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Messages - EJParrott

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41
General Mach Discussion / Re: Zapp Automation - anyone used?
« on: July 28, 2012, 03:24:19 AM »
Thanks for the reasurance Hood!

As far as the rapids go, its not an industrial machine anymore, and its not like its costing me the same £40/hr as the machines at work do.  What I want is accuracy, and longevity, so oversized and reduced down is good for me, as it means they'll not be working hard all the time, and are hopefully going to last longer. 

Anyway, I might try and see if MCP will do an offer on 8.5's instead...

In answer to the original question to get back on track, I've been having email discussions with Gary Higgins of Zapp about MPG's.  He's been really helpful, and has tipped me off about a rather nice looking pendant designed for Mach3 which will be going on the new website hopefully during the next month.  I think I'll give them a try!

42
General Mach Discussion / Re: Zapp Automation - anyone used?
« on: July 27, 2012, 06:24:26 AM »
I'm putting 4:1 on the X and Y, the Z I can only get about 2.5:1, there isn't room to get a bigger pulley on the end of the ballscrew.

So you think 8.5Nm is plenty big enough then?  I searched and searched Google but could not find any way to calculate what I needed.  Never having designed stepper motors for a CNC machine I've got no gut instinct on what's man enough for the job!

43
General Mach Discussion / Re: Zapp Automation - anyone used?
« on: July 27, 2012, 05:55:44 AM »
My Bridgeport clone...was actually thinking about going up to a 12.2Nm....Motion control have a package of 3 12.2 motors, 3 drivers, 2 PSU's and a BOB....

44
General Mach Discussion / Zapp Automation - anyone used?
« on: July 26, 2012, 05:09:08 AM »
Apologise if this is in the wrong section but I couldn't find anywhere better.

I'm looking to purchase one of the Nema 34 8.5Nm steppers I plan to use on my Bridgeport clone, as I'd like to have one in my hand while building the mounts and everything.  Zapp is currently coming up as the cheapest supplier, has anyone used them before?  Any experinces to share?

45
General Mach Discussion / Re: Spindle speed sensing on a Bridgport
« on: July 25, 2012, 12:36:50 PM »
You really do not have to change out the vari drive unless you just want to. You can use a cheaper commercial flange mount 3phase and add a shaft adaptor to the motor shaft to replicate the original BP motorshaft. Works fine here. AND much cheaper.

You're absoluty right, and as a CNC turner it would have been no problem for me.  However, there's a number of other factors that come in to play.  Courtesy of planning regulations, my workshop roof isn't as high as I'd have liked, and I'm actually turning the new motor upside down from normal, and hanging it over the side.  I can't actually get the drawbar in and out without rotating the head - not a huge problem.  There's also the fact that we're now paying about £100+VAT for the drive belts, and they just ain't lasting like they used to.  I've checked all the pulley faces and the bearings and everything else, but the belts are only last a year or so.  Thats far too much of an outlay for me every year.  By swapping to A section belt, its only ten quid for a new belt, which going by my drill and lathe should last 20 years or more!  The material for the pulleys is only costing about £40, so I'm well below the £100+ for the new belt - which was also needed by the way, when the motor went it took the belt with it!

You can also do it quite simply by using a reflective optical pickup on the timing belt.  Just paint a section of the belt white.

I've never had much luck with reflective pickups, for me they just don't work, but you're right, it is a good answer.

When I had the old step pulley Bridgeport I just cut a slot in the top pulley as I never used that ratio with the VFD. I then used an opto, Optek OPB917b.
If you are going to be making the pulleys then it should be fairly easy just to leave a bit extra meat on the top then shove in a grooving tool deep enough for the opto to fit in and then just slot out a bit about 10mm wide on the mill to trigger the opto.
Hood

Thats an excellent idea...I might just go with that.  I was pondering how to hold the pulleys while leaving enough metal and turn it off again when second ending.  Alternative, I could just bolt a disk to the top.

Thanks for all the input guys, you've given me lots to think about tonight - its too hot to go in the workshop!

