Re: [CAD_CAM_EDM_DRO] DIY Router Design questions ?

How aboout building a 3D duplicating machine that can be set up to run as
both a manually operated (for one off jobs) AND a CNC (for machining many
copies) machine?

Smoke

>
>----- Original Message -----
>From: <rab@...>
>
>> My first thoughts are to use bolt together aluminium extrusions with
>> linear slides, leadscrews and servos, but have a lot of questions.
>
>Aluminum extrusions (i.e. 80/20) are nice but very expensive. They are
>worth the price if you don't have welding capability. Steel box tubing

will

>produce a better router for less money and more work.
>
>
>> In gantry style systems where the gantry is driven from both sides,
>> what's the best way of synchronising both the leadscrews in case the
>> gantry skews ?
>
>Les Watts built a nice router using dual X leadscrews and a jackshaft. The
>cost of precision right angle gearboxes outweighed the savings of using one
>motor. Friction losses were also high - on the order of 500 watts.
>
>> Does a rack and pinion have any advantages over a leadscrew ?
>
>R&P is definitely less expensive and less sensitive to contamination. The
>other, often overlooked problem with screws is shaft whip. Long screws

will

>buzz like a guitar string if you spin them fast. We are having problems
>with a machine in my shop that uses a 1 inch diameter 6ft ballscrew at 400
>rpm. The low budget ballscrews have quite a bit of drunkenness to them and
>tend to excite easily. We are designing the 10 foot router table with
>rotating ballnuts to get around this problem.
>
>I would go with R&P if I had it to do over. The X axis screws and nuts

were

>about $900. The custom spindles for the ballnuts will have a fabricated
>cost of about $300 each.
>
>> Is it worth looking at linear motors ?
>
>What is your budget?
>
>> Given that each part would need use of a roughing and a finishing
>> (fine detail) tool, I'm looking at ways of mounting two router heads
>> to save tool-changing, has anyone tried this ?
>
>We looked at a Colombo high frequency spindle and a six position ATC. The
>toolholders alone are $170 each. The spindle was $5000. The ATC would

have

>been about $5000. Porter Cable routers are $130-$290 each and dirt cheap

to

>rebuild. I can mount four of them on a Z axis turret for little more than
>the cost of four ISO-30 toolholders alone. The Colombo can cost $500-$1000
>just to rebuild.
>
>Doug
>
>
>
>
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