2001 PRT 4g Spindle Upgrade Question?

[David Iannone]

I have been running the PC router that came with my bot since the start. (I have a backup unit also)
-2001 PRT 4g, new pinions installed.

I am looking towards the next upgrade.
The Spindle for the desktop is: HSD 1HP 110V Single-Phase Spindle for the Desktop (#12604) $1,595.00

Is this to under powered for my 4G PRT?

Thanks,
Dave

[bleeth]

I would recommend going to t least the 2.2. The 4 would be better.

[tlempicke]

Remember that if you are going to run it on single phase power it will only run at 1/2 of the rated power. The small unit used on the tabletop is designed for single phase, the others are not. In this case bigger really is better! On my tabletop I have run into situations where the spindle bogs down. This is really bad! The power supply ups the output to compensate for the load that the spindle sees and so it puts the max to the spindle motor when it does that.

I have been using a 4 HP spindle that I got from Shopbot on single phase power for the past three years on my other machine with no problems whatsoever. Since it only puts out 2 hp (The limitation is in the power supply) it should last for a good long time.

[Brady Watson]

Is this to under powered for my 4G PRT?


Yes. Don't skimp on the spindle. At the very least get the 2.2 HSD (18,000 RPM max) or 3hp Colombo (24,000 RPM max). I've dogged out the 2.2 on my BT48 Standard a few times pushing it hard. I've never bogged down the 5hp Colombo.


Remember that if you are going to run it on single phase power it will only run at 1/2 of the rated power.

Who told you this? (so I can beat them with a wet noodle) If you ordered a 4hp spindle in single phase config - you get a 4hp spindle. The ONLY difference is that the VFD pulls in single phase and converts it to 3ph. My 3ph VFD for my 5hp spindle has the capacity to run 10hp - this could be where the confusion is coming into play.

-B

[Ajcoholic]

The spindle is identical when you order the single or three phase version.

The VFD is different. For the single phase version, the VFD is actually a larger unit so it does convert single phase power to three phase, to supply the spindle adequate power. That's why the setup costs more for a single phase setup - you are buying a larger VFD.

In both cases you are getting the 4 hp spindle which will indeed put out the same power to the bit.

Converting single phase to three requires "extra" power so to speak. Similar to a mechanical converter where you use a motor and caps (rpc) to provide the extra phase, you have go over rate the supply to get the required output.

[Brady Watson]

My 3ph VFD for my 5hp spindle has the capacity to run 10hp - this could be where the confusion is coming into play.


What I meant to say was, "A single phase VFD for a 5hp spindle, for example, has the capacity to run 10hp - this could be where the confusion is coming into play.

What Andrew says is correct...

-B

[Ajcoholic]

What I meant to say was, "A single phase VFD for a 5hp spindle, for example, has the capacity to run 10hp - this could be where the confusion is coming into play.

What Andrew says is correct...

-B

The 10 HP VFD can only run up to a 10 HP spindle IF the feed is already three phase. The VFD is just controlling the frequency in that case to vary the rpm, plus control braking and so forth.

If the feed is single phase and you are using the VFD to both create the three phase supply AND control the spindle, the VFD has to be over rated by a certain percentage (not sure of the actual #).

I think some people assume there are two separate spindles, those that operate on single and those that operate on three phase power... ain't so. ALL spindles in this case are basically precision three phase motors. They will not run on single phase power. It is the VFD that is supplying that power.

In the world of standard motors, I do know of certain instances where a three phase motor can be run on single phase, once it gets mechanically spun up to operating speed (you see some guys do this with a cord etc). And if the motor continues to run (some will some wont) it will only develop a fraction of the rated HP. This really has nothing to do with these spindles since they will never be run on a single phase direct feed.

Over the years, before commercial RPC's and now VFD's were as "cheap" and plentiful as they are now (relatively speaking) many home brewed versions of three phase converters were brewed up, many of which could only run a motor in a highly de-rated state. Maybe this is what was implied?

