Denford Software & Machines

Hi

First I'd just like to say that it's great that Denford have setup this forum to provide support for the older machines. We have a 1984 Orac and 1985 Triac at work which we rescued from being in store for about 5 years and got them going again. Now they're used almost continuously and the work that has been done on them has put some of the much more expensive machines to shame!

Now to my question. We have a dead starturn 4 here - the controller blew when someone shut the case on a cable! I am thinking of fitting it with a PC based controller (Mach 3) instead as I have done to my small milling machine at home. I have a manual here for the starturn 4 and 8. Under electrical it states 1/2HP DC spindle motor and 200steps/rev 2.9V 3.8A stepper motors. Are the same stepper motors fitted to both the 4 and 8? The reason I ask is that the guys who used the starturn tell me that it used to lose steps quite often - were the steppers run on reduced current as the 4 was a smaller machine? I can't imagine those steppers stalling easily - the Orac certainly doesn't!

Also do you have any details of the spindle drive - presumably an analogue voltage - any ideas of the range?

Cheers

Dave

Hi David...

Noticed you haven't had an answer to your post so thought I'd try and give you some pointers.

From what I remember the Starturn 4 used smaller stepper motors - and the Starturn 8 used bigger ones which were the same ones as those used on the Orac.
But unfortunatly I can't remember what spec they were (only that they were a smaller frame size and lower current rating).

We used to use CD20 or CD30 axis drives which are 2amp and 3 amp drives respectively so this may also give you a clue (or we may have used Digiplan ST2 or ST3 drives which again are 2amp or 3Amp drives)

Hope this helps

Hi Mr Magoo

When you say 2/3 amp drivers, do you mean that those were the actual ratings of the drivers? I'm helping convert a friends Orac to new drivers and the motors are marked up as 3.8A - so were they being run below their actual capability?

There is a link to a startrun 4/8 brochure here -
https://www.gandmtools.com/makerspages/Den_starturn.pdf

As you can see it lists both sets of specs, but only one spec across both machines for the motors.

Thanks for the reply.

Cheers
Dave

Hi Dave...

so were they being run below their actual capability?

Exactly! Back in the "old days" 2amp drives were relatively expensive. 3 Amp Drives were very expensive

But stepper motors are a bit of a law unto themselves too. Sometimes increasing the current to a motor can actually increase the likelyhood of stalling at low feedrates (depending on the the inertias involved)

Also take a look at some typical speed vs torque curves of stepper motors like you can see here
https://www.pennmotion.com/pdf/Size23.pdf
It's sometimes good to select a motor that gives you the torque at the speeds where it's needed most, even if that means that the motor doesn't exactly match the drive. It's a compromise between getting good rapid traverse rates and at the same time getting decent torque at the slower cutting feedrates.

And at the end of the day you can't beat good old trial and error

Hi Mr Magoo

Thanks for the reply - its easy to forget that in their day the machines were 'state of the art'.

If you don't mind me asking, you don't have to answer this, but what is your connection to Denford? You seem to know a fair bit about the older machines so I was curious!

Cheers

Dave

Up until a couple of years ago I was part of the R&D team back at Denfords - and worked with them for 18 years
Great bunch and still keep in touch with them (I just fancied seeing what life is like in Sunny Brisbane and haven't looked back )

But always happy to help with the old legarcy stuff - I don't think there's many of us older buggers about these days who remember the Oracs and Starturns

Hi

So its all your fault ....... only joking the machines are great and still hold their heads up amongst the big boys. The Orac and Triac we use for making race car bits easily puts the big machines we have here to shame - all you need to be is a little clever in your programming and setups!

Now - i've just been doing some hunting round our place - and would you believe it, I have come across 4 Starturn 4s kicking about. All 1986/87 models. Only one is intact, one with a half complete big stepper motor replacment, one completely mechanically stripped, one with no motherboard and another with no stepper drivers!

I'm hoping to try and persuade the people here to let me rebuild one with a PC controller (Mach3 - I use it already on my mill at home) but I could really do with knowing the rated current for the steppers and I wonder if anyone happens to now the rated torque of them ?

Also would anyone have any info on the DC spindle motor controller ? Wiring diagrams etc would be useful.

It seem such a shame to see these machines lying around!!

Cheers

Dave

I have come across 4 Starturn 4s kicking about

Correct that - just found a 5th one!

Cheers

Dave

Talking of finding old Denford bits see what you think:

https://denfordata.com/bb/viewtopic.php?t=394

I can't vote -says it's locked. Unfortunately not mine to get rid of!

Cheers

Dave

oops - of course - its in a locked forum

Have moved it into vintage stuff:
https://denfordata.com/bb/viewtopic.php?t=394


Back to the topic - I've found a load of drawings and documents for the startturn 4 and 8 - will make an announcment under Machines when i've uploaded the images (it'll be a big file)

Excellent - I look forward to seeing them.

Cheers

Dave

hi
the current rating for these drives (stated in the manual)are :-
cd20/cd25/cd25m = 3 amps
cd30/cd35/cd35m = 6 amps
cd40 = 9 amps

don't know that much about them i just read the manual.

col