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Ross77
23-05-2009, 10:45 PM
Hi All
I need some help please regarding the conversion of a pillar drill to a mill. I know this isnt the best base for a mill but I need a machine to build the proper router.

I recently bought 2 meat slicing machines from a scrapyard so have the rails and motors for the X Y table.

My first question is if the 120N-cm Vexta steppers driving a 2mm leadscrew will be strong enough?

And since the spindle has no through hole i cant fit a collet chuck and draw bar, so what is the best solution for minimum run out?

As I said I dont need this to be fast but would like it to be accurate.

Thanks in advance
Ross

BillTodd
23-05-2009, 11:30 PM
And since the spindle has no through hole i cant fit a collet chuck and draw bar,
Tool holding is going to be your biggest problem (apart from the spindle bearings failing because they won't take side load). You cant use a normal jacobs type chuck to hold an end mill; it simply will not grip it tight enough for safe use (been there, have the scars) . You'll need to find some way of fitting a collect chuck (i.e. a cheap chinese one) to the drill spindle. If your current spindle has a taper fitting you'll need to supplement it with a bolt up into the the spindle else it will fall off (once it has come off the first time it'll never fit as tight again).

Once you've sorted the above, find yourself a reasonable (4" or bigger) cross slide vice and you will be able to make fairly good light cuts in ally.

Ross77
24-05-2009, 01:21 AM
Thanks Kip/ Bill
you have confirmed me suspisions about the spindle, have to have a re-think!

I'll post some pics tommorow. Ive got 3 more weeks of college work then Im good to go, so trying to get everything sorted/ordered for then.

It sucks working and studing, but it pays the bills :sad:

Thanks again
Ross

Lee Roberts
24-05-2009, 02:58 AM
2mm leadscrew will be strong enough?

Yea i think you should be able to cut Rizla with that no problem, i would use some kind of coolant with that though. :heehee:

Smiler
24-05-2009, 10:45 AM
Hi All


My first question is if the 120N-cm Vexta steppers driving a 2mm leadscrew will be strong enough?


Ross

2mm? is that pitch or a typo?

Jeff.:smile:

Ross77
24-05-2009, 01:24 PM
yeah sorry effective 2mm pitch, the screw is 3mm pitch (i hope, could be 1/8 imperial) but I plan to use a 3:2 reduction on the belt drive to gain a small increase in motor power and reduce loading on the screw.

cheers for the coolant advice hadnt thought about that. I have some ideas for the spindle but will wait till i can sort out the pics, will be easier to describe

P.S How do I up load pictures? Tried uploading to the media centre but it failed.:exclaim:

Lee Roberts
24-05-2009, 04:43 PM
P.S How do I up load pictures? Tried uploading to the media centre but it failed.:exclaim:


What was the error it gave you ?

Ross77
24-05-2009, 05:20 PM
Hi Lee
The error message was "Sorry, Ross77: No Item or Item is Now in Moderation Queue - Check Back Later"

Ups just re read it, may its in the moderation queue! if not amI doing something wrong?

Cheers and sorry if you have lots of the same photo in the moderation queue:whistle:

Ross77
25-05-2009, 01:05 AM
Ok worked out how to attach photos, sorry Lee if it isnt the prefered way with the media centre.
here is the pillar drill with x axis attached
463
I plan to cut down the upright once i know the height needed

464
The rails are 22mm and have a solid brushing on one side and a skate bearing set up on the other side

466
This is the the y axis,once its cut down, with the 3mm lead screws

468
This is the drive from the machine but it only has a half drive nut and not enough travel, any one know if you can get a acme nut for a 16mm dia. with 4mm pitch?

465
And the biggest problem is the quill. The bearings are shot so I plan to get new taper bearings anyway. I have a couple of ideas to mount a collet chuck.

1. get a 2no. taper ER25 collet chuck and dowel/glue it to the quill through the knock out hole(if thats what it is called)

2. use a 20mm straight shank collet chuck to got through the bearings and then cut and turn down the qull to preload the bearings and secure the collet, leaving the spline section to function

3. the most favourable, but hardest to acheive, is to use an ER 25 morse taper collet and drill down the centre of the quill to fit a drawbar. not sure if this will leave enougth strength in the quill.

Any way I had better stop now before you all fall asleep:heehee:

Lee Roberts
25-05-2009, 03:26 AM
Hi Ross, looking good mate !

I'v had a look and yes all your pics had gone to the mod que, thats now been turned off and your pics will go strate into the pub gallery as soon as you upload them. You did me a favor telling me you had this problem as i didnt know that was happning for standard members so thanks for letting me know.

Look forward to seeing your machine come to life !

:beer:

Ross77
25-05-2009, 09:49 PM
Phew! Thanks Lee I thought it was me being stupid, can i delete the duplicate?


Did I see one of Bungalowdogs ballscrews there? What diameter is the splined end of the quill...and what taper is it?

Kip
Dam you have good eye sight, it is a bungalowdog ballscrew, bought it before I saw the coments on here about how usless it might be, Shed load of backlash in the reduction gears, need to isolate the ballscrew to check that, but it dosnt look up to much.

The quill is a morse 2 taper and the spline is 14.75mm outside dia. and an effective dia. of 11.25mm minus the splines and would require a 225mm long drill bit. The collet chucks have an M10 thread so would need sleeving I presume.

Im a little concerned about the quality of the internal taper on the quill so was wondering if I could cut the end off and put an M10 thread on that and screw it in to 20mm straight shank holder? or will I have allignment problems and is it likely to shear off under load?

Cheers

Ross77
25-05-2009, 11:07 PM
cheers KIP, I understand the comment about ditching this project and just buying a proper mill, but not only do I need this to make the bits for the VMC but I think the learning curve will be usefull and give me a chance to use a CNC machine.

I always thought that the hard bit was building the machine! but from what i read there is quite a skill to using it properly! zeroing, feeds and speeds etc.

It hasnt cost much so if I reck the bed or Its goes in to self destruct because I didnt set it up properly them it wont mater.

Out of interest what would be the biggest size hole for the centre of the quill? Maybe I can get it done locally. The other option is to forget the collet chuck and just use it for accurate drilling :smile:

BillTodd
25-05-2009, 11:25 PM
The draw-bar hole in my (MT3) ER32 collet chuck goes right through. If your chuck is the same, you could always screw up, through the chuck, into the spindle (with a smaller bolt). I find I don't need to tighten the draw bar on my morse taper quill quite as tight as on most R8 devices, since the taper is fairly secure on its own. I'd have thought that a long M6/M8 allen bolt would hold the chuck in place perfectly well for light use.

Ross77
25-05-2009, 11:35 PM
Cheers Bill
That sounds like a plan :beer:
Better get on flea bay and find a collet chuck like that. keep you posted
Thanks again

BillTodd
25-05-2009, 11:55 PM
possibly 6mm and then it will be a springy drawbar
If it screws upwards it'll only be about 6" long



Those heatsinks are 425X300mm :eek:

I built an amplifier with a similar sized one :)

Ross77
26-05-2009, 10:29 PM
Bill, just re-read your first post and realised you suggested mounting the chuck from underneath then, sorry I didnt twig.

Anyway just ordered the angular contact bearings for the spindle and found a suitable ER collect chuck. But not sure wether to go for the ER32 on a morse 2 taper so i can use the collets on the big mill when I make it.

Any one know if will this be ok on that size taper? and In reallity will I need 20mm capacity for milling Ali?

Any one used the cheap chineese stuff? ER32 collet set is still 50 so not that cheap if its useless
Cheers

BillTodd
26-05-2009, 11:54 PM
Any one used the cheap chineese stuff? ER32 collet set is still 50 so not that cheap if its useless
Cheers
I bought a 6.50 one direct from china via ebay (for my T&C grinder). The chuck is as good as the one I bought from <TILT - brain failure> someone??? - very good, bugger all run-out, but the nut was so badly machined I had to take a dremel to the ejection ring in order to fit a collet.

I don't see any problem using a ER32 with a MT2 and it'll save money in the long run.

Ross77
29-05-2009, 10:30 PM
I bought a 6.50 one direct from china via ebay (for my T&C grinder). The chuck is as good as the one I bought from <TILT - brain failure> someone??? - very good, bugger all run-out, but the nut was so badly machined I had to take a dremel to the ejection ring in order to fit a collet.

