New user looking for advice about buying MC4VA

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01-30-2023, 01:50 AM
bryanbdp

New user looking for advice about buying MC4VA

Hi. I am looking to buy a much more capable machine than the X4 I have now. My son is a CNC technician, and he recommended an Okuma MC4VA or similar. He really likes the box ways which he says are much more durable and crash resistant than typical linear bearing machines.
I'm trying to get a handle on what I'm looking for.
What years were this machine made? Are there similar Okuma machines with box ways I should consider?
Machine I'm looking at now has the 5020 control. Uses 3.5 floppy discs, although it seems like you can purchase a USB/floppy adapter for these.
Is the control system modern enough for most jobs? Is memory size a real issue? I'd really like to get good at using mastercam.
Should I consider swapping out the control for something more modern, whether based on EMC or something commercially available?
I don't have 3ph power, so I'm planning on adding a new vector drive to allow for single phase power. Any links or builds for this process?

Also, really stupid question, is there any way to test machine using single phase 240? Is there a quick and dirty workaround just to power up and move everything? Going to look at a machine, no 3ph on site. Maybe rent a big generator for the day or perhaps a phase converter?

Really appreciate any advice,
Thanks,
Bryan
CT USA
01-30-2023, 07:32 AM
Superman

Re: New user looking for advice about buying MC4VA

Machine is probably an OSP5000 that has had a 5020 (lathe control) screen replaced

Machine is 1980 era, so it could be 40 year old.

IMHO...
Don't touch it unless you know it's history.
It must have its system disks, (Should be in rear elect. cabinet), you may find they are paper tape or 5.25" floppies, and you will need them if machine backup battery has gone flat.
It must boot with no errors
Limited program storage, not suitable for complicated, long CAM programs
May not like 3 axis moves on arcs (arc startpoint at different level to the endpoint).
Spare parts or upgrading may be difficult to find (and $$$$$).

Other that that.... it is a solid machine
01-30-2023, 01:55 PM
Algirdas

Re: New user looking for advice about buying MC4VA

Quote:

I don't have 3ph power

forget the MC4VA then.

Quote:

a big generator for the day

check the power capacity required to see the sky high price.

Quote:

a phase converter

sure, no.
You are welcome :)
01-30-2023, 10:21 PM
Superman

Quote:

Originally Posted by Algirdas

forget the MC4VA then.

check the power capacity required to see the sky high price.

sure, no.
You are welcome :)

He's talking about the site where the machine currently resides. He wants to turn it on before commiting any $$$
01-31-2023, 11:17 AM
ospcontrol

Re: New user looking for advice about buying MC4VA

H?
OKUMA MC-4VA I USE
GIVE A SPECIAL MASSAGE I WILL HELP YOU
01-31-2023, 11:56 AM
Superman

Quote:

Originally Posted by ospcontrol

H?
OKUMA MC-4VA I USE
GIVE A SPECIAL MASSAGE I WILL HELP YOU

Special massage.... where do we line up ? ;)
01-31-2023, 11:58 AM
servtech

Quote:

Originally Posted by bryanbdp

Hi. I am looking to buy a much more capable machine than the X4 I have now. My son is a CNC technician, and he recommended an Okuma MC4VA or similar. He really likes the box ways which he says are much more durable and crash resistant than typical linear bearing machines.
I'm trying to get a handle on what I'm looking for.
What years were this machine made? Are there similar Okuma machines with box ways I should consider?
Machine I'm looking at now has the 5020 control. Uses 3.5 floppy discs, although it seems like you can purchase a USB/floppy adapter for these.
Is the control system modern enough for most jobs? Is memory size a real issue? I'd really like to get good at using mastercam.
Should I consider swapping out the control for something more modern, whether based on EMC or something commercially available?
I don't have 3ph power, so I'm planning on adding a new vector drive to allow for single phase power. Any links or builds for this process?

