Hi,
I'm experimenting with using Repetier for my 3 axis CNC router I built. I've chose Repetier because it allows for the fastest and smoothest speeds of all the G code interpreting Arduino firmwares I've tried (GRBL, Teacup, Marlin).

I have 2 questions though:

CNC routers need a much slower acceleration than 3D printers since they have much greater mass to move. Obviously I can just adjust this in the config, but if I set acceleration to anything lower than 350 mm/s/s it no longer decelerates. i.e. it accelerates to speed, reaches the set distance and stops abruptly. Anybody know a cause or solution for this?

Is there a way to set default speed for G1/G0. I see they're one in the same in Repetier but there doesn't seem to be an option to adjust it and it defaults pretty slow. Since CNCs typically use G0 for travel and G1 for feed my travel moves end up being slower than my feed moves. Not having a separate G1 is no problem though. My gcode processor adds feed rates to all G1s.

Thanks

Edited 1 time(s). Last edit at 04/23/2013 12:36PM by miro87043.

Have you tried moving X, Y and Z at the same time? There's a comment in the Repetier source code which says it can't do such things. I guess this firmware is pretty thightly coupled to the layered printing process (and doing well so).

If you want to speed up Teacup, make sure you set the allowed max speeds in config.h. Opposed to other firmwares they're set low by default to be on the safe side. If this is still not sufficient, look at the second half of this post: [forums.reprap.org]

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Traumflug Wrote:
-------------------------------------------------------
> Have you tried moving X, Y and Z at the same time?
> There's a comment in the Repetier source code
> which says it can't do such things. I guess this
> firmware is pretty thightly coupled to the layered
> printing process (and doing well so).
>
> If you want to speed up Teacup, make sure you set
> the allowed max speeds in config.h. Opposed to
> other firmwares they're set low by default to be
> on the safe side. If this is still not sufficient,
> look at the second half of this post:
> [forums.reprap.org]
> #msg-196672

I'm not sure why it says X, Y and Z cannot be moved at the same time, because this is not the case. I've ran many dry-runs with no problem there.

Thanks for the link! I'll try teacup again. I must have been using an older version. I was hitting the 16,000 steps/s limit. Repetier gets around this by step doubling/quadrupling at a loss of smooth operation at high speeds. You claim 48,000 steps/s on a 20 Mhz ATmega; does this mean I would get 38,400 on a 16 Mhz ATmega? This may suffice. Using teacup would also solve my other two issues of default travel and acceleration <300 mm/s/s.

For a better understanding I'll give my setup. Arduino mega 2560 (using ramps 1.4 pins, but shield not needed for this implementation), Compumotor DB drives (4 amp drivers capable of 1/127 stepping, they're set to 1/50 though) to NEMA 34s. In Repetier (with its doubling/quadrupling function) I can effectively run at 125.313 steps/mm and 400 mm/s or
50,125.2 steps/second.

Traumflug,
I tried your new accel_clock branch and did not achieve an higher steps/second. I maxed out at just over 12,000 steps per second before the firmware locked up. With my settings shown in my previous post this limits my speed to under 100 mm/s or 6000 mm/min.

Quote

You claim 48,000 steps/s on a 20 Mhz ATmega; does this mean I would get 38,400 on a 16 Mhz ATmega?

Yes.

Quote

I maxed out at just over 12,000 steps per second

That's disappointing. Looks like I have to review this again. Having it lower than the previous code is a bit strange, though. ACCEL_CLOCK definitely removes quite some code from the step interrupt.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY