Time for X rails...

[harryball]

I have the PRT with the extruded aluminum sides not the steel C channel.

I have 3 options: Grind, rail caps, rail replacement with aluminum pillow block mount.

Cheap = grind but I'd like to avoid that if possible.

Rail caps is my default plan but before I do that...

I'm intrigued with the total rail replacement that I think would be easy to do on top of the PRS style alulminum sides.
http://www.talkshopbot.com/forum/showthread.php?t=506&highlight=replacement+rails
Post #17 has photos. It looks like that would bolt on top of my current aluminum PRS style sides with easy adjustment (no drilling on C channels or rails for caps).

I see the extrusions and extrusion nuts came from Bosch-Rexroth and hardened rails and wheels from Superior.

To the point: ideas on how difficult this might be? what am I missing?
It looks like the X rollers might have to be moved in/out. i.e. how much modification would be needed to the X rollers position?

Thoughts?

/RB

[bleeth]

Work your dimensions out carefully in section. You need to make sure that the current width of your gantry doesn't need modification beyond fractions or you will be going down a steep slope!! The solid aluminum bar overhangs for the rack gear as well as mounting the hardened rail and must be precisely drilled for the bolts to keep it straight when you bolt it to the extrusion.
If you need to widen your table that is easier than widening your gantry. Making either narrower could mess up your cutting width.

It's never as easy as it looks!!

[harryball]

After consideration and comments from Gary and Dave I think I'm going to go with the rail caps. It' not just a large amount of work, gantry resizing, rack re-mount etc... but the economy of it as well. Caps will be good and give it years more life, otherwise the money would probably be better spent toward a newer model.

I was told the Superior Bearing T2 track is what I need but 5/8" doesn't seem like enough.
http://www.superiorbearing.com/docs/guidewheels_track.html

Should I go with the T3 track instead?

I can get undrilled 120" lengths for about $80 ea plus shipping.

Did you guys get them with holes already drilled or drill them yourself? How tough is that?

/RB

[br928]

Stay with the T2 rail. I am more familiar with Bishop Wisecarver rail. If the Superior rail is hardened then it is better to pay for them to drill it for you. They can do a much more accurate job. That is one less headache. Use the Bot to drill the mating holes in the aluminum bar.

This is an upgrade that a lot of guys with older Bots will soon be doing.

The extrusions, nuts and screws can be bought from 80/20, T-Slots or Faztek.

[bleeth]

Let them drill it. Since you are simply going to use it as a cap the easiest thing to do is mount the new hardened rail on "opposite" sides. That means if one is on the outside of the existing the other is on the inside. Then your gantry needs no resizing at all. T-2 is fine. Going to T-3 only has use if you are going to upsize your wheels.

If you don't already have one get a center punch (machinists type-not woodworkers) the size of the predrilled holes to center the holes you will drill in your old steel rail. It will make your life much easier. The rest is pretty basic common sense.

[lex]

I was at the ITW show in Atlanta last year when I saw the new integrated systems that use a hardened cap attached to an aluminum extrusion. This could be a very low cost method to get this done. this particular profile is from PCB but I am shure bishop and others have something similar.

[Brady Watson]

About an hour of hand work with a file and 150 grit sand paper will make those rails as good as new. You just want to deburr the bottom of the pyramid. If it has a point at the top of the rail, you can flatten it - knocking down the peak does not need to be precise. Pay attention to where the v-roller is contacting the rail. File or sand as necessary.

I just did this for a customer yesterday & installed fresh pinions. The machine no longer sounds like a box of rocks when moving & cut quality improved substantially. Keep them smooth & clean with a scotch pad once a week & they will stay like new.

I know it is not nearly as sexy and glamorous as capping rails and fooling around with all kinds of linear rail options...but it is simple, straight forward and cheap. Don't be skeered :eek: - It ain't rocket science. And...don't be lazy either. It doesn't take more than an hour to do correctly.

-B

[gc3]

why not buy new angle 2.5 x 1.5 x .25 and use a #3 roller on the factory edge with no grinding

[harryball]

I'm going to go with the T2 rail.

I have worked the rails heavily by hand about 5 times now and who knows how many times to de-bur it. The last time was the most work as the "saddle back" is becoming pronounced and the line is off. i.e. the rail is straight but the peak is off center on the rail. It has become much easier to de-rail lately when under pressure. I'm also tired of working them and I don't want to run a power grinder over them in the shop.

I thought about replacing the rails with the same angle iron... but if I'm going to spend the money I may as well get the hardened rails and save some filing.

/RB

[lex]

How long is your machine? Would Ina slide/bearing work?

[Brady Watson]

I'm going to go with the T2 rail.

...I'm also tired of working them and I don't want to run a power grinder over them in the shop.

I thought about replacing the rails with the same angle iron... but if I'm going to spend the money I may as well get the hardened rails and save some filing.

/RB

I don't recommend using a power anything to dress the rails. I don't care how good one may think they are with a grinder or disc - you just can't properly dress the rails this way. Use a file & finish with sandpaper when you are all done. It's not as daunting as it appears. Let the file do the work, get into a rhythm and before you know it, you've got them done. I say this for the lurkers...

A little tidbit of info regarding 'angle iron' rails. The rails you have on your machine are most certainly not ground angle iron. They are soft, maleable steel that was ground & CNC bent. Very few machines built after 2000 have true angle iron rails.

I am one of the fortunate recipients of real angle iron rails. Since my 18' rails were too long to get into the CNC bender at the time, I've got real angle iron. The rails wear like a pigs nose - unlike my 2006 Alpha gantry with CNC bent soft rails, which need to be dressed frequently. I can still see tooling marks on my original angle iron rails...which is a testament to how durable real angle iron is, considering how many hundreds of thousands of parts I have cut on this machine over the past 10 years.

I think you will be happy with the W2 rails. Make sure you use enough fasteners.

-B

[gc3]

http://www.youtube.com/watch?feature=player_detailpage&v=XExmmSlB2-E

[harryball]

Thats interesting. I still have to install my rails but I'm going to have to grind my current rails first to get a flat surface wide enough for it to hook over. I didn't realize that when I bought the caps. I thought I could debur the current rails and put them right on top.

/RB