Author Topic: The basics  (Read 14283 times)

Offline spuddevans

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Re: The basics
« Reply #25 on: July 23, 2016, 02:41:34 AM »
I'm sure X & Y will be fine but what about Z? (Uses counter weights/gas struts may maker for zero'ish loading on Z

I used the same size stepper for all 3 axis', but on the Z-axis I used a timing belt to reduce 2:1, figuring that I wouldn't need the same speed of movement as X or Y, and that the increased resolution and extra torque would be handy. I also got rid of my gas strut as well and it copes fine with no mechanical assistance.

Tim
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Offline Imagineering

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Re: The basics
« Reply #26 on: July 24, 2016, 06:50:45 AM »
I did the same with my Z Axis for the same reason. I rigged up a Sprocket above the Spindle Head and another at the back of the Column. This carries a Bicycle Chain running from the Spindle Head to a 16Kg counterweight at the back.
I'll try to get a Photo tomorrow. Nice & simple, and works perfectly.

Offline Will_D

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Re: The basics
« Reply #27 on: July 26, 2016, 05:53:24 PM »
Now what about the handle end. As already mention my SX2P has a fair amount of backlash at the handle (no thrust bearings). I posted a potential fix (http://madmodder.net/index.php/topic,10428.msg118625.html#msg118625)based on the ARC Myford cross-slide fix.

An update:

Fitted the 2 thrust bearings and the ordinary bearing and great result - no backlash at the handle end.

There is very little clearance under the tables - so fitting ballscrews maybe a nono!

There is only 32 mm on the Y axis and only 25 or so on the x-axis.

I have read up on the EvaNut and ordered some Delrin bar to have a go!

So just remembered that I have some 20 mm nylon offcuts (Ok Higher Mp but free) so can have a go while ePray and Parcel Motel do their thing

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Offline PK

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Re: The basics
« Reply #28 on: July 26, 2016, 05:55:47 PM »
For low clearance applications, you might consider a spinning nut ballscrew installation. Not as pretty, but it works well and can be easier to keep swarf out of...

Offline John Stevenson

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Re: The basics
« Reply #29 on: July 26, 2016, 06:13:34 PM »

There is very little clearance under the tables - so fitting ballscrews maybe a nono!

There is only 32 mm on the Y axis and only 25 or so on the x-axis.



Rubbish, Read up on this thread

http://www.model-engineer.co.uk/forums/postings.asp?th=119249&p=2

Where only tonight I mocked up a SX2P to take ball screws.
John Stevenson

Offline PK

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Re: The basics
« Reply #30 on: July 26, 2016, 06:21:42 PM »
That's a neat install

Offline Imagineering

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Re: The basics
« Reply #31 on: July 27, 2016, 05:19:35 AM »
Counterweight System for my SX3 CNC Conversion as promised.

Offline Joules

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Re: The basics
« Reply #32 on: July 27, 2016, 06:03:21 AM »
Excellent, multi story milling.  Re purpose some of those old lift panels.


4: Setup and air cutting
3: Fine surfaces and finishing
2: pockets and slots
1: profiles and loose parts
B: Bed
: Below Bed
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline Will_D

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Re: The basics
« Reply #33 on: July 27, 2016, 08:51:57 AM »
Rubbish, Read up on this thread

http://www.model-engineer.co.uk/forums/postings.asp?th=119249&p=2

Where only tonight I mocked up a SX2P to take ball screws.

Many thanks John for this link. What a co-incidence!

I will try the Delrin EvaNuts first and see how that goes. I may well do a few mods to the X2 and the ball screws.

I see you used 1605s would you recommend these over 1204s?
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Offline spuddevans

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Re: The basics
« Reply #34 on: July 27, 2016, 02:36:08 PM »
I used 1605's on my X2 cnc conversion, http://madmodder.net/index.php/topic,3535.msg40209.html#msg40209 shows the X axis ballscrew and nut fitting.

Tim
Measure with a micrometer, mark with chalk, cut with an axe  -  MI0TME

Offline Manxmodder

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Re: The basics
« Reply #35 on: July 27, 2016, 03:27:44 PM »
Rubbish, Read up on this thread

http://www.model-engineer.co.uk/forums/postings.asp?th=119249&p=2

Where only tonight I mocked up a SX2P to take ball screws.

Many thanks John for this link. What a co-incidence!

I will try the Delrin EvaNuts first and see how that goes. I may well do a few mods to the X2 and the ball screws.

I see you used 1605s would you recommend these over 1204s?


Will, I seem to remember there being debate on that forum about making the  Evanuts from 'Delrin' which is  Acetal homo-polymer.

There was discussion about the varying sectional density of Acetal homo-polymer bar causing a less reliable result than using the Acetal copolymer.

I used Acetal copolymer for mine,but I believe some of the ones seen being made in various videos may be using 'Delrin'

Do it in a well ventilated area,whichever plastic you use.....OZ
Helixes aren't always downward spirals,sometimes they're screwed up

Offline John Stevenson

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Re: The basics
« Reply #36 on: July 27, 2016, 04:18:26 PM »
Counterweight System for my SX3 CNC Conversion as promised.

Why a counterweight ?

