Ok so I wrote out a couple gcode scripts the first is to show linear motion, I had meant to run it at 100mm/s on the first video but had the feed rate at 150% so I believe that should be 150mm/s the motion is nice and smooth Then I took the gcode for a circle with a diameter of about 41mm and stripped the Z out of it. I ran it 37.5mm/s for 3 circuits which was okish 66.6mm/s for 2 circuits which was not good then 100mm/s which is terrible

Ok it would be helpful if you describe what you mean in word too. Videos and pictures have room for interpretation. But I think I know what you mean. First you do not think it is a slicer problem. Second it is not a problem limited to RC4 or RC5 but it is also in RC3 aka the official BB firmware. Third it is the strange side sounds you hear on that circle and I think I had that too in circles like I write in my other post... Is that correct?

Yes that seems like a good summation. In words: As it travels around the circle it starts to hesitate/stop/jitter at certain points. These points most notably seems to be when one of the steppers has to reverse motion to which there are 4 such spots on a circle. When the hesitation happens it ends up destroying the outer perimeter making the print useless. It seems if I run the big box slow enough the probable diminishes or goes away which seems to be maybe around 30mm/s which to me seems to me like the motion system shouldn't choke at that speed, I should think I should be able to at least be able to slice at 50mm/s

I am currently running your RC4 now, Here is a link to the object that kicked all this off. http://www.thingiverse.com/thing:1480191 Here is a link to the current S3D settings I am using, beware I have a 0.8mm nozzel on right now as I wanted thicker walls for the container. Hopefully it works.

Here is a couple prints in PLA the left was at 25mm/s the right was 20mm/s The side with the messed up extrusion is when y is reversing, the smooth side is when X is reversing.

That is a ballpark, they do not need to be that high in practice. Best to tune them. Currently I'm running 0.576/0.253/0.654/0.510v (XYZE). I reduced the Y a bit as it is geared down by the belt drive, this quieted travel considerably. I increased the Z a bit as it is being split between the two motors. I found the recommended ~0.55v was about the best for X and E. Tuning was done by ear, with testing at 125mm/s for skipping steps.

@Miasmictruth it looks to me like stalling, which is when the motion control algorithm can't get data fast enough out of the SD card. If memory serves Simplify3D is particularly bad about this. I think you said you don't experience this with Slic3r, is that true? IIRC Simplify3d breaks segments into smaller segments than most slicers.

Thats partially true it seems less bad with slic3r after further experimenting I was having an issue there too. I need to work on the slic3r profile more as I haven't been able to get it to print right yet I was just running it without filament and watching the motion. I did try those numbers for the voltage, I will again tomorrow if I get a chance to work on it, thanks.

I just had a thought as I am about to go to bed... If I lower the polygon count of the model maybe it will create less gcode when sliced and therefore print smoother... Something to try tommorow.

So I think @elmoret you are right I saved the model as low instead of high resolution on fusion360, resliced the model in S3D and right away I could see a drop in the number of lines per layer probably about a 10-20 percent difference. I extracted 1 layer and stripped away the Z like before and made a script with the before and after with both the new and old code. The first 4 passes are the low resolution code at 55mm/s, the second 4 passes are the high resolution code at 55mm/s Low res runs smooth in my opinion as soon as it switches to high you can hear/see the chatter as it stalls. Slicing past 55mm/s and I get in the same trouble with the low res. I will see what slic3r makes of it tonight, aside from that what can we do to prevent this? A way maybe to force the print to slow down if there if the line segments are too short but alow it to speed up when they are long? I am sure if can happen like this it could happen in the middle of other prints depending on geometry.

It looks as though you're running into a limitation of 8-bit electronics. You can likely tweak with slicer settings and whatnot to mitigate it, but 32 bit electronics (Duet, for example) are better equipped to cope with high polygon/low segment length models.

