[EMS Discuss] Why are CNC Kits so Expensive?

Kassandra Kaplan EMAIL HIDDEN
Mon Jun 18 16:02:55 PDT 2012


You are right on about high tolerances and slop (backlash), but there is more to it.

1) small market=high cost . particular since they use "custom" (compared to a  threaded rod) part in each design. 

2)The machining time can't decrease exponentially.  Cutting is based on material limits.  lead screws are cut with the best technology.  Threaded rods are made with the best tech that is good enough.

3) CNC are made for big budget and fill that budget with the best.  This is particularly true where better machine means you can sell more expensive product.

4) cost equal importants.  With 10 dollars more I can make anything better!  Even if I just add an extra conformation that it's perfect.  If your business was on the line would it be worth it.

4) printer ports have direct pin support and predictable latency.  No other common technology (USB, FireWire) can say that.  With milling requires moving carefully and even small hiccups could mess things up. Particular if you use you mill with a lathe. (micro controllers are changing this game slowly).

That said CNC can be cheaper.  Heck the hundred dollar CNC is possible. So go for it and I would love to help.

どうぞおげんきで 
Kassie

On Jun 18, 2012, at 3:20 PM, Rick Osgood <EMAIL HIDDEN> wrote:

> I don't honestly know the answer but I would guess that maybe it has something to do with the fact that these parts have to be machined with really tight tolerances.  If they are off by even a little it can add slop and make your CNC machine less accurate.  I would think that in order to make parts with such tight specifications they might need more expensive equipment and maybe a lot more careful calibration and maintenance.  I could be totally wrong but it seems to fit.
> 
> Kassie has built a few 3d printers so I wonder if she would have discovered the answer in any of her research.
> 
> Rick
> 
> On Mon, Jun 18, 2012 at 2:40 PM, Josh Marinacci <EMAIL HIDDEN> wrote:
> I realize this is an extremely broad and open ended question, so please allow me to narrow it down a bit.
> 
> A few weeks ago I came across a video of a tiny drawing robot. It can draw using a regular pen controls on the x and y axes with what appears to be a screw + stepper drive, plus a tiny servo to move the pen up and down. The builders think they can mass produce it for 80$ but their design is not ready yet, or for sale.  Inspired by this video I began to research drawing machines, which led to plotters, which led to general CNC machines.
> 
> Now, a few weeks later I know far more about stepper motors and linear motion systems than I would like.  I still want to know why, however, they are so expensive?  Not the electronic parts but the mechanical ones.  Why is a linear slide so expensive? Why are steppers 30$ or more each.  Why is an ACME linear screw as much as several hundred dollars.  Why is a simple coupler over 10$?
> 
> My real question is what are the market and manufacturing reason that these parts are so expensive, especially since the base technology hasn't changed in many years (also, why do all CNC drive kits require a Parallel Port?  USB is nearly 2 decades old now).   
> 
> Am I simply spoiled by software and moore's law where things become drastically cheaper every few years?
> 
> 
> Once I figure this out, I can go onto my next challenge: designing a < 100$ CNC plotter.
> 
> Thanks.
> - J
> 
> -- 
> Josh Marinacci
> joshondesign.com
> 
> 
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