Striatech DVR motor for PM's 2-3 HP lathes 1236,1236T,1340GT.. etc

[JimDawson]

Striatech called me back. It's as expected, no interface to externally control their motor. However, they are working on it for their future controller. With some custom mods, they may have something I can do now but they have to talk to their engineers before getting back to me again.

While I'm going with the single phase on the PM-1236T to start I still plan to keep my eyes open for an "easy" way to put a variable speed motor on it. Ha, easy.... after hours of research and lots of questions . Everything is easy... once you understand it and have done it once.

I guess it depends on your budget. Most likely the least cost and easiest method is a standard 3 phase motor and a sensorless vector VFD. The 3 phase motor/VFD combo will give you a wide speed range, using the lathe gearbox for the course speed adjustment and then use the VFD for the fine speed adjustment. On that machine I would not increase the motor size too much, maybe up to 1.5kW (2HP). If you want to go top shelf, then a servo motor would be a good choice.

Having said that, the stock 3HP, 3 phase motor and static phase converter + the lathe gear box (8 speeds, 72 to 2000 RPM) has given me all the range I have needed for about 30 years. I thought about putting a VFD on the machine, but I just haven't figured out a good reason to do so.

Seems like with all the variable speed motors out there, why not do away with the gear box, just a low/high pulley set and do the rest from a motor that has torque through the range... out of the box of course .

This is certainly possible if you put enough motor on the machine. My CNC lathe has a 7.5kW (10HP) servo motor direct driving the spindle at 1:1, about the same torque capability of a small auto engine, but I think a motor that large would twist your lathe into a pretzel. It will run 0 to 3000 RPM. I replaced the original 7.5kW spindle motor (0 to 5000 RPM) with the servo so I could have a C axis for making some parts, I lost 2000 RPM in the process, but nearly doubled the torque. I rarely run it over 2500 RPM anyway.

Based on RPM calculators, turning 1" aluminum stock, I should be around 500 SFM which calculates out to 1900 RPM, double that for .5" stock. The PM-1236T only goes to 1800. Though, on my atlas 618, I max out at 1500 RPM and can get a decent finish... so, for the newbie, it's hard to know where to start. Seems like most lathes top out around 2000 RPM. Do people actually turn at 2000-4000 rpm?

My brain is just hurting from trying to nail down what lathe, motor combo, electronics if I go the VFD route eventually, DRO choices, so many particulars.

On my manual lathe (13x40), most turning is done at < 500 RPM no matter the material. Maximum spindle speed is 2000 RPM and I only use that with collets when working on tiny parts. Don't worry about the speed charts, they are geared for production work, using flood coolant, and under ideal conditions. On my CNC lathe I generally turn aluminum at about 400 FPM, and SS in the 300 FPM range, but normally keep the spindle speed below 1800 RPM in all cases.

 

[mksj]

I am not sure where you are going with this motor thing and making it more complex then it needs to be. This typically happens when you do not have the lathe in front of you and you overthink things, part of this is experience and also making past mistakes and learning from them. First off the tooling SFM is based on ideal conditions, CNC level type machines that are many tons, for the most part they are not achievable on most manual lathes. It also is not only about SFM but many other parameters like depth of cut, feed rate, tooling/insert geometry, stiffness, etc. The type of tooling you use is also specific to the size, Hp, weight, rigidity.... of the machine. You might get a copy of David Best's book "Introduction to Indexable Tooling for the Metal Lathe: A User Guide" which gives some great guidance and specific tooling and their use. In general, when using metal cutting inserts, I end up using about 1/2 the SFM of those on the box. Lathes with splash lubrication typically top out at 2000 RPM (maximum 2500) , beyond that you are risking bearing failure. There are also other limits such as chucks, gears, gearbox, etc.

There is no need to upgrade the motor unless you want to break something, the space is very limited, and there is "0" reason to go to a larger motor in a machine like the 1236T that is too light to handle it. With the stock 3 phase motor, with a VFD, you can convert it to a single speed belt drive by flipping the motor pulley and belting it from the large motor pulley to the large headstock pulley. You then can use just the Hi/Low right lever for most turning and the left lever if you need a bit lower or higher range. There is no free lunch that you cannot just turn a knob an expect a motor to deliver full Hp/Torque form 0 speed to maximum speed, you also loose the mechanical advantage of the gearbox. There are many posting in this forum and on-line that review the performance characteristics +/-'s. In either case, you will never be at a loss of power with the stock 3 phase motor and a VFD. If you happen to only be able to get a single phase 1236T, then there are only a few "2 Hp" motors that will fit, they are all TENV types and require mods. Since the Striatech DVR motor cannot be controlled by external controls, it is out of the picture for this application. If you want to keep it for say a belt sander, go for it.

