[EMS Discuss] Why are CNC Kits so Expensive?

[Ben Hallert - Vipmail]

I wonder, do threaded rods trade speed for accuracy?  I think I heard the belts are preferable for extrusion printing because you HAVE to be moving at least sort of quickly to keep the melted plastic under control, but I may have misheard.

- Ben

On Jun 20, 2012, at 2:59 PM, Bob Miller <EMAIL HIDDEN> wrote:

> On Wed, Jun 20, 2012 at 2:50 PM, Josh Marinacci <EMAIL HIDDEN> wrote:
> 
>> Why does the Parallel Port latency matter?  I would think that the computer
>> would download the instructions into some sort of board inside the CNC
>> machine which does the actual drawing.  It seems like 1k of RAM would be
>> enough to have a decent buffer of a few instructions.
> 
> Hi, Josh.
> 
> If you have a dedicated processor driving the motors, then latency at
> the host does not matter.
> I believe that most parallel port designs are using the PC to drive
> the motors directly, so sub-
> millisecond timing is necessary.
> 
>> Another question:  belt and pulley vs threaded rod? What's the better way to
>> create linear motion?
> 
> I'll look forward to learning that, too.  I believe Kassie's RepRap
> uses belts for the X and
> Y axes and threaded rod for Z.
> 
> -- 
> Bob Miller                              K<bob>
>                                         EMAIL HIDDEN
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