@elmoret I think there is something more going on. My first printer is a cheapo Chinese printer off ebay, I can run the same script and hit around 75mm/s and it still seems smooth as silk. Now while its true that the lower res script preformed better on both printers there no reason I can think of that the BigBox should under preform a 400 dollar printer. Could someone run the following scripts on their BigBox and tell me how fast they can run before the motion starts to go wrong. The first script is a low resolution circle I can hit around 55mm/s (less while I am printing for some reason maybe becuse there is no extruding or Z commands) The second script is a high resolution circle I am running both of Repetier host. Both are set to 50mm/s currently Script 1 G1 X115.065 Y85.938 F3000 G1 X115.558 Y85.432 G1 X116.590 Y84.476 G1 X117.132 Y84.024 G1 X118.257 Y83.180 G1 X118.843 Y82.786 G1 X120.049 Y82.062 G1 X120.672 Y81.730 G1 X121.946 Y81.133 G1 X122.600 Y80.868 G1 X123.929 Y80.405 G1 X124.606 Y80.208 G1 X125.976 Y79.885 G1 X126.670 Y79.758 G1 X128.065 Y79.578 G1 X128.769 Y79.523 G1 X130.175 Y79.487 G1 X130.881 Y79.505 G1 X132.283 Y79.614 G1 X132.984 Y79.705 G1 X134.367 Y79.957 G1 X135.055 Y80.119 G1 X136.405 Y80.512 G1 X137.072 Y80.744 G1 X138.375 Y81.274 G1 X139.014 Y81.573 G1 X140.256 Y82.234 G1 X140.861 Y82.598 G1 X142.028 Y83.383 G1 X142.593 Y83.807 G1 X143.673 Y84.708 G1 X144.191 Y85.187 G1 X145.173 Y86.195 G1 X145.639 Y86.725 G1 X146.512 Y87.828 G1 X146.921 Y88.403 G1 X147.676 Y89.590 G1 X148.024 Y90.205 G1 X148.653 Y91.463 G1 X148.936 Y92.110 G1 X149.432 Y93.426 G1 X149.646 Y94.099 G1 X150.005 Y95.459 G1 X150.149 Y96.150 G1 X150.366 Y97.540 G1 X150.438 Y98.242 G1 X150.511 Y99.647 G1 X150.511 Y100.353 G1 X150.438 Y101.758 G1 X150.366 Y102.460 G1 X150.149 Y103.850 G1 X150.005 Y104.541 G1 X149.646 Y105.901 G1 X149.432 Y106.574 G1 X148.936 Y107.890 G1 X148.653 Y108.537 G1 X148.024 Y109.795 G1 X147.676 Y110.410 G1 X146.921 Y111.597 G1 X146.512 Y112.172 G1 X145.639 Y113.275 G1 X145.173 Y113.805 G1 X144.191 Y114.813 G1 X143.673 Y115.292 G1 X142.593 Y116.193 G1 X142.028 Y116.617 G1 X140.861 Y117.402 G1 X140.256 Y117.766 G1 X139.014 Y118.427 G1 X138.375 Y118.726 G1 X137.072 Y119.256 G1 X136.405 Y119.488 G1 X135.055 Y119.881 G1 X134.367 Y120.043 G1 X132.984 Y120.295 G1 X132.283 Y120.386 G1 X130.881 Y120.495 G1 X130.175 Y120.513 G1 X128.769 Y120.477 G1 X128.065 Y120.422 G1 X126.670 Y120.242 G1 X125.976 Y120.115 G1 X124.606 Y119.792 G1 X123.929 Y119.595 G1 X122.600 Y119.132 G1 X121.946 Y118.866 G1 X120.672 Y118.270 G1 X120.049 Y117.938 G1 X118.843 Y117.214 G1 X118.257 Y116.820 G1 X117.132 Y115.976 G1 X116.590 Y115.524 G1 X115.558 Y114.568 G1 X115.065 Y114.062 G1 X114.136 Y113.006 G1 X113.698 Y112.452 G1 X112.883 Y111.306 G1 X112.504 