Done over fourty X3's and SX3's and none needed counterweights and any that had a gas strut fitted it got removed.
350 oz/in motor at 2:1 reduction on 5mm pitch screws
John Stevenson

Offline Will_D

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Re: The basics
« Reply #37 on: August 16, 2016, 06:36:42 PM »
No great progress on the Eva nuts but a 500mm by 12 ball screw arrived by slow boat.

Am making progress in fitting a VFD motor and controller to the old girl (Myford ML7!!)

Now the nut is fitted to the shaft and I recall somewhere NOT to take it off the shaft less the balls fall out!

Can someone please explain a bit more as to how to safely remove the nut so I can machine the ends?

As a laugh at bede-time I love this comment from the Rio Equestrian commentator on Irish TV:

"Her ears are pricked back, so she's ready for riding!"
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Offline mattinker

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Re: The basics
« Reply #38 on: August 16, 2016, 06:43:36 PM »
Although I've never done it, instinct tells me not to take the nuts off, but to fix them in place whilst machining! Some kind of split tube that bolts together with "U" bolts or something. Or maybe just "gaffer" tape? Anything but have to play with all those escape prone balls!

Good luck, Matthew.

Offline PekkaNF

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Re: The basics
« Reply #39 on: August 17, 2016, 01:57:34 AM »
Can you butt to ballscrew a plastic pipe that OD is thread ID and screw the ballscrew onto this plastic pipe?

The way we have used is:
1) to make sure this pallscrew is filled proper grease - grease will retain the balls.
2) use plastic pipe to substitute ballscrew, you will fumble at one point...

Assembly in reverse order. Plastic pipe OD should be "snug" fit into the ball screw and ID should slip over the future spigot.

Pekka


Offline Will_D

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Re: The basics
« Reply #40 on: August 17, 2016, 06:26:19 AM »
Thanks for replies - I think I will leave the nut in-situ and see what happens, with Pekka's idea as backup.
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Offline awemawson

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Re: The basics
« Reply #41 on: August 17, 2016, 10:05:12 AM »
My only experience dismantling ball screw nuts was unintentional a few years back  :bang:

I bought a job lot of ball nuts each on a short length of screw as a retainer, and fiddling with one of course it all came apart in my hands  :bugeye: Fortunately it was over a tray and I retained the balls but it was quite a palaver re-assembling it !

Fiddly little things
Andrew Mawson
East Sussex

Offline Will_D

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Re: The basics
« Reply #42 on: August 26, 2016, 05:54:28 PM »
So digging deeper and order hardware and RTFM 9all I can get)

So what are "Home Switches"?

Limit Switches I ubderstand, Kill Switch also.

Is it some kind of auto zeroing?

And one more:

How to calibrate steps versus mm travelled?
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Offline efrench

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Re: The basics
« Reply #43 on: August 26, 2016, 06:33:27 PM »
Limit switches kill the machine. Home switches set accurate home position.  Basic homing routine is to move the carriage until the home switch is triggered, move back a small distance, then move towards the home switch at a slower speed.  When the home switch is triggered this time, set the home position.  This is just one homing strategy, there are several others.

Offline PK

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Re: The basics
« Reply #44 on: August 26, 2016, 06:55:45 PM »
To add confusion, many machine controllers will allow you to use the limit switches to home.

Offline Will_D

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Re: The basics
« Reply #45 on: August 27, 2016, 04:02:16 AM »
Thanks, it seems there is a lot to learn still.

Its not just about engineering the mechanicals is it?
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Offline PK

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Re: The basics
« Reply #46 on: August 27, 2016, 05:41:47 AM »
A machine controller is a fairly simple thing. You can expect.some minor frustrations as you learn how it does.things. Hobby level Geode is so simple you can almost ignore it's existence.  Most of the grief comes from electrical noise and idiosyncratic software.

Offline Joules

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Re: The basics
« Reply #47 on: August 27, 2016, 11:00:43 AM »
Will, start out with something really basic like a desktop router.  Forget limit and home switches, play with belt and lead screw designs.  You can try out different arrangements based around the same basic frame, add bells and whistles as you like.   Get a grip on the software side, see how much force your drive can produce (luggage scales) then move onto a mill or lathe as the fancy takes you.   Even start with just one axis !!!    Most of all, have fun playing.

Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline sparky961

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Re: The basics
« Reply #48 on: August 27, 2016, 11:19:02 AM »
Thanks, it seems there is a lot to learn still.

Its not just about engineering the mechanicals is it?

Funny, it's the mechanicals that usually turn around and bite me - not the electronics and software.  I blame myself for this though, as my shop space and access limitations give me a legitimate excuse to avoid quality (big and heavy) equipment.

Wanna team up? :P

Offline John Stevenson

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Re: The basics
« Reply #49 on: August 27, 2016, 11:19:31 AM »
Good advise from Joules. Convert a dividing head or rotary table into a 4th axis.
At least this way you will still have something of use.

I never fit limit switches to my machines or homing. Homing wastes far too much time. just set work co-ordinates and machine co-ordinates to the same point and then zero on the corner of the work or vise and you always know where you are.

OK for the big boys who use the bottom paddock as a bed [ you listing Mawson ? ] and use G53, G54, G55 etc to machine 10 of the same item at one setting.
Us mere mortals are had pressed to get a fag packet central on the bed and under the cutter.
John Stevenson