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MakerBot's 3-D printers will soon be able to produce items that look like bronze, limestone, and wood, thanks to a new line of plastic-based composite materials shipping later this year. But the launch may be too little, too late: Entrepreneurs and artists interested in working with metal and wood are already embracing desktop milling machines that can handle the real deal.
The calculation is simple: Buy a MakerBot Replicator, the leading desktop 3-D printer, for $2,889, and you can produce plastic prototypes or the kind of trinkets that you might find in a Happy Meal. Buy a small-scale milling machine like the Othermill, which retails for $2,199, and you can make jewelry and mechanical parts out of everything from aluminum to walnut.
"Once you can cut metal, you can make things that last," says Danielle Applestone, chief executive of Other Machine Co. "For the first couple of months that I was working here, I was scared of cutting with metal. It was louder, I was worried I was going to break the tool. But as soon as I jumped in, it quickly became like wax to me."
"Metal is power, it really is," she says. "You don't go back."
It should be noted that MakerBot's base model also went from $400 to almost $3K when Stratasys acquired them.
Original Submission
(Score: 5, Informative) by LoRdTAW on Thursday June 11 2015, @12:14PM
You would be surprised how accurate timing belts can be. I have talked with Aerotech, makers of high end motion control systems, about compact stages that use a brushless servo motor mounted 180°. The motor drives the ball screw through a timing belt and can still maintain 0.0001" inch or better accuracy. I also have a short acme screw Z stage here on a laser welder that has a brushless servo motor with a timing belt. Has no problems keeping 0.001" accuracy.
Simple step motor drivers from an arduino are stuck at 200 steps/rev or what ever the motor count is, 200 is almost a standard. Good drivers can microstep which employs a current control method to hold the rotor between the poles. Some drivers can easily divide a single step into a hundred or more steps. So a step motor can have thousands of steps/rev. I worked with an X-Y table from newmark systems that was driven by a Galil motion controller and IMS all-in-one stepper drivers (IMS = Intelligent motion systems, now owned by Schneider electric). The stages screw pitch was 10 revs an inch and the micro stepper was set up for 20,000 steps/rev! I had to move the system 200,000 counts to go one inch. So you can go really high resolution with steppers if you need.
(Score: 1) by WillAdams on Thursday June 11 2015, @01:58PM
I've got 400 step motors on my Shapeoko 1 --- I've found mention of 800 step motors, and have been trying to find a supplier w/ a reasonable price --- anyone got one?
(Score: 2) by LoRdTAW on Thursday June 11 2015, @03:32PM
LIN engineering has 0.45 degree/step which is 800 steps/rev: http://www.linengineering.com/stepper-motors/5704.aspx [linengineering.com]. They also have 400 count motors too.
Oriental motor also carries 500 and 1000 step/rev motors from but has a weird 5 phase bipolar setup which needs its own drive: http://www.orientalmotor.com/products/stepper-motors/stepper-motor-only.html [orientalmotor.com]. But they also carry 200 and 400 count motors as well.
(Score: 1) by WillAdams on Thursday June 11 2015, @04:29PM
Thanks, I think that's where I learned of them --- the problem is they seem to only sell in large quantities.
I'd like to find a storefront which sells direct to the public in small quantities. Even better would be a U.S. manufacturer (are there any left for stepper motors?).
(Score: 2) by LoRdTAW on Thursday June 11 2015, @05:29PM
Dumb question but what CNC controller are you using? Something arduino based?
I ask because instead of hunting for motors you could simply stick with cheap 200 step/rev motors and use microstepper drives to run the motors. Then set the microstepping to whatever you need and roll from there. The only signals you need are a step clock and direction signal, two wires. Maybe your CNC controller has a step/direction mode. An arduino could do it with the right code: http://www.airspayce.com/mikem/arduino/AccelStepper/ [airspayce.com]
Then use a driver based on the Allegro Micro A4988 which can andle 35V @ 2A. Enough to run a 61 oz-in stepper which is just above what your shapeoko calls for.
Also, I forgot to mention Automationdirect who I use regularly for Automation parts. They have pretty cheap step motors which I have used on a number of projects here. Cheapest motor is a 61 oz-in NEMA 17 for $18. Though all of their motors are 200 step/rev. Their drives are easy to use as well though not exactly cheap. The intelligent drive is easily programmable though you need windows and a serial port to do it (no problem for a VM.) It is also quite expensive. I built a few little motion systems using those parts and 10,000 step/rev using micro stepping.
And one last tip: Steppers work best on higher voltage buses. So use a power supply with the highest voltage you can for your driver. That allows for the current to rapidly build in the motor windings allowing for more torque at higher revs. A good drive operates using a closed current loop to run the motor. The larger step systems I have built which run at 100+IPM are ran by Aerotech CP drives which pretty much rectify the 120V coming in and feed that strait to the bridge driver.
(Score: 1) by WillAdams on Thursday June 11 2015, @05:51PM
I want actual, discrete steps, plus further microsteps --- I don't want to fake precision w/ finer microsteps.
(Score: 3, Informative) by LoRdTAW on Thursday June 11 2015, @07:04PM
May I ask why you want 800 full steps and microstepping? How much precision do you really need? I say this because you might want to take a step back and re-evaluate your requirements. Using hard to find 800 step motors makes things difficult in the short and long run. 200 step motors are very common and cheap.
Microstepping certainly isn't fake precision. As long as the controller is able to hold the current, the precision is there. As I am typing this I have a stand alone stepper controller I am building right next to me. It is uses an Aerotech Soloist MP drive which is pretty much all-in-one. I have the microstepping set to 4000 steps/rev or 20 microsteps per full step. Using the full 2.7 Amps of holding current I can twist the shaft pretty hard and the shaft will turn a bit. But once I let go, the rotor snaps right back to position as it aligns with the magnetic field.
Our requirements here are pretty strict so we wouldn't use "fake" precision if it could not do what we need. I have two steppers running in microstepping mode in a fixture for 4 axis electron beam welding of fuel nozzles that go into GE jet engines (sitting on a brushless driven XY table). Trust me, if we can do that and satisfy GE engineers, then microstepping will get you to where you want to be.
And BTW, that newmark system was designed for repeatability at 0.0001 inches or better with 20,000 steps/rev and a 10 turn/inch screw. If you need precision beyond that, you may probably need different hardware.
(Score: 1) by WillAdams on Thursday June 11 2015, @07:35PM
Yeah, that was a bit curt.
Let me rephrase:
I'm curious about 800 step motors, what their prices are in small quantities and what advantages, if any, they afford over 400 or 200 step motors.
(Score: 2) by LoRdTAW on Thursday June 11 2015, @08:31PM
No worries.
In my opinion, going for more discreet steps has no real benefit unless you are looking for crazy high resolution per rev using microstepping. That or more steps when not using microstepping (e.g. when using a dumb step driver without current control.)
And crazy high resolutions are not necessary when you are driving lead screws as they have imperfections in them such as backlash and winding. Winding? Hold a straw on one end and twist the other. The straw winds up. Happens on screw stages when the loads are high and the commanded move very small. The motor moves, the encoder sees the move but the table has not moved as the shaft and/or coupler twists slightly. Even with a stepper without feedback the same thing happens.
Crazy high precision usually means linear or piezo stages with laser interferometer feedback. Then you can enjoy submicron precision.