Y110.710 G1 X111.811 Y109.486 G1 X111.496 Y108.854 G1 X110.932 Y107.565 G1 X110.683 Y106.905 G1 X110.256 Y105.565 G1 X110.076 Y104.882 G1 X109.788 Y103.505 G1 X109.679 Y102.808 G1 X109.535 Y101.408 G1 X109.498 Y100.703 G1 X109.498 Y99.297 G1 X109.535 Y98.592 G1 X109.679 Y97.192 G1 X109.788 Y96.495 G1 X110.076 Y95.118 G1 X110.256 Y94.435 G1 X110.683 Y93.095 G1 X110.932 Y92.435 G1 X111.496 Y91.145 G1 X111.811 Y90.514 G1 X112.504 Y89.290 G1 X112.883 Y88.694 G1 X113.698 Y87.548 G1 X114.136 Y86.994 Script 2 G1 X114.227 Y86.874 F3000 G1 X114.717 Y86.307 G1 X115.228 Y85.758 G1 X115.758 Y85.228 G1 X116.307 Y84.717 G1 X116.874 Y84.227 G1 X117.459 Y83.759 G1 X118.060 Y83.311 G1 X118.678 Y82.886 G1 X119.310 Y82.484 G1 X119.957 Y82.106 G1 X120.617 Y81.751 G1 X121.290 Y81.420 G1 X121.975 Y81.115 G1 X122.670 Y80.834 G1 X123.374 Y80.579 G1 X124.088 Y80.350 G1 X124.810 Y80.147 G1 X125.538 Y79.971 G1 X126.273 Y79.821 G1 X127.012 Y79.699 G1 X127.756 Y79.603 G1 X128.502 Y79.535 G1 X129.251 Y79.494 G1 X130.000 Y79.480 G1 X130.749 Y79.494 G1 X131.498 Y79.535 G1 X132.244 Y79.603 G1 X132.988 Y79.699 G1 X133.727 Y79.821 G1 X134.462 Y79.971 G1 X135.190 Y80.147 G1 X135.912 Y80.350 G1 X136.626 Y80.579 G1 X137.330 Y80.834 G1 X138.025 Y81.115 G1 X138.710 Y81.420 G1 X139.383 Y81.751 G1 X140.043 Y82.106 G1 X140.690 Y82.484 G1 X141.322 Y82.886 G1 X141.940 Y83.311 G1 X142.541 Y83.758 G1 X143.126 Y84.227 G1 X143.693 Y84.717 G1 X144.242 Y85.228 G1 X144.772 Y85.758 G1 X145.283 Y86.307 G1 X145.773 Y86.874 G1 X146.241 Y87.459 G1 X146.689 Y88.060 G1 X147.113 Y88.678 G1 X147.516 Y89.310 G1 X147.894 Y89.957 G1 X148.249 Y90.617 G1 X148.580 Y91.290 G1 X148.885 Y91.975 G1 X149.166 Y92.670 G1 X149.421 Y93.375 G1 X149.650 Y94.088 G1 X149.853 Y94.810 G1 X150.029 Y95.538 G1 X150.179 Y96.273 G1 X150.301 Y97.012 G1 X150.397 Y97.756 G1 X150.465 Y98.502 G1 X150.506 Y99.251 G1 X150.520 Y100.000 G1 X150.506 Y100.749 G1 X150.465 Y101.498 G1 X150.397 Y102.244 G1 X150.301 Y102.988 G1 X150.179 Y103.727 G1 X150.029 Y104.462 G1 X149.853 Y105.190 G1 X149.650 Y105.912 G1 X149.421 Y106.625 G1 X149.166 Y107.330 G1 X148.885 Y108.025 G1 X148.580 Y108.710 G1 X148.249 Y109.383 G1 X147.894 Y110.043 G1 X147.516 Y110.690 G1 X147.113 Y111.322 G1 X146.689 Y111.940 G1 X146.241 Y112.541 G1 X145.773 Y113.126 G1 X145.283 Y113.693 G1 X144.772 Y114.242 G1 X144.242 Y114.772 G1 X143.693 Y115.283 G1 X143.126 Y115.773 G1 X142.541 Y116.242 G1 X141.940 Y116.689 G1 X141.322 Y117.114 G1 X140.690 Y117.516 G1 X140.043 Y117.894 G1 X139.383 Y118.249 G1 X138.710 Y118.580 G1 X138.025 Y118.885 G1 X137.330 Y119.166 G1 X136.626 Y119.421 G1 X135.912 Y119.650 G1 X135.190 Y119.853 G1 X134.462 Y120.029 G1 X133.727 Y120.179 G1 X132.988 Y120.301 G1 X132.244 Y120.397 G1 X131.498 Y120.465 G1 X130.749 Y120.506 G1 X130.000 Y120.520 