[CNC] Ball screw lube? - Page 1
Forum section: electronics / projects

author: DTJ
author_rank: Super Contributor
timestamp: July 14, 2016, 12:48:38 pm
content: My 12mm ball screw & bearing mount order has arrived from Robotdigg. Less than a week between order and delivery, they look OK.Do ball screws need lube? My machine runs dry (no coolant or misting) and I only cut plastics.Shall I run them dry or give them squirt of silicone oil or WD40 occasionally?

author: bitslice
author_rank: Frequent Contributor
timestamp: July 14, 2016, 01:19:44 pm
content: Why do people still consider WD40 for anything requiring lubrication? Maybe if the part is constantly getting wet, other than that, no.Grease will just attract gunk, it's only suitable for where you can seal in the bearing.Use a normal low viscosity motor oil and wipe it down occasionally.A pro guide if this is going on the next rocket to Marshttp://www.thomsonlinear.com/downloads/articles/Design_Engineer_Guide_Selecting_Lubricant_Ball_Screws_taen.pdfhah, oops, didn't realise the next chap had posted this too

author: Ian.M
author_rank: Super Contributor
timestamp: July 14, 2016, 01:33:14 pm
content: Don't use WD40 - it gums up and traps dust to form a grinding paste.Seehttp://www.thomsonlinear.com/downloads/articles/Design_Engineer_Guide_Selecting_Lubricant_Ball_Screws_taen.pdfFelt wipers either side of the nut, + a squirt of light machine oil into the nut, or between the wiper and the nut while in motion on a daily basis when in active use should be OK. However if you are using the machine for production, you'll probably want some sort of continuous or periodic automatic oiling system.

author: CJay
author_rank: Super Contributor
timestamp: July 14, 2016, 02:20:57 pm
content: Not sure I'd want to use anything liquid on it with a cutter that makes dust, maybe one of the 'dry' lube products?Is there no advice on robotdigg's site or in application notes for similar leadscrews?

author: Koen
author_rank: Frequent Contributor
timestamp: July 14, 2016, 03:59:20 pm
content: As the nut does not contain a lubrication "tit", it should be pre-greased by the manufacturer. Leave as-is.

author: bitslice
author_rank: Frequent Contributor
timestamp: July 14, 2016, 05:28:09 pm
content: Quote from: Koen on July 14, 2016, 03:59:20 pmumm, that's fine if something is spinning in one spot, like an axle,but this is dragging the greased balls up and down a foot of screw thread, I'd suggest that any grease applied at manufacture is going to be wiped off on that rod eventually.If the balls were in their own isolated compartment, then different story.Although you do make the point that some ball screw bearings come with a grease nipple, but I suspect that's a cost saving on those that don't, rather than a recommended maintenance idea.It's not going to crash and burn either way.

author: Koen
author_rank: Frequent Contributor
timestamp: July 14, 2016, 08:58:39 pm
content: I do not understand your reply. The balls are in their own isolated and greased compartment protected from external elements by two seals.

author: Fraser
author_rank: Super Contributor
timestamp: July 14, 2016, 09:15:44 pm
content: LUCAS White Lithium Grease NLGI #2 as used on my lathes. Works well for me. Great stuff.Fraser

author: langwadt
author_rank: Super Contributor
timestamp: July 14, 2016, 09:18:03 pm
content: Quote from: Koen on July 14, 2016, 08:58:39 pmin a regular round ball bearing the balls and races are both inside the sealin a ballscrew the screw is outside the seal

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: July 14, 2016, 09:25:26 pm
content: Quote from: bitslice on July 14, 2016, 05:28:09 pmOn smaller ballscrew nuts, the lubrication point is often a simple hole, rather than a nipple. Some screws you lubricate at the seal or the screw.

author: Koen
author_rank: Frequent Contributor
timestamp: July 14, 2016, 09:32:49 pm
content: Quote from: langwadt on July 14, 2016, 09:18:03 pmI get that but it's the role of the seals to wipe the dust and the role of the grease inside the nut to keep things smooth. Same thing for guide rails, wipers keep the carriage balls sealed from the rails dust and carriage balls are lubricated from the inside of the carriage.Adding anything to the screw or rail itself will only get it wiped by the seals.

