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Tentatively wired the hybrid Z axis motor up today, a bit of light relief after doing the VAT return.
Only had 2 Amps spare for it to play with but it doesn't seem to mind one jot, even though it is moving the quill at twice my normal speed :beer:
Also rough cut the honking plate on a bandsaw, see pic, don't know if I'll get anything done tomorrow.
Robin
Milled out the honking plate, still needs a slit and a couple of holes opening out but nearly there.
Not sure I actually need it, I sank the detail 20mm in and it cut it 20.04mm with the bodged plate.Wish I'd tried harder setting the Z in retrospect :rolleyes:
Pic shows honking plate next to the Warco depth stop plate it replaces :beer:
Robin
Oops! :whistle:
Bugger!Quote:
Originally Posted by Robin Hewitt
Is that cast AL? (doesn't look like cast)
Looks cast to me.
Do you want it welding Robin ? or are you going to make a new one.
I can stitch you that back for the price of the postage.
Quote:
Originally Posted by John S
I weakened it by putting in steel insert nuts then went a bit wild tightening the bolts :naughty:
All part of life's rich tapestry but still a silly mistake, looks like I'm further down the learning curve than I thought :rolleyes:
I was going to run a bolt down through, maybe fillet the cracks with Al solder but this here welding sounds interesting, I could use a smaller bolt. See what you are up against before volunteering though :beer:
No problem with that, wouldn't put the broken bit back anyway, just build the whole end up with filler weld, 15 minute job.
.
A generous offer, OTOH I am more than a bit impetuous and an M8x40 looks rather inviting. If I can close the gap I could be up and running today :naughty:Quote:
Originally Posted by John S
I have a spell in the dentist's chair at half past ten, a good opportunity to cogitate :beer:
M8x40 did the trick, gap closed, put an arrow on the pic in case you couldn't see where it was :beer:
Did you drop some loctite in the gap before closing?Quote:
Originally Posted by Robin Hewitt
Because if it gets the faintest jiggle it will never close that sweetly again :nope:Quote:
Originally Posted by irving2008
Good idea, but then I'd have had to clean off the RTD and I was rather enjoying putting it together :naughty:
If I take it off I promise to Loctite it :beer:
Kip, I don't know how it compares to driving the handwheel because I've never tried that. If I had to guess I'd probably plump somewhere between amazing and freakin' miraculous :whistle:
Curious.
I wound up the feed rate on that hybrid stepper and it would do 18mm/s but clacked out at 20 mm/s
I disconnected the Y axis to get some spare Amps then switched the hybrid peak current from 1.9A to 4.2A peak.
Wouldn't do 18 mm/s anymore :nope:
Possibilities...
The cable on the Z is altogether too long and it's having problems controlling the current.
The stepper driver can't actually cope when you increase the current.
I imagined it :heehee:
So, any ideas what driver/PSU combination I need to shop for?
However, 18mm/s is a lot better than I had before so I made new plates to fit them on the X and Y. Stuck a fanciful strain relief bracket on the X so I can bolt the flexy trunking to it.
Speed is a factor of voltage, not amperage, try it at 440 volts and see how fast it goes.
Hi Kip
The cable goes from the front of the cabinet, out the back, up by the column and then forward again.
I'm using the MSD542 driver at 40 Volts.
18mm/s is top whack, would never dare run it at top whack, 10-12mm/s is probably credible for the G00 though.
It's a bit cluttered at the top, but I could probably mount a driver and PSU within 6-10" of the motor if I had to :naughty:
Robin
As John said, speed is a factor of voltage and, I'll add, inductance of the motor. Higher inductance, lower voltage = lower speed. Also remember torque, speed and power are related. So it may well be that these motors running at that voltage simply can't produce enough torque to operate reliably at a higher speed. Can you get higher revs (step rate) off load under the same conditions?Quote:
Originally Posted by Robin Hewitt
Cable length is going to make little difference unless its so thin as to be dropping considerable volts.
What size/spec of motor are you running?
Yes, but the question is...Quote:
Originally Posted by irving2008
Why did the max speed decrease when I doubled the Amperes? :whistle:
Did you saturate the motor?
Quote:
Originally Posted by BillTodd
Possibly right :beer:
I'm sitting looking at the motor spec sheet and it shows parallel as 4.2A/phase, but series as only 3A per pair. Sounds illogical :joker:
If I knew what "hybrid" meant it could explain it...
...perhaps
That motor is 4.2A in unipolar and 3A in series and 6A in parallel.
If you are connecting it is parallel and only giving it 4.2A, you are under powering it.
Quote:
Originally Posted by Robin Hewitt
As I understand it, Hybrid motors have a magnetised rotor as opposed to the soft iron cores used in earlier types.Quote:
If I knew what "hybrid" meant it could explain it...