46
General Mach Discussion / Re: Spindle speed sensing on a Bridgport
« on: July 25, 2012, 09:11:14 AM »
I think then, setting a proxy switch on the top of the pulley and having 6 pulley setting - 3 automatically reversed for back gear - is probably the way to go then.  I can also consider cheaper alternatives to the proxy switchs we use at work, maybe going for one of those things that go each side of a disk instead.

Thanks for your help Hood!

47
General Mach Discussion / Re: Spindle speed sensing on a Bridgport
« on: July 25, 2012, 08:32:24 AM »
I am planning to use Mach to control the spindle speed yes.  I have no problem with having to drop into the Mach settings to tell it what pulley its on when I have to change the belt.

Would I be right in thinking that if it was in the wrong range Mach would tell me?

48
General Mach Discussion / Re: Spindle speed sensing on a Bridgport
« on: July 25, 2012, 08:22:19 AM »
Hmm..you've got me thinking.  Maybe a bit of background would be a good idea, maybe I'm trying to overcomplicate things.

I bought the machine from work.  The original motor (for vari-speed pulleys) had killed its bearings, fretted the shaft, and chewed up the windings.  We were quoted £750+VAT to have it repaired, at which point they decided to scrap it instead.  Not being able to afford the £750 myself, but not going to pass on an otherwise good machine, I've opted to replace the vari-speed with an equivliant of an earlier stepped pulley version of the bridgeport, and drive it with a 3-phase variable speed motor and drive.

To that end, I've worked out that in order to use a good frequenzy and speed range on the motor, and still have power and torque at the tool, I should fit a 3-step pulley drive using 1:1 and 2.8:1 and 1:2.8 drives.  I originally calculated a 5mm pitch x 15mm timing belt would handle the power, but being unable to source pulleys that I wanted, I've swapped to A section v belt instead.  This came with its own problems in that the motor spindle isn't long enough for 3 pulleys with taperlock bushes, but I've overcome that with a plan to machine my own pulleys.  Being a CNC turner by trade that will present no problems.

From what you say, I'd be better off just mounting the proximity switch on one of the pulleys up top, where its easy to get at too, and setting up 3 pulleys in Mach for Hi range and 3 for Lo range?

49
General Mach Discussion / Spindle speed sensing on a Bridgport
« on: July 25, 2012, 01:48:17 AM »
Hi guys,

I'm finally making progress with my NC conversion of my Bridgeport Series 1 clone - guess I'll be around a lot from now on!  I've got the head all in bits removing the quill self act and stuff, and it's in need of a new drive system anyway, and while I'm in deep I was looking at fitting the spindle speed setup, so I don't have to take it all apart again. 

As I see it, the only sensible place to put it is below the back gear on the splined end of the spindle.  That is always going to be true spindle speed then, instead of having to work it out from the top pulley or some other bit of the drive system.  I reckon a proximity switch would work well, its what we use at working for counting rope lengths, and they are very acurate and trouble free.

I've been doing some research and found that Mach3 looks for one input per rev to work with the C3 card to generate a spindle speed readout.  Can the system cope with more inpulses?  I was oriignally thinking about bolting a block of stainless onto the side of the splines to trigger the proximity switch, then hit on the idea of setting it up to see the high points of the splines, which would mean 6 impulses per rev - is that possible?

50
Hi,

Names Ed, and I live in Rugby, England.  Ive been a CNC machinist for 5 years, programming long-hand G-code for most of the time, but recently becoming a Mastercam programmer.  All my work is on lathes and vertical borers.

I'm a model engineer in my spare time, and build miniature steam engines which I run at the Rugby Model Engineering Society, of which I am Vice-Chairman.

I'm just in the process of buying a Lillian turret mill from my workplace.  Its got a damaged spindle motor and CNC unit, and is uneconomical to repair - for work.  For me however, it represents an opportunity to buy a good machine for scrap prices, and give it a new lease of life with new motors and new CNC.  I've been introduced to Mach3 by a friend, and have looked throught the website and am hugly impressed - but it looks like Ive got a lot to learn!

I hope to be around a bit, but if I disappear for a while dont dispair - I've got really busy times ahead of me at the moment, and I've got some pretty big projects on the go with my other hobby, Land Rovers.

Cheers!

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