Can I use these lubricants of my MK2 or 3?
Delrin is a Dupont brand name for an acetal plastic. It's like Jello is a brand name for gellatin. Kleenex is a brand name for facial tissue. Truth is we don't know whether the guides are made of acetal from the Dupont factory or not.
If you Google "Dupont Acetal" you'll find this link to their website where they will introduce you to:
The High-Performance Acetal Resin
So you are saying the article is factually incorrect in this:
"Delrin, is an acetal homopolymer unless otherwise specified by Dupont. When you buy acetal without a trade name attached, you are usually purchasing acetal copolymer. These are the two most common names for POM, but there are other formulations out there under different branding and it will take some research to figure out what you are buying.
There is a mechanical difference between homopolymer (Delrin) and copolymer (Acetal). Delrin has a higher melting point, is a little stronger, and has a few other slightly more initially desirable properties."
"Don't let any form of lubrication touch the lead screws. It will damage the Delrin trapezoidal nuts." @robert-rmm200
That is the comment I originally responded to and am still concerned with. I applied lithium grease to my MK2 kit lead screws in October 2016 and my MK3 kit in January 2018. I applied it to two of my customers MK2 kits in 2017. Based on your warning I have damaged the acetal nuts. I use the term acetal because there is no way to know who the plastics manufacturer is that supplied the acetal material for the trapezoidal nuts.
The bottom line is that I can find no source for a warning of using mineral oil based lubricants with Delrin or any of the acetal blends. I can only find the opposite information.
Would you please share your source of info that supports the theory that the Prusa trapezoidal nuts will be damaged from lubricant?
From the Dupont design guide for Delrin: "Lubricants and Hydraulic Fluids Delrin acetal resin generally has good resistance to base oils. The presence of chemical additives in some oils may have a marked effect on performance, particularly at temperatures above 66°C(150°F)."
So go ahead and lubricate them. It is still not something I would recommend. When I was using oil to help form my cross-threaded nut - the oil came away black which I took to be disolved plastic. But then we don't know the nuts are Delrin either.
My preference for both the smooth and threaded rods is clean and dry.
Would it be fine to use the WD-40 Specialist Lithium Grease?
I am no expert on lubricants.
the WD40 information says
Specialist, high performance, thick white lithium grease formula for long lasting protection against rust and corrosion. Will not drip or run. Ideal for metal-to-metal applications to ensure tools and equipment keep moving smoothly, without friction or seizing. For use on load bearing metal connections such as towbars, gear and brake mechanisms, and CV joints. Ideal for maintaining gardening tools. For use outdoors in all weathers and temperatures. Water and heat-resistant.
- High Viscosity Formula
- Reduces Friction & Wear
High Viscosity, Thick grease doesn't sound a good idea, the balls are supposed to roll along the guideways in a circulating motion, to give good service, if this grease is thick enough to stop that happening, you are likely to get increased friction and early wear...
(on different Prusa Printers, each one has been a success... (I got the TF2, off Ebay)
I agree 100%. I use either an acid-free grease for POM bearings, which doesn't harm them, or, for the Prusa, a nano-coating based on ceramic, e.g. this austrian product (fluna gun coating): https://www.earms.at/zubehoer/reinigungpflege/401/flunatec-gun-coating-100-ml-flasche
Just for everyone's information in case they are thinking of using a grease that contains graphite or molybdenum disulfide also known as plain moly.
Avoid greases with graphite or molybdenum disulfide, because they reduce friction so much that it promotes ball skid and interferes with the rolling process of the ball bearings. But, if your using a sliding bush, then these types of grease are ideal but be careful with yellow metals or alloys as sulphur / sulfur can cause issues with these metals.