That makes it very unlikely to be motor saturation :(Quote:
If you are connecting it is parallel and only giving it 4.2A, you are under powering it.
I wonder if it's a resonance (force/mass) issue - extra current = extra force. Might be worth trying a mass damper on the motor (i.e. I would stick a large/heavy washer to the motor pulley with a bit of double sided tape and re-test)
[edit] ISTR you have a spare pulley, try sticking that on top of the existing one (use DS tape or blu-tack something with a bit of 'give')
Today I reworked the tapered Gibb strip fixings.
The original adjusters are totally naff allowing the the Gibbs to move, so they went from tight to loose as you reversed direction on the slide :nope:
To fix it I fitted 35tpi x 3/8" studs, screwed the adjusters on to them, (still sloppy) then bolted on end caps to pinch it all together... TIGHT :beer:
That's a good idea Robin, consider it stolen ;)
I have a small snippet of steel wedged between the adjuster and gib ATM doing the same job.
Next, tramming it 'cause it ain't square :thumbdown:
I chucked up a dti on a 9cm radius and measured to the bed at 4 points of the compass. Plus is a dip, minus is a bulge.
North 0.0"
East -0.004"
South +0.0035"
West -0.0087"
As I measured each point I drew a circle around the DTI tip so I could measure all four points moving the bed rather than the dti...
North 0.0"
East +0.002"
South +0.001"
West +.0025"
Yes, my column is out of square and the bed is a ski jump :nope:
RS do pre-cut shims with a MOQ of 10, so I ordered the 0.05mm (0.002")
Never tried this before, think I need 8 of them and a bed skim :whistling:
Did you use a parallel or similar between the bed and the DTI? It helps to smooth out bed irregularities.
My base was shimmed from new. The shims are brass coloured and less than 1 thou" (fitted near the bolts).
BTW Don't get too carried away - the head on these things can be flexed a few thou" with not too much trouble.
Quote:
Originally Posted by Robin Hewitt
I measured it two ways to compensate for the lumpy bed, but seem to have cocked up :nope:Quote:
Originally Posted by BillTodd
I reckon my -4 mils East measurement was actually a +4 mils, giving a +-6 mil East West tilt. I mean the tilt has to show even either side, doesn't it? :whistling:
6 mils over a 9cm radius translates to nigh on 0.3mm of packing at the column base, it's around 0.1 degrees out. I could see it was a bit bent when facing with larger endmills but didn't think it was that far out.
New plan. I have some 0.47mm brass sheet, I'll put a strip of that down the West side of the column base then shim the East side until it comes true(ish).
Not much of a plan, but hey, it's a plan. Now where did I put my piercing saw? :naughty:
Seems a long way out even for a Chinese tool. Have you checked the column and base for paint or rust intrusion? Is it bolted down onto something level and flat?Quote:
6 mils over a 9cm radius translates to nigh on 0.3mm of packing at the column base, it's around 0.1 degrees out. I could see it was a bit bent when facing with larger endmills but didn't think it was that far out.
You think I might have done a Hubble? :naughty:
It's a cheap mill bolted down to a cheap stand, I don't think level and flat were ever really part of the equasion.
Don't know about paint and rust either, I've never separated it. I will certainly have a look see before I put the shims in. Engine hoist job, wasn't actually planning to remove any of the bolts beyond loose. Don't want to risk it getting away from me :whistling:
How anal is too anal? :naughty:Quote:
Originally Posted by BillTodd
It is now 0.005 degrees out east/west and 0.002 degrees out north/south. Trying to resist going for better but whaddya do.
Started on attempt #2 at a faster spindle because the bearings are unhappy if I try to run the main spindle up to credible small tool speeds.
The fast spindle is an ER11 chuck fitted to the honking plate and driven using a 1:3 timing belt off the main spindle.
Same axial bearings and Belleville washers that have served me well so far, but less than the 1/4 ton preload this time.
I've been looking at those splendid tool location doo-dads based on an electrical contact between tool and workpiece. As featured on this very site :beer:
To that end I have added Tufnol insulators to the shaft housing. No electrical contact between tool and machine body until it hits the workpiece.
Spindle housing now bolted together and impossible to assemble :nope:
Have to add a bit of internal clearance so the pulley can get past the belt :whistling:
Measured the resistance top to bottom, slightly worried when I found 8 million Ohms then realised I was in the circuit. Moved fingers and it went away :rolleyes:
Stuck waiting for bits :rolleyes:
Did add an air driven spindle lock, now working on the suds nozzles.
Bill says it's a z axis lock and he's right :beer:
Is that a spindle lock or a Z axis lock?Quote:
Originally Posted by Robin Hewitt
Have you a picture of the whole 'honking plate' z axis? (looks good :))
By Jingo you're right, I used the wrong word :heehee:Quote:
Originally Posted by BillTodd
You want a picture from a different angle?
