Turning a PRT into an Alpha... is it worth it? Or should we look at other upgrades in

[jeffreymcgrew]

Hey everyone! Our machine is five now, and while still in fine shape and working hard, we're looking at maybe making it faster & better this year.

Now, does it even make sense to swap a old PRT 4G up to an Alpha? Swap the motors and controller onto our older frame?

Or should we just buy a new PRS Alpha? We could either go with a whole new machine, or we could just maybe buy the upper half (rails & y-gantry) and mount that on our existing table base. If we did go with a new machine, we could then take our old machine and add that revamped Z-axis with a 12" travel and just have it carve foam all day!

I'd love to get away from the older style gantry (and all it's issues) and have the newer style big aluminum extrusion. But I'd also love to save some money! ;-)

What would you do?

[ken_rychlik]

Depends on if you have more time, or more money. lol

I have been from a prt std, then 4g, then prs std 4g, and now prs alpha.

Now I'm thinking about building another one just for the heck of it.:rolleyes:

To answer your first question, post a picture of your y gantry and then I can answer. The older ones were not very strong as far as putting more powerfull motors on it. The later models can handle it better.

[bleeth]

Jeff:
I went through the same questions as you and have made a partial upgrade. To me the first limit was definately the old style gantry. It just had too much flex in it. (Mine was the bolted together z car type). At this point I have done the following (Which you can read about and see a couple pics of in the "Upgrading the PRT" thread in mods to Shopbot section of the forum):
Replaced original control box with 4g type Gecko driver box, replaced x rails with hardened rail on extrusions mounted directly to original steel frame, Redid entire gantry with SB endplates and Z, Bosch extrusion, and hardened rails. I am still using my original geared PRTmotors. My optimal cutting speed for clean cabinet parts is 3-3.5ips and I jog at 8ips. I have not added up the cost exactly but as I recall the control box that I did several years ago was around 12-1400 and I spent around $2500 altogether on the mechanical changes. I am satisfied as far as it goes as at this time I have what amounts to a PRS Standard with its advantages over the original PRT. I would like to have more torque and cutting speed in my motors however. I have 2 choices for this: New motors that run on the existing drivers with minor adaptation which Mike Richards has written extensively about, or replace the 4g controller with an Alpha controller and go to the Alpha motors. I like this idea a lot as it opens up other possibilities to me. It is also another 6k plus. Recently I had the Engine blow in my Truck. It sure made more sense to replace it rather than junking it. Also, if I sell my current machine as is with spindle, vacuum, etc, and buy a new one it would cost me more to buy an all new Alpha then upgrading at this time. Much of my decision was based on economic limitations as well as the fact that I enjoy the "tinkering" and planning, etc that goes into souping up the PRT.
I believe that putting new Alpha motors and controller on your older frame without redoing the gantry and z is putting too much power on a frame that just can't handle it and when cutting parts quickly you are going to have issues from the frame twisting, etc. There are other answers as some have manufactured their own gantries from scratch or even simply welded and re-inforced the PRT gantry with a few other modifications and gotten good results. What is going to be the right answer for you ultimately can only be decided by you after you have considered all the options as well as the downtime for any re-building.

[jeffreymcgrew]

Already got the 4G upgrade & the one-piece PRT-style Y-gantry on the machine.

Good to know that upgrading the motors without upgrading the frame isn't going to give us great results due to the frame just not being all that.

We've got our x rails mounted to a big aluminum extrusion already, that's mounted onto a steel base of our own design that is a little heavier than the shopbot one.

Seeing that power-wise we'd also have to probably put in a new subpanel to drive an Alpha (breakers maxed out, plenty of power coming into the building, no more breakers to feed anything) that's another big cost. That came up in recent research on this.

So maybe we start by swapping the gantry for a 'modern' PRS style one and then go from there. I wonder if I can do that and give us some more Z-travel at the same time...

[ken_rychlik]

It doesn't really take very much more electricity for the alpha. Depending on which version you get, and if you decide to go to a spindle.

Mine runs off of a 220 volt 30 amp circuit and I am running a 4hp spindle with that also.

With the one piece prt gantry, you could probably get by with an alpha, but I don't think you could push it for all the power available.

If you are happy with your cuts and just don't want to loose steps and have more power to play with, then the answer is alpha.

If you are after cleaner cuts and not worried about speed so much, then the new gantry would be the choice.

If you want both, then you gotta do both.

[michael_schwartz]

Don't forget you can probably sell your old motors/controller and any old parts pretty easily to help reduce the cost of any upgrades.

[jeffreymcgrew]

Don't forget you can probably sell your old motors/controller and any old parts pretty easily to help reduce the cost of any upgrades.

We've already got a Spindle wired up 3-phase and such. Problem is we're maxed out. I could run an Alpha with two 20-amp 110 plugs, but then we'd still probably be putting in a subpanel to do so.

Good to know that we'd need both the Alpha and the Gantry to get more speed. Our cuts are pretty clean, but we do have to keep a very close eye on our machine to keep them that way. That's one problem the new gantry could certainly solve, but it isn't enough of a problem yet for us. Going faster would be great however, that would really impact what we're doing.

One thing I'm wondering is how much faster we'd really get to go. We cut at 3-4 inches per second most of the time, 1/4" compression spirals in very dense 13-ply hardwood plywood with .25" to .375" passes. With our 2.2 HP spindle, I don't know if we could really drive much faster than that, Alpha or no, due to the bit limitations & chipload.

I mean, if we could run 1/4" compression spirals at like 8 IPS that would be awesome, but I'm thinking that's just not possible due to the cutters and our 2.2 HP spindle not being able to take it. But I'd love to be wrong about that.

Selling our old motors & parts is certainly interesting, but then so is keeping our old 'bot, putting a 12" Z on it, and having it carve big blocks of foam into sculptures while we buy a new PRS Alpha for the 'heavy' cutting. Old bot for softer 3D jobs that take a long time, new bot for production. Kinda like how Brady took one of his old bots and made it into a laser scanner. How much can you really get for 5 year old motors, controller, and gantry anyways?

Thanks for all the info!