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What kind of grease do you use on your CNC router ball screws? How often are you re-greasing?

***Updated for Tony!*****

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Brad
Avon, OH

I thought this thread was about something else entirely.


Posted using letters to form words, sentences and thoughts.

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http://www.CostaGuitars.com
PMoMC

If the ballnuts on the Fadal weren't permanently lubricated then they were using the same lube as the ways: Shell Tonna 68 or Mobil Vacra #2. I use that stuff for -everything- : tapping, machining, throw it on anything that should be slippy. I highly recommend getting a pail of it.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

depends upon your machine. do your nuts have zerk fittings? then go with a synthetic grease like mobil 1. if you want oil then try vactra #2/iso68 or "medium way lube" (it's not a cutting fluid by any means btw, -buy the real thing for machining) keep in mind that if your lead screw and nut are exposed they will collect sawdust which will act like a sponge and soak up the carrier oil out of the grease and/or any way lube over time.

were it mine and the nuts had wiper seals, i'd go with a synthetic grease.

Thanks for the help. I have a gallon of Vactra 2 which I can easily use on the screws. For the ball nuts I have grease fittings so I probably wouldn't hurt to pack them with a grease. The Ball screws are sealed so I shouldn't have too much problems with dust collection.

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Brad
Avon, OH

why mix the oil with the grease?

Haven't you heard? It the cool new thing to do

Really I see no reason to mix them. Funny thing though, on my new haas vf1 they have switched to using grease in stead of the vactra #2 that the older machines use, but for some reason they still use oil (Mobil shc625) for the spindle. Makes no sense to me why they would want to have both but hey I'm no engineer

at typical Haas spindle speeds 7,500/10,000/15,000/30,000 rpm, grease won't be able to move through the tight clearances of the bearings to lubricate them and will blow through the seals (among other things). also the spindle oil is filtered and re-circulated through the bearings to help remove heat in order to control spindle growth and reduce bearing failure.

Good answer!! That's why you get paid the big bucks

Makes sense. Still wish they would just use the oil for everything so I wouldn't have to mess with grease and oil.

I guess my thought was to grease the bearings because they have grease fittings?!? I have heard that putting grease on the screws can cause problems.

Is greasing the bearings a bad idea?

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Brad
Avon, OH

I wouldnt say its a bad idea. It just seems redundant when you could use one or the other. Ive never heard of problems with grease on ball screws. In fact on a bar feeder I have for a Lathe I have to manually grease the ballscrews. It isnt directly connected into the lubrication system of the lathe (which uses vactra 2) so i have to manually grease it up. The grease holds on better than the oil anyway. Dont get me wrong I like oil but it needs to be on an automatic system to dispense it or you will have to apply it with much more regularity than grease.

Thanks!

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Brad
Avon, OH

I was the one who mentioned to Brad that grease on the screw caused me all sorts of troubles. When I first got my machine I put some grease in the nut and smeared the screw as well and it wouldn't run at all until I cleaned all the grease off e screw.

I also have to be careful when I re-grease the nut to clean any grease that ends up on the screw because if I don't, my motors will stall the instant a ball touches grease on the screw. It doesn't make sense to me that this would happen but it does.

I use grease in the nut and oil on the screw for that reason.

Mind you though, I have a stepper driven system and my experience might not apply to servo machines.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

For the zerk fittings any general purpose lithium grease is fine.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

That's very interesting. I've never heard of an issue like that. By saying it wouldn't run are you saying that it was overloading the drive motor? I guess I could see that as an issue if your motors are lightweight. All my machines are used for cutting metal so they have pretty heavy duty servo motors. With wood you wouldn't need all that power. So I guess if you have lighter duty motors oil would be a better choice.

I learn something new every day

I have no idea what the heck was going on. I have 381 oz-inch steppers driven with a gecko G540, screw is 2510. If there was a little blob of grease in the ball channel the motor would stall as soon as the ballnut hit it. It sounds the same as a stepper that's accelerated too quickly and stalls. Once this happened I investigated and this is very common problem for stepper systems - ballscrews must be kept clean!

My procedure is to grease the ballnut maybe once twice a year and oil the screws (I'm just using motor oil at the moment) when they start to get loud. I worry that perhaps oil on the screw might be diluting the grease in the nut but just don't know enough to know if that's significant or not. Keeping the screws oiled also let's me up my acceleration and max speed.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com