I previously outlined a simple method to do a basic VFD install for many of the PM lathes, including the 1236T, 1340GT, 1440GT. 1440TL series, etc. that many people have used and been very happy with the end result. It is much less $$ then your current path, and at the end of the day will have as good or better performance. The last iteration is listed on page 9, but lots of information in that thread. PM/QMT also has a similar install document. A few things about the 1236T is it is a 12" swing so the belt length is shorter, the motor compartment would be smaller, and the front panel for switch gear is smaller. If you need some specific guidance on the conversion below, you can always PM me, or ask a lot of other knowledgeable people in this forum.

Pm1340gt Lathe Basic Vfd Control Conversion Using The Stock Control Board And Switches

Not really and issue since the resistor's I recommend are completely sealed and the wiring is embedded. You could also mount it on the inside of the VFD cabinet which I have seen done. It does not get warm so heat is not an issue. My original 1340GT VFD with the WJ200 had it in the headstock...

www.hobby-machinist.com

 

[skcncx]

I guess it depends on your budget. Most likely the least cost and easiest method is a standard 3 phase motor and a sensorless vector VFD.

I didn't realize that was an option, I assume that's what @matthewsx was referring to by static converter. And I assume that pretty much leave everything in tact control/wiring wise of the PM-1236T.

On my manual lathe (13x40), most turning is done at < 500 RPM no matter the material. Maximum spindle speed is 2000 RPM and I only use that with collets when working on tiny parts. Don't worry about the speed charts, they are geared for production work, using flood coolant, and under ideal conditions.

Good to know! I'll have to slow my Atlas 618 down to 500 RPM and turn some .5" to 1" aluminum and see what happens. I've been using carbide CCMT inserts and I purchased a couple of the AR Warner HHS inserts as it seems I get better results with the HSS inserts. I guess, start slow, good results, no need to go any faster.

 

[Ischgl99]

Listen to what Mark is telling you, switching the motor is not going to be a simple swap. I have the 1236T and got three phase. The three phase version comes with a 2hp motor and not 1.5 like the single phase model. I have a vfd on the stock motor and haven’t found any reason to switch to a different motor yet, but others here have reported smoother performance with the motors they switched to. The performance of the stock motor is good enough for my uses that I don’t feel it necessary to go through the trouble to change, and I would rather spend that money on tooling.

If you think you will want variable speed in the future, I would recommend getting the three phase now since you might not be able to get a drop in 3 phase motor from PM, and your choices are very limited on what will fit even with modifications, let alone without. I took measurements of my motor and it does not fit any off the shelf IEC motor I could find, but I did find one motor that looks like it would fit without modifications, but would need a different pulley bore. And it’s definitely not a NEMA size motor, hence the comments you will need to make modifications to get one to fit.

Keep in mind, with a VFD, you need to modify the stock controls to work with the VFD. You can’t just hook it up to the power input and use the stock controls, a VFD must be connected directly to the motor otherwise you will damage the VFD. If you wanted to keep the stock controls, you could use an rotary phase converter, static phase converter, or if you had plenty of money burning a hole in your pocket, a Phase Perfect.

 

[skcncx]

I am not sure where you are going with this motor thing and making it more complex then it needs to be. This typically happens when you do not have the lathe in front of you and you overthink things, part of this is experience and also making past mistakes and learning from them.

I'm not sure where I'm going with this either . Given these lathes are so expensive (for a hobbyist) and all the components have to work together, change one part and you need to change other parts (generally speaking). I partly was exercising in my mind my options for a future upgrade from single phase to a variable speed motor... whatever technology it would be.

You might get a copy of David Best's book "Introduction to Indexable Tooling for the Metal Lathe: A User Guide"

Thanks for the reference, I'll have to get that. He gave me a couple other docs I read and was super helpful.

There is no need to upgrade the motor unless you want to break something, the space is very limited, and there is "0" reason to go to a larger motor in a machine like the 1236T that is too light to handle it.

I have zero desire to add more HP. I assume the 1.5 HP for the single phase is plenty. The Striatech was 1.75 HP anyway. The "upgrade" was entirely for variable speed to hit more in the range from 90 to 1800. All this is speculation on my part as to the actual need. However, looking at the RPM ranges on the PM-1236T you get quite a few options from 90 to 1160 then a big jump is to 1800. A 640 RPM gap from 1160 to 1800. There's also a 380 RPM gap between 780 and 1160. I'm coming to the conclusion the single phase will go a long way as it is. Especially since I hear some say they hardly turn stuff over 500-700 RPM any way.

I just need to learn what I'm doing first, that's for sure. I'm just trying to avoid making a bad purchase but also not just thinking I have to upgrade everything either.... hence why I think my best decision was to not pull the trigger on the PM-1228 (as good as it would be for me) and jump to the PM-1236T (Taiwan quality). I would have hoped, going to the PM-1236T I didn't have to think about motor options... or at least think I need to.

