Slow progress is also a progress I think.
The sides are welden. Paint and machining left.
Playing around with the Y-axis design. Taking into account your advices I came up with this.
I will make som sort of curtain and maybe a fan to make overpressure to reduce dust collection. The stepper may be happy with a fan too.
One thing is for sure, this thing is gonna be heavy.
Edit:
Well, what do you say about the bolts that joins the side towers to the base frame? Is six M12-bolts enough?
M12 is plenty.
Strength is not the issue at all - flex is.
Bigger bolts is better because the head has so much more area.
You wont stress the bolts by more than 1/10 - 1/50 of its strength.
Hi, weight.....in the main frame........ is not a problem, except for the moving entities where inertia plays a big role.
To mill steel you need to have the rigidity and strength of steel to resist deflection, so heavy sections are the way to go.........if you were building with castings it would weigh a ton or more anyway..
If it weighs a ton you just need to continue construction on the base it's going to be working on......might be a good idea to start constructing the base that will be stand alone.........nothing "tinny" will be any good......think in terms of 50 X 50 X 3mm wall square steel tubing.
Ian.
Inertia does not actually matter too much in the real world, because the speeds the hobby machines move at are fairly low (relatively).
Thus, even lowly steppers accelerate to full speed pretty fast (in about 1 cm travel, about 1 sec)
And, most people build really light, small moving stuff, is using steppers.
Even steppers of nema 23 size, move my 200kg plus table, with stuff on it (upto 100 kg).
Push force with 3N steppers == 500 kgf.
Means it can lift a 500 kg load vertically at zero rpm.
It practice, you get about 1/3 torque from steppers, so 3Nm => 1 Nm => 150 kgf or so, at 600 rpm or so.
Best practice is actually a (HTD) belt drive, imo, ime although most dont use them.
Force = Torque (Nm) x 2 x pie / screw rise (in m) * screw efficiency (90% ballscrew)
Example.
F= 1.3 Nm (Nema 23 servo, continuos) x 2 x 3.14 / .005 m screw / 2 (2 is belt drive at 1:2)
= 3625 Nm x 90% = 2939 Nm = 293 kgf.
A direct drive re: stepper is problematic for milling machines, but ok for woodworking re: actual accuracy.
If you want more speed and accuracy and acceleration, you get outstanding results from servos, that cost approx. the same as bigger 34 size steppers and big stepper drives for them (80V and up).
Hi Han.....what you say is perfectly true......for a continuous motion........ but in the case of CNC anything the motion is a constant stop start and that translates into acceleration and deceleration of the load member every time the stepper moves from a standing start.
The fact that hundreds of thousands of CNC users are using steppers of varying strengths without too much drama is an indication that inertia is not a problem at all.
I think for simplicity, a sliding scale could be applied to state that for a given weight a certain size stepper will adequately do the job............eg, a 500kg weight on linear rails could be at the maximum weight capacity for a Nema 23 size stepper of 400oz/in whatever etc......dovetails or box way slides would have a different weight factor, and the pitch of the ball screw is another factor to consider.
I think that when you tune your motors with Mach 3 the accelerating and deceleration settings will take care of getting the load on the move without too much drama.,,,,,too abrupt a setting either way will lead to a stepper motor overheating.
Ian.
DAMN! I hate it when this happens. I was looking forward to the completion of this build. This happens so often. Must be frustrating to the participants that offered advice. Did his wife throttle him for spending all his waking hours in the shop or at work? Did it fall on him? We may never know.
Re: Yet another fixed gantry machine...
Originally Posted by Hartzell
Re: Yet another fixed gantry machine...
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