G1 X129.251 Y120.506 G1 X128.502 Y120.465 G1 X127.756 Y120.397 G1 X127.012 Y120.301 G1 X126.273 Y120.179 G1 X125.538 Y120.029 G1 X124.810 Y119.853 G1 X124.088 Y119.650 G1 X123.374 Y119.421 G1 X122.670 Y119.166 G1 X121.975 Y118.885 G1 X121.290 Y118.580 G1 X120.617 Y118.249 G1 X119.957 Y117.894 G1 X119.310 Y117.516 G1 X118.678 Y117.114 G1 X118.060 Y116.689 G1 X117.459 Y116.241 G1 X116.874 Y115.773 G1 X116.307 Y115.283 G1 X115.758 Y114.772 G1 X115.228 Y114.242 G1 X114.717 Y113.693 G1 X114.227 Y113.126 G1 X113.759 Y112.541 G1 X113.311 Y111.940 G1 X112.886 Y111.322 G1 X112.484 Y110.690 G1 X112.106 Y110.043 G1 X111.751 Y109.383 G1 X111.420 Y108.710 G1 X111.115 Y108.025 G1 X110.834 Y107.330 G1 X110.579 Y106.626 G1 X110.350 Y105.912 G1 X110.147 Y105.190 G1 X109.971 Y104.462 G1 X109.821 Y103.727 G1 X109.699 Y102.988 G1 X109.603 Y102.244 G1 X109.535 Y101.498 G1 X109.494 Y100.749 G1 X109.480 Y100.000 G1 X109.494 Y99.251 G1 X109.535 Y98.502 G1 X109.603 Y97.756 G1 X109.699 Y97.012 G1 X109.821 Y96.273 G1 X109.971 Y95.538 G1 X110.147 Y94.810 G1 X110.350 Y94.088 G1 X110.579 Y93.374 G1 X110.834 Y92.670 G1 X111.115 Y91.975 G1 X111.420 Y91.290 G1 X111.751 Y90.617 G1 X112.106 Y89.957 G1 X112.484 Y89.310 G1 X112.886 Y88.678 G1 X113.311 Y88.060 G1 X113.759 Y87.459

I have a vast improvement but even printing much slower then I think I should have to 20-35mm/s I am still getting artifacts most notably focused in one quadrant of the print. Tired embedding the photos this time.. Still have to click on them :/

Here is something interesting, it seems that when I slice using Slic3r the reason it was different it seems it caps the max velocity of circles at 30mm/s somehow. Which the reason I though Slic3r wasn't working either is that I manually boosted the feed rate with repetier host so of coarse I would end up too fast. Which I have to award @elmoret another victory lol, thank you again. Also Thank you @Alex9779 for running some interesting experiments with me. I am still getting some odd things out of S3D before I bought the BigBox I always used Slic3r so still getting used to S3D

@Miasmictruth so the conclusion is that, in fact, more bits DOES make a difference in certain situations? I remember when this came up last year the conclusion at the time was that the software had not yet been written to take advantage of 32bit systems so Marlin / Rumba was an excellent choice. I must admit that, when I printed some cylinders, I didn't notice any jerkiness, but BB did faithfully reproduce the mesh in plastic: the polygonal nature of the "medium" setting export from Fusion360 was VERY visible (and to touch) and even the "high" setting is perceptible if you turn the part at the right angle to the light (on 200 and 250mm diameter cylinders respectively).