I don't see any problem using a ER32 with a MT2 and it'll save money in the long run.

Cheers Bill, going to go for the ER32 then, Just waiting for the shipping costs then its on order. 13 for chuck and 27 for 19 collets (sounds to good really) where did you get yours from?

Bearings arrived today! Whats the best way of determing the torque for the preload on the angular contact bearings, im guessing its just enougth to stop runout, and loose enough to reduce friction/heat build up?

cheers

Robin Hewitt
09-06-2009, 08:42 PM
Whats the best way of determing the torque for the preload on the angular contact bearings?


The torque is zero, zip, nada.

Tighten them down until the slop is within your acceptable tolerance.

Ross77
09-06-2009, 09:01 PM
Cheers, so I probably need a lock nut as well then? The original one just squeezed the inner race on to the step on the shaft.

The other problem is how to drill the hole in to the end of the quill for the chuck lock bolt. I foolishly thought it would fit in the lathe but that also has an M2 taper, Duh

Is it safe/accurate to hold a drill bit (facing up) in a vise and lower the quill down over it?

irving2008
09-06-2009, 09:11 PM
Cheers, so I probably need a lock nut as well then? The original one just squeezed the inner race on to the step on the shaft.

The other problem is how to drill the hole in to the end of the quill for the chuck lock bolt. I foolishly thought it would fit in the lathe but that also has an M2 taper, Duh

Is it safe/accurate to hold a drill bit (facing up) in a vise and lower the quill down over it?Safe - maybe if you can hold it tightly - drills have been used as lathes by holding the tooling in a vice and the workpiece in the chuck (I've done it).

Accuracy, its hard to see how you'd get the drill absolutely in-line with the quill. Here's an idea tho.
Acquire a block of MS say 50mm cubed. Drill an M4 tapping hole through the center of one face and tap M4. Put the cube in the vice with the M4 hole horizontal and accessible through the side of the vice jaws then drill down through the centre of the face with the drill you want to use to drill the quill. Remove the drill and without moving the vice put the drill shaft in the hole and lock in with a M4 bolt.

Remove the chuck and lower the quill onto the drill... careful with speeds and use coolant if poss.

You might need to grind a flat on the drill shaft to locate with the locking bolt.

The accuracy depends on how square the chuck was to the quill initially...

So, JohnS, Robin, BillTodd, etc (as real engineers) where's the flaw in my suggestion?

BillTodd
09-06-2009, 09:43 PM
I wouldn't call myself an real engineer, or indeed, any kind of engineer but...

That sound like a good plan to me :)

Ross, What's the end of the quill look like? e.g. does it have a centre spot from the taper machining operation?


The accuracy depends on how square the chuck was to the quill initially...
Actually, your clever plan means the new drill 'chuck' will be properly aligned with the quill travel regardless of vice alignment.

Ross77
09-06-2009, 09:51 PM
Sounds good to me :clap:, have to scavenge a block of steel, sounds quite big. Ive got Al that size but suppose its not ridged enough.

Hope to make a start at the weekend, so ordering last few parts

Just looking at the uniport from DIY CNC (from a thread on here) , looks to to be perfect for a mill, is it beter than the opto board?

Ross77
09-06-2009, 09:56 PM
Bill
Didnt see your post as I was replying to the previous.



Ross, What's the end of the quill look like? e.g. does it have a centre spot from the taper machining operation?


Cant remember, I'll have a look tommorow, Is this an issue if there is a centre spot?

BillTodd
09-06-2009, 10:28 PM
Is this an issue if there is a centre spot?
Just makes it easier :)

irving2008
09-06-2009, 11:31 PM
Added thoughts...

Size of block = size of drill x 2-ish need enough metal for the locking bolt to remain rigid

If drill shaft < drill size (as it might be if its a big drill) then drill out the hole shaft sized first then use the proper drill to bore down 10-15mm to provide a locating seat... then remove drill etc as before....

Ally instead of MS... can't see why not, maybe go for a bit more 'meat' on it. Only issue might be getting a good lock on the drill... if you never want to use the drill again without some effort you could try loctite in the hole!

thanks for the +ve feedback

Robin Hewitt
10-06-2009, 12:24 AM
So, JohnS, Robin, BillTodd, etc (as real engineers) where's the flaw in my suggestion?


Hang on, reality check.

Just how long is this drill bit?

Sounds like it has to reach up through the morse taper, past the taper knockout slot and then all the way up through the quill?

You reckon this pipe auger is going to start on centre without some kind of guide bushing :heehee:

Ross77
10-06-2009, 08:16 PM
Uhmm. How do I say this.........

It dose fit in the lathe. :redface: I forgot the splined end was narrower than the 20mm shank at the taper. Just fits in far enough, about 25mm projecting from the chuck.

SORRY,SORRY, SORRY



Sounds like it has to reach up through the morse taper, past the taper knockout slot and then all the way up through the quill?


Not all the way through as this was the point, securing the collet chuck from the underneath, 90mm for the taper and knock out section + shank in chuck + depth of hole for new bolt thread. so long enough.

Ross77
14-06-2009, 02:51 AM
Finally got some workshop time this evening and finished setting up the lathe. :dance:

Spent 30mins centering the quill in the 4 jaw chuck. What a nightmare!think Ive got it sorted now. (when I realised that 0.001" run out is F**k all) Ive drilled out the knockout slot to 10mm and created a start point for the tap drill.

The hole through the ER chuck is about 9mm , so the max bolt size I can use is M8, Problem is getting a drill bit and Tap that will reach the 150mm
required.......

Any one know of a source of long reach taps? or will i have to make up some sort of extension bar?

irving2008
14-06-2009, 11:14 AM
Finally got some workshop time this evening and finished setting up the lathe. :dance:

Spent 30mins centering the quill in the 4 jaw chuck. What a nightmare!think Ive got it sorted now. (when I realised that 0.001" run out is F**k all) Ive drilled out the knockout slot to 10mm and created a start point for the tap drill.

The hole through the ER chuck is about 9mm , so the max bolt size I can use is M8, Problem is getting a drill bit and Tap that will reach the 150mm
required.......

Any one know of a source of long reach taps? or will i have to make up some sort of extension bar?Let me get this right... you're drilling out the quill to allow a draw bar through to pull the ER collet chuck into the quill... so what are you planning to tap? did I miss something?

Ross77
14-06-2009, 08:18 PM
Let me get this right... you're drilling out the quill to allow a draw bar through to pull the ER collet chuck into the quill... so what are you planning to tap? did I miss something?

I decided against drilling all the way through the quill as I could only get a 6mm hole through the splined section and the chuck needs M10, resulting in a long thin drawbar and some sort of thresd adaptor.

Bill suggested drilling from the chuck end up into the quill and then use a bolt through the chuck to secure it (similar to some drill chucks)

So i need to to drill a 7.5mm hole in the quill and then tap it for M8, dose that make sense?

Robin Hewitt
14-06-2009, 08:54 PM
Can't you just put a fancy nut through the taper knockout slot and save driling anything?

Ross77
15-06-2009, 01:12 AM
Can't you just put a fancy nut through the taper knockout slot and save driling anything?

with the extra long tap at 7 and probably the same for the correct drill bit. That's looking like a good idea, it's only a 10mm slot tho so M8 tread is pushing it a bit...

Would a M6 be good enough?

Irving
Thanks for the info on inverters. just got one to play with :beer:

Robin Hewitt
15-06-2009, 11:35 AM
M5 even, so long as you use a good quality screw and key. HT would be overkill, just avoid stainless and cheapies.

If you buy a box of screws you could torque one to destruction in a piece of scrap. Then you'd know :beer:

Ross77
15-06-2009, 07:53 PM
M5 even, so long as you use a good quality screw and key. HT would be overkill, just avoid stainless and cheapies.


Thanks Robin. HT ? high tensile?



10mm slot width or height? It's ok to engineer a twist fit solution.....


10mm wide. Approx 30mm high. What do you mean twist fit :question:

Robin Hewitt
15-06-2009, 08:17 PM
Thanks Robin. HT ? high tensile?
10mm wide. Approx 30mm high. What do you mean twist fit :question:

High tensile, yes.

