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Messages - BluePinnacle

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General Mach Discussion / Re: EStop problem/question
« on: March 17, 2008, 07:07:29 AM »
That's about the strength of it, my 9v supply feeds the coils of several relays. One has its coil in series with the limit switches, the other in series with the Estop mushroom. Hitting a limit or punching the mushroom cuts the current through the coil and allows the NC contact of the relay to snap shut and short out a pin. (10 for estop iirc).

The relays areTyco T7S S5E6-12 single pole changeovers, about sugar-cube sized, 57pp from RS, part number 616-8714. They're 12v rated but run fine on 9v.

General Mach Discussion / Re: EStop problem/question
« on: March 16, 2008, 07:46:14 PM »
I had a similar problem with Estops in particular. Slightly leaky circuits, long wires in particular, can trigger a pin. All my estops and limits feed into relays, which short the PC pins via a short length of printer cable. The relays run off my 9v control circuit that also powers the hall effect home switches. i used to suffer all the time from false Estops, now life is easy with relayed signal inputs. Why, i liked it so much i bought the company*

[/victor kyam]
* more relays, anyway

General Mach Discussion / Re: Thread Milling hardware requirements?
« on: March 14, 2008, 07:00:14 AM »
Maybe worth clarifying a few differences here, I thought we were talking of rigid tapping which is a different ball game altogether. That would require a very well controlled spindle.

i had some thoughts about the wire - it would be prone to expansion and creep if the temperature changed. I saw a heater with a length of wire as a thermostat today, it's not a new idea but it got me thinking. Of course if your workshop is blessed with a steady temperature you may well be ok. Best way is to try it out :)

General Mach Discussion / Re: Power Supply Question / Problem
« on: March 13, 2008, 09:39:10 AM »

That's the way! nice and simple. use a rather slow relay for best results.

General Mach Discussion / Re: Power Supply Question / Problem
« on: March 13, 2008, 05:53:32 AM »
You may need a different breaker type instead of a different rating. Over here at least they are to be found in B, C and D flavours. So a B60 would protect a 60A (running current) circuit, and have close protection, tripping instantaneously at 5x the rated current for fault protection. So you'd use it for resistive loads like heaters, boilers etc. A C type breaker allows its magnetic trip to operate at 10x its rated current value for motors and fluorescent lamps, and a D type at 20x for induction heaters and transformers. The thermal response curves are the same, but the magnetic fault protection differs.

A microwave oven transformer - hefty kit - tramsformers often suck in 10 to 15x their maximum running current as inrush so do consider some current limiting measures. Even a series resistor shorted out by a delayed contactor will help, allowing the core to saturate then giving it full power. You will need a high power, low value resistor. incidentally, a lot of the high-voltage guys use microwave oven magnetron transformers to drive the primary tank circuits of Tesla coils and other insane devices... 4hv.org will tell all. Summary: bonkers ;D

General Mach Discussion / Re: Steppers DEAD!
« on: March 12, 2008, 11:32:19 AM »
silly, I know, but i saw the headline "stepper motors dead!" and the sticker "very hot!" and thought there was an electrical fire issue... i think I've been up too long

Different arrangement here, 4hp 3-phase motor driving the spindle through an expanding-sheave continuously variable drive system. A stepper driving the sheaves would be a tasty upgrade later in life, has anyone tried this before?

General Mach Discussion / Re: phantom limit switch
« on: March 11, 2008, 05:41:15 AM »
I have this as well, on G00 the motor spins up fine then clunks and bangs horribly. I slowed it down and it stopped doing this, was it just going too fast or do i need to be cleverer? mine's quite a big machine so i could do with a decent fast-move rate.

1 - adjust out the play where you can
2 - If you're using mach3, use software backlash compensation.

Why not cut a spiral on an aluminium drum, fit a clock spring and a length of steel bowden cable to it and use linear motion to drive a rotary encoder? these can be had for comparatively little, compared to linear encoders at least.

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