Hi Martin,

On my milling machine with a brushed DC motor I turn the speed down before turning off, and start at low speed and turn the speed up to what I need for the job.

Thor

If it's a machine that 'remembers' the previous speed it should ramp gently up to running speed which will avoid any stress on the motor or electronics. My SC4-520 and the inverter on my mini-lathe both behave like this. They both require me to start from zero on a fresh startup or if the emergency stop has been pressed.

In contrast, my mill (and the mini lathe as supplied) forces a start from zero rpm at every start.

Non-variable speed lathes always start at flat out, and even if equipped with a clutch this does (strictly) limit how many starts they can do in an hour.

Variable speed machines which ramp up the speed can generally start and stop as often as needed as long as the ramp up is not too fast.

Neil

I just start my WM280 at whatever speed I want it in seems to have survived almost 10 years use that way same with the X3. Neither ramp upto speed though the newer brushless SX2.7 on test does.

The low risk option is to manually ramp up and down from the lowest speed setting. Doing so makes no assumptions about the electronics fitted to your particular machine. Early Chinese controllers were primitive. Later ones are much better. Unless the manual says otherwise it's safer to assume the electronics are delicate and treat the lathe with respect.

Dave

Just like not tuning for minimum SWR on full power! Those transistors don't like it up em!

Dave

Hi I have been fiddling with variable speed DC drives for a number of years now and found that controllers that the ramp up to speed with variable adjustment will give the best service.

Read the manual for your machine and follow the instructions there are far to many speed controllers out there to be able to offer a universal answer covering all.

If you have deep pockets go for an industrial controller rated for higher power than the motor Horse Power.

Properly adjust the settings to suit the motor then you can expect a long and trouble free life from it.

The advice given in the operator handbook for mini lathes with brushed motors, is always to set the speed control to Minimum before starting. This has been my practice, and for the little use that the lathe has had, (and its previous owner) without damage.

From what I've read on this Forum, failure to do this is likely to result in damage to the control board. It seems to blow the output FETs, and result in a bill near to £100 for a replacement board.

Inverter VFDs are usually programmed to ramp up the speed from Zero to the selected level over a few seconds.

(Mine has survived fourteen years of casual abuse, without problems; so far!)

My advice? Err on the side of safety, and always set to minimum before shutting down, or starting up.

Howard

The manual I found made for a dodgy startup in my mind so had kept quiet.

1 Switch on

2 Select forward or reverse

3 Adjust speed.

Would have preferred number 2 to have been first but……?

Brian

Edited By Brian Sweeting on 08/12/2017 14:39:09

The manual for my milling machine says :

"The (speed control) knob should be turned to zero each time the machine is stopped. Always start the machine with the knob set at zero."

So I have tried to follow the advice given by the manufacturer.

Thor

The slower the start, the shorter the flight of the chuck key The 40+ years since I saw anybody do that doesn't seem long enough!

Perhaps a little more likely, a slow start makes things a bit gentler if you moved the saddle too far when bringing the tailstock chuck close for drilling, left the self-act engaged, started in reverse, didn't realise just how out of balance that job in the 4-jaw was, or any other of the myriad things that should never happen but sometimes do.

Brian

Edited By Brian G on 08/12/2017 20:33:26