Excellent start !
A tiny nema 23 stepper, on my machine, moves my bed mill, effortlessly.
The bed is 1600 mm wide, 60 mm thick on ribs, tool steel.
Mass is 200 kg, with upto 200 kg of stuff on it.
The "right" way to do it is drive the moving bit at 1:3 with the stepper with HTD belts.
This provides better overhead, much better acceleration, better accuracy, and about the same speeds.
If nema 23 steppers dont work, get ac brushless servos, at 130€ each, or 290€ for servo motor, driver, cables, encoder, everything.
They cost == the same as 34 size steppers, and
-5x more accurate
-5x better acceleration (more than you need)
-3-5x top speed (too much. You wont want all the speed).
The top speed is not important,
the cutting speed is very important,
accuracy is vital,
and rigidity is everything.
Just my experience.
Modern brushless servo motors are
-not noisy, (IMPORTANT),
-dont backdrive and activate with back-emf (VERY IMPORTANT),
-wont take off if the cables get cut or disconnected,
-have anti-jitter circuits,
-can be used with differential connections (less sensitive to noise)
-have a disable-input on them.
Building cnc stuff since 2002, mostly full-time.
The Following User Says Thank You to hanermo2 For This Useful Post:
Yes, and thanks for great input JAZZ, it is just me, whenever I am working with something I always start thinking if it can somehow be improved - even if it is great to begin with.
Actually, I think it will be very rare that I need to clamp very thick material, and if so I could clamp it to the frame with normal wooden clamps, or even make some kind of spreader bar as you suggest. So I will use the toggle clamps - and they are cheap too.
Thank you hanermo.
I am really impressed to hear that a Neme 23 can move a 200kg gantry - even with some gearing. So my measly 60kg gantry should not be any problem?
I have not really considered servo motors because most DIY people seem to be using stepper motors, and it is my empression that servo motors are more complicated to use and much more expensive. Also, I think you can get a Nema 34 and driver cheaper than 290 Euro (cannot find that symbol).
I am convinced that brushless servo motors are excellent - maybe I should look more into that.
Euro symbol is along with dollar and pound, one more to the right.
€ alt-5 on most keyboards (.fi),
€ alt/4 on .en
alt-5 on .es
The nr1 imporant piece of gear is the motion controller.
The Pokeys for example, with hardware MPGs ! and thats crucial, move my machine with an MPG as well as a 100 grand Haas.
The MPG is wired directly into pokeys, no USB.
MPG wheels cost about 30€ each, and I put one on every axis of every machine.
Pokeys supports 3 at once with Mach3, and will likely support more (they sort of tole me they can).
CSLabs also told me that they can support dedicated MPGs.
Trust me, dedicated wheels like on a lathe, where the same MPG, in the same position, always moves the x axis, is the dogs danglers.
Just like manual, but clean, fast, 10x more accurate, perfectly repeatble.
Important point !
A usb MPG cannot be good as .. ! Because the USB has variable latencies (to 1 ssecond 100.000 less).
On a Pokeys, the engine runs at 125 kHz,
so every 0.01 ms, it checks if it needs to move an axis.
This makes it "feel" like its solidly connected to the machine.
Ah - thanks for help with € - it is on the 5 key, but not marked.
Did not know that motion controller (MPG) is so important. Is it so much better to have separate ones for each axis? It seems that many of them can be used for all axes. What does "100 grand Haas" mean?.
I did look at the Pokeys Electronics (controller and BOB) - what is your impression with that?
With respect to servo motors - what specifications should you be looking for if you want to replace Nema 23 or 34?
MPG is nice but it's not required for general use and on a machine used mostly for wood ie: router then individual MPG's are wasted money to me. On lathe or Milling machien with lots of setting up etc then yes I'd probably consider them but not on wood router.! One is enough and then it's more of a luxury than needed.!
Same goes with servos for me with Small/Med router based machines like this. The price difference is 3 x that of Decent steppers. AM882 or Em806 Digital drives with 3-4Nm steppers will be less than £100 per axis and they easily push 60Kg around at 10,000mm/min or more with 10mm pitch screw which is plenty fast enough for any DIY machine.
Last edited by JAZZCNC; 26-09-2015 at 02:16 PM.
The good part about dedicated MPGs is that they work like a manual machine.
Ie you are never switching on the pendant to a given MPG.
It makes the machine extremely productive for one-offs, for manual use, and for setups.
Most faster than any manual every made.
The 2 best controllers I know of are;
1. CSMIO. Very good, expensive full-on (1000€ and up, industrial).
2. Pokeys. Very good, cheap (150 € ish).
Both have excellent drivers, excellent support, and good features.
Use ethernet !
It may be instructive to note, I am not mentioning anything else, I have stopped using 3 other solutions.
The others that may be good are machmotion and something else, .. no personal experience.
Use ethernet !
Ethernet is galvanically isolated and has very low latency.
The average cost of the Haas machines I worked with, and sold, were 73k€, approx 100.000 $ at the time.
Haas is a large, very succesful, builder of large industrial machine tools. Nr in the the USA, nr 1 by nr of machines, in the world.
Disclosure: I used to be their sales manager for Spain.
Hi Hanermo2. Thank you for your input, I will consider an MPG - it sounds like a nice feature. But you are way out my league. I am building this machine because I cannot afford to buy a similar machine (and because I think it is fun). Obviously for professionals and companies a difference of a few hundred € per axis is no big deal, but for for my little private project it makes a difference. Also buying one or three MPG's makes a difference.
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