Electronic speed controllers ?? Which one ?

[wemme]

Hello All.
I'm interested in cutting Metals and I've noticed some of you are using electronic speed controller to adjust the speed of your routers.

Which models have you guys used and with what results.
I am worried about switching harmonics causing damage to my router.

[Brady Watson]

Bart,
Just about any of the ones available thru Grizzly or Harbor Freight will work, provided that your router doesn't have a 'soft start'.

-Brady

[wemme]

I have a 230V 50hz porter cable on the way from shopbot.
it is a single speed only and i don't think it has a soft starter but i'll have alook into that.

[dvanr]

Bart,

Try this thread. http://www.talkshopbot.com/forum/messages/29/87.html

In the second post there is mention of using a Variac to control the router.

[wemme]

Hmmm I might give that a go as i have a few Variacs laying around.

[gerald_d]

Bert, for cutting metal you need reduced speed together with increased torque. No electric/electronic speed controller will increase the torque.

Take your car as an example. Imagine you only had one gear, the top gear. Now you want to reduce the amount of gas to reduce the speed for crawling in traffic?

If you do use electric/electronic speed controllers, you have a very much reduced horsepower available to you, and you will only be able to do lighter cuts.

The gearbox in your car, or the various pulleys on your drill-press, are the right ways of increasing torque while decreasing speed - these systems preserve the horsepower.

[dvanr]

Bart,

The biggest problem with the speed controls is that they run "open loop" no feedback to the controller as to what is exactly happening at the bit. There is some "natural" feedback in the motor design itself. As it is loaded it slows down, draws more current and resists slowing down.( hence the dimming lights when you cut heavy).

A controller with feedback, PID and current limiting would be the minimum requirement, I have looked but so far haven't found one that fits the bill. I doubt that they would be reasonably priced as well.

a possible alternative

You might want to look into the Sherline mills or ones similar (designed for cutting metal). They sell their motor, controller and head stocks seperate , http://www.sher.com.au/ it all depends on what you want to cut really.

[wemme]

Thanks for the info
One of my collegues has given me a schematic for a closed loop speed controller for univeral motors which i will build a try.
I'll post back if it works out ok

[dvanr]

Bart,

I would be really interested to hear how it works out. If you can, PM the schematic to my address in my profile.