author: Ian.M
author_rank: Super Contributor
timestamp: July 14, 2016, 09:57:08 pm
content: Unfortunately dust will stick to anything except a dry film lubricant and lubricants containing significant quantities of solid particles are not recommended as they tend to clog the ball return path. Once you have a clog resulting in balls rubbing on each other under load, the wear will rapidly become excessive as sliding point contact lubrication is extremely challenging.If you have abrasive dust on the thread and you let any seals act as wipers, the seals will soon either be worn sufficiently to be worthless, or will be so loaded with abrasive that they lap the thread till its sloppy.A total loss lubrication system with sufficient light oil flow to keep the ball nut flushed, and external wipers from which excess oil is allowed to drip into a catch container, + a slotted enclosing cover with a downward facing opening for the ball nut mount support leg would be your best chance of minimising the buildup of abrasive dirt in the system, short of arranging sealing flap(s) on the cover and positive pressure ventilation.

author: Koen
author_rank: Frequent Contributor
timestamp: July 14, 2016, 10:15:09 pm
content: As usual, we have to keep it in context. He mills plastic on a machine with 12mm ballscrews as an hobbyist. He doesn't need to make any changes now. Add covers when the time allows, change grease when the time comes. Keep it simple.

author: bitslice
author_rank: Frequent Contributor
timestamp: July 14, 2016, 11:35:40 pm
content: Quote from: Koen on July 14, 2016, 10:15:09 pmSo we are not going to develop the bearing wear sensor circuit and the oil viscosity meter?

author: Ian.M
author_rank: Super Contributor
timestamp: July 14, 2016, 11:53:55 pm
content: Plan B - if you cant be arsed to add felt wipers, dust covers and keep them, lubed, buy a spare set of ballscrews and put them on the shelf for future servicing. If the lifespan you get out of the first set is too short, you can add a wick oiler, wipers and covers when you fit the replacement set or if compatible ones are still available at a good price, just treat them as a 'wear' part and order another set of spares each time you replace the ones on the machine.A soft brush attached to the carriage contacting the screw from the bottom either side of the nut (on a spring mount so it self cleans on every direction change) to reduce chip and dust build-up at the nut would be an easy cheap improvement if you are going to run them dry or nearly so.

author: Koen
author_rank: Frequent Contributor
timestamp: July 15, 2016, 12:44:47 am
content: His nuts already contain nylon wipers.

author: Ian.M
author_rank: Super Contributor
timestamp: July 15, 2016, 01:21:29 am
content: *GREAT*!A nylon wiper loaded up with glass fibre reinforcement dust or Titanium Dioxide pigment dust, makes a lovely lap. There should be plenty of slop after a few hundred operating hours.The O.P is routing/milling plastic enclosures and parts (previous topic) so the chances of producing abrasive dust are significant. If he was cutting Vinyl or similar soft plastics, it would be a different matter.

author: Muttley Snickers
author_rank: Unknown
timestamp: July 15, 2016, 01:32:53 am
content: If the OP’s ball nuts and screws are anything like the ones I received from Asia the nuts do not incorporate wipers of any type and as Ian mentioned it is a very good idea to add them if possible, there's no grease or oiling ports on these and the two holes you see on the top of the nut in the second picture are in fact very loosely tapped threads with small grub screws for the retention of the nylon insert and may be used to adjust any backlash, these screws should be addressed with Loctite or similar compound during adjustment otherwise they may eventually come loose and fall out.Fortunately a very close friend of mine is a design engineer with a large bearing manufacturer which is also one of my best customers, based on his inspection and advice I nominated to make my own bearing blocks and used Nachi sealed bearings for the lead screw ends, I also added felt wipers to each end of the ball nuts which meant making a retaining sleeve and washer, I made these caps out of PTFE-Teflon as I have stock piles of the stuff and also make my own hammers with it, these are mostly left overs and off cuts from that same customer.

author: DTJ
author_rank: Super Contributor
timestamp: July 15, 2016, 05:01:35 am
content: Thanks for all the ideas guys.I've just installed one of the screws and it runs fine. A little noisy but I think its mainly the stepper and framework resonating.It looks like the way to go might be to run the ball screws either dry or with a tiny amount of light oil. The X & Z axes are above the work so they stay quite clean. The Y axis is under the table, I might need to add a little more shielding to keep it completely covered. Realistically the screws are unlikely to see more than a 100 hours over the life of the machine so hopefully they'll survive.Brushes would be nice but I think shielding will keep the crud away altogether.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: July 15, 2016, 05:43:53 am
content: I have these miniature ballscrews in a machine. At least on these, the oiling hole is on the flange (see drawing)