No extra space in a knock out slot to twist into, they are cut to fit the taper tang.

Hopefully you will have room between the spindle nose and the chuck so you can slip a fat spanner in the gap to lever it out.

OTOH you can cross that bridge when you come to it :beer:

Ross77
15-06-2009, 11:52 PM
Yeah not worried about getting it back out. just as long as it stays in:dance:

Just cut a piece of steel to go in the knock out hole, but cant find my M5 tap, why is always the one you want that disapears in to thin air......

I'm going to try this route first, If it wont hold then I'll drill up into the quill from M8 bolt. I'll get some new taps tomorrow and a selection of bolts.

Let you know if it works................

Ross77
16-06-2009, 09:26 PM
It will be a miracle if i ever finish this... with every day comes a new problem

Drilled and tapped the new key for M5 but cant find any bolts long enough. (125mm). Would studding be ok? The other option is to make up a small drawbar 8mm dia. to go thro the chuck then turn down the end for an M5 thread, problem is making it strong enough and providing some sort of slot in the head for tightening.

The next challenge is deciding wether to cut down the main post and fix the head at a set height or allow it move up and down to suit the job, like a proper mill :tongue: I will need to sort out a better clamp than the existing grub screw arrangement , may be cut a slot and then bolt up to pinch the main post? would this help remove the current play, and provide an accurate reposition when moved?

BillTodd
16-06-2009, 11:05 PM
Why did you abandon plans to drill & tap the quill?

Although, I think M5 should be OK. (you won't be taking it in and out all the time)


would this help remove the current play, and provide an accurate reposition when moved?
Might work.

I'm happy with the way my wishbone stabiliser works if you want to copy.

Ross77
16-06-2009, 11:48 PM
Why did you abandon plans to drill & tap the quill?


Cost..lol the depth into the quill is over 100mm so I needed to buy extra long taps and drill bits. In hind sight it would have been worth it tho as it is definatly the best solution. M8 bolts over 100mm no problem.

Try the cheap option First eh.

Cheers for the stabiliser idea, Not quite what i meant tho. not bothered about rotational postion. I was refering to the the existing head rocking on the post (out of tram(I think..))

In the picture of yours, is that the locking bolts I can see at the back of the head casting?

BillTodd
17-06-2009, 01:05 AM
is that the locking bolts I can see at the back of the head casting?
Yes.

Re: long drill and tap - quick n dirty fix

In your lathe with the appropriate tapping drill (6.8mm?), drill into a length of 3/8" bar , grind a small flat on the drill, insert it into the bar and dot-punch into the flat - it should hold well enough to drill into the quill

Similarly, drill a hole just small than the square end of your M8 tap and hammer the tap into it .

Ross77
18-06-2009, 12:11 AM
Re: long drill and tap - quick n dirty fix

In your lathe with the appropriate tapping drill (6.8mm?), drill into a length of 3/8" bar , grind a small flat on the drill, insert it into the bar and dot-punch into the flat - it should hold well enough to drill into the quill

Similarly, drill a hole just small than the square end of your M8 tap and hammer the tap into it .


Now you tell me.. cheers any way. may still need to do that.

Attached some pics of the progress so far. My brain must be playing tricks on me, I could have sworn it was 125mm last time I measured it. :rolleyes: M8x100mm bolts on order, so see how it goes.

Seen a few other modded drills on the net and the ones that seem to work are like mine, with the X-Y table mounted on the base(lose the flexible table) and then lower the head to suit.

There will be no going back once I cut the pinch groove in the head casing..:eek:

BillTodd
18-06-2009, 11:58 AM
My brain must be playing tricks on me, I could have sworn it was 125mm last time I measured it.
It'd have to be 125mm to screw into the quill ?

You'll need to mill/file a slot into the block to clear the end of the taper (the draw-screw must pull the taper into the quill - it's not just there to stop it falling out)

Ross77
18-06-2009, 10:42 PM
It'd have to be 125mm to screw into the quill ?

That'll be it then....


You'll need to mill/file a slot into the block to clear the end of the taper (the draw-screw must pull the taper into the quill - it's not just there to stop it falling out)

Damm you people have good eye sight. Realised that after I made the key....Thought about grinding a bit of the chuck, but dont want to damage it. Theres not much of the quill at that point to support it tho, might have to remove to bevelled edge. This option isnt looking so good now.:thumbdown:

Decided to drill for both options just in case the key idea fails. May help someone else who wants to do this but dosnt have a lathe.

Started your drill extension holder tonite. should work fine. Just my poor machining skills letting me down now. Still practice makes perfect, (havent used a lathe for 15 years) :whistle:

Ross77
20-06-2009, 07:11 PM
Ok quick up date.

M5x100mm bolts arrived and modified the key to clear the chuck. Glad I didnt grind any off as I can now sill use the wedge to knock out the chuck. :smile:

Should make some good progress tomorrow as I've finally got a full day in the workshop :dance:

Ross77
21-06-2009, 10:19 PM
Ok. drilling the quill has turned into a nightmare, made the drill extender and drilled it no problems, however I couldnt get a 6.8mm bit locally, so thought a 6.5 would be ok. However the tap was extremly tight.

So I measured the narrowest part of the thread on an M8 bolt and it was 7.2mm, Re drilled the quill with a 7mm bit but the tap still jams when only a quarter of the way in :sad:

Dose this sound correct or have I just got a useless tap? (new but a Machine Mart cheapy)

Ross77
21-06-2009, 11:31 PM
What thread exactly are you wanting to make?


An M8 tread, inside the quill for the full length of the tap (30mm or so)

Ross77
21-06-2009, 11:45 PM
So what pitch is the thread you require? 8mm 1.5=6.5mm drill.....I'm hoping you have an M8x1.0 tap for a 7mm drilled hole? Use cutting fluid it helps ;)

8mm with 1.5 pitch......Must be the tap then. Have I buggered it by drilling the 7mm hole?

I have used cutting fluid as well

Ross77
22-06-2009, 12:07 AM
By my number crunching.. :D you have 0.25mm of thread left....Do you have a 9mm tap for round 2 :D

Very funny. I have a few hens teeth tho...Its still a very good fit when i screwed a bolt in......Is this likely to be the tap then. now problem with buying a better tap, just want to make sure I need it.

HankMcSpank
22-06-2009, 12:14 AM
M8 thread with a 1.5mm pitch?

I've been tapping a whole heap of holes for my recent CNC build. For an M8 thread with the more common 1.25mm pitch, a 6.8mm hole is the norm (you sure it's a 1.5mm pitch? as this might account for why your tap is getting stuck!)

http://www.efunda.com/designstandards/screws/screwm_coarse.cfm

John S
22-06-2009, 12:27 AM
Yup,
M8 is 1.25 pitch with 6.8 tapping drill.

7.0 mm will do in a push, that's the usual size for tough stainless.

Wouldn't have thought Machine Mart did specials like 1.5 pitch.

The reason it won't thread is probably because it's a crap tap, can you borrow one off someone ?

Ross77
22-06-2009, 11:52 PM
The reason it won't thread is probably because it's a crap tap, can you borrow one off someone ?


A problem I've noticed with cheap tools is they aren't always the size they claim....I remember drilling the last hole in a big expensive job 18mm instead of 17.5mm caused me no end of trouble...New glasses fixed it ;)

Thanks All, new expensive tap it is then, dont like borrowing tools (sods law it will break) and its not like I'm never going to use it again. The quill must be tougher than I gave it credit. Did a trial run with the 7mm hole in some Al and it worked fine, a bit loose even.



M8 thread with a 1.5mm pitch?

I've been tapping a whole heap of holes for my recent CNC build. For an M8 thread with the more common 1.25mm pitch, a 6.8mm hole is the norm (you sure it's a 1.5mm pitch? as this might account for why your tap is getting stuck!)


Im going to have to take a note pad out to the workshop as it appears my memory is useless..:whistle: yeah the tap is 1.25 pitch

Thanks again and sorry for the duff info

With the stalemate on the quill I've been looking at the X-Y table, bit concerned with the flex in the 22mm rails and skate bearing arrangement on one side, and then making up some sort of T slot table.

