Circle Smoothness ‘beta’

I’ll talk a bit more about development at ShopBot and expand the ‘resolution’ theme from last month, more broadly taking up the issue of smoothness in cutting with ShopBots, and specifically reporting on some progress we are making. For a number of months now, we have focused software development on creating strategies for smoother tool motion by making improvements to both PC and Control Box software. Using a new algorithm that borrows somewhat from the anti-aliasing system of computer graphics, we’ve now improved on how ShopBots cut circles, arcs, and diagonals — providing motion that is more vibration free with an edge that is considerably smoother.

The improvement will be available for existing PRTalpha tools and PRTstandard tools that have been upgraded to the new Version 4g control board. The new software capabilities rely on the speed of the PRTalpha micro-controller and outboard software (also now used in the PRT V4g control boards) — which means, that at least for the moment, it will not work on older PRTs that have not been upgraded.

Because the software has been significantly modified in the process of implementing this new contouring system, it represents a major revision number change (now Sb3.5.xx) and needs more extensive testing than a minor revision or maintenance upgrade. For this reason, before we make an official release of the software, we are going to make it available for ‘beta’ testing by those who have an interest in trying it out and hopefully providing us a little feedback on what is working well and what is not. [Link for Downloading Beta Software]

Our expectation is that after a few weeks of thorough testing here at ShopBot and testing by those who try the beta version, this new upgrade in cutting performance will be ready for production use on all PRTalpha and PRT V4g ShopBots. Beta testers will notice that there are also several other enhancements in the new version of the software, including more efficient buffering of the streamed motion commands which allows high-resolution tools (and V4g boards) to attain higher speeds in cases where PC capabilities may have been limiting. We’ll detail all these changes when we release the official version. Nonetheless, our primary focus in this recent work has been on cutting smoothness improvements that can be achieved with software and made broadly available to existing ShopBotters.

So let me put this software improvement in the context of the earlier resolution discussion and with reference to specific tools:

PRTstandard. Upgrading to the Version 4g control board will improve cutting smoothness by increasing the resolution of stepping (as provided by the higher resolution stepping of the Gecko drivers and higher speed of the controller; you’ll also get 2-3 times greater speeds). The new Sb3.5 version of the software will provide further enhancement to cutting smoothness (and in some cases higher speeds) because of the improved strategy for contouring.

PRTalpha. Upgrading to the new Sb3.5 software will provide smoother cutting for all PRTalpha tools. Even greater enhancement to smoothness can be gained with higher resolution gearing on PRTalpha tools. As discussed in the previous installment, we are now optionally offering 7.2 gearhead motors and drives on PRTalpha tools (for $750). We are making this same option and pricing available as a retrofit for any existing PRTalpha owner interested in upgrading. Our new PRSalpha tools, available next year, will come standard with the 7.2 gearheads.

new PRS ShopBot

new PRS ShopBot

With PRTalpha tools there is an additional option. Because the control system is now faster, you could exchange your drives with us for ones that run at a higher step resolution. As indicated previously, increasing microstepping ratios in this way does not offer the full advantage of improved resolution through mechanical gearing, it nonetheless may offer some enhancement to smoothness. At this point, its hard to say how much improvement. Over the next few weeks we will collect data on the effectiveness of this change and develop some guidance on whether it is worth the effort.

Here’s what I’d suggest if you are interested in upgrading the smoothness of your PRTalpha cutting:

  • 1. Try the new software, either the current beta version, or in a few weeks the official release version.
  • 2. Switching to higher resolution drives may offer some additional enhancement.
  • 3. And going even further with smoothing, higher resolution stepping and increased power is available if you decide on the optional 7.2 gearheads.

new PRS ShopBot

new PRS ShopBot

We are highly committed to providing tools with the same performance capabilities as much more expensive CNCs. That includes cut smoothness. We’ll continue to work on making cutting improvements through creative software, and gearing and drive solutions. In addition, our development group is working to improve the mechanical capabilities to enhance smoothness. Next month I’ll report on advances made on our new PRS line of ShopBots. For now, keep in mind that smoothness of cutting depends on many factors. Cutter quality is very important as is overall stiffness and rigidity of your gantries. If smoothness is your highest priority you will always want to make sure that your cutter is sharp and speeds and feeds are optimized. You will also want to make sure that there is no excessive play in your tool, particularly in the Z axis. Keeping things tight goes a long way to reduce chatter. If your tool has seen a lot of use, also check the pinions for wear. We are expecting that by attending to these factors the new software will provide you with very impressive cut quality from PRTalphas and PRTstandard 4gs.

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