Re: BENCHTOP CNC SYSTEM

At 12:09 PM 8/21/1999 , you wrote:

>From: "CG" <cnk@...>
>
>

Please don't take my comments as being too biased, but I've been through a
lot of what you are contemplating now.

>To all benchtop CNC mill enthusiasts/dreamers:
>I've just finishing designing my 3-axis CNC benchtop milling machine, and I
>figured before I start making chips, I'd do a sanity check and try to get
>some feedback.


>Here is some of what I wanted:
>* zero-backlash
>* high rigidity (for limited steel-cutting, and accuracy)
>* decent feedrates (120 ipm)
>* generous travels (16" x-axis, 8" y- & z- axis)
>* low friction slides and screws (for speed and power requirements)
>* PC-based (Windows, pref.)
>* affordable (under $5k minus PC)
>* compact (forklift and crane not required...)

>To buy or not to buy?:

How about buying a small Rong Fu 45 bed mill with a dovetail column for the
Z-axis? It is same size as a mill/drill but with a longer travel on the z
axis (16" maybe??) Just add 5/8" ballscrews to it - pretty easy to do.
I am sure you could add a bigger diameter ballscrew to the column.

>CNC control system (currently available):
>* FlashCut CNC (max 7300 steps/sec)
>* serial cable to signal generator (MPU) box
>* Windows-based
>* lookahead capability
>* reads G-code and DXF
>CNC control system (if/when it is available):

>* Windows-based CNC control interface to IndexerLPT device driver
>* parallel port step/direction output
>* 90,000 steps/sec (allows more steps/rev for microstepping)
>* unlimited lookahead
>What do you think?

Set your PC up to use the EMC controller. The price is right- free and it
has a GUI. It reads G-codes, sorry not DXFs but a CAM program works for
generating G-codes. Why would you need a serial connection to a signal
generator when the parrallel port works just fine. Or if you want servos,
buy the Servo to Go card and then you can really move the table fast.

>
>Well, I was willing to spend $5K for a complete system, minus PC, but I
>think I will be spending more cash than that to build my own. The economy of
>scale is working against me on a one-off. Fortunately, I have access to a
>small machine shop. The mechanicals will require some tooling fixtures for
>assembly, most of which I can jerry-rig with a granite surface plate and
>some parallels, and there are other things that are hard to amortize over a
>production run of one unit.
>In any case, the breakdown of costs for purchased items (new), and estimated
>costs for machined items (in medium production quantities), not including
>tooling, assembly costs, etc., is:
>* MACHINE - $1500 - 3 Linear stages (complete, inc. ballscrews, bearings,
>etc.), machine base (welded 8" x 4" x .250" wall steel tube), and basic
>headstock
>* DRIVE SYSTEM - $1800 - Motors, drivers, power supplies, cables & switches
>* CNC CONTROL - $1100 - software and signal generator box
>* TOTAL: $4400
>

Here's what I would do ( and probably will for my next machine):

Machine $2000- Rong Fu 45 bed mill already built
Drive system - $250 Dan Mauch's 5 amp controller (price depending on how
many parts I have laying around to reuse. I buy lots of stuff from a
surplus shop for cheap)
Motors - $300 - triple stack steppers bought used over the internet (price
depends on timing of purchase and a lot of luck)
CNC Control- FREE
Total $2500

Dan


There's not a word yet for old friends who've just met...
~ Gonzo, The Muppet Movie