Have to fix a front gate this afternoon. Strict instructions, on pain of nagging :naughty:
Just a wider angle showing the whole of the axis would be good :)Quote:
You want a picture from a different angle?
Testing out my new quill lock then the quill jammed :eek:
Two hours finding the problem. Thought I'd got cast iron dust in the guide when I drilled the holes for the pneumatics. Hadn't. Though the clamp was binding. Wasn't. Thought I'd deformed the quill with excessive locking force. Didn't. Thought it had to be gunge, fetched the quill out and got it clean enough to eat off. Did no good.
If your Warco quill seizes up for no apparent reason and defies all efforts to free it I have the solution. 2 minute job, miracle cure, no disassembly required, will cost you a bottle of Hobgoblin posted to Sussex :beer: :naughty:
Quill now tracks up and down easy peasy, the Z depth on the computer screen agrees with the linear scale on the mill +-0.01mm moving in either direction. However, cutting forces can put them up to .05mm out. Hence pneumatic quill lock.
Yes, I know 0.05 is only 2 thou :joker:
Quote:
Originally Posted by BillTodd
Here 'tis, and here's a link to the 1.7Mb original image http://www.robinhewitt.net/big.jpg
I left the Z screw detached from the honking plate, it bolts on from below sort of thing :beer:
Next I have to fix the ball screws, I didn't look after them and 10u backlash has become 75u, at least I think it's the screws. Have decided to spring the nuts and go for true zero backlash :naughty:
Assuming 1Nm on the screw is enough to move the table under all circumstances, that's 1256N force on the nuts, call it 280 lbf because I don't think in Newtons :heehee:
I have the design, appropriate Belleville washers have been purchased, waiting for the oil pipe fittings, blooming postal strikes, grumble moan complain.
You've made a nice job of that Robin :)
I pre-loaded my roller nuts to about 400N per roller. There isn't any actual axial load on my lead screw; the pre load stops the roller moving axially within the nut. That seems OK for manual milling with my machine.Quote:
Assuming 1Nm on the screw is enough to move the table under all circumstances, that's 1256N force on the nuts, call it 280 lbf because I don't think in Newtons
It's actually hard to tell exactly what pre-load you've set with a belleville you have to guess using a displacement and trust the manufacturer's table for the spring.
I know, but whaddya do? :whistling:Quote:
Originally Posted by BillTodd
The extended ball nut housings are now cut, see pic. I plan to rip it all apart tomorrow and try for zero backlash by preloading the nuts :joker:
Ran the fast milling collet today at a tentative 4150rpm and looking good. I'm driving it with 44:13 pulleys off the main spindle.
ZERO BACKLASH ON X AND Y :yahoo:
Well, none that I can feel anyway :heehee:
First pic, horrible things done to Gary's ballnuts :naughty:
Pic 2, Belleville washers just about to get bolted onto nuts.
Pic 3, My extra speed ER11 collet chuck thingy :beer:
Added a set of Gary's 240 VAC driven stepper drivers and a splash guard.
Don't know how fast they go yet because my computer can't crank them up past top whack and refresh the screen at the same time.
I suddenly feel a need for belt guards on the steppers.
[ame="http://www.youtube.com/watch?v=bAoUW5bszRA&layer_token=c1adb91cff5d14e3"]YouTube- Noise[/ame]
Would you describe this as "quiet"? :heehee:
I added the belt covers on the X, Y and Z motors.
The factory fitted screws holding the z axis motor together stopped 3mm short of the base. Not much but enough to hold a flexi conduit fixing so I could tidy the wiring up.
If I'm doing pretties I must be nearly there. The ultimate aim is to cut injection tooling, so thought I'd try the fast spindle and instantly found I needed yet another belt cover :heehee:
I cut a 3mm slot 0.5mm deep across a piece of aluminium at 6100rpm. A fairly good mirror finish resulted except the centre of the cut where the tool proved a mere approximation to centre cutting :rolleyes:
Extreme close up of the cut below. I measured the width at 3.00 to 3.01mm so runout is around 5um, not bad considering the ER11 collet was only finger tight.
Next the electronics...
I currrently run DOS because it leaves the PC timer interrupt free which is nice. OTOH, new computers do better graphics, are much faster and prettier, even if serial and paralel ports have now both been consigned to the dustbin of history.
Obviously I need a processor on t' mill end of the wire. I am opting for a Freescale 8 bit micro running C. It comes in a dinky little 48MHz, 64 pin, square package with buckets of I/O pins, 32k of flash, 2k of RAM, timers, serial port for the phase converter and a full speed USB 2 connection for the PC link. (Real reason for this choice is that our tech bod is looking at it for another product so we already have all the dev kit, programmer and free samples) :naughty: