Reply with QuoteAgreed. Although I'm philosophically opposed to the idea of pounds of force.Originally Posted by ger21
It's very interesting for this project.
Agreed. Although I'm philosophically opposed to the idea of pounds of force.
don't like pounds?
I like pounds just fine it just seems a bit round about use mass units to define force
I have some additional questions before I go ahead and start ordering electronics.
So far I'm working with the idea of using the G540 and the 371 oz in steppers from Keling.
Question 1: Regulated or unregulated power supply?
For example: The KL-350-48 48V/7.3A (switching power supply) vs KL- 4875 48V/7.5A. Some of the unregulated PS have lower regulated voltages which would be handy but not a deal breaker either way. Opinions?
Question 2: Inputs to G540.
I would like to have home switches and a spindle speed sensor. I'm torn between optical and magnetic (hall effect) switches. Both would be protected from direct swarf. Having a magnet picking up ferrous particles doesn't seem great but the optical switch could get blocked as well. Opinions?
The G540 manual shows NC switches going from the inputs to ground. The specs mention TTL inputs so I assume 5VDC? The optical switch is on (allows current to flow) when the gate is unblocked. The hall effect switch is the opposite (on when magnet is near). It seems easier to wire the optical switch so that a break in the system trips the home switch. Is there an easy way to do this with the hall effect switch?
Question 3: Spindle axis
In the future I may want to try setting up the spindle as a positioned axis maybe using a servo. Am I limiting myself by using the G540?
As always thanks for the help.
Will
Will, in the Imperial system the pound is the unit of force. The slug is the unit of mass.
Randy
never heard of slug before. I learn at least one new thing a day here.
Maybe it will show up on the next edition of "Trivial Pursuit"...The "dirty little secret" is that all those electronic kitchen scales are actually measuring force, reading truly in pounds/ounces and just backing out the mass in kg/grams by factoring in standard gravitation. Take one up on a really high mountain and it will correctly show that the weight of the object in pounds has decreased, but will incorrectly say that the mass in kg has decreased... But our entire life experience (except for a select few) is spent in 1g that we tend to blur the distinction between mass and gravitational force in our daily lives.
Anyway, I didn't come to heckle (I'm a mechanical engineer and had to struggle with slugs back in school--the MKS system was just coming into play then) but to watch the progress on your very cool lathe. It's looking mighty fine so far!
Randy
I didn't take it as heckling. How else would I learn if no one told me something new or corrected me for being wrong?
As for the lathe:
I'm still undecided about regulated vs unregulated power supplies.
I'm now leaning towards a breakout board and Gecko 203v or maybe the 251 drivers. Similar price for 2 axis (using 203v) and it will be easier to hook up more inputs/outputs and potentially a servo driver for the spindle.
I've pretty much decided on optical home switches as I won't be running limit switches to start and the normally closed type circuit on the home switch will hopefully prevent me from overtraveling if something goes wrong.
I am an ME too, but i love the rabbit hole arguement of imperial vs metric. i use both . i think every forum needs to have a thread devoted to that so it does not creep into threads.
I worry less about regulated vs unregulated than about price.
It comes down to, "can the power supply deliver the current RIGHT NOW?" Everything else is a detail. A decent regulated supply will be fine. An unregulated supply is capable of fast current, too.
I don't know much about power supplies and haven't taken the time to learn yet. Any advantage to the more expensive unregulated PS?
$59.95 KL-350-48 48V/7.3A (switching)
$99 KL- 4875 48V/7.5A (unregulated)
http://www.kelinginc.net/SwitchingPowerSupply.html
I would go for the switcher supply. I saw the motor drive from your part number, but not the motor. Which motors (and how many) are you using?
I wouldn't run a low cost switcher all the way to the rated power (maybe 3/4 power?), continuously - just to be conservative. Also make sure it isn't getting hot.
Make sure you check the rail voltage to the drive when you get everything hooked up and running. If the power supply doesn't do what it says it should, send it back.
Back in the old days, people were (still are?) suspicious of switchers for servo drives (and steppers to some degree). I think those days are gone. Consider that your stepper drive (and any vaguely modern servo drive) is a switcher of a type.
Your project is really cool. I had a machine tool customer that had an enormous VMC made of granite, linear bearings, and ball screws. They had it doing over 1 G accels and were in love with the performance. Particularly the stiffness and damping of the structure. They never brought it to production because of the price, but had no reservations with the performance.
I really hope it works well for you.
Waffling between G540 and G203v for drives.
Motors pretty well set on KL23H2100-35-4B http://www.kelinginc.net/NEMA23Motor.html (specs: http://www.kelinginc.net/KL23H2100-35-4B.pdf )
The power supply would only be for two of these motors. 3.5A each * 2/3 rule of thumb = 4.67A so either PS is significantly (50%) oversized.
The nice thing about the G540 is is has a breakout board in it. It could control a VFD for a 3 phase motor for a spindle. If anything ever happened to one of the drives inside the G540 your would have extra ones that could take over for it. The G540 is also setup to work with inputs and outputs that can work with limit switches and to control other things. It makes the wiring simpler at a reasonable cost and will handle the motors you want to run.
Only thing I would want to make sure is if it would work with whatever method you want to keep tract of spindle position for threading. If you can do that using a VFD and a three phase motor I would go that way. That is something I don't know a lot about. I'd like to learn if anyone knows if that would work.
Sounds good to me. Time to click Add To Cart and make this thing happen. You've made so much progress, and this looks like it's going to be a fun project!
Is that a educated vote for the switching PS? (My vote doesn't count for much
Yes. Go for the switcher. Spend the money you save somewhere else. It'll pay off more there.Is that a educated vote for the switching PS? (My vote doesn't count for much
I would go with the switching supply. I would be more stable and have less chance of ever going over the rated voltage of the stepper controller. Switching supplies are what computers use. You will also get a cleaner voltage that should ensure that things run with as little glitching as possible.
I would like to mention that CNC router parts has a nice system in the range that you are looking at. He may get the parts from Kelinginc. I'm not sure. What he does is have a current set resistor already in the motor connector so you don't have to add that. His power supply works great with his motors and the G540. I'd email him to make sure everything is in stock before you order. Most likely it will be.
http://www.cncrouterparts.com/index....2dqn3jpav8km13
His 48v 7.3A supply would work fine with his 380inoz motors.
