Disclaimer:
My MPCNC isn’t running yet, but I have assembled it except electronics and belts.
/Disclaimer
I think my plan is to cnc holes in my table, and a few layers (~6" deep) of MDF, to support the verticals, and make them too long(like a foot or so), and adjustable height.
Second thing I’ve given some thought: Unsprung weight.
If the xy motors were stationary, the xy carriage would be less massive, so the forces would be reduced at the same speeds.
Also, if the Z motor were attached to the middle asm, it wouldn’t need to lift itself or the leadscrew.
Third thing: If the z axis could be suspended with a spring to counter its own weight(or the weight of the tool attached + z axis…), it could be belt drive, and equal speeds in x/y/z would be no sweat. That would be differentiating performance for a diy cnc machine.
Lance, maybe I can put up an option later this evening. I have all the parts but pricingg might be tricky. I have to take a real hard look at the numbers and labor savings.
Christian, adjustable height was the intended reason to have the feet hollow, most of us just take so much time leveling it we don’t move it. The option is nice though.
XY steppers, having them on the corner means more parts, longer belts, bigger footprint. The speeds at which we cut I feel effect would not be noticeable. So I made assembly easier and the machine cheaper having them on the rails/rollers.
Z stepper on the gantry would be awesome but it means the leadscrew would need to stick up. I chose the current setup to keep the screw covered from dirt and debris in the little tunnel and the footprint at a minimum. I am always looking to change this. I have tried a belt driven Z, but would like a higher gear ratio because I don’t like working with springs (they are expensive and would limit the expandability of the machine and raise the price).
Steve, New firmware is coming for the mini rambo. The current firmware is based on the later version of RC8 so there is not much difference at all.
Are you having some sort of issue?
It can go much much higher, 80mm/s max before losing much power… but I still have the firmware limited to 8.4mm/s. I haven’t done any real testing on speed yet. The weight of the spindle might have a big effect, and the accel will severely limit it as well since it is such a short distance traveled.
The bigger picture is more power at slow speeds, so builds with Z issues have a better chance of not irritating the builder!
If my math is right. 60rev/min1min/60sec32000steps/rev*1mm/400steps=80mm/s and that is under the 40k limit for the rambo at 16th stepping, so 50mm/s max for the Ramps at 32nd stepping.
“Flash or correct the firmware Z steps, with 32nd stepping 788 steps for the Z axis seems to give me the most accurate results.”
Where does the edit go, Configuration.h?
I down load the firmware again, Z is still 2267.72 the seconded bock of code is what I edited, and was looking for conformation that I put the edit in the right place.
By the way thanks for the screws for the LeadScrew nut. Service above and beyond!
If you bought it from me, chances are really high it already has the new firmware on it, I think I only shipped out two with the RC8. Are you sure you even need to flash it?
No, I’m not sure, but my parts kit came with the threaded rod and the Rambo. So it may be one of the two.
There’s no rush on the firmware. I was just going through the the check list in my build notebook, and got to check firmware rev.
I’ll probably be putting power to it in the next week or two as I only get Sunday’s work on it.
What would be an awesome improvement would be to have a tool changing system.
Or at least some no brainer device who could help changing manually the bit while keeping perfectly accurate positionning.
An other awesome thing would be to have motor feedback positioning, so the CNC wouldn’t lose step in any condition.
Dont’ know if any of those are realistic, seems to be quite a big challenge… But I really hope this could be achieved!