For 80 I can get a cast iron compound table (not as big as I would have liked) or I can use some of my THK rails, but still need to sort a table.
Is 8080 extrusion ok for a table if the rails are bolted to it? Still want it to be as cheap as possible but realised that cutting corners still costs in the end.lol

Ross77
25-06-2009, 12:17 AM
Ok feed up with messing around and decided to take the advice of you guys (think it was the 2nd or 3rd post) and buy a compound table...:clap:

Got this one
http://www.axminster.co.uk/product-Axminster-Axminster-CT1-Compound-Table-21825.htm

Free delivery is a bonus. Bit of work and it it should be ok. T slot tables of the same size where the same price, so at least I will have a decent table. If it works I will have only spent 100 as the drill was free and the other tools are useful for other projects

Extra long tap and suitable bolt also on order. Hoping it will all be here for the weekend. :biggrin:

Ross77
28-06-2009, 10:03 PM
A problem I've noticed with cheap tools is they aren't always the size they claim....


Problem solved, new tap cut like a hot knife in butter. Wont be buying any more tools from Machine Mart...........

Compound table is useable after all lot of rework. (Think it was cast, rough milled and bolted togother)

The bit I'm struggling with is eliminating backlash in the acme screw. I've Cut a slot and fitted a pinch bolt, but as the screw and thread are so rough the friction caused is not good.

My question is how critical is it to completly eliminate backlash or is the compensation in Mach able to overcome it?

I can probably improve the current state (about 2 or 3 deg. as a guess) but will take more time...

Photos soon If anyone is interested

BillTodd
28-06-2009, 10:13 PM
The bit I'm struggling with is eliminating backlash in the acme screw.

How about using a Delrin nut instead of the brass(?) one (or a second nut made of delrin to remove backlash)

Ross77
28-06-2009, 10:42 PM
How about using a Delrin nut instead of the brass(?) one (or a second nut made of delrin to remove backlash)

Cheers. The originals are cast iron, will the delrin be strong enough on their own if I replace them?

Wheres the best place to get ready made ones? as the thread is imperial (1/10 inch) Or is it still cheaper to buy a tap and make them my self?

BillTodd
28-06-2009, 11:47 PM
I'd guess they'd be strong enough, although wear rate might be high.

I think one of the guys on the forum has been making and selling them (I don't know whether he has the correct tap for your threads)

What diameter are the lead-screws?

Are the nuts cast in place or are they removable?

Pictures would be good.

Ross77
30-06-2009, 12:28 AM
Ok you'll have to excuse the photos and the state of my workshop. For some reason if i dont use the flash then there not in focus..:cry:

The screws are 16mm dia. (15.65 on the calipers) and have a 2.54mm lead (imperial 0.1") Cleaned and polished the screw so thats looking better but just noticed the nut has cracked where I have been tighting the pinch bolt, so definetly need a new one, ups.

The nut on the x axis is removable and the y axis is fixed.

Ive had a quick look on tinternet and found lots of different ideas but I'd like to know If any one has a tried and tested method, I've fitted bearings to the screw which was a major improvement, so just need to sort out the backlash in the nut..

Hopefully when its finished it should be a good MILL.....:whistle:

John S
30-06-2009, 12:36 AM
Screws are 5/8" x 10 tpi not metric,
Unfortunately 5/8" usually comes in 8 tpi.

Is it definitely an Acme screw or square thread, acme has tapered sides at 29 degrees ?

Then are they both RH, LH or one of each.

Ross77
30-06-2009, 12:54 AM
Screws are 5/8" x 10 tpi not metric,
Unfortunately 5/8" usually comes in 8 tpi.

Is it definitely an Acme screw or square thread, acme has tapered sides at 29 degrees ?

Then are they both RH, LH or one of each.


Bugger.. I thouht Acme was square, and trapazoidal had the taper?

Anyway they are square and both RH, y axis moves correct but the x is opposite to the lathe (clockwise rotation moves it towards you)

John S
30-06-2009, 01:07 AM
Square is square.
Acme is 29 degrees and usually imperial [ not always ]
Trapezoidal is 30 degrees and always metric

Let me have a look tomorrow to see what taps I have, definitely got 5/8" x 8 LH Acme but not sure on the rest.
.

Robin Hewitt
01-07-2009, 10:30 AM
My question is how critical is it to completly eliminate backlash or is the compensation in Mach able to overcome it?

This rather depends on the accuracy you are trying to achieve.

The software can add extra travel when you reverse direction but that means the slides have to be tight enough to resist side forces from the tool so only the nuts can move them. Once the slides are set tight you have to worry about spring in the system.

Alternatively use two nuts. If you lock them together then wear becomes your problem. Spring them together with sufficient force to resist the tool pressure and you need monster size motors to turn 'em.

If it was easy to eliminate backlash with cheap screws nobody would sell expensive screws :beer:

BillTodd
01-07-2009, 02:51 PM
My question is how critical is it to completly eliminate backlash...
40 years ago men were sent to the moon. Most of the machines that built the rocket that got them there had backlash to some extent.

The critical bit is reducing the backlash/play/give/flex/strain/vibration/call-it-what-you-like it the whole machine down to workable level and working the machine to reduce the effect of the errors.


If you lock them together then wear becomes your problem. Spring them together with sufficient force to resist the tool pressure and you need monster size motors to turn 'em.
The important thing it to lock them together with the smallest possible clearance. This can mean that, with a poorly formed lead-screw thread, the nut will be slack in places while tight in others (lapping the thread with a nut and abrasive e.g. metal polish can reduce the tight spots).

Ross77
02-07-2009, 12:47 AM
Thanks for all the advice, Taken it all on board. From looking on here and the CNC zone I always planed to use servo motors, linear rails and ballscrews for the main machine, and now I know why.....

Still all good practice, dont know If I can justify ballscrews for this one. No point in having an ultra precise table if the head flexs all over the place. May be I should just get it working and then if its just the backlash thats an issue, I can sort it then.

Made the tap tonight and tried it on some plastic I had kicking around. Worked fine but I think the plastic is to springy and the tap wont cut the last bit for clearance, very tight over a 40mm length. Ive tryed tapping fuild and a drill but the end result is a very hot and shiney leadscrew, Still at least I know the best way to polish them now :clap:. I'll have to order some delrin,or try narrower sections.

Changing the subject, what is the best way to hone the dove tails on the slides? I've got them really smooth, with no play, except for the the first 30mm or so where i can feel an bump, Cant get the oil stone in and dont want to over do it by using a grinder.....If I carry on lapping it will both parts wear and then cause problems over the whole length?

Thanks again

Robin Hewitt
02-07-2009, 01:00 AM
Changing the subject, what is the best way to hone the dove tails on the slides? I've got them really smooth, with no play, except for the the first 30mm or so where i can feel an bump, Cant get the oil stone in and dont want to over do it by using a grinder.....If I carry on lapping it will both parts wear and then cause problems over the whole length?

If it is cast iron you scrape it, use engineers blue to find the high spots. I would be very careful about introducing any kind of abrasive unless you are blessed with a Rowlingesque magic wand, "Accio grit" :beer:

Ross77
02-07-2009, 01:16 AM
If it is cast iron you scrape it, use engineers blue to find the high spots. I would be very careful about introducing any kind of abrasive unless you are blessed with a Rowlingesque magic wand, "Accio grit" :beer:
Cheers. whats the best tool to scrap it with? looked in to this when setting up the lathe but looked like a "Black Art

What is Accio grit? Im sure Ive read that it ok to use abrasive compounds as long as it is properly cleaned with parrifin afterwards...

Robin Hewitt
02-07-2009, 09:54 AM
Requires manual dexterity

The famous Mexican bandit :heehee:

BillTodd
02-07-2009, 02:40 PM
You could try just lapping the parts together dry (i.e. degrease it and rub). Cast iron is fairly abrasive stuff so a few dozen cycles should polish the machining marks.

BTW Use proper 'way oil' e.g. Mobil vactra. (Keep that old can of Duckhams for the car use only ;) )

Ross77
02-07-2009, 06:37 PM
If you want to scrape the ways then a scraper is the best way forward....made from an old file or similar.

Requires manual dexterity and mastery of hand tools....not for the office workers :naughty:


No need to get personal.:heehee: Office workers can very usefull....making tea, sweeping the floor etc.


You could try just lapping the parts together dry (i.e. degrease it and rub). Cast iron is fairly abrasive stuff so a few dozen cycles should polish the machining marks.

BTW Use proper 'way oil' e.g. Mobil vactra. (Keep that old can of Duckhams for the car use only ;) )

Unfortunatley its not just machining marks, there is a proper lump that needs removing. Still I'll give it try.


The best tool to scrap it with is a grinder......

Is that a typo? or did you mean scrap it

Ross77
02-07-2009, 09:43 PM
Your typo? my implication :naughty:


Bugger, thought I had you then. Dont know how that happened! I'm normanally reeelle gurrd @ speiling ;o)



Ever see the fanboy posts on cnczone where they all went mental and set about knocking the stuffing's out of their dovetails with grit lmao


No I havent, better find it and have a look, make sure Im not doing the same......:whistle:



You got me on the making tea strike.....Can't call em completely useless eh :D


All this oil is playing havoc with my manicured nails...lol

Ross77
02-07-2009, 11:20 PM
[quote]
I can only imagine the ruin it's doing to those dainty fingers... :whistle:
[/QUOTE

The middle one is very dainty, do you want to see it......:yahoo:

Just ordered some delrin as a last attempt to salvage the leadscrews. Think I've got a worn 10mm lead, ballscrew kicking around that came with a motor I bought. Probably would be easier to rebuild that with new balls than mess around with delrin and leadscrews......

Ross77
08-07-2009, 11:29 PM
More questions if I may.........

Made the 2 delrin nuts no probs, mounted one each side of the connector block (what was the original nut that I trashed).

The problem I have is that although the backlash is almost gone the resultant friction caused is making the screw difficult to turn. Theres still a bit of alignment to do which will hopfully reduce it a bit and Ive also got the gibbs set to tight. However I noticed that the last bit of backlash/play is actually the delrin flexing. Is this correct or have I made a mistake some where?

Once the alignment and gibbs are set correctly there should be no play under no load conditions.... But I cant help think that under load this problem will re-appeer and cause problems.

Has anyone else experienced problems between static/no load measurements and actual machining measurements? or am I worring about nothing :rolleyes:

I've looked around on the net and some people seem to swear by leadscrews and delrin and some only use ballsrews...
From what I can see the only way to reduce flex in the nut is to use a metal one with delrin as the antibacklash, but surley this will only "smooth" out the play as ultimately the delrin will have to compress for the metal nut to make contact with the screw during change of direction to increase the strength......

Hope this makes sense. pretty much finished the x axis motor mounts so changing to ballscrews will be a major redesign.

I cant make up my mind If an accurrate small small mill (ie ball screws) will still be usefull after its built the bigger machine....

BillTodd
09-07-2009, 12:21 AM
and Ive also got the gibbs set to tight.
Just like the nut, there should be a tiny amount of play in the gibs (you can always tweak it once it's up an running, so leave them a little slack). If they're too tight it'll cause you as many problems as too loose.

Does the table slide freely now? There'll be an initial stiction (about 40lbs worth on my drill/mill) but, once moving it should move easily.

Ross77
09-07-2009, 02:12 AM
Just like the nut, there should be a tiny amount of play in the gibs (you can always tweak it once it's up an running, so leave them a little slack). If they're too tight it'll cause you as many problems as too loose.

Does the table slide freely now? There'll be an initial stiction (about 40lbs worth on my drill/mill) but, once moving it should move easily.


Thanks Bill, that was the advice I was after. Ive found that if I use both hands then the tables moves easily once the inertia is bult up, but this is too tight for the screw. I have readjusted it so that if i try to push it with a finger it wont budge, bit more force and it flys to the other end. with it set like this there is a small amount of side ways movement but I can only see it when there is oil on the ways.

Maybe I will stick with the leads and see how it performs with the motors. As much as I want to get it finnished I also want to get it right. Its been fun learning on this tho...I seem to only be able to learn when I've tried it and F**ked it up for myself:heehee:

HiltonSteve
09-07-2009, 01:55 PM
I seem to only be able to learn when I've tried it and F**ked it up for myself:heehee:

Best way of learning.....!

If I made a list of all the things that I have fucked up I would need a lot of paper, 2 catogories, minor and major f**k ups. I am pleased to say that as you get older you don't add as many things to the list.

My best major f**k up was ripping the cross slide clean off my newish CNC lathe because I did not set the chuck pressure high enough, the part came out of the jaws when I was screw cutting and got jammed between the chuck jaws and the toolholder at about 1000rpm. I was standing right next to it when it happened and I can tell you it went with a bit of a bang, had to add a new pair of pants to the repair bill!

Repair cost - 8,000 - thank god for insurance!

Robin Hewitt
09-07-2009, 03:10 PM
I am pleased to say that as you get older you don't add as many things to the list.


That's something to look forward to then :heehee:

Ross77
10-07-2009, 06:47 PM
Nice to know Im not the only one then :biggrin:

readjusted the antibacklash nut alignment and its much better now, so it seems perseverance is key. Spent ages the other nite trying to work out why it was binding, next day I spotted the problem in 5 mins.

Thanks again for all the advice. Its ok reading from a book or off the net, but being able to ask specific questions when you get stuck is brilliant. Definetly wouldnt have got this far on my own.......:beer:

Ross77
04-08-2009, 10:25 PM
Had to put this on hold for a while and then when I got started again last week I crushed my finger whilst honing the ways.........:eek:

So decided to move on to the electrical side and sort out the stepper controller, after hours of trying to bypass the optos and feed the chips direct the L6203's (H bridge) decided to put on an impressive firework display.... @ 40V these things sure go bang.:whistling:

So all in all things arnt going to well.

Any body make curcuit boards for L297 + 2x L6203's with diode protection so I can transfer the remaining parts over to a less complicated board?

After a lot of serching on the web I think I've found out why I couldnt get it to work, There is an enable pin on the L297 that has to logic high! Am I right in thinking that will stop the chip from working?

Ive got another board to try, but not to keen to fry that one as well

Ross77
04-08-2009, 10:59 PM
I have 2 dead boards and 2 good ones....all to go in the bin and good riddance to the worst 700 I ever spent.


You dont rate these as drivers then? Your not throwing away the good ones are you. :whistling:

Just want to get this thing running. Nearly finnished the x-y axis:yahoo:
Just the spindle, motor and z axisto do....

Swarfing
04-08-2009, 11:06 PM
Never put them in the bin pass them on..........Ross check for signal on the output of the Opto's if none is found when you fire the circuit up it maybe because they require some voltage. I've built a few opto isolated circuits for interfaces to my radios, every time they do not work is because they need power to one of the pins??? check the spec of the ic you are using with the manufacturers specs

irving2008
04-08-2009, 11:24 PM
@ 40V these things sure go bang.

They go bang because of excessive current not voltage...usually if upper and lower devices in the bridge are 'on' simultaneously... 40v across .5 ohms = 80A peak, 3200W instantaneously.... your PSU will do that for a few 100uS no problem!

Ross77
04-08-2009, 11:33 PM
Opto's if none is found when you fire the circuit up it maybe because they require some voltage


Cheers, I did check the outputs when the onboard processor was controlling the motors and could see the logic highs and lows on the step and dir. pins, but when I tryed to inject a signal in to it my self nothing happened. I was just wondering if anyone knew if the enable pin can completely switch off the chip? as the board is double sided and very crowded it is difficult to see what is going on. (and after the last one went bang , I'm not keen to randomly test points) I was hoping that the enable switch is also controlled by the processor, which would explain why the motors wont work when I try to control them.


They go bang because of excessive current not voltage...usually if upper and lower devices in the bridge are 'on' simultaneously... 40v across .5 ohms = 80A peak, 3200W instantaneously.... your PSU will do that for a few 100uS no problem!

Looks like I must have shorted something whist I was trying to get it to work. Is this driver set up usually Ok?

P.S if you are throwing them away KIP, my bin has plenty of space:beer:

Ross77
06-08-2009, 09:36 PM
I have a good arm...although the bin in Devon is a throw too far for me :D


Fair play, It was worth a try tho eh :naughty: Damm you yorkshiremen....

