So I have the kit assembled and printing. I ordered a proper E3D V6 hotend, and had to rework the hotend mount to lower it below the axis endstop switch, but not that big a deal and now I'm comfortable the hotbed won't cook the microswitch on homing and the lower layers. Of course now trying to dial in the speeds for printing seem to be rather difficult so I was curious to what config / speeds others are achieving with the Smartrapcore Alu Kit. I'm also wondering if changing the XY motors for something with a higher torque and lower impedance might be better for higher speed? The kit had 17HS3001-20B, but I have a few 17HS16-2004S1 motors on hand that makes me wonder if it'll will increase speeds or not.

Right now, I'm still trying to get it to travel without the decel skipping steps and going "clunk" at the end of the travel, but currently I have the following in my Marlin config:

#define DEFAULT_AXIS_STEPS_PER_UNIT   {160,160,160,290}  // GT2 Belts with 1/32 step count, MK8 extruder
#define DEFAULT_MAX_FEEDRATE          {500, 500, 70, 50}    // (mm/sec)
#define DEFAULT_MAX_ACCELERATION      {7000,7000,2000,10000}    // X, Y, Z, E maximum start speed for accelerated moves.

#define DEFAULT_ACCELERATION          900    // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION  3000   // X, Y, Z and E max acceleration in mm/s^2 for retracts

// The speed change that does not require acceleration (i.e. the software might assume it can be done instantaneously)
#define DEFAULT_XYJERK                20.0    // (mm/sec)
#define DEFAULT_ZJERK                 10.0     // (mm/sec)
#define DEFAULT_EJERK                 5.0    // (mm/sec)

The DEFAULT_MAX_ACCELERATION for 7000 was established with trial and error moving with G1 X10 Y180 F7000 commands before it stopped going clunk on those commands. But every now and again it will go clunk during a print on a travel move a lot smaller of distance. And DEFAULT_ACCELERATION was established during a print until it stopped going "clunk" using the LCD to manipulate this on the fly.

I've been trying to use the default speeds in a slic3r for the moment, and it works (sort of) but with my bowden setup I would think unless I'm into a processing limit in the Arduino Mega it should be capable of going much faster still. And it doesn't seem to make a difference on the "clunk" when I mess with XY jerk.

Can anyone else post perhaps a slic3r config file or the marlin setup to make sure I'm not off in the weeds somewhere?

Well I was very unimpressed with the supplied motors (casun ,17HS202-3C) they are underpowered for this application and at the current level that is sufficient to avoid skipped steps, they run hot. I'd change them for any 40-48mm motor with 1.68A current capacity. They will be quieter, cooler and smoother at the same current.

Haven't really maxed out this printer in speed terms I stopped tinkering at the point I was getting good quality prints, but I am curious. You say you arrived at 7000 acceleration by testing to see how high you could go before motor stall? How much headroom have you allowed? I don't know if 7000 is ambitious I haven't pushed it up that high I'm set at 6000. But you might be getting the clunk as it's on the limit.

I've encountered stuttering from the arduino maxed out using a full graphics controller but none with the discount smart controller attached.

As for jerk I do find that changing these values seems to have less effect than I expect. This thread seems to have a technical description of jerk [forums.reprap.org]

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions