New build – input/comments appreciated

[ngundtoft]

Thanks JAZZ. This is actually a brilliant design. It is simple to make, it can be removed from the machine when you are not using it and the width it can accomodate is adjustable.

The only thing that may not be optimum is the thickness of the material you can clamp. I remember using this type of clamps (although much smaller) and the reach is not so big. I tried to find the reach for similar types. I only found this specification for a single one and it was 3". I am not sure if that means it will go from 0 to 3" or if it is just the maximum. Maybe you can use this type of lever clamp instead (although they are quite expensive):

[JAZZCNC]

There are many ways to do this and many types of clamps to help but the simple and easy way's are often the most affective. In this case it would be a simple spreader bar which is bowed so when clamping wide boards pressure is applied in the centre.

I was only really offering simple example of how to do it but not really being specific regards clamping etc.

[hanermo2]

Excellent start !

One point.
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.

Best,
hanermo

Building cnc stuff since 2002, mostly full-time.

[ngundtoft]

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.

[ngundtoft]

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.

[hanermo2]

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.
Huge difference.

[ngundtoft]

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?