Potential upgrades

[sawkerf]

I have a 2004 PRT Alpha and I am wondering what would be a worthwhile enhancement or upgrade other than gears and rails. Are there control box upgrades that might improve performance? What about the retro Z upgrade, is that worth it? Please share your thoughts. Thanks, Kip

[bob_reda]

Kip, I upgraded a 1997 prt with the rbk control box, 7.2 motors, new hardened rails, didn't do the z I have to look at that. Don't know exactly what that involves and how much better it would be than i have right now. I did all my upgrades over a two year period. runs like a prs!

Bob

[bleeth]

If you have the 1:1 motors changing to geared ones or adding belt gear drives would make a huge improvement in resolution. A much stiffer gantry would allow you to cut and jog much more quickly. The new Z is an improvement over the old.

[davidp]

Hi Kip,

We have a 2004 PRT Alpha.

We have upgraded to 7.2 motors on all axis, X,Y & Z. We replaced the rails with BWC hardened rails on both the gantry and the X Axis and all of the rollers with larger rollers. We replaced the Z Axis with the retro Z, we have also installed a 5HP HSD Spindle with Auto Tool changer and 8 tools on the tool bar. Our last modification was to replace the springs on the X axis motors with longer springs. We now have a machine that cuts beautifully and reasonably quickly.

We have not touched the electronics or the control box. There has not been a need. In fact our next modification we are planning is to strip another brand CNC and replace all of its electronics with the shopbot gear. We will probably do that in the next year or so.

Regards,
David
Sydney

[gc3]

Hi Kip,

We have a 2004 PRT Alpha.

We have upgraded to 7.2 motors on all axis, X,Y & Z. We replaced the rails with BWC hardened rails on both the gantry and the X Axis and all of the rollers with larger rollers. We replaced the Z Axis with the retro Z, we have also installed a 5HP HSD Spindle with Auto Tool changer and 8 tools on the tool bar. Our last modification was to replace the springs on the X axis motors with longer springs. We now have a machine that cuts beautifully and reasonably quickly.

We have not touched the electronics or the control box. There has not been a need. In fact our next modification we are planning is to strip another brand CNC and replace all of its electronics with the shopbot gear. We will probably do that in the next year or so.

Regards,
David
Sydney


the other brand cnc have linear rails?

[sawkerf]

I've seen these 7.2 motors mentioned here before. Where do you get them? How much do they cost? How difficult is the changeover? Keep in mind, I'm more of what's known as a "power user". For example, when I read a book, I read the first few pages, skim the middle and then skip to the end.;) Thanks for the info gentlemen.

[davidp]

Kip

The 7.2 Motors are from Shopbot. They simply bolt on to the bot, you do have to change the drivers in the control box and change the unit values in the control software a couple of hours all up max. The hardest part is re running the cables. One of the best upgrades you can do IMHO

Gene

The proposed machine has BWC rails and rollers the same as the one we upgraded to, with rack and pinion drives.

David
Sydney

[blackhawk]

David - What are the major differences with the Retro Z axis? Shopbot's description on the website is pretty vague.

[Brady Watson]

The RetroZ uses a PRS style Z axis, but is made to fit onto a PRT. It uses 3 rollers per side that sit in a profiled track and an aluminum extrusion instead of the T-rail.

I'm not sure how much interest there is, but I was thinking of fabricating replacement T-rails for PRTs since I could use a couple on my own machines. If I am making some already, what's a few more? If interested let me know. FYI - these will be out of A36 steel, precision ground - NOT that soft malleable CNC bent steel that wears out very quickly - which you probably have on your machine now.

One thing that really makes a huge difference in longevity on the PRT T-rails is running 8 V-bearings opposed to 4. 4 bearings was the original setup, but 4G PRT & later PRT Alpha machines had 8 of them. It makes a BIG difference not only for wear, but for stiffness. Combine 8 bearings with good steel with higher Rockwell hardness & it will outlast the soft steel by a factor of 3:1 or more. At least this has been my experience.

-B

[danhamm]

Here is a pic. of the one Brady mentioned, can be mounted in many ways.

[davidp]

Brady,

That sounds to be a really good upgrade to the Z axis. The 8 bearings and hardened rails would make the Z much stiffer. It would also last much longer as you say. We wore out two of the old PRT Z's before replacing it with the Shopbot Retro Z. The ShopBot Retro Z had a lot of fiddling and rebuilding to get it to fit into the old PRT Carriage especially with a 5 hp HSD Spindle.

The retro Z also has an air ram instead of the springs to assist the travel. You will also definitely need the 7.2 motor as the old direct drive motors did not have enough torque to lift the spindle even with the air assist.

In all the upgrade was worth it as the bot owes me a fraction of what some other equivalent machines would cost and so far, since the upgrade 2 1/2 years ago, we have been running it for around 12 hours per day 4 days week with very few problems.

