Tech Info and Detailed Price List Section
• Servo vs. stepper? Not that simple.Many people are confused by all the hype surrounding the choice between step or servo type motors. We hope that this factual summary will help answer your questions on the subject. It is not a matter of one being good and the other being bad. It's simply an issue of price and performance. Both kinds of systems can cut the same parts for you.
Ah-ha! uses 1990's technology, and our motors and electronics are as advanced as any servo system. We use pulse width modulated MOSFET chopper drives, just like servos. Our motors are brushless just like modern servos, etc., etc..
• What's the difference?
Steppers and brushless servos are virtually identical motors. The only real difference is the number of poles. Typical brushless-servos have 4 poles. Steppers usually have 50.
• Benefits of servos
Servos provide two benefits over steppers: First, servos need encoder-feedback to work at all, and this encoder inherently provides an out-of-position indication when something fails.
Some people think that having encoders means the machine will never be out of position. Not so! Complex servo systems have all kinds of potential errors, such as: following, dither, overshoot, etc.. In most cases, the encoder does not tell you when you have a following error, an overshoot, etc.. And the boards can and do blow up, just like any other product. So, the encoder is nice, but it's not a cure-all.
Second, servos give a faster rapid-rate, if your ballscrews can take it. 900ipm sounds great, but many screws can't handle more than 200-300ipm regardless of the motor type.
• Benefits of steppers
Simplicity: Stepper systems are easier to build, easier to install, and easier to maintain. Fewer moving parts and fewer connections. This equates to a much lower cost for you.
Resolution: Steppers let you achieve very high resolution at very low cost, typically 8,000-16,000 steps/inch. Servos need expensive hi-res encoders to do the same thing. Steppers are also very accurate, with no errors larger than 1 step.
Robustness: Servos are sensitive to changes in mass, like putting a 1,000lb mold block on the table; and to changes in friction, like getting a little dirt on the ways. Steppers are less sensitive to these things. The tuning of a stepper system is built right into the motors themselves.
When properly set up, they'll run all year without missing a beat. They're reliable, very affordable, and easy to install.
• Look at the functionality per dollar.
As you ponder this subject, remember that a high-tech Ah-ha! stepper system costs only $2,500 to $6,500. A typical servo control runs between $12,000 and $35,000. $35K? For a 2nd ops machine or a manual conversion? Hmmmm.....might be worth a call to ah-ha!
• So, does it really matter after all?
The functionality of your machine is determined by the CNC software, not by which kind of motor you use. Both types can cut the same parts. Some applications do need the faster rapid rate or the out-of-position indication of servos, but many other applications do not.
• Prices and Technical Specifications
The following 8 pages give details and costs for each system component. We carry a wide variety so that we can match our control to practically any machine tool, including yours.
In some cases it will be obvious what you need. In other cases it may seem confusing. Please don't be discouraged or concerned about doing a CNC installation yourself. Our specialty is making it easy for you. You have questions? Ah-ha! has answers! Call us at 651-641-1797.
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