[Brady Watson]

Many VFDs are derated by 50% when running on single phase - which is where the 10hp capacity VFD for single phase use for running a 5hp 3ph motor comes into play. If you feel like reading about it, here's an example: HSM VFD Confusion (http://bbs.homeshopmachinist.net/threads/51655-VFD-more-confusion?) - by no means the complete picture, but it will provide some deeper understanding and clarity.

This is exactly why single phase spindle/VFD packages for single phase input are more expensive than their 3ph counterparts. You need twice the VFD for the same horsepower - depending on the VFD manufacturer.

-B

[David Iannone]

Thanks guys for the answer I needed. I was just hoping I could make the smaller spindle work, but I will just have to wait on this one for a few months.

Price difference between the 2.2hp and 4hp from SB is about $876. Which is a lot of money.....BUT when your at the $2619 price range, double the HP for $876? I think I gotta spend the extra when I can scrape up the cash.



Dave

[bleeth]

You will be glad you did. Of course, then you are going to want to beef up your gantry so you can utilize more of that power.
My PRT came with a 5HP Columbo. Max cutting through plywood with a 5mm or 1/4" bit was around 1.5 ips. and jog at 4ips That was before 4g. I then got the privately built forerunner to the 4g and cut went up a little to 1.75 but jog went to 10 ips. After I rebuilt gantry and x rails to PRS style cutting went to 3.75 but jog down to 8. After Alpha motor and controller upgrade (It has been a lot of fun!) I now jog conservatively at 12ips and cut at 6. I have run it a lot faster than 12 but that's enough, although I keep thinking about going to 16 there. Naturally, softer materials like mdf or foam will cut faster.
Note the discussion in the other thread about 3ph vs 1 ph. If you don't have 3ph available you will need to get double the VFD to control the spindle. I didn't have 3ph when I bought mine so I have a 10HP Delta VFD and it has been fine for over 10 years. In fact I am on original bearings and always warm up and cool down. Several years back fan started making occaissional noise so I bought a replacement but it's still in the box. The Columbo is a workhorse for a machine like a SB.

[Brady Watson]

It was $3900 back in 2001 for my 5hp Colombo...but she still runs and makes me money. Just in case, I have a brand new fresh one (and VFD, cable etc) sitting on the shelf I bought 8 years ago...I spin it by hand every so often to keep the grease moving around in it.

Investing in commercial or industrial quality equipment is never cheap...but it is like investing in a tractor. Buy a good one, and it will last you a long, long time. That won't mean much if you are a city slicker :D

-B

[David Iannone]

You will be glad you did. Of course, then you are going to want to beef up your gantry so you can utilize more of that power.
My PRT came with a 5HP Columbo. Max cutting through plywood with a 5mm or 1/4" bit was around 1.5 ips. and jog at 4ips That was before 4g. I then got the privately built forerunner to the 4g and cut went up a little to 1.75 but jog went to 10 ips. After I rebuilt gantry and x rails to PRS style cutting went to 3.75 but jog down to 8. After Alpha motor and controller upgrade (It has been a lot of fun!) I now jog conservatively at 12ips and cut at 6. I have run it a lot faster than 12 but that's enough, although I keep thinking about going to 16 there. Naturally, softer materials like mdf or foam will cut faster.
Note the discussion in the other thread about 3ph vs 1 ph. If you don't have 3ph available you will need to get double the VFD to control the spindle. I didn't have 3ph when I bought mine so I have a 10HP Delta VFD and it has been fine for over 10 years. In fact I am on original bearings and always warm up and cool down. Several years back fan started making occaissional noise so I bought a replacement but it's still in the box. The Columbo is a workhorse for a machine like a SB.


Dave,
Thank you for the feed and speed data as you upgraded. That is great data for me. Of course you see I am trying to catch up...lol

Actually, the next trip I make back home (800 mile) my Gantry was going with me in the back of my covered pickup for beefing up. Thank you for letting me know the expected improvement at each upgrade.

[David Iannone]

Ya darn right this is fun. That's why I bought a Shopbot back in 2001.

Great machine, great company, and the best forum.

[bleeth]

You're welcome Dave.
Now you'll have to start your own thread on upgrading your PRT project as you make progress. Post Pictures! Pre-PRS there was a lot of that. The PRT is so like an erector set that all kinds of mods were done by buyers.