If you happen to only be able to get a single phase 1236T,

Well, single phase I can get in October this year, 3 phase next year (Feb/March). So, impatience is in play for sure and if I don't think I need to upgrade, single phase is just easier. I guess that tells me that the 3 phase is more popular as they are sold out (or they just sell fewer of them).

I previously outlined a simple method to do a basic VFD install for many of the PM lathes, including the 1236T, 1340GT, 1440GT. 1440TL series, etc. that many people have used and been very happy with the end result. It is much less $$ then your current path, and at the end of the day will have as good or better performance.

I downloaded that doc, well done... I'll have to go through it thoroughly as it seems pretty easy to follow. Thanks for the detail info!

 

[skcncx]

Listen to what Mark is telling you, switching the motor is not going to be a simple swap. I have the 1236T and got three phase. The three phase version comes with a 2hp motor and not 1.5 like the single phase model.

I hear ya... it sounds like single phase motor, unlikely to upgrade because of challenges. 3 phase with static converter is the easiest to get started and easiest to upgrade by swapping the static converter to VFD + the extra controls and wiring etc.

And to say it out loud... the VFD primarily gets me variable speed ranges (more between the gaps the gearbox provides), slow start and braking? I know other fancy stuff can be done, but is that the primary advantage.

Conversely, Is the 1.5 HP enough power and RPM ranges via gear box likely to suffice most stuff? I have no doubt 3 phase w/VFD is better.... I think it comes down to the extra cost of a static converter and longer wait time... Single or 3 phase are the same price from PM... just have the added cost of static converter.

If you wanted to keep the stock controls, you could use an rotary phase converter, static phase converter,

Yea, I didn't realize that was even an option until someone mentioned it last night... as stated above, that makes me think about it as I don't HAVE to go the ALL IN VFD route right way.

 

[skcncx]

I realize now, the question I should have asked... how many PM-1236T with the single phase owners out there are perfectly happy and feel there's no need to upgrade to 3 phase with VFD?

In my head... the 3 phase using static converter is just a pre-cursor to adding the VFD option down the road. Other than going from 1.5 to 2 HP motor from single to 3 phase, the 3 phase with static converter is equivalent to single phase.

 

[Ischgl99]

The static converter will not generate full motor hp since it is not generating three phases, rather artificially creating the phase angle difference to get the motor started. I think I heard motors run on a static phase converter are not covered under warranty, so you might want to check on that. I had a static converter on my mill when I first got it from the previous owner, but it always sounded like the magic smoke would come out of the motor when I was using it, and it was easy to stall the motor, so quickly switched to a VFD and never looked back. It runs a lot smoother now. My mill has a custom motor, so I need to be careful with it since changing that is not going to be fun, or cheap. I only have experience with that one static phase converter installation, so don’t know if that is typical.

I still haven’t added a speed pot to change speeds on my VFD. I used the coolant switch to give me 60hz and 30hz, so I get all the standard speeds at the flip of a switch without having to change the motor belt position. That is fine for most of what I do, but I will add a speed pot to dial in the speeds at some point, but it hasn’t been a priority. The likely reason the larger motor is installed on the three phase version is the motor hp is proportional to the motor speed when run on a VFD. At half speed on the VFD, that is about half hp of the motor. I haven’t had any issues turning at a 30hz motor speed, so the 1.5hp single phase should be fine for anything this size lathe can handle.

If both were the same delivery, three phase without a doubt. But, having to wait that much longer for the three phase might push me into the single phase machine and just plan on upgrading at some point in the future. You can also look at Eisen and see if they have this machine in stock, or coming sooner. They are the same machine made in the same factory. There could be some minor differences, but I couldn’t find any between the two. Shipping times are estimates, and with how screwed up the logistics supply chain is, I would take any stated arrival times as best case, and likely longer.

 

[skcncx]

I used the coolant switch to give me 60hz and 30hz, so I get all the standard speeds at the flip of a switch without having to change the motor belt position.

Brilliant and creative!

I'll likely just leave it in high range.. that's 205 to 1800 RPM in the "A" pulley setup.

One thing that did cross my mind was I could change the pulley sizes... if for some odd reason I need a slightly different motor pully to spindle/gear box pully setup.... but that's pretty limited in how much you will affect it.

You can also look at Eisen and see if they have this machine in stock, or coming sooner. They are the same machine made in the same factory.

I have checked them out, a slightly better pricing but it has to be shipped since they are a Canadian company... I can pick up locally from PM and just my impression from the 2 emails with Eisen and many with PM... PM has better support.. not worth saving just a couple hundred.

 

[skcncx]

The only advantage I can see is the slight power savings

Ya know... the power savings is starting to look like a pretty big deal... I just got my new electric rate for our local aggregation program... it's going from .0495 to .0979... my per kWh just nearly doubled .