Upgrading daito fuses
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  1. #1
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    Default Upgrading daito fuses

    I'm running an old nakamura tmc2 and having a bit of trouble popping the daito PL4150s fuses on the axis drives. While I'm trying to trouble shoot the overloading issue, I was wondering if anyone has ever tried upgrading these fuses with circuit breakers? I'm getting tired of replacing them.

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    When I was doing field service, we all had modified fuses that used standard 1/4" bussman glass fuses. We used them while trobleshooting/testing. Once everything was fixed we put in the proper fuses.

    If you are blowing fuses during normal operation, it seems you might be pushing the machine too hard. IIRC a TMC2 is a pretty small machine.

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    First time it blew, I had programmed a G1 move a bit too fast and it popped trying to do it (1000ipm vs 10). This time it was running all day at 50% rapid and when I switched it to 100% rapid it blew returning to home position. It's an old machine. I picked it up used as part of a set and only have a couple jobs I want to put through it.
    I was thinking of modifying a set of these burnt daitos to accept standard fuses like you say you had, but wasn't sure if it was a good idea considering the daito fuses seem to close another circuit when they pop. Not sure what this feature is for

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    The set of contacts that close when the fuse wire breaks creates an alarm condition on the drive. If you convert to regular fuses for troubleshooting purposes, just jumper that out. For regular operation, I would use an unmodified fuse and not bypass the alarm circuit.

    Blowing under 100% rapid is an indication that there is a mechanical issue causing excessive load on the motor.

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    I suspect I need to go a bit deeper into the machine and do some cleaning for sure. This poor thing was just run by its previous owner and the maintenance program left much room for improvement. That being said, it still runs solid and turns out some nice parts.
    Thanks for the info on the fuses! Now to search for circuit breakers that have built in alarm circuit. Would be awesome if someone already made some that would go right into where these fuses plug in.

    By the way, you wouldn't happen to have a picture of that modified fuse would you?

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    Quote Originally Posted by Spruewell View Post
    ......By the way, you wouldn't happen to have a picture of that modified fuse would you?
    I stopped doing field service ~20 years ago. I probably have them around somewhere, but no idea where.

    It was pretty simple. Radio Shack fuse holder hot glued to the back of the Daito fuse case. A hole drilled in the Daito fuse case for the wires to run through. Piece of plastic stuck between the alarm contacts.

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    What do these look like?

    Télécom devices have alarmed everything and use either "grasshopper" fuses that alarm when blown or breakers with an internal switch for alarm.

    There are many shapes and sizes so worst case scenario one could build a breaker bar/panel to remote mount with breakers and maintain the alarm function.

    However breakers have a much different personality regarding how they trip where fuses are usually faster acting so one may introduce additional risk of damage via a breaker that requires more time to trip.





    Sent from my SAMSUNG-SGH-I337Z using Tapatalk

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    Quote Originally Posted by Tony Quiring View Post
    What do these look like?

    ...

    However breakers have a much different personality regarding how they trip where fuses are usually faster acting so one may introduce additional risk of damage via a breaker that requires more time to trip.
    Wise words of caution on the fuse/breaker blow rates. There are fast and slow blow fuses/breakers and all other kinds.

    I would suggest using airpax type breakers (push reset) if you go that route.
    They are available with a very wide range of specs, inexpensive and compact. Finding the right specs is a whole other rabbit-hole...

    airpax_20.jpg

    The Diato fuses I'm sure he's talking about are these little green ones.
    They have a spring lever inside pulling tension on the fusible link.
    When the link burns, the spring lever is released, flipping over to close the alarm contact.
    The alarm contact also shows in the little square window when the fuse is blown.

    diato-fuse.jpg

    You can open up those diato-fuse cases with a pin-vise and a small twist-drill, or a razor knife. Just cut the two little "rivets" on the side.

    Then, remove the alarm lead from the fuse entirely. Solder in a pair of leads from your airpax breaker and use a hot-punch to re-rivet the fuse-case.
    I would just let the breaker dangle if you've insulated all of the metal on it, or zip-tie it to a mounting point on the top-board in the drive.

