Okuma mc4va

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12 Mar 2021 18:58 #202005 by Jorgefv
Okuma mc4va was created by Jorgefv
Hi I'm about to buy an old Okuma mc4va, the machine is in not working condition, the z axis drive does not turn on and also All of the contactors need replacement.
I wanted to buy it anyway until I realized it doesn't have linear rails on the z axis.
The price is 7k which is reasonable for my country Bolivia.
Now I'm doubting, it has a 32 tool magazine on the tool changer.
I wanted to convert it to LinuxCnc
What do you think especially if the lack of a linear rail on the z axis is a big deal.

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12 Mar 2021 21:04 - 14 Mar 2021 22:35 #202011 by scotth
Replied by scotth on topic Okuma mc4va
There is nothing wrong with box ways. They will handle more load and distort less if you have a small "oh S____!". It should have Yaskawa drives and motors that you should be able to interface to.
Last edit: 14 Mar 2021 22:35 by scotth.

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21 Mar 2021 01:11 #203073 by Jorgefv
Replied by Jorgefv on topic Okuma mc4va
I have checked the machine and it has an OSP5020M controller, Okuma branded servos and Okuma branded servo controllers. The z axis servo controller does not turn on (all leds in off state) and we have the over travel alarm for the z axis so the controller will be locked so I cannot try the other 2 axis.
I also have read that many users have problems with the encoders that happened to be resolvers, even with the original control they need to be changed regularly, I think the z axis is dead because they told me they tried to fix it themselves so I think I will have to get a new driver or to make my own, that it won’t be a first for me (at least experimentally) I built successfully a driver once and then sold the parts because I needed the money.
I have fixed some drivers and VFD’s in the past but I don’t want to be overconfident because the machine has some serious power, I also will see the possibility to swap the resolver for a regular encoder so I won’t suffer from that infamous Okuma resolvers that are to prone to fail.

After all that I think the budget to get the machine going will be much more from what I expected

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21 Mar 2021 22:23 #203165 by andypugh
Replied by andypugh on topic Okuma mc4va
Resolvers generally have a reputation for being very reliable. There really is very little to fail with them (especially in the case of a brushless resolver)

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22 Mar 2021 15:17 - 22 Mar 2021 15:20 #203251 by Jorgefv
Replied by Jorgefv on topic Okuma mc4va
I know it, but as I read about it on other forums it turns out to be not a resolver but an absolute encoder, it is a thing about the "special" okuma resolvers that gives the absolute position of the axis. I'm still reading about so I’m not really sure there is one and they are becoming rarer as time goes by
www.pmidsizema.com/index.php?main_page=p...o&products_id=723711
I also read on other forum an owner of 5 okumas used to replace at least 3 of those yearly so that's where my concern started.
I hoped after all the time waiting and saving this would be my first machine but if cannot be repaired that would be really bad for me.
maybe if I could get the servo running with another controller and a replaced encoder or resolver it could still be an option for me.

I'm looking at the STMBL and the other option from mesa but it seems that they are not powerful enough ffor the task, maybe a comercial one.
Last edit: 22 Mar 2021 15:20 by Jorgefv.

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