Upgrading the PRT-Continued from 2007 Archive!!!

[bleeth]

Wow-I had no idea that's how long it's been since I last did anything to "old faithful" but so much has changed conceptually since then that entire plans and concepts have been reworked. In the interim, after Dirks "Bot Rod" controller and the hardened Y rails were installed she's just been humming away with a couple of idiosyncrocies that we got used to and compensated for.
But now the parts are rolling in and the rebuild is in progress. Possibly disappointing to some I decided finally to adhere to a modified version of the PRS design built on my PRT steel frame. So therefore the original angled steel x rails are going away and being replaced by a 1.5" x 1.5" 80/20 extrusion with a solid aluminum pillow block on it that is 2" x 3/4". The extra thickness from the PRS design is to allow for GW3 hardened rails from Superior Bearing and their correspondingly larger wheels. By pre-assembling the three components it should be stiff as a-----well you get the idea!
Leveling and making sure they are straight and parallel will be fairly straightforward. Original racks will be used but its time for pinions anyway. I got ShopBot standard endplates and an extrusion from Bosch for the Y. Again larger rails and wheels (already have the rails and wheels) and re-use the original pinion.
I also, given the parameters of the rest of the design, asked SB to sell me a y/z car with no motor or Spindle mounting plate and will, once it comes in and I verify some critical measurements, modify the wheel holes for the larger wheels or use a different size pillow block and make the adjustment there. For the aluminum spindle plate, I want to engineer my own for the final step in this stage which is to add a small spindle to the front of the Columbo mounted to an air activated linear slide for use as a drill.

The additional extrusion, thicker pillow bolock, and larger wheels on the x will raise the whole thing higher off the existing table height and my purpose of this is to raise the table base higher off the ground. The reason for the secondary spindle is to use it primarily as a drill and be able to rig up end panel boring. The overall goal is to end up with an easy 36" clearance off the ground to the top of the table surface so I can bore cab bottoms and stretchers for dowel construction. Also, of course, I can do all my Euro 5mm holes with the spindle/drill and cut faster and smoother with a 1/4" bit for back dado and parts cutout. I'll post some shots shortly and if any of you other PRT guys would be interested, I'll send you parts lists as it is updated. As things are being wrapped up I'll also put on the Columbo speed controller.
A special thanks to Ted who helped guide my needs and some explanations of the current engineering through SB.
I'm really going to enjoy bugging him when this is done to work out a functional toolchanger!!
It may be easier to sell my rig as is and just buy a new one but then there's no fun involved.

[bleeth]

Well, we're really moving now! A friend of mine volunteered to drill and tap the 1/2 x 2 aluminum flat bar for mounting my new hardened rails for the x axis since he has a custom metal shop and I always use his services for bar rail, sneeze guards, custom metal glass racks etc. Dropped off the rails last week and a couple of days ago he brought them by. He not only did all the drilling and tapping for me but he picked up the cap screws to screw the rail to the flat bar and had it done for me!! Unfortunately the holes to bolt it down to the extrusion were 3/4" from the wrong edge of the flat bar!!! He's taking care of it but I really feel bad for him. These guys are known for their absolutely gorgeous and perfect metal work and this is the first time in over 10 years that something wasn't right.
The Y beam came in from Bosch Rexroth via UPS about a week and a half ago. You would think that a 67" hunk of aluminum that costs as much as this would be packed for shipping, right? Wrong. Several large knicks and a huge ding on one corner knocking the whole thing out of shape!! Well the distributor got ahold of Bosch, Bosch had the beam picked up and sent out a new one in a day. Great service. Not only that, but the distributor came by a couple of days ago and had the Bosch Factory rep (who definately knows Shop-bot-He saw an endplate in my office and immediately asked me if the part was for a SB) with him. I told them how great I thought their customer service was and how nice it was that they stopped by.
So today after normal hours I finally started putting parts together. Tapped out one end of the extrusion for the M-12 bolts, screwed on the end plate, got out my machinist square and checked it out. Perfect! We're cookin now! So I'm standing there looking at the beam and sliding a bunch of T-nuts and springs in it for the y flat bar and looking at the bot and after looking back and forth a few times I take a measurement. The beam is 69 7/16" long!!!. Go in the office, turn the computer back on, check out my parts list and sure enough-part ordered was 67 3/8"!!! Called the rep. First question he asks after hearing the issue is "What's my tolerance if he knows a local machine shop to cut it down". I wonder what part of 1711.25mm and absolutly square he didn't hear!!

I will say that the GW3 size v bearings are a bear and I reccommend doing the other minor modifications to use them if you ever need to replace your bearings at least on the x.

Stay tuned for more fun and games as we continue on the path of ever better botting!!

[ken_rychlik]

Dave, Take us some pictures. I am running a prt daily and am very interested in your progress. I had thought about building a machine before I found this one and still have a notion to do that.

Kenneth

[bleeth]

OK-Here are a couple before shots to kick it off. Previous mods are:
1. E Chain on Y
2. Hardened rails over existing steel
3. Upgraded Control Box to Dirk's "Hot Bot" (Forerunner of the 4-G)
4. 8 zone vacuum grid with 1" PVC pipe and valves.

42672.jpg

42673.jpg

42674.jpg
Besides the gantry and x-rail replacement I'll be redoing the PVC to at least a 2" system. The increased volume will enhance the current holding, which is pretty good with the 7.5 regen blower but has room for improvement. The Hardened Y rails, e chain, and a couple of other things will be recycled along with the motors and spindle.
Next shots will show some in progress stuff. Most likely parts on bench.

[jon]

Dave, I just replaced the rails on my PRT alpha, with the BWC hardened y2 rails that were suppposed to come with the dual vees that we all have on our machines. I've seen tubular rails with semi circular cars elsewhere on this forum, and really wish I had been looking there first. One thing I did, in addition to the rail add on, was have the cast iron side beams the rails mount to milled flat on a very large upright mill (forestry machine shop had a 40 foot upright mill!), and it allowed me to mount the factory bent rails and hardened rail combos directly without shims. I believe this eliminated a lot of vibration, and need for shimming.

[bleeth]

This is it-all parts on hand, toolbox ready to go-local temperature heat index over 100 and predicted to stay that way-3 days to get her done by Monday AM.
Large coffee in the morning and away we go! Even I don't believe it!!

[Gary Campbell]

Onsite QC inspection scheduled for Fri the 9th, late afternoon

[bleeth]

Viewing tickets available at the discounted price of 2 green bottles from Holland (Unopened)!

[gc3]

Watching this thread with great interest!!!

Attached is a virtual "cold one"...enjoy

Gene

[bleeth]

Midday Saturday: Torn down. Next step is to remove the racks from the x rails for recycle onto the new rail assembly. I already took the rack off of the Y gantry and it was easier than I thought it would be. The biggest thing I'm going through is all the memories of the original assembly. Although it has been moved several times it has never been taken apart. Even when I put the hardened rails on the Y I just blocked the Z up and never really took it apart!!

The old mounting holes will work but there aren't enough of them to suit me so I'll be adding another between each existing pair. You can see the end of a new x rail in the picture I used a pillow block of 1/2" aluminum to mount the hardened rail on and attached it to a 40 x 40 mm extrusion.

By the way-to get the large picture I just took the shot in fine mode with my camera, opened it in Adobe Elements, and saved it in a smaller resolution without changing the overall size. This may be the first time I posted a picture on the new forum.