VFD'ing my lathe (Takisawa TSL 1000)

Your machine, your choice.

RPC can live in a shed outside the shop though.
 
I “silenced” my VFDs by increasing the carrier frequency. I believe that was 15khz on my Fuji. As far as I could determine the motor couldn’t tell the difference. YMMV.
 
I run both VFDs and an RPC in my shop. Personally I find the RPC quieter, less annoying. I built The RPC from about $250 parts including a used 7.5 hp. idler motor.

If you do decide to go the RPC route here's a link to my build thread:
 
I use a static phase converter on my Takisawa TSL-800D. I use the same converter for the Bridgeport and the Kalamazoo horizontal saw. I don’t see that a VFD would add substantial features to any of these machines...they all have worked fine for decades, and have adequate speed control capabilities.

I did add a VFD on my Powermatic wood lathe, because the original Reeves drive is a bit clunky.

I would rather spend my time machining than rewiring...and I’m an Electrical Engineer.
 
Last edited:
Static converters loose 1/3rd to 1/2 the motor Hp depending on the design, in particular with a 2 speed motor. I have also seen a number of reports of surface finish issues with static converters vs. RPC/VFD. On a mill, less of an issue, lathe and surface grinder I would just go with an RPC/VFD. Cost wise, a VFD is a reasonable alternative to an RPC for smaller motors, beyond 3 Hp the costs of a VFD increase significantly. VFD's have many features like speed control, soft start, electronic braking, slow speed jog, etc., but if you do not need these then an RPC is probably a better choice. I have done a few shop system installs where the shop was run off of an RPC, and we installed several 3 phase input VFD's on specific machines that benefited significantly from there additional features. One doe not negate the other, and there is minimal to no derating of the VFD in this arrangement.

Cost wise up to 3 Hp, VFDs are probably more cost effective and simpler to install on machines like mills and surface grinders, but lathes take a little more effort to do it right. As far as VFD whine, depends on the VFD, motor and software/parameters. My mill and lathe (both 3 Hp) with Yaskawa VFDs, the carrier frequency is 12 kHz, I no whine whatsoever. The Yaskawa also has programs for variable switching frequency settings as opposed to fixed. Higher switching frequencies can lead to more motor heating and insulation breakdown, but this is not an issue with newer motors. Old motors should use a lower carrier frequency.

Machines are an investment over time, we spend numerous hours adding accessories and modifying the machine to fit our needs, adding a VFD is no different. The time consuming portion is figuring out the design, materials and getting everything in house. Building the system correctly and understanding the wiring connection the VFD and the programming parameters are a bit of a hurdle, so sharing one's experience helps others to get started. The system build time is trivial in relation to the years of use and benefits if you use the features of a VFD. Investment/cost wise, you can go super cheap these days with a VFD, or invest a bit more and get more features. I have installed numerous VFDs and worked with 100's of people doing VFD installs, I can't recall anybody that would have done otherwise and almost everyone wishes they had done it sooner. Also know many RPC owners that are just as happy, recently I have seen a number of small shops using the AMP RPC's which are plug and play, they were super quiet. Plug the cube into the wall, plug the machines into the cube and you are up and running. There are also other less expensive RPCs that work great.

www.wnysupply.com

Below is an old thread on a G4003G VFD conversion, it is a very simple 3 relay design, and did not take very long to install. If this is something you are interested in, I will update the schematic to include provision for the foot brake, differential braking etc. to the VFD of your using and provide you with a basic parts list. I have previously outlined the suggested VFD enclosure components, