Help with x axis stepper

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Wadewilson
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Help with x axis stepper

Post by Wadewilson » Fri 05 Mar , 2021 16:35 pm

Hi all,
Have an orac, old one which work threw away because it kept blowing the breaker every time you switched it on.
I managed to fish it out the skip and bought it home.
Fixed the issue with the breaker blowing, by removing the car stereo tape player, and blowing all the rubbish out from inside.

So now, I have a lathe which switches on, everything works and I can program it.
BUT......

IT SEEMS the x axis measurement is out completely.
I set tool 0 and tool 1 but when programming to say a basic dimension, it’s out by an odd figure.

Example.
I program the lathe to cut an 18mm diameter 5mm long on a 3/4 inch piece of alloy.
At first the settings are out, and I have to adjust the x axis offset by about 8.mm to achieve the correct size (with offset at 0 its cutting way big)
Ok, so once I can repeatedly get the cut at 18mm, I reprogram and make the part start at 7mm,Dia in 2mm and then to 12mm dia
Moving along the z axis, and moving up in size diameter. Starting the program, it tries to begin at something like x-1.0.
it gets further and further out of size.

I reset offsets to produce the 7mm dia, get that right but then the 12 is about 16mm, and the 18mm is now roughly 25mm.

I cannot work out why it’s out so bad.
Any help would be appreciated.

Thanks

TDIPower
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Re: Help with x axis stepper

Post by TDIPower » Fri 05 Mar , 2021 20:41 pm

My only dealings with the Orac were seeing one in a corner of the workshop in school back in 1987 and noticing it had a sharp car cassette deck less the radio section. i wish someone had known how to use it and shown me back then but no one did.

Anyway I was thinking and doing a comparison to the more modern equipment i am familiar with. In the new software you can set the number of steps per mm of movement, so say 50 steps would move 1mm, now if for some reason that had become corrupted and was say 48 steps per 1mm then you would get an error but one that could be proved mathematically by doing a series of cuts say starting at 18mm, then 17mm down to say 5mm measuring the actual size cut at each size but not making any changes to compensate.

Now from my work with the Routers and mills over the years if there is any binding on the lead screws/nuts or gibs (caused by crap getting into them) then the machine will say send 50 steps to move 1mm but only move on say 43 of them and then the next time its told to move 50 steps 1mm it might only move 42 steps due to the resistance in the travels. Doing the test cuts would prove this as a random amount rather than a repeatable amount.

It doesn't solve the problem but gives you something to look at

Pete

Wadewilson
Posts: 6
Joined: Fri 05 Mar , 2021 16:25 pm
Hardware/Software: Home: Orac denford lathe with standard software and hardware.
Bridgeport minimill manual
Colchester student 6
Solidworks 2021 edgecam and autocad,

Work:
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All kart software

Re: Help with x axis stepper

Post by Wadewilson » Fri 05 Mar , 2021 20:54 pm

Thanks Pete.

I am kinda guessing it’s something to do with the stepper out of sequence.
It’s not a random difference, it’s exponential as the diameter gets larger,

So for instance, if I set the tool at X0.0 then take a cut at 20mm using manual control, it’s perfect,
But if I set it to do a series of different diameters within a program, it is out.

In fact I just rerun the program, and when it calls tool 1, and goes to a start position (g50) which is set at X20.0 and Z 5.0 it goes to that point perfectly, then waits for the start button to be pressed to continue the program. Then it goes awry,

Confused.....

Wadewilson
Posts: 6
Joined: Fri 05 Mar , 2021 16:25 pm
Hardware/Software: Home: Orac denford lathe with standard software and hardware.
Bridgeport minimill manual
Colchester student 6
Solidworks 2021 edgecam and autocad,

Work:
Citizen M16, M32
All kart software

Re: Help with x axis stepper

Post by Wadewilson » Sat 06 Mar , 2021 17:07 pm

Ok, bit of an update.

I’ve measured everything and it is strange.

If I write a simple program, and use RADIUS rather than DIAMETER (ie- for cutting an 18mm length, I program 9.0)
Then, when I come to set the tool, I set both tool 0 and tool 1 (my cutting tool) to z0 and touch on the 20mm bar and put in 20mm DIAMETER.

In my tool offset page, I add about 9.8mm to the x and run the program.
The display says it’s going to x20.0 (my g50 position) which looks right.
Then the next line of the program sends the tool to X 9.0 and the tool moves to a display of 9.0 but on the machine, it’s cutting 18mm
I have found this to be consistent at any measurement, as long as I program in radius dimensions not diameters.

Anyone else had this? I can’t see any jumpers on the driver boards to change the step but I’m guessing the stepper is reading double.

TDIPower
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Re: Help with x axis stepper

Post by TDIPower » Sun 07 Mar , 2021 18:03 pm

As i say I'm not familiar with the orac at all and only have very limited experience 5yrs ago with my Starturn 5 (many other projects have got in the way since I got it so it's sat in the corner waiting for its turn) my manual lathe works on Radius, so if I set the tool to touch on a 20mm dia bar and then wind the cutter in 1mm on the markings it will reduce the Dia to 18mm. I don't know G code so unsure what G50 is (the down fall of software that does it for you). So is it just a case of lathes work on Radius rather than Dia?

Pete

Wadewilson
Posts: 6
Joined: Fri 05 Mar , 2021 16:25 pm
Hardware/Software: Home: Orac denford lathe with standard software and hardware.
Bridgeport minimill manual
Colchester student 6
Solidworks 2021 edgecam and autocad,

Work:
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All kart software

Re: Help with x axis stepper

Post by Wadewilson » Sun 07 Mar , 2021 19:38 pm

I don’t think so,
Reading the manual (and the associated literature on here) the Denford Orac works in diameter.
The sample programs all show diameter readings, and the written samples are all in diameter.

I’ve played today, and it’s fairly simple to set a program, running it in radius, but I’m concerned when I come to do a thread.
Again the X value for the final depth of thread I’d assume will be in Radius, but the thread depth is worrying. Would I put it in as Half?

It also takes a few goes to switch on properly, seems like the first time you turn it on, there’s no vDU or power to drives(spindle, and you have to switch on and off a few times, then it kicks in and is perfectly fine.

Originally it was tripping the breaker due to a faulty EM switch, which was snorting to the casing, (tripping the safety in the household board) but that’s now fixed.
I’m sure it’s the 24v big relay, but unsure where to get one from.

I wonder if that has something to do with the x axis issues?

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