RAPY

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RAPY

Postby DJNOS1978 » 2014-Jan-Thu-10-Jan

http://www.kickstarter.com/projects/122 ... ref=search

Guys and gals.....can someone please explain to me how DC motors top and reverse on the dime??????? What am I missing here?
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Re: RAPY

Postby RetireeJay » 2014-Jan-Thu-11-Jan

I used to work in industry, where we had robotic actuators. It's true, DC motors can start and stop extremely rapidly, and they can be very powerful. However, the position control now depends absolutely on high-accuracy feedback. For example, I remember a particular system we built with a DC motor controlling an arm position in a feedback loop. Although the system could remain stationary with zero current flowing in the motor's coils, the feedback system was so sensitive that if I tried to push the arm out of position, it felt to my hand as if the arm had been welded in place; it was extremely rigid - and only because the position sensor detected a tiny deviation from setpoint and sent counterbalancing current to the motor to prevent any further motion.

Of course, when you introduce a control loop (sensor plus actuator) you have completely different dynamics than stepper motors. Properly tuned, you can get excellent results - but control loops can be quite unmerciful to those who don't understand them. This technology is not going to migrate easily into the hobbyist build-a-printer-yourself realm.

BTW, DC motors are a totally different animal than AC motors. AC motors gotta move, and their RPM range is relatively limited. DC motors can operate from stationary up to rather high speeds.
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Re: RAPY

Postby DJNOS1978 » 2014-Jan-Thu-11-Jan

So it appears they are targeting the wrong customers, if they are targeting DIY people? Or they may be claming "plug n play"?
That is what I wondering about the control sequence of DC motors. Different animal than stepper motors.
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Re: RAPY

Postby Nickies08 » 2014-Jan-Thu-12-Jan

They seem to be targeting the DIY people who wish to use the printer to make objects and components for projects rather than the DIY group that wishes to actually work on the printer itself. It seems they are trying to compete with bots like the Replicator by using different technology to compete with the cost. Honestly, I think it could be a nice plug-and-play option for anyone that prefers not to tinker with their bot, but wants a printer solely for making objects.

I'm like many of you, working on my printer is my hobby. The things I make are the rewards of the time spent making the bot better. I really like auto levelling though, might be worth a little time investment.
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