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: July 15, 2016, 05:51:36 am
content: Quote from: DTJ on July 15, 2016, 05:01:35 amA typical ballscrew has a hour service life something like 100-300X that... you should be fine even without oil unless they are exposed to something really really horrible like carbide grit, something corrosive+extended sitting, or material locking up the balls. Also, the assembly was probably shipped with a light coating of oil already to prevent corrosion during storage.

author: Koen
author_rank: Frequent Contributor
timestamp: July 15, 2016, 09:39:39 am
content: Quote from: Ian.M on July 15, 2016, 01:21:29 amThen he should be vacuuming the dust at the endmill to avoid fine particles in his lungs anyway.Quote from: DTJ on July 15, 2016, 05:01:35 amThey'll live don't worry. You'll even find them to be incredibly resilient. The best way to know how something is done is to look at the industry solutions at that price point, for that application. Forum topics always drifts to quotes from SKF and Schneeberger service manuals like you're milling Titanium 365/24/7 on your Hermle C62.

author: DTJ
author_rank: Super Contributor
timestamp: July 15, 2016, 09:51:07 am
content: Quote from: ChunkyPastaSauce on July 15, 2016, 05:43:53 amMine are cheap chinese knock offs (not nice SKF units). They have the same lube holes on the nuts.

author: Koen
author_rank: Frequent Contributor
timestamp: July 15, 2016, 09:52:59 am
content: Quote from: Muttley Snickers on July 15, 2016, 01:32:53 amThe nylon inserts are your wipers. They aren't there for backlash. Yeah you can screw them tighter to the ballscrew and it will give you the feel of less backlash if you move it by hand but it isn't their role nor will it last nor does it have any impact on the balls in the nut.The nylon comes loose and falls out because it's made to be changed whenever it shows wear. Which might be in two years as an hobbyist.You don't have an oil plug because you won't need one. The balls are greased between both orange plugs by the manufacturer.

author: DTJ
author_rank: Super Contributor
timestamp: July 15, 2016, 09:53:48 am
content: Quote from: Koen on July 15, 2016, 09:39:39 amI've put slow spindle on it and I use 2 flute routing bits. I'm sure there's some small dust particles created but most of the debris is large & chunky.

author: Koen
author_rank: Frequent Contributor
timestamp: July 15, 2016, 09:57:27 am
content: Quote from: DTJ on July 15, 2016, 09:51:07 amThese are niceSFK. Place a drop of oil in it and plug it for now.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: July 15, 2016, 01:10:46 pm
content: Quote from: DTJ on July 15, 2016, 09:51:07 amOh mine aren't SKFbrandballscrews, they are "SFK"seriesfrom a company in Asian (Taiwan) lol

author: jh15
author_rank: Frequent Contributor
timestamp: July 16, 2016, 03:43:42 am
content: WD-40 is like three-in-one oil of my grandfather's days to ruin your equipment. 3 in 1 is good for rifles I hear, but not for capstan bearings and the like.Use it for water displacement, not lube. It turns to epoxy after a few months. Another application frees up the glue for a short time.Prevent people from using it as a lube!

author: Mr J
author_rank: Regular Contributor
timestamp: July 16, 2016, 04:12:36 am
content: depends on the lead screw, I have a T-Tech 5000 PCB mill machine and it has a Teflon coated screw that is not lubed, it's about 20 years old now and i've replaced the lead screw twice in that time, the machine is used every day and is exposed to FR4 dust constantly. Even when the Teflon wears down it's still usable but screams like a banshee.Mr J, N1IR

author: DTJ
author_rank: Super Contributor
timestamp: July 16, 2016, 05:55:19 am
content: Quote from: jh15 on July 16, 2016, 03:43:42 amYeah I'd forgotten that it does tend to gum up when it dries out. It does make a good cutting lube for machining or tapping aluminium. I've read that it's mainly kerosine, it must be the additives that gum up.

author: jh15
author_rank: Frequent Contributor
timestamp: July 19, 2016, 04:17:27 am
content: Wired magazine some time ago had a page called 'what's in it?' or the like. WD-40 was mostly baby oil with a bunch of additives. How much oil can you get from a baby? Is it collected as runoff or is the baby squished like seed oils?

author: DTJ
author_rank: Super Contributor
timestamp: July 19, 2016, 04:42:15 am
content: Quote from: jh15 on July 19, 2016, 04:17:27 amCord oil? Surely they don't use whole babies.