[TangentAudio]

Greetings,

I'm working on a partial linear rail conversion for the Z axis of my benchtop CNC mill. I'm using four supposedly genuine Hiwin HG25 blocks and matching rail, purchased new. Given the relatively modest non-production use for my machine, I decided manual greasing via zerks is perfectly fine. I settled on using Mobil Mobilux EP 1 grease as it's a readily available general purpose lubricant recommended in the Hiwin documentation.

I was attempting to do the initial grease procedure for my blocks last night, and I'm not confident in my success. Following the procedure in the Hiwin documentation for pumping 0.8cm^3 of grease (determined to be 2/3 of a lever pump of my particular grease gun), moving the block 3x, and repeating this process 3x, only one of my 4 blocks seems to have grease reaching the bearings. I can tell there is a difference in feel on one block, as its movement became more "viscous" and quieter as the grease worked its way into the ball bearings. The other three blocks still feel and sound like they are running on the lightweight protective oil that the blocks had in them from shipping.

I tried to pump some additional grease into the other 3, which is also recommended in the documentation for cases when you don't see a film of lubricant on the rails after the standard procedure. The grease is definitely making it through the zerks, as it eventually squeezes out between the green plastic and metal body of the block on the side where the zerk is installed. But, still not much of any change in the feel or sound of the blocks running on the rail.

One thing of note, the one block that did seem to work, is of slightly different appearance from my other 3. I was told by the vendor that this is merely an earlier production run from Hiwin, but they should all be the identical specs.

Here's how I have the zerks set up. Assuming I'm reading the documentation right, nothing special needs to be done to use these end ports, other than capping off the end you aren't using, which I've done with the included screw. It's only when you use the top or side lubrication points that you need to poke holes in plastic to open up orifices for the grease.



Here's the one block of the four that seemed to take lubrication as expected. Note the slightly more "rough" appearance of the non-ground surface on top where the laser etching is.



Any suggestions?

thanks,
Steve

[jaideepshinh]

Hi Steve,

We do many linear rail installations in house (we recondition our own machines every now and then).

You should be concerned if the block feels rough. The difference in feel between the one block and the other three could be on account of a different preload grade or a different accuracy class. You need to check the boxes in which they came to see what the marking is (I am not sure if Hiwin marks their blocks properly with regard to preload and accuracy class, but I do know its mentioned on their boxes usually by the distributor/retailer/seller).

If you still doubt the process, I suggest pumping grease in without the front zerks. The blocks are not sealed very well in standard configuration, and once you overdose the grease you should see it come out from below and into the rail bolt holes. I hope you have dailed the rails to check parallelism on their sides and tops. Once this is done you should close the bold holes with rail caps.

When in doubt, first pump a solvent through the block (Note- not a corrosive solvent, we use Diesel) to flush out the block, and then we usually lubricate it using a heavy oil or an NLG000 grade grease (its a low viscosity grease).

Best of luck!

Jaideep

[TangentAudio]

Thanks for your reply, Jaideep. I purchased these from a USA reseller, not an "authorized" Hiwin distributor, so they were shipped in sealed plastic bags, not boxes. The only info I have about the individual blocks is the laser etchings, and unfortunately the majority of the info is hard to decipher - presumably coded production information, like this:



I attempted more greasing last night, by removing the screw plugs opposite the zerk, and also moving the zerk to the opposite lubrication port and pushing in grease from that side. This seemed to help, now all of the blocks feel like they are running on grease instead of the thin protective shipping oil. Thanks for the suggestion!

Both of my rails run against precision reference edges, and I clamped and pushed them around while checking a dial test indicator to get the last few fractions for parallelism. And they appear to be very flat across the tops according to my precision straight edge. However, everything needs to come back off as I have more machining on the assembly to do, so I am not ready to loc-tite the screws or put on the rail caps yet. I'm aware running the blocks on uncapped bolt holes this can potentially damage the seals, so I'm trying to be gentle with them while I am in this phase of the project.

regards,
Steve

[jaideepshinh]

I have never seen these come without boxes! :nono:

Good that its working better now.

There is a lot of "tuning" to be done when dialing these, even if its against a precision reference surface.

It sometimes takes us a full day or more to dial these rails into a precision level we consider acceptable (within 5 microns in side to side parallelism, within 10 microns top to top). Some of the machines we purchased are not manufactured well enough, and are never able to achieve this spec. It all depends on your application and the accuracies you are looking for from your machine

Best of luck!

Jaideep

[TangentAudio]

I have never seen these come without boxes! :nono:

I suppose it's possible that these are counterfeit Hiwin being sold as the real thing, but I don't have any evidence to prove that. I'm not quite ready to accuse the vendor of such.

As for tuning - this is a hobby machine and this project is for learning and hopefully making some improvements over the original dovetail ways. I'm aiming for alignment as close as my machining skills, measuring tools, skills and patience allow.

cheers,
Steve

[TangentAudio]

This was my first test of parallelism right after I did the machining for the rails. Using a 0.0005" (12.7 micron) per division test indicator. I also own a 0.00005" (1.27 micron) indicator but haven't checked with that yet since this all needs to come apart soon. This was about 30 minutes of work mounting and aligning, so I feel okay about my first attempt at this.

https://www.youtube.com/shorts/JO9OSPqBIVk