Well here goes... Aluminium frame router design

[sinnsvak]

I also have a set of 600mm PDF 20mm profile rails, which dont run smooth at all. I will change them out with hiwin down the road when I get some leftover money to do so. For now Im gonna keep it as it is until it proves to be a huge problem.

[CharlieRam]

I also have a set of 600mm PDF 20mm profile rails, which dont run smooth at all. I will change them out with hiwin down the road when I get some leftover money to do so. For now Im gonna keep it as it is until it proves to be a huge problem.

Lee Roberts is sending me some ball bearings, I'll see if it makes a difference and if not I will fettle the carriage a little......Now wheres that bastard file ;-)

[sinnsvak]

Good Luck! It may be, and I sincerely hope so, that the smoothness will show up after a couple of hours use.

[CharlieRam]

Well that's been a few days of discovery I won't forget in a hurry!

I stripped the carriage again, gave it a good clean and scotchbrite on all ports and ball ways, reassembled the carriage temporarily, put it back on the rail and started to slide it up and down to check the tightness and then....the end came off and 120 balls all over the floor! F$%k, I found 118 of them and still had 2 spare from Lee luckily.

Oh yeah, I also decided to check the other carriages now I'm confident the balls wont go flying if I remove them a couple of the others seem to have one ball missing too!

Cleaned it all again and secured it properly this time but it still felt tight, that is when I noticed the carriages looked slightly different on the exterior, so I checked the serial numbers again, both are DFH20A but the nice fitting ones have S01411040 and the tight one has S01207841. Does anyone know if any of these numbers signify the preload, I'm thinking I may have a higher preload carriage or is it just a batch number and one was made at a different time with not such a good QC?

More Importantly, will it affect the build having a mis matched carriage?

Cheers, Charlie

[Lee Roberts]

Hi Lee,

so I checked the serial numbers again, both are DFH20A but the nice fitting ones have S01411040 and the tight one has S01207841. Does anyone know if any of these numbers signify the preload, I'm thinking I may have a higher preload carriage or is it just a batch number and one was made at a different time with not such a good QC?

Cant help there sorry, what you could do is mic the ball's and see if they are diffrent, this may give you the anwser.

More Importantly, will it affect the build having a mis matched carriage?

I can’t see it being a problem, so would just go with it, others may know better but I can’t think what problems it may introduce, ultimately if it is a preload difference then its unbalanced but would suggest it’s going to be such a small amount, just leaving you with the least amount of preload as your best number, so again not a problem.

.Me

[CharlieRam]

Hi Lee,

Cant help there sorry, what you could do is mic the ball's and see if they are diffrent, this may give you the anwser.

.Me

Is that how the preload is set then? with slightly larger ball's?

[Lee Roberts]

Is that how the preload is set then? with slightly larger ball's?

Hiya,

Pretty much yes, if you use slightly bigger ball bearings than the distance between the carriages and rail.

The ball bearing size (relative) determines the amount of preload achieved. From what I've read, the most common amounts of preload used for linear guides are 8, 5 and 2 percent of their load rating (dynamic).

For ballscrews and nuts you can do the same thing with the ball sizing, use an adjustable nut or use two nuts.

.Me