Messages

421

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: February 25, 2018, 08:22:16 AM »

Assessing spindle runout...

Yes we all know zero is nice but in the real world, on an old Bridgeport we also know that's not going to happen

Measuring inside the QC30 spindle socket, I get these TIR figures...

Near mouth = <0.005mm
Half way up = <0.01mm
Near top = 0.01mm

Measuring an ER32 collet holder....

Near mouth = 0.04mm
Mid way = 0.01mm
Near top = <0.005mm

Seem ok??

This is not taking into account the collet/tool yet, this is with budget tooling.

422

General Mach Discussion / Re: Limit Switches Hard and Soft

« on: February 24, 2018, 02:22:50 AM »

I fully agree limits are pointless on a machine with steppers as they will stall if soft limits fail or were turned off, but on a servo driven machine i would prefer hard limits wired to the safety circuit not the controller - if an axis runs away it will kill the power.

423

General Mach Discussion / Re: Limit Switches Hard and Soft

« on: February 23, 2018, 11:59:46 AM »

Sounds like your steps-per is out maybe, if its only moving 50% of the instructed distance, you need to do some tuning before messing with soft limits.

As Craig said above, you cannot use or set soft limits until the machine is referenced or homed.

424

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: February 23, 2018, 07:50:55 AM »

Turns out there was a reason for my insanity - the supplier does not do an ER20 Their range goes ER16-ER25-ER32 so i just ordered ER32 and the next one down

My stuff is ER20 & ER32

Easy fix is to order some ER25 chucks and ER16/ER25 collets - sorted.



If anyone is interested I will have a lot of nice R8 stuff for sale soon, will pop it in the forum section before it goes to the 'bay.

425

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: February 23, 2018, 07:02:08 AM »

QC30 spindle and BT30 drawbar fitted

Pretty easy task after all. Whether the bearings will hold up i don't know but they sound ok and did not get hot after 30mins of variable speed idling.

Of course, some idiot ordered the wrong tool holders and didn't notice, ER16 instead of ER20

426

General Mach Discussion / Re: Limit Switches Hard and Soft

« on: February 22, 2018, 04:45:57 PM »

I always start a few mm away from the switches and see how it goes -its easy to change.

Yes, 0mm is usually the homing end and the other would 50 or 60 in your case, make sure the table is in the middle area, set the values then turn on "soft limits" and try jogging into the end, a little fine tuning and thats it.

427

General Mach Discussion / Re: Spindle orientation on a Bridgeport...

« on: February 22, 2018, 06:48:29 AM »

Interesting stuff.

Yes quite possible the import can take it but I just don't like pushing the envelope on that stuff.
Somedays your'e just happy it turns on - Huanyang VFD's for example

428

General Mach Discussion / Re: Spindle orientation on a Bridgeport...

« on: February 22, 2018, 04:33:22 AM »

That 16mm tool at 6mm deep in steel - was that profiling or slotting, only asking as there is a big difference in power used.

I have read something on field weakening but nothing further, i would have doubts about pushing these cheap import servos too far.

The setup is HTD belt drive now at 1:1 so going 1:1.6 would just be a new pulley/belt.

429

General Mach Discussion / Re: Spindle orientation on a Bridgeport...

« on: February 22, 2018, 03:08:36 AM »

Hi Dave,
I recently bought a second hand 1.8kW Allen Bradley AC servo and drive for a spindle. I needed a spindle motor with some decent torque at slower speeds for steel.
This servo has turned out great. The main reason I went with a servo is that they are the most powerful/torque-y motor for the size.

Its the first time I've really ever played with a modern AC servo and I am impressed, very, very impressed! They are extremely capable and while it was not even
on the radar, stopping the spindle to line up the drive dogs is trivial with a decent servo. My 'zero window' is 4 counts of an 8000 count encoder ie 10.8 arc min!
Easily good enough to line up surely!

I had always been put off by the cost of servos but after playing with one I wont be looking for any other solution anytime.

Craig

How big was the machine, what sort of cuts have you taken with it?

I was thinking to just throw on a 2.6kw servo and see what happens, my experience of servos on the axis drives has shown that they are extremely powerful for the size. I can get a 2.6kw 10Nm cont motor and drive delivered for £500

I would need to gear it up to get 4000 rpm by 1:1.6 as they only do 2500rpm but at top speed it would not be using max power anyway.

430

General Mach Discussion / Re: Spindle orientation on a Bridgeport...

« on: February 22, 2018, 02:17:27 AM »

All sounding good, lots of options - pictures are always good

I gather that as nobody is tackling the AC synchronous -> AC servo swap question, it really is as difficult as i thought ??