Im not one to be beaten so had another crack at the control board. Rewired the inputs to the L297, bypassed the output relays and it worked.............:dance:

......Until I turned the Vref pot the wrong way and fryed the output chips AGAIN. So at least I've found something i'm good at. :rofl:

Question time. If all 3 motors are 2 phase, 8 wire and configured in parallel, then why is one of the motors wired differently at the board plug? surley the phases cant change as the motor wouldnt turn...

Hope to make some real progress this weekend. so post some more pics soon

Ross77
06-08-2009, 11:36 PM
Forgot to ask if anyone knows of a good cuircuit to test stepper drives? I'm looking for an MPG type thingy that dosnt require a pc or mach, but will generate the correct pulse voltages, timings etc for step and direction

Maybe i should post In the drivers section?

Cheers

irving2008
06-08-2009, 11:55 PM
Forgot to ask if anyone knows of a good cuircuit to test stepper drives? I'm looking for an MPG type thingy that dosnt require a pc or mach, but will generate the correct pulse voltages, timings etc for step and direction

Maybe i should post In the drivers section?

CheersFunny you should say that, i was just thinking along those lines...

I'll post it up later...

HankMcSpank
07-08-2009, 12:11 AM
For a really simple 'get you up & running testing a stepper nice & quick', it's really handy to have one of these in your component tray...

http://www.datasheetcatalog.org/datasheet/allegromicrosystems/5804.pdf


They don't make 'em anymore so they're getting a little scarce, but still available here...

http://www.cricklewoodelectronics.com/Cricklewood/product.php?productid=15150&cat=0&page=1

Pin 11 is the step input - switch that pin low/high - your steppers move. Job done.

John S
07-08-2009, 12:39 AM
I have a good arm...although the bin in Devon is a throw too far for me :D

Tell you what, Nottingham is nearer and I can take them down to Bristol on the 22nd when I go to the show.

Let's shame the bastard :clap:

.

irving2008
07-08-2009, 12:52 AM
Forgot to ask if anyone knows of a good cuircuit to test stepper drives? I'm looking for an MPG type thingy that dosnt require a pc or mach, but will generate the correct pulse voltages, timings etc for step and direction

Maybe i should post In the drivers section?

CheersRoss, are you saying to exercise the stepper drivers directly without a PC, or to drive the motors without a stepper driver?

Ross77
07-08-2009, 07:25 PM
Cheers guys.

For a really simple 'get you up & running testing a stepper nice & quick', it's really handy to have one of these in your component tray...

http://www.datasheetcatalog.org/data...stems/5804.pdf

That sounds perfect for testing the motors, I was also after something to control the whole driver/ motor setup without a pc.




Tell you what, Nottingham is nearer and I can take them down to Bristol on the 22nd when I go to the show.

Let's shame the bastard


Good idea, he's not biting yet tho..... maybe have to offer some cash:heehee:
Is that a CNC/ machinery show?



Ross, are you saying to exercise the stepper drivers directly without a PC, or to drive the motors without a stepper driver?


Yes I would like to be able to control the whole driver and motor system without a pc. I was thinking along the lines of a varible pulse generator that could feed each axis as required by using a joystick, (like on a Playstation controller) That way i could control direction with the pad and the speed with a trim pot, If it works i might look at using a ps3 analouge type joystick so the speed it proportional to the stick movement.

Ive been looking on the the net at 555 timer circuits feeding a schitt trigger, but I'm not skilled enought to design it for the correct voltages and pulse timings:sad:

HankMcSpank
07-08-2009, 08:04 PM
That sounds perfect for testing the motors, I was also after something to control the whole driver/ motor setup without a pc.



Oops...that'll be the speed reading. Sorry!





Ive been looking on the the net at 555 timer circuits feeding a schitt trigger, but I'm not skilled enought to design it for the correct voltages and pulse timings:sad:

you wanna tread carefully there ....you could end up with a stinking mess :tongue:

Ross77
07-08-2009, 11:57 PM
Oops...that'll be the speed reading. Sorry!

No probs, still useful



555 timer circuits feeding a schitt trigger


That will be my speed typing....:heehee: Or at least thats my excuse....

Another evening of tinkering and I think Ive finally got the board sorted so I'll leave it for now. Now my finger is better I can hopefully finish the honing and anti backlash nuts. Just got to hope I dont make a schitt job of it :rofl:

irving2008
08-08-2009, 02:20 AM
Ross,

Try the attached for size...

If you are driving opto-isolated inputs to the drivers let me know as it'll need a couple more parts...

ptjw7uk
08-08-2009, 11:41 AM
Hi Irving,
on the small pic I think I can see the link to the dir out pin but it is missing if you enlarge the picture, I assume it goes to the divider part of the 2 resistors.

peter

Ross77
08-08-2009, 12:26 PM
Thanks Irving thats exactly what I was looking for. :beer:

For this board I'm going direct to the driver chip but it will be useful to have the opto verision as well if you dont mind. Is it posible to do single steps with this circuit as well :whistling:.

Thanks again

Peter, seems to be ok when I look at it, dir pin is linked to the resistors

irving2008
08-08-2009, 02:04 PM
Thanks Irving thats exactly what I was looking for. :beer:

For this board I'm going direct to the driver chip but it will be useful to have the opto verision as well if you dont mind. Is it posible to do single steps with this circuit as well :whistling:.

Thanks again

Peter, seems to be ok when I look at it, dir pin is linked to the resistors

Here is the opto version...

Single steps I need to think about (and why would you want them?)

ptjw7uk
08-08-2009, 02:40 PM
well i dont understand whats going wrong with my pc display, I downloaded pictures and the links are there but not on the display!

Another fine point of MS IE7 I expect!

Peter

Ross77
09-08-2009, 01:29 AM
Thanks Irving, your a star. have a couple of beers :beer::beer:

The single steps are for fine tuning, I'm planning ahead really. Once it has built the machine I want, this mill will probably be redundant and not worth selling, so I thought that It might be useful if I just need a part skimmed or holes drilled at set distances. If I also fit a DRO of some discription I can manually control the machine as a stand alone without having to draw the part and produce g-code etc. etc.

tribbles
10-08-2009, 11:39 PM
Farnell will charge the first time you use them, I think (that's what happened to a mate of mine [who asked me to order the bits for him instead, since I tend to chuck about 200 a month at them] and my brother).

I'd also put RS in that list - although RS I've found are generally more expensive for components, except LCD displays where RS are about half the price.

I've used Digikey before, but not Rapid nor Cricklewood (yet).

irving2008
11-08-2009, 12:22 AM
Farnell will charge the first time you use them, I think (that's what happened to a mate of mine [who asked me to order the bits for him instead, since I tend to chuck about 200 a month at them] and my brother).
Not as far as i am aware... just signed up, threw an order of about 30 at them, job done...

HankMcSpank
11-08-2009, 12:29 AM
+1 to that.

I've only just started dealing with Farnell, as I'd always had in my mind that they were Draconian with their postal charges & minimum order requirements and made you jump through hoops as a private individual (they used to - & RS were worse from recollection!)


I'm actually pleasantly surprised at how they've changed (I guess it's 'adapt or die' in this new Global commercial market place we now live in) & I've put in some pitifully small orders with Farnell & never yet had a postage charge yet....normally get the stuff the next day too.

tribbles
11-08-2009, 12:35 AM
Not as far as i am aware... just signed up, threw an order of about 30 at them, job done...

I think that's only if you don't order below 20 the first time.

Certainly they used to have an MOP of 20 (which meant I always over-ordered on items), but now they don't for me.

irving2008
11-08-2009, 12:59 AM
I think that's only if you don't order below 20 the first time.

Certainly they used to have an MOP of 20 (which meant I always over-ordered on items), but now they don't for me.No, its because i used a debit card, the 20 MOP applies to credit cards only.

Ross77
13-08-2009, 12:53 AM
Ok In case your thinking this tread is getting a bit stale I'd better post some pic's. Again apologies for the quality, need a new camera really.

The motor mounts are finished as is the MK3 anti-backlash nut for the X axis. Its all a bit messy as Ive had to use alu angle and modify bits from the original machine. some bits are still mock up and I may remake them if I get time.