Regards,
David

[sawkerf]

What is the cost for the 7.2 motors?

[kurt_rose]

I'm in Brady. Do I get the South Jersey discount?:D

[blackhawk]

How are you guys that have BWC rails mounting them up on a PRT? I see that the BWC rails have a shoulder. Are you just resting the shoulder onto the existing PRT angle iron rails and then bolting them on through the side?

If anyone has a picture of their setup, please post.

[Brady Watson]

The T-rails that I am going to make do not use BWC hardened rail. They will be precision ground mild steel, which I have on every axis of my machine except the Z T-rail. The mild steel replacements will last about 3x longer than the originals because of Rockwell hardness of the steel.

Scabbing BWC hardened rail to the side of your existing rails is tricky - and to be honest, looks like **** when it is all done. SB has come up with a solution for this - they sell CNC bent steel 90s that have the holes punched out to accept BWC hardened rail. All you have to do is bolt them together & it is a clean replacement for your existing X or Y rails. However, prepare to swallow hard when you hear the price.

I like PRTs - to be honest, more than I like PRSs - so I plan to keep mine running and in tip-top shape. I'm going to start with T-rails for me & make a few extras. They'll be machined to spec & have the gear rack mounted on them. Pretty much a direct replacement and easy bolt-on deal. Later on, if there is interest or demand, I would consider making replacement rails for other axes. My PRTAlpha gantry could use a set on the Y soon, since these are bent rails. My original gantry has angle iron rails and still have the original cross-hatching on them (as do my X rails!) from when they were ground. True angle iron wears so much better than the bent stuff.

If you look at your X&Y rails from the side, and you see a square outside corner & rounded filet inside corner, you have true angle iron. Otherwise, you have the soft bent stuff. Chances are you don't have the angle iron on your machine because it was only used for a year or two, or on extra long rails that couldn't fit in the bender.

-B

[bleeth]

When I changed my bent x rails to BWC type (I bought them from superior bearing company for much less money and equal or superior quality), I ditched the bent rails, and mounted them on a solid aluminum pillow block that was then bolted to a square 20/20 extrusion. This I bolted directly to the steel frame. Since the rack on the bent rails was in fine shape I moved it to the pillow block. With careful planning it makes a perfect replacement with no further modifications needed. At the same time I went to larger v-rollers.

[blackhawk]

Brady - The replacement T-rails that you are going to make are just for the Z-axis, correct? I agree that setting up BWC rails on the Y and Z-axis would be tricky.

For the X, it seems like mounting the BWC rails on the existing angle rail would be pretty straight forward. If you bought the BWC rails with the pre-drilled holes, you could sit the shoulder down onto the angled rail. Clamp it in place, then just use the pre-drilled BWC holes as a guide to drill new holes in the angle rail. Bolt it together.

[sawkerf]

.....so......does anybody know how much the 7.2 motors cost?

[steve_g]

Kip...
You better call ShopBot for current pricing. You'll need the motors and the drivers and drivers cost more than the motors! Current list price of the motor is $399.00 and the drivers at $883.00. Remember, you need three each. If you like to live dangerously... There are some drivers listed on EBay in the $200.00 range. Most of these are used and located in Korea, China, Philippines Etc. Used motors, when available, are the same story and in the $200.00 range. If you buy a used driver you'll likely need to send it to ShopBot to be custom reprogrammed for a reasonable fee.

When faced with the above pricing, I chose to go with a belt reduction unit... details here----->
http://www.talkshopbot.com/forum/showthread.php?t=15760 (http://www.talkshopbot.com/forum/showthread.php?t=15760)

Hope this helps

SG

[blackhawk]

Steve - I just upgraded my Z-axis to a 7.2 motor and drive that I got from Ebay. I asked Shopbot to re-program the drive for me and I was told that they could no longer do this because of an agreement with Oriental Motor.

The only difference that I know of between the standard drive and the Shopbot version is that the resolution settings are programmed differently. For example, if you set the resolution dip switches to 10,000 on a Shopbot drive, it is actually 8,432. (I made up 8,432 but you get my drift.).

I made the Ebay drive work, you just have to calculate the correct unit values to go with the motor.

There are no differences in the motors, so it doesn't matter where you buy those from.

[steve_g]

Brad...
Thanks for the update and the correction!

SG

[Brady Watson]

If you have AS911s, I would strongly suggest going with a 3:1 synchronous timing belt reduction instead of the 7.2s. The AS911s will twist your arm off with proper reduction & will outperform the 7.2s - plus it is cheaper.

There are a few people out there that know how to program those drives...but you should be fine with any AS drive running it as-is, as long as you don't take a SB drive & combine it with a surplus drive because the unit values will be different. E.G. - the X axis no; Y or Z ok.

If you want a 'cheap' solution, prepare to do your own research and R&D to figure it out. Otherwise, ante up for the motors & drives.

-B