Aluminum profile and alu plate 1500mm x 600mm x 150mm working area, first cnc.

[Boyan Silyavski]

I believe ~10m.min is very good for a DIY machine, not servo driven. i would not trust steppers for faster speeds. Also there is that thing that the machine to benefit from the fastest speeds it must be big. See the formula at the bottom of that page http://www.prusaprinters.org/calculator/

My machine is servo driven and as snappy as a bullet , acceleration 3000mm/s2 and at >15000mm/min looks bloody dangerous and i am very very careful not to make a mistake. Stepper driven machine i am not sure that could achieve that. Think more 1000mm/s2, if i am wrong sb correct me.

What i am saying is you need distance to achieve that theoretical speed. Your aim should be to achieve higher acceleration, than speed.

PS Plus all must be perfectly rigid, especially Z to benefit from that speeds

[JAZZCNC]

I believe ~10m.min is very good for a DIY machine, not servo driven. i would not trust steppers for faster speeds. Also there is that thing that the machine to benefit from the fastest speeds it must be big. See the formula at the bottom of that page

Fact using stepper doesn't mean can't have higher feeds. The feeds depends on pitch. Could have 50,000mtr/min quite easily and still have acceptable acceleration with the right pitch.
What stepper does restrict is having High Feeds and High Resolution. The price you pay to achieve high speed is Low resolution.

Also To answer your question if Stepper can achieve 3000mm/s/s and 15,000mm is yes.!! . . . . . . Could it do this and hold the same resolution at your size/weight of machine then No.!! . . . Hence why you wouldn't fit steppers.

However on smaller machine with lighter gantry then yes it's possible with careful selection of pitch and motors etc.

Good machine will have nice balance of speed and Acceleration. IME for Medium machine size which this is, 10,000mm/min and 1500mm/s/s is all thats required.

[Boyan Silyavski]

Good machine will have nice balance of speed and Acceleration. IME for Medium machine size which this is, 10,000mm/min and 1500mm/s/s is all thats required.

I think also that one should be very happy he found this forum and all information here. I will give a reward if sb finds me commercial machine that is not servo driven that could actually achieve that, speaking about cheap Chinese knockoffs and other ebay style machines.


Actually for intricate carvings on aluminum i lower the acceleration to 1000-1500 for better results. Its difficult to have all in one. Its not a big deal, just change one number in the controller. For wood i could push it even higher than that 3000 but not a real need.

[JAZZCNC]

I will give a reward if sb finds me commercial machine that is not servo driven that could actually achieve that, speaking about cheap Chinese knockoffs and other ebay style machines.

Not quite sure what your saying here Boyan.? . . . . Are you trying to say this isn't achievable with steppers.? Because if so then your very wrong.!
Just about every machine I build will or should say is designed to achieve these speeds or very close to them. Some Smaller machines will achieve well in excess of 10mtr/min and 1500mm/s/s.
Don't actually run them or tune them at those speeds for reliabilty reasons but they will do it if required.

I find above 2000/s/s gives negative affect to machine as it's far too jerky on short moves leading to poorer surface finishes.

[Boyan Silyavski]

Not quite sure what your saying here Boyan.? . . . . Are you trying to say this isn't achievable with steppers.? Because if so then your very wrong.!

I am saying you are our hero and i am happy that i found this forum and we learned to build machines that are superb for the money and better than crappy commercial ones where usually they have some major flaw in design.

[Clive S]

I am saying you are our hero and i am happy that i found this forum and we learned to build machines that are superb for the money and better than crappy commercial ones where usually they have some major flaw in design.

creep

[JAZZCNC]

I am saying you are our hero and i am happy that i found this forum and we learned to build machines that are superb for the money and better than crappy commercial ones where usually they have some major flaw in design.

Ah ah now your just blowing smoke up my jacksy.! . . . . . I understand.

[Davek0974]

Your aim should be to achieve higher acceleration, than speed.

This is the vital fact, I have found the negative side of this equation - low accel/high speed and what it does with Mach3 is give terrible contour following because of the constant velocity engine Mach uses. Its not just a little bad, it's the difference between turning out scrap and turning out parts.

I have retuned with lower speed as higher acceleration was too jerky on my old Bridgeport conversion and its all working nicely now.

[JAZZCNC]

This is the vital fact, I have found the negative side of this equation - low accel/high speed and what it does with Mach3 is give terrible contour following because of the constant velocity engine Mach uses. Its not just a little bad, it's the difference between turning out scrap and turning out parts.

I have retuned with lower speed as higher acceleration was too jerky on my old Bridgeport conversion and its all working nicely now.

Exactly Dave. Like all things in life Balance is the Key. Good machine is tuned with nice balance of speed and Acceleration.
Getting wrong either way will have negative affect on machines performance in different areas of work type.

For instance your case of high feed but with low accelration caused corner rounding. This was on relatively small parts with tight radius on small machine. On larger machine like router with larger parts say doors or shaped work tops etc with no or large radius sections then high feeds with Lower Accel will be ideal.

Different strokes for different folks, Or machines in this case.!

This is why Mach3 and some other Control software will let have you have different profiles which can be used to have machine tuned or setup differently to optimise the type of work your doing.