Thanks to John S for the idea for anti backlash solution. I had to change it slightly as the first incarnation of just sandwiching the orignal nut with delrin kept twisting slightly and producing more BL. This design uses the first to plates to sandwich to original nut, and prove a fixed base, whilst the delrin is fixed to the end plate, the spring in between means that i can back of the tension on the adjusters as well. Having played around with this there seems to be a very fine line between zero BL and too much friction. Comments and abuse welcome :heehee:

Robin Hewitt
13-08-2009, 10:38 AM
there seems to be a very fine line between zero BL and too much friction.


Why have you got nuts behind the stator plate? If you tighten them the spring does nothing and the line will be fine :beer:

Ross77
13-08-2009, 10:18 PM
Why have you got nuts behind the stator plate?

Hi Robin
Not sure what you mean by a stator plate? in the 2nd picture the left hand and middle plate are clamping the original nut, tightened by the middle nuts (to resist rotation). the delrin nut is fixed to the right hand plate and is adjusted by the end nuts to compress both drive nuts to reduce backlash.

The spring is purley overkill and just pushes the delrin nut on to the adjuster nuts and also ensures that if I back of the adjuster nuts then the delrin nut moves with them to give positive control over the pre-tension.

Ive tried 3 or 4 different versions and this set up worked the best, is the easiest to align and easiest to adjust.

I presumed that there is always a fine line between eliminating backlash and excessive friction?

Ross77
17-08-2009, 12:02 AM
Made some good progress this weekend.

Gave up honing the ways as they were so far out of true and had to scrape them. I used a 60 deg. Carbide tipped lathe bit (held in a 3-4 MT adapter :whistling:)

I can see why people dont like doing it, very time consuming, repetative and hard work.

So with the ways sorted, motor mounts done and the antibacklash nuts finnished I decided to give it a lick of paint. :dance:

Lee Roberts
19-08-2009, 09:22 PM
Amazing Ross, coming along nice mate !

What paint did you go with in the blue ?

Ross77
20-08-2009, 08:11 PM
Thanks Lee. Hope to get it assembled soon....Other projects and uni looming...........................

Can't remember the makers name but its supposed to be a hardwearing hammered finnish same as Hammerite. The casting was so so rough I thought a flat paint would look terrible.

This should be a good test for the paint. If it can resist way oil, coolant, grease and all the other nasties that will be thown at it.

Ross77
26-10-2009, 09:35 PM
After 2 months I've been able to fit in some workshop time:yahoo:

So the z axis is done and I've managed to hot-wire the controller board to work with step and direction so "IT WORKS" just need to find a better way to transfer the IC to another board.

Tested the x axis and there is no backlash, using a 0.001" gauge it always returned to the same place

The breadboard circuit is the stepper exerciser that Irvine designed for me. Thanks again it works great, no need the drag the pc out.

Now for the question........
Should steppers hum/crackle whilst holding? it only seems to happen on certain motor positions. It also gets worse/louder when I turn up the Vref to increase max current.

It also seems to buzz/miss steps at about 300 rpm, is that normal?

Thanks in advance.

Robin Hewitt
26-10-2009, 11:35 PM
Should steppers hum/crackle whilst holding? it only seems to happen on certain motor positions. It also gets worse/louder when I turn up the Vref to increase max current.

It also seems to buzz/miss steps at about 300 rpm, is that normal?


Steppers usually make their best noises when in action, on hold the current is usually cut because you don't need the pulling power.

300rpm is not bad for a stepper, but it isn't good either :nope:

Ross77
26-10-2009, 11:52 PM
Thanks Robin, not sure i understand, so is the buzzing/ frying noise when holding ok then? or Have I got problems?

I have basicly had to rewire the driver chip and followed the data sheet and other similar designs but I not sure about the control pin. It sets the chopper for either the 4 phases or on the inhibit wires, could this be causing the noise?

If the noise is ok (typical) then I can increase the vref to gain more current which seems to help with the missing steps at the higher speeds. At the moment its set at 0.5v which i think means I've only got 1amp going to the motor. As it uses 2 L602 output chips I belive it is capable of 4amp but I'm too chicken to just crank it up.

Thanks in advance

Robin Hewitt
27-10-2009, 09:58 AM
Thanks Robin, not sure i understand, so is the buzzing/ frying noise when holding ok then? or Have I got problems?


The frying noise is probably a sympathetic vibration to the chopper frequency, possibly worse if you pause between half steps. Nothing to worry about so long as the motor isn't getting hot.

I'm no expert on this, my max stepper speed actually decreases if I wind up the current which seems totally wrong, so I am not understanding something. My motors clack out if I set the G0 to 12mm/s so I keep them set 8mm/s to avoid losing position. I'm waiting for Gary to send me some fancy 220 volt drivers which will hopefully make everything wonderful.

I suggest you wind up the current slowly, test the top speed and see if motors, or heatsinks on the driver start to get excessively hot.

Good luck :beer:

Robin

Ross77
27-10-2009, 08:37 PM
Thanks Robin, :beer:

The motors dont seem to get hot if left holding but they get dam hot in use, almost untouchable!! I'll have to see how it goes.

Thanks again

irving2008
29-10-2009, 02:16 PM
Get a cheap thermoprobe from Maplin (19, here (http://www.maplin.co.uk/Module.aspx?moduleno=48318)) and check motor case temp. Anything above 85degC and you need to be thinking cooling/heatsinks on the motors.

Ross77
30-10-2009, 09:08 PM
Thanks Irving, Already got that on my meter, and one of those infrared jobbies.....Just forgot to use them.:whistling:

So is it ok for the motors to get hot if i provde cooling to hopfully keep below 85 degC?

With regard to your L297/ 6203 driver do your motors buzz whilst hold?
Also have you got the contol pin set high or low?

Cheers

Robin Hewitt
30-10-2009, 09:26 PM
Anything above 85degC and you need to be thinking cooling/heatsinks on the motors.


D'uh :eek:

I've never run a stepper past comfortable to touch, usually lukewarm to tepid. Am I not trying hard enough :naughty:

Isn't there something about eddy currents heating things up? No possibility he's driving one coil with the other shorted out I suppose? That would be the perfect recipe for slow'n'hot :heehee:

Robin

Ross77
04-11-2009, 09:22 PM
Problem solved........:whistling:

It all went up in smoke tonite, flames an all. quite impressive :heehee:

Looks like I need a new 3 axis stepper driver.

2 steps forward 5 steps back eh.

Robin Hewitt
05-11-2009, 01:31 PM
It all went up in smoke tonite, flames an all. quite impressive :heehee:

Bit late for a photo i suppose :whistling:

Unless you chuck a bit of paraffin over it :naughty:

Ross77
05-11-2009, 07:45 PM
Glad you found it funny.:smile: I'm 50-60 out of pocket now to replace it tho :eek:



Unless you chuck a bit of paraffin over it :naughty:


Could be arranged, and very tempting, but being a tight git i'm going to rob the heat sink ect from it first.:dance:

I cant find any cheap drivers that work over 40v so looks like I cant even use the psu.

irving2008
05-11-2009, 10:03 PM
Glad you found it funny.:smile: I'm 50-60 out of pocket now to replace it tho :eek:



Could be arranged, and very tempting, but being a tight git i'm going to rob the heat sink ect from it first.:dance:

I cant find any cheap drivers that work over 40v so looks like I cant even use the psu.

Sadly most stepper driver chips are 35 or 40v max... so 30 or 35v supplies. To go above that you need to be looking at discrete MOSFET drivers, but these tend to be are rare and expensive..

Robin Hewitt
05-11-2009, 11:02 PM
Glad you found it funny.:smile: I'm 50-60 out of pocket now to replace it tho :eek:

I've done worse, not on the large hadron collider scale perhaps, but whaddya do? Personally I remind myself that it's business and in business you always start from where you are now.

OTOH, being business I do get to buy the cloud of smoke pre-tax and reclaim the VAT :whistling:

I understand your pain :nope:

Ross77
13-03-2010, 10:29 PM
Seems like ages since the last post but finally managed to find some workshop time and have made quite a bit of progress. bolted the headstock to clamping collar, fitted new bearings to the spindle and modified the belt guards. just need a new belt and stepper drivers and it should be good to go..... :smile:

For now I have decided to use the original 1 phase motor as a test. I think it will be better to just get it working and then upgrade parts if needed.

