Okuma LT300 X-axis belt breakage

[MIKEL12]

So, one of our machines stopped today with an over travel alarm on lower turret X-axis.
After some disassembly I opened the hatch to check the belt that drives the screw for the x-axis. The belt had broken off and fell out.

So it seems that the belt broke, the turret fell downward until it reached the over travel switch and hopefully engaged some kind of brake at that point.

Tomorrow i'll order a new belt but i thought i would ask what the procedure would be when reassembling and getting it up and running again?

I noticed that the position for the X-axis on screen changes when i "move" the turret, so this will probably mean i need to readjust the zero value for x-axis.

Does the LT have scales on this axis? or will i need to adjust?
If so how do i adjust the position for the axis?

[OkumaWiz]

Welcome to the club! We've been through a belt about every 6 months on our two LT300-MY's. Make sure to order at least 2 of them. We've talked to Okuma about this, but with no luck on a better stronger design.

There are no scales on the X axis, so you will just need to re-establish the Zero on the X axis which is the spindle center aligned with the center of a boring bar holder.

1. Write down your X axis Zero Set #.
2. Position boring bar holder to spindle centerline.
3. In Zero Set, CAL 0 for X axis.
4. Calculate difference between old # and new #.
5. Adjust PR ZERO OFFSET for X axis by this amount in your SYSTEM PARAMETERS. (You will get a power on effective parameter set alarm.)
6. SET Zero Set back to original #.
7. Cycle power. (If older control, you may need to press Backup key first.)

You should be good to go now.

If you follow this procedure, you will not have to reset your variable limits or stroke end limits or change any paperwork or programs that have Zero values in them. You may need slight offset adjustments depending on how accurate you find zero again.

Best regards,

[MIKEL12]

Awesome, this will hopefully get me up and running much quicker. Thx a bunch.

One belt every 6 months :/. Kinda a hassle to disassemble and get to the belt. Must be a pain to do it that often.

Seems like a pretty straight forward fix, we did a belt replacement on a different machine that had a similar problem and upgraded to some steel wire reinforced ?synthetic? belts. The guy that runs that machine said that it went from one replacement every year to running for 4 years straight without a problem now.

I'm ok with the downtime right now though, that machine is ahead in the planing so it gives me some time to do some light maintenance and give the machine some love

[OkumaWiz]

I'd be interested in knowing where you got the special belt and if it is available for the machine in the metric pitch.

The belt replacement is definitely a PITA. I'd rather not go through the change any more than necessary. We currently get ours though a company in Chicago. 4x cheaper and lasts just as long since it's the SAME BRAND!

Still needs to be stronger though so please let us know.

Best regards,

[MIKEL12]

We sourced the replacement belt locally for the LT , cost was about 50 USD.

The other belt for the other machine was bought about 4 years ago so cant help there.
But was going through the bando lineup of belts. The belt that broke was a Bando STS S8M. And in their product catalogue they have the KPS II belts.
They claim: "The KPS II belt transmits up to 5 times more power than a standard STS belt." (Page 13 in the pdf)
http://www.bandousa.com/html/pdfs/bu...ower_trans.pdf

They come in 8mm and 14mm pitch, and i guess S8M means 8mm Metric. so it should be equal.

Might be worth a try?

[OkumaWiz]

I talked to BANDO about the KPS II King power belts and they only recommend them to 800 RPM. Based on my calculations, the motor on the LT300 will spin @ 2500 RPM during the rapid, so it is not recommended for this application.

That being said, they do have a High performance STS belt that will allow double the torque and take the RPM as well. (250-HPS8M-728) On the plus side, it only costs $19.10. Almost the same as the standard belts we have. On the negative side - 16 weeks delivery! Yikes! Glad my machine isn't down.

I ordered 2 of them and hopefully they will come in before my next failure. At least I have 2 of the std ones here, so I won't be stuck if it happens before they come in.

Thanks for the tip - Guess we're even now!

Best regards,