Upgrading the PRT

[bleeth]

Shawn: This is now going to be the 2nd step in my looong planned gantry upgrade. I have had the laser cut and bent parts for Gerald's design gantry and car on the shelf for a while now. The only thing about it that I don't like is angle iron rails and had looked into block and track but it is out of budget although I really like it. The T-3 track will work just fine with the SB standard #2 wheels or #3 wheels for a beefier upgrade. For now I will probably just adopt the new rail to the existing gantry and car while having the parts welded and gather the remainder of the pieces. Depending on budget at the time I may go block and track for the X rails, but will at least go hardened rail for them.
I upgraded to Dirk's Gecko box (the AGEK) a while ago and replaced the old broken and patched bow with Igus chain. This is all starting to remind me of hot-rodding my first car years ago!!

Dave

PS: This is a continuation from:
http://www.talkshopbot.com/forum/messages/11097/22112.html?1183064281#POST53372

[jay_p]

Dave,

Sound interesting. Be sure to post photos.

Jay

[conceptmachine]

Dave,
I was planing on making a new gantry but i thought i would modify the stock one first to see how it went.My original plan would probably be overkill for the stock SB equipment so if i end up doing it i'll probably just build one from the ground up.On the stock gantry i removed the unistrut and welded some angle iron in it's place which will also be used for a tensioner using v rollers.I then took the x car to my horizontal milling machine (after i welded it together)set it up by locating on the x car v rollers and machined the rails.I could not believe how far out of parallel the rails were to the v rollers it took 1/8 of an inch to clean it up.I then machined a healthy 45 deg edge on the rails so the v rollers would have a good contact area. I'm in the process of putting it back together now,i'll try and take some pic's when i get it finished.
shawn

[bleeth]

I'll look forward to seeing them. I have a feeling that the problems in mine have been around for a long time (possibly even factory), but due to the nature of what was being produced the inaccuracy was not very detectable. It is interesting that the most basic of uses, cabinet parts and doors, are among the most demanding in dimensional and square accuracy and smoothness of cut. I have been following the thread regarding the new PRS Alpha and am surprised to see more chatter in the cuts posted by Ted then I am getting with my PRT/AGEK running the same SB3.53 software. My cabinet edges have been so smooth they require no sanding prior to edgebanding even when using .5mil PVC and that's with a simple 2 pass straight through with no cleanup pass cut from a 1/4" downcutter. I think, like you, when I get the new rails in from Rick, I may do a bit of welding on my existing gantry and see if I can raise the cutting speed on it some.

[conceptmachine]

Well i finaly had a chance to get some pictures.The modification worked as planned,it takes very little spring tension to hold the y car down.I'm still not satisfied with the v roller setup,i'm already designing a prs style gantry but it will have linear bearings instead of v rollers.
shawn

387

388

[bleeth]

Looks great Shawn. How is your cutting smoothness? I wish I had your horizontal mill for a while!! I made a round of phone calls to some local machine shops and got nowhere. The rails have arrived but I'm mired in production right now and can't spare the time to tear down and rebuild. I have to get it done in a couple of weeks though as I just booked a fast track project that needs accurate boxes and I am determined to not do them on the table saw and machine by hand.

[conceptmachine]

Dave,
It's a lot better than stock but it still isn't where i would like it to be.I'm looking at the linear guide's that techno sell's for a retro fit.I'm thinking about just making a whole new carriage for the bot,linear guides on all axis,that shuold do the trick(i hope)
shawn

[bleeth]

Well I just got done assembling the first batch of boxes made since installing the hardened rails on the stock gantry and the result is outstanding. All parts came out perfectly square and matching in size. Before I hooked the motor back up the car would slide back and forth on the gantry with the touch of a finger. At this point I have not added any hold down at all on the high side of the gantry and had no jitter or any other problem signs whatsoever, even when plunging in to cut hinge holes. Smoothness of cut is as good as expected and needed almost no touch up prior to edgebanding. This project was p-lam on plywood and the 1/4" downcutter left my cuts smooth top and bottom. Other tests such as cutting out some larger circles, stars, and some v-carve work will tell me more. I believe the welded up new gantry parts and hardened rails for the x will be sufficient for this machine. I just wish I could adapt some kind of a tool changer to my spindle.
I'll post some pics later.