I've also been wondering if I should take off the steppers and refit the hand wheels so I can check that it works as a manual mill. anybody agree?

Ross77
23-03-2010, 08:14 PM
Nearly there, should be making chips at the weekend, :dance:

For the sake of my sanity and desire to get this working I've put the homemade drives on hold and splashed out on some PM542's from Gary. very nice drives no buzzing or crackling like the other ones.

Just need to fit the limit switches and get used to mach 3 now.

BillTodd
24-03-2010, 12:08 AM
Look's nice and purposeful :)

Love the drill-table monitor stand :LOL:

Ross77
24-03-2010, 09:20 PM
Love the drill-table monitor stand :LOL:

yeah I like it :smile:. its got to be one of the most over engineered monitor stand

Ross77
28-03-2010, 06:44 PM
:dance::dance::dance::dance:It works..............not finnished by any means but milling Al under Mach 3 control...

Its happy cutting 0.5mm deep in Al and seems to have a 0.02mm resolution (probably change when I cut a bigger test piece)

the surface finnish is quite good, not very good pics tho. I think the mill is a little out of tram (if thats the word) the cutter is leaving small ridged as if each pass is sligtly semi-circular.

Is there an easy way to fix this? as I can only think of shiming the X-Y table but that will be a nightmare.

BillTodd
29-03-2010, 02:28 PM
Is there an easy way to fix this? as I can only think of shiming the X-Y table but that will be a nightmare.
You could try adjusting the tension of the base mounting bolts; on a small machine like yours it might flex the post enough to correct the tram. Are the semi circles left by the cutter the same side when machining left to right and right to left? If the side swaps (i.e. the cutter is only cutting on the leading edge, then it could be the whole machine is flexing with the cutting load) lighter finishing cuts should fix it.

BTW the correct way to test the tram is with a DTI mounted on arm a few inched away from the chuck, so it can be rotated aroung the table (use a parallel between the table and the dti to even out irregularities in the table surface)

Robin Hewitt
29-03-2010, 06:36 PM
The bottom of the groove looks like something has come loose in the tool chucking.

The sides of the pocket look like a tool which can't decide if it is rubbing or cutting. Maybe a tool cutting uphill that is flexing to remove the allowance for the next pass.

I think you have other things to fix before you start worrying about tram :naughty:

Also 0.5mm sounds awfully light.

Ross77
29-03-2010, 09:18 PM
You could try adjusting the tension of the base mounting bolts; on a small machine like yours it might flex the post enough to correct the tram. Are the semi circles left by the cutter the same side when machining left to right and right to left? If the side swaps (i.e. the cutter is only cutting on the leading edge, then it could be the whole machine is flexing with the cutting load) lighter finishing cuts should fix it.


cheers didnt think of adjusting the pillar :redface: I'll have to check the cutting again to see if its flexing, before i go adjusting anything



BTW the correct way to test the tram is with a DTI mounted on arm a few inched away from the chuck, so it can be rotated aroung the table (use a parallel between the table and the dti to even out irregularities in the table surface)


I'll try that then, I've seen the dual gauge ones and always asumed you need both gauges to cancel the error, Duh..



The bottom of the groove looks like something has come loose in the tool chucking.


I think thats from when i tested the repeatability on the z, it produced a different cutter pattern for half the length but is the same depth.


I think you have other things to fix before you start worrying about tram :naughty:


Im sure your right, :cry: I was just so happy it was finally working. the other point is that I only have the single phase motor running at 1:1 so the cutter might not be quick enough.

Robin Hewitt
30-03-2010, 11:12 AM
I only have the single phase motor running at 1:1 so the cutter might not be quick enough.

Or, maybe, too fast :eek:

Irving may disagree with this next bit :naughty:

There are published tables for cutting speeds but there are also tables for chip loadings. If you go for the official cutting speed the feed rates have to increase in proportion to keep the chip removal rate and up goes the side loading.

I simply don't have enough iron in my round column mill to hold against the side loading and smaller tools don't have enough meat to avoid bending. I reduce the revs and feed rates dramatically, I may be wrong but it works for me.

Get it wrong and first the tool digs in removing too much, then it rubs for a bit before the next dig in. Surface finish goes to pot.

When a tool starts to rub, rather than cut, it introduces a bending force. You can go around the finishing cut until the cows come home without fetching it to size. Increase the hole cut size to get past the rub and Whammo, you've cut oversize.

The trick is to rough out and leave an even excess all the way round the job then get the revs and feeds right on the finishing pass. Ignore the tables, find out what works on your machine. Even then the problems may come back when you change direction.

The routers of aluminium cut uphill, but they are usually making pretties rather than working to tolerance.

The millers of aluminium have a lot more rigidity in the system so they have can afford to cut downhill, meaning the tool shies away from the finished size rather than in to it. This does mean removing the backlash. If you compensate for backlash in the software you can't afford any side loading on the tool which can move the slides, a severe restriction on feed rates, and hence, spindle revs.

Ross77
31-03-2010, 02:01 AM
You must be a mind reader I was just going to ask about the tables for speeds and feeds........ Is it not worth me knowing what it should be so I can work back? where can i finf these tables?

I'll have to check the flexing, The quill was hardly down and the bit was 10mm dia, 20mm long in a ER32 collect chuck so I hope it wasnt tool flex. And im not sure how i can slow the spindle down without a major redesign and a shorter belt. I was hoping to check it worked properly before I bought a 3 phase motor.

Certainly shallower cuts and plenty of cutting fluid improved the surface finnish, just how noisy should a rough cut be??? maybe I'm erring on the side of caution.

I'll have to refresh my memory on up hill and down hill milling. I always thought that learning how to use it would be harder than making it :oD

Robin Hewitt
31-03-2010, 10:12 AM
Here are cutting speeds, milling is second table down, calculator below.

http://littlemachineshop.com/Reference/CuttingSpeeds.php

It suggests 1600 rpm for 10mm in aluminium. Personally I'd go for about half that. If the suds gets diverted for a moment by a fixing bolt, I prefer it if the tool doesn't go red hot :whistling:

My mill came with a 2hp motor but no way on God's green do I want to put anything like that down a small cutter, it's just too much. I replaced it with a 1hp on a digi phase inverter and I never work it hard.

How noisy should it be? Any loose fittings on a bench mill will rattle. The cutter should make cutting noises, if it becomes noisy that usually means you've lost the tool tip.

Ross77
31-03-2010, 07:53 PM
Thanks once again for your advice, It definetly looks like I just need to learn how to use it..........The mini mill beginers guide was quite useful too, its suprising how much you read and then forget :heehee:

Ive ordered some 2 flute ali cutters 3,4 and 6mm so i can keep the speed up and find the right feed. Hopefully get there in the end.......

Ross77
01-04-2010, 10:02 PM
Ok cutters arrived today, tryed the 6mm one and what a difference. 3mm deep cut in one pass with nice clean sides and no burrs on the edge. not sure on the cutting speed but the velocity is set at 400 mm/min. but the feed rate said 18mm/min I think . still need a bit more practice with mach.

You where definetly right Robin, I think I,m getting closer to the machines capabilities, althougth for what it is I'm more than happy with how it performed with the 6mm cutter. I'm sure that I can improve on the 3mm depth with a bit more tuning.

now its cutting clean edges It appears to be 0.3mm out, not sure if this is a step unit error ( had to round up to whole no.) or backlash. When I first tested it under no load I was getting 0.02 accuracy, is it possibly that the machine is still settling down? I dont think it can be machine flex as i was only typing the G-code line by line so it would have plenty of time to straighten up before the change in direction. I wont be to happy if the delrin nuts need constant attention tho...

Robin Hewitt
02-04-2010, 11:25 AM
I'm sure that I can improve on the 3mm depth with a bit more tuning... now its cutting clean edges It appears to be 0.3mm out, not sure if this is a step unit error ( had to round up to whole no.) or backlash.


3mm deep sounds about right for a 6mm tool, so does 1420 rpm suggest you experiment with feed rates.

Measure the backlash, find out how much of the 0.3mm is accounted for. Perhaps a man has to ask himself, is Delrin better suited to free rolling gantry style machines?

I spent a lot of time and money removing the backlash from my machine, if I could have done the same with a plastic nut it would appear somewhat futile :whistling:

Robin