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    image.jpeg
    It is an old control and these fuses are $8-$10 a "pop" and 2-4 days for delivery. They are easily opened up with the removal of the screw on the side. The two tabs lower tabs are the main contacts with the upper tab being double sided for the alarm circuit

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    Looks like it is plug in with male lugs on the back.

    If you have extras that are bad then it seems easy to open one up and attach wires to the connectors and drill a hole in the front for the wires to exit allowing a remote fuse holder or breaker to be used.

    One also can add a direct reading ammeter to measure current draw to see what is really going on.

    Sent from my SAMSUNG-SGH-I337Z using Tapatalk

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    Quote Originally Posted by Spruewell View Post
    image.jpeg
    It is an old control and these fuses are $8-$10 a "pop" and 2-4 days for delivery. They are easily opened up with the removal of the screw on the side. The two tabs lower tabs are the main contacts with the upper tab being double sided for the alarm circuit
    Fanuc used to sell the fuse wire in a little roll so you could repair those fuses. I doubt they do any longer as it has been so long since that style was used. You can find fuse wire in different ampacities on Google. Then it is a simple soldering job to repair those.

    On larger drives those fuses are run in parallel with a larger cylindrical fuse. usually like a 25-30 amp cylindrical and a 1.5 amp Daito. The Daito would blow simultaneously with the corresponding cylindrical fuse just to trigger the fuse blown/overload alarm signal.

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    image.jpg

    Was looking at something like this to replace the fuses. The pl4150s fuses are 15 amp 125v slow blow. There are 3 required on each drive. Trying to do this without having to do a lot of serious modification of the original circuitry.

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    Quote Originally Posted by Spruewell View Post
    image.jpg

    Was looking at something like this to replace the fuses. The pl4150s fuses are 15 amp 125v slow blow. There are 3 required on each drive. Trying to do this without having to do a lot of serious modification of the original circuitry.
    As an alternative to the airpax I mentioned above, I use these to replace everything in my old machines. They were standard in a lot of CNC applications.
    Buy a chunk of DIN rail to mount them on (each breaker is 1" wide).

    Fuji Electric Circuit Breaker, CP31 15A, AC25V | eBay

    fuji-cp31d.jpg

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    New fuses arrived the day before I had to leave for vacation. Just got back and put new fuses in. Cleaned out under the way covers and checked the lead screws on the X and Z axis. All free and clear. Turned on the power and it immediately blew the fuses again. Didn't even have a chance to move an axis. Going to start chasing wires now. Wondering, does this sound like a short in the servo motor?

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    Short in the motor possibly. I've seen more often that coolant has gotten into the motor power connector causing the short or the power cable has chafed on something in the run from the cabinet to the motor.

    On larger drives, the alarm fuses are run in parallel with higher amperage fuses. If the high amp fuse blows then the alarm fuse also blows. If you just replace the alarm fuse in this situation it will immediately blow.

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    Thanks for the tip! I will start tracing through the cables and make sure they don't have any external signs of damage. Then I'll start checking the all the other fuses.
    Going to modify a set of these daito fuses to accept standard fuses while I'm at it

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    Well, I have not been able to trace down the cause of the blown fuses yet. I modified the daitos to accept standard fuses. It continues to blow the same two fuses on the z axis as soon as the control comes on. Started tracing wires, so far have not been able to find any damage to the power or encoder cables to the z axis servo motor or any other cables. I disconnected the cables on the z axis servo motor and it still blows the fuses.
    It is a Fanuc 6T control on a nakamura Tome TMC2

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    Post a picture of the drive. Z axis drives often used the alarm fuse in parallel with a larger cylindrical fuse. The alarm fuse would blow to generate the alarm signal when the cylindrical one blew in response to an overload or short.

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    Here are some pictures of the drives. If you need more detailed images, let me know and I will zoom in on specific areas. I also threw in a picture of the machine and the servo motor.
    Attached Thumbnails Attached Thumbnails img_2126.jpg   img_2129.jpg   img_2128.jpg   img_2125.jpg   img_2123.jpg  


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    OK, yours does not have the fuses in parallel to anything.

    I think I might have some schematics on this drive or one similar at my shop. I'll try to remember to have a look for them this weekend. I think this drive uses SCRs and you may have one or more bad ones.


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