Also, really stupid question, is there any way to test machine using single phase 240? Is there a quick and dirty workaround just to power up and move everything? Going to look at a machine, no 3ph on site. Maybe rent a big generator for the day or perhaps a phase converter?

Really appreciate any advice,
Thanks,
Bryan
CT USA

I was a service tech on Okuma machines back in the day, these machines were solidly built and the OSP5000/5020 was a reliable control. Many users were able to drip feed long programs from a PC because of the memory issues. Extended memory from Okuma was very expensive for not a lot as I recall.

They were a very accurate machine, but box way machines are slower with rapids no more than 8 metres per minute (27ft/min) due to friction and motor type.

Good advice below regarding backup control disks and functional disk drive in the cabinet. Back up programs and parameter if you get one.

Given the age of these machines, even a good one if a fault develops could be a money pit. As a service tech we carried an entire rack of Okuma circuit boards for testing faults on all the controls, many needed revision boards depending on machine age and options.

Regards a single to 3 phase converter, you would need a high current single phase supply to run this machine. Up to 3 times it's rated supply connection. Motor starting loads on these machines are quite high. The phase converter OEM should tell what you need if you provide machine supply requirements.
01-31-2023, 11:59 AM
kurmay

Re: New user looking for advice about buying MC4VA

:)
01-31-2023, 07:17 PM
bryanbdp

Re: New user looking for advice about buying MC4VA

In the back of my mind, I am thinking to replace the control system with something more modern. I think my big question is can I use the existing servo's and encoders? I need a new vector drive for the spindle no matter what to run on 3ph.
Perhaps using Mach4 or a DIY EMC control system.
01-31-2023, 10:33 PM
servtech

Quote:

Originally Posted by bryanbdp

In the back of my mind, I am thinking to replace the control system with something more modern. I think my big question is can I use the existing servo's and encoders? I need a new vector drive for the spindle no matter what to run on 3ph.
Perhaps using Mach4 or a DIY EMC control system.

I may be wrong on this, but Okuma axis motor absolute encoders were quite unique. They stored a distance unique to each, for example, if you imagine a linear measurement 1 foot to 300 feet, an axis stroke of 6 feet could be anywhere along this line. So for example could be 100 feet to 106 feet in the parameters.

If you removed the encoder and spun it round, the 6 foot axis stroke would be somewhere else along the line. It was very clever and the OSP could be set quite easily, I don't think another control could use these encoders and drives.
01-31-2023, 10:34 PM
servtech

Quote:

Originally Posted by bryanbdp

In the back of my mind, I am thinking to replace the control system with something more modern. I think my big question is can I use the existing servo's and encoders? I need a new vector drive for the spindle no matter what to run on 3ph.
Perhaps using Mach4 or a DIY EMC control system.

I may be wrong on this, but Okuma axis motor absolute encoders were quite unique. They stored a distance unique to each, for example, if you imagine a linear measurement 1 foot to 300 feet, an axis stroke of 6 feet could be anywhere along this line. So for example could be 100 feet to 106 feet in the parameters.

If you removed the encoder and spun it round, the 6 foot axis stroke would be somewhere else along the line. It was very clever and the OSP could be set quite easily, I don't think another control could use these encoders and drives.

You will need a control, drives and motor package.
02-01-2023, 10:02 AM
deadlykitten

Re: New user looking for advice about buying MC4VA

Quote:

can I use the existing servo's and encoders?

hy bryanbdp :) i am not into electronics, but seems worth trying; contact some guys that do retrofits, and check their opinion, or give them acces to machine for tests; so far, i know only full retrofits cases; i think it's easier / kindly :)
02-01-2023, 11:27 AM
servtech

Quote:

Originally Posted by deadlykitten

hy bryanbdp :) i am not into electronics, but seems worth trying; contact some guys that do retrofits, and check their opinion, or give them acces to machine for tests; so far, i know only full retrofits cases; i think it's easier / kindly :)

