to go with the option that has the highest safety margins.

    And if the closed loop is not an option for me, will the other two options also impact this concern?

    At the same RPM setting, will the 1.7kw be less likely to get slowed down by an irregularity and therefore be less likely to meet with resistance that causes slipping? That seems intuitive, but I'm learning not to assume anything here.

    And what's not as intuitive is whether a slightly stronger stepper with more torque will not slip when it meets resistance. That seems to require I understand both the torque and power curves. Still, if the higher torque motor has more torque and power at any RPM, will that also decrease the risk of slipping if everything else is held the same, and are there more powerful motors in both the NEMA 23 and 34 sizes?

    Edit : Gary, you answered that last post before I could enter mine. I'm typing on a cell phone so I'm slow. It sounds like the question I posted on closed Loops isn't accounting for everything the loop does, since it sounds like a closed loop system will actually try to increase the torque to make up lost ground. Since an open loop won't even know it's lost ground when it in encountered a section of increased resistance, that means that as soon as it slips a little bit, the rest of the job is off by that much, doesn't it?
    Last edited by todd werner; 03-11-2018 at 3:57 PM.

  12. #42
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    Would such a system potentially let me re-zero and adjust my feed rate before the piece is ruined?
    Depends on if the error went into or was outside the part

    At the same RPM setting, will the 1.7kv be less likely to get slowed down by an irregularity and therefore be less likely to meet with resistance that causes slipping?
    Possibly

    And what's not as intuitive is whether a slightly stronger stepper with more torque will not slip when it meets resistance.
    Of course it will. But that's not saying it may ever be enough, if you are smart, it can be. The OEM's are not dunces, they put out matched systems that perform pretty equally in each price class. Users overdrive them.

    Since an open loop won't even know it's lost ground when it in encountered a section of increased resistance, that means that as soon as it slips a little bit, the rest of the job is off by that much, doesn't it?
    Absolutely
    Gary Campbell
    CNC Replacement & Upgrade Controllers
    Custom 9012 Centroid ATC

  13. #43
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    Todd...
    Read your PM
    Gary Campbell
    CNC Replacement & Upgrade Controllers
    Custom 9012 Centroid ATC

  14. #44
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    Your closing of the loop is largely a check. Servo is told to move, moves, and while doing so it is constantly sending a message back of the counts to know it has done (or is doing) what it was instructed to do. If it thinks it has or is moving incorrectly it corrects itself. That is done with software. It would have to measure the power demand to know something like extra stress caused by a knot. That is likely out there, but not in the entry level machine class. Closed loop steppers are similar, just not as many counts per rev.

    The force applied to the cutter is not that much larger at a knot. The problem with losing steps tends more to be when you have operations with lots of rapid stops and starts where the power demand is fluctuating constantly. If you really want to go sideways with the stepper discussion you can look at the reality of microstepping. I cannot speak to that very well, but Gary has before in the ultimate desktop discussion.

    If you are concerned about cost, this will all be sorted out soon enough when you talk to the suppliers. Steppers for this machine cost a few $100 each, servos are $600 - $1500 each for a reputable brand (that is not Fanuc or Fagor because those are more). The cables cost a bunch more too. On my project one supplier quoted $2k for cables. Yes, just wires for four servos. WinCNC will only close the loop at the amplifier, and if you want it in the software (referred to as true closed loop by some) you will need a different controller. That will really ramp up the cost. Go look at what others are doing with the two machines you are looking at. Is that what you want to do? There are tons of people making guitar parts on entry level machines. Is that someone like Fender (assumed you are interested in guitars with neck reference), no, but they have money to spend. Are you going to be measuring things relentlessly after they are cut and would you be annoyed by cut errors in excess of 0.02" or so? If you are the measuring type, you might need to increase your budget. I am the measuring type, so I know that problem. If you are the measuring type I would be talking to Gary about one of his. These type of questions are handled better by someone that can customize things to suit your needs. Product suppliers have a stricter limit on how far they can go to customize a machine. I suspect the limit of the discussion with the two you are talking to will be is steppers, or servos using WinCNC. Knowing multiple controllers is a big deal for a product supplier. Gary has vast knowledge gained over years of taking things apart. There are others too that do this, but the majority of them are working on steel milling machines.

    By the way, spindle power is kilowatts, not kilovolts. kW, not kV. Hp works too, but you need to convert using google.
    Last edited by Brad Shipton; 03-11-2018 at 1:01 PM.

  15. #45
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    The really scary thing here is that I kinda understood all of that...
    --

    The most expensive tool is the one you buy "cheaply" and often...

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