Is this mill viable for CNC conversion?

[Ejdepalm]

Hello guys!

Greetings from Sweden!

I have wanted to have a CNC mill for a long time now and I found this particular one for sale:



I have talked to the owner by phone and managed to get some more info on the machine. He was also kind and sent me some pictures.

Model: SAJO VF54 NC
Year: 1970-1980
Previous use: Used in a small machine shop that made prototype parts for Bofors Arms
Condition: Rebuilt with new bearings and ball screws etc. Not used since rebuilt. Seller describes it to be in very good condition
Tool holder: Pneumatic grip ISO50

The mill has been controlled by some sort of Slo-Syn tape reader. Seller has the original manuals for it.


Here is the electronics:


Movement is provided by 6-lead 0.8V 20A Slo-Syn stepper motors:


I have been operating CNC machines at school (aeronautical engineering) and I’m used to working in CAD /CAM software but when it comes to CNC conversions I’m a total noob.

So what I want to ask is if it’s possible to do a modern CNC conversion of this old NC mill and run it of a PC or should I just go and look for a manual controlled mill and start from there?

Would be great to know your oppinions before bothering the seller to much and wasting his time.

Best regards

Erik

[keebler303]

Erik

Welcome to the Zone!

This mill is definitely a lot better than starting from a manual mill. It already has ballscrews, motor mounts, etc. The kinds of parts that make a manual mill conversion expensive. I am not sure if you will be able to find current stepper drives capable of driving these motors. If it is working, maybe you could figure out how to reuse the old drivers with a computer.

Few things to consider:

tooling- Can you find cheap used toolholders to fit the machine?
Can you buy new ones locally if you need something particular?
Is the Z axis motorized or manual?
If its manual, how will you adapt it to CNC?

It looks like a pretty heavy duty machine and in pretty good shape. I would make sure it runs smooth before getting serious. Does the spindle sound good? Axes move smoothly/properly?

Good Luck
Matt

[Ejdepalm]

Originally Posted by keebler303 I am not sure if you will be able to find current stepper drives capable of driving these motors. If it is working, maybe you could figure out how to reuse the old drivers with a computer.

Thats the thing that deters me. Don't want to spend money on steppers that migth be "useless".

I have read about BTR:S that can be used to eliminate the old tape reader.
This site sells BTR:s for Slo-Syn tape readers: http://www.fastec.com/btr/index.html If the driver is working would this be a alternative to consider?

Anyone with experience using BTR:s?

Originally Posted by keebler303 Few things to consider: tooling- Can you find cheap used toolholders to fit the machine? Can you buy new ones locally if you need something particular? Is the Z axis motorized or manual? If its manual, how will you adapt it to CNC?

From what I have understand the mill was factory converted to NC by SAJO (the company that built it) back in the days so all three axis is motorised. I checked Ebay and ISO50 tool holders and collet seems affordable.

Originally Posted by keebler303 It looks like a pretty heavy duty machine and in pretty good shape. I would make sure it runs smooth before getting serious. Does the spindle sound good? Axes move smoothly/properly?

Yeah it's a big mill. Seller estimated it being 2.3m high and weighing in between 3-4 tonnes. The mill is 190 miles away so I will have to trust the seller on the condition.

I'm not sure wether or not to buy this mill. Help me out guys!

[Al_The_Man]

This machine appears to be controlled in the manner that existed prior to CNC, i.e. NC.
This operated from paper tape where the command were sent on a one to one basis, a line at a time direct from tape.
The fact that it has the steppers and obviously the drives, I would think that all you would need is something like Mach hooked up to it to work CNC.
A BTR is intended to eliminate the tape reader on a CNC machine where it was normally used to load a program in to memory and then run from there.
Al.

[LeeWay]

Those motors look like they may work okay. Should run on 24 VDC and 20 Amps.

The only concern I have with them is the 20 steps per rev. That may not be an issue, just something I haven't seen. They may work fine with Mach 3 using included drivers. Maybe even TurboCNC (DOS based) or EMC (Linux based). Both the later controllers are free.

You need more of an electrical guru's input on it though.
Nice looking machine too.

[Al_The_Man]

Originally Posted by LeeWay The only concern I have with them is the 20 steps per rev.

I think that is meant to be 200, the standard 1.8 degree step angle?
The 0 digits probably got spaced!.
Al.

[LeeWay]

If that is the case, I'd take a chance on those motors. They worked well enough to run the machine at one time. If not damaged, should do so again.

[Ejdepalm]

Thanks for the positive replies!

OK so I’ve been reading through the entire Mach3 manual and from what I understand a PC running Mach3 can control a machine as long as the driver has a parallel port.

I didn’t notice a parallel port in the driver cabinet in the pictures in the first post but I shall contact the seller again and ask him. Was it common for tape readers to connect to the machine via parallel port on machines as old as this one?

Since this mill is a “factory” NC it should already have axis limiters and e-stop right?

If we assume that the drive electronics are working and connected properly a PC and Mach 3 should allow me to get control over the machine?

It would be great if it would be as simple as this but there must be something I’m missing.

[veteq]

Hey,

If it has 3ballscrews and 3stepper motors with the drives on it, you only have to buy a pc and mach3.
Mach3 gives a signal through the paralelport for 3 stepper motors, these sinals are called step and direction, the stepper drives are just connected to the paralel port. (and betwwen stepperdrive and aralelport a device called breakoutboard, it seperates the high vlotage from the drives and the pc,(security))

regards,

roy

[Al_The_Man]

Originally Posted by Ejdepalm OK so I’ve been reading through the entire Mach3 manual and from what I understand a PC running Mach3 can control a machine as long as the driver has a parallel port. I didn’t notice a parallel port in the driver cabinet in the pictures in the first post but I shall contact the seller again and ask him. Was it common for tape readers to connect to the machine via parallel port on machines as old as this one? Since this mill is a “factory” NC it should already have axis limiters and e-stop right? If we assume that the drive electronics are working and connected properly a PC and Mach 3 should allow me to get control over the machine? It would be great if it would be as simple as this but there must be something I’m missing.

It is pretty much that simple, as others have mentioned, you are most likely not going to see a PC compatible parallel port on the machine, although the Tape reader operates in parallel date mode it is more important to find a PC with one, than one on the machine!
I would check to see what documentation there is on the machine, especially as to schematics, it avoids the need to do a lot of 'Reverse Engineering' which even on the simplest machines can take some time.
Al.

[keebler303]

You will have to find where the command signals are sent to the drive. It may be step and direction or it may be "wave drive" which means there is one signal for each coil. If you can get the machine running, you can poke around with a logic probe or multimeter to find the wires. Then its just a matter of connecting those wires you find to a Breakout Board. That breakout board cna provide isolation between the computer and machine and will connect to the computer using a parallel port.

Matt

[cjjonesarmory]

If you would be using this for a hobby, might be worth trying to get it to run, but if it has to be easy to fix, and stay up and running 90% of the time, I'd forget it. I imagine you would not be able to find replacement parts for any NC/CNC components that go bad. So you may end up scrapping the electronics anyway if anything goes wrong.

Not sure if you covered this question, but why didn't the current owner use it after the rebuild? Just struck me as odd....