I am a CNC electronics engineer and worked on Okuma machines of this era. It may be possible to use the the axis motors with new encoders, but in my opinion, certainly not the current abs encoders and drives with a new control.
So control, axis drives and motor encoders at a minimum would be required.
02-01-2023, 12:01 PM
servtech

Re: New user looking for advice about buying MC4VA

Just to emphasize my point about Okuma absolute encoders "This Okuma patented device is used for axis speed and position feedback. The D6 type is onlyused on DC axis servo systems (LDU's). The axis servo systems which utilize the BL motor(BDU, BLD, or BLIID) use the E,F,FB, or FC type absolute position encoder. The E and F typesare being phased out. If an E or F type is replaced, it is replaced with an FB or FC. The FC typeabsolute position encoder is the newest and is physically shorter (approx. 3/4 of an inch) then theolder styles. Hence, the FB,F, or E types cannot take the place of an FC. The E, F, FB, and FCtypes are capable of making 2048 revolutions before turning over(back to zero). An HC typeabsolute position encoder has been developed for high speed turrets and rotary tables. Theoutput shaft of the HC can turn 7200 revs before turning over.The absolute position encoder uses a multi-pole resolver (MPR) for lower digit positioning(.0001) along with pulse type heads for upper digit positioning (123.4560). The control sends a5 kHz sine and cosine signal to the MPR in the absolute position encoder"

It's not just a digital pulse encoder :-)
02-03-2023, 08:21 AM
deadlykitten

Re: New user looking for advice about buying MC4VA

Quote:

I am a CNC electronics engineer

hy servtech :)

Quote:

making 2048 revolutions before turning over(back to zero)

i think i may have reached that limit, a few years ago : i was machining a wavy shaft, using C axis, thus it was a piece like a snake ... i was using C axis at full speed, so to avoid breaking the tool, and each time, i noticed that i have got same error at the same point of progress inside the program

i think now, that i have been rotated the C axis way too many times :)

Quote:

Just to emphasize my point about Okuma absolute encoders D6 DC LDU's BL BDU BLD BLIID E F FB, or FC E and F E or F FB or FC FB,F, or E E, F, FB, and FCt HC MPR

that's a long list; don't forget LV FDS TRED FE and FG4

Quote:

The control sends a5 kHz sine and cosine signal to the MPR in the absolute position encoder

5 khz ? that's really nice :)
02-04-2023, 09:15 PM
GuntisK

Re: New user looking for advice about buying MC4VA

As an owner of MC-4VA I can say that without 3ph power line there is no practical sense in buying such machine. Each axis servo motor is approx. 1.2kW, spindle motor power are from 3.7kW to 7.5kW (depending on machine modification), total required power for machine is 20.8kW (according to manual)- this is too much for 1ph power line. As it was said earlier OSP5000/5020 CNC system (without additional options like drip feed) is not able to hold large programs, without that there is some more limitations, but You must keep in mind that these machines are 30 or more years old. From mechanical side they are real beasts in a good sense. Converting it to other control system (EMC (LinuxCNC) would be ok, but definetly not MACH4- not my favorite, better would be specialised Chinese CNC controller with full PLC options)- it would require complete retrofit- new CNC control, new axis drives and motors. Original OKUMA drives and absolute encoders are made to work together only with SVP Servo processor boards- they are not classic analogue +/-10V servo drives. The biggest problem in retrofit would be controlling of ATC- its logic is pretty complex. I would suggest to download maintenance manual for MC-4VA (they are available for free download) and take a look on it.
03-09-2023, 02:59 AM
bryanbdp

Re: New user looking for advice about buying MC4VA

I ended up with a 1989 or 1990 machine. Date on Z axis motor was 11/89, would this be a 1990 model?
I just finished installing a 40HP RPC, which does start up OK on a 125A breaker.
Still getting machine ready, haven't powered up yet. Rated power is 26kVA 3ph, which works out to about 65A 3ph maxed out. I think converter should be able to handle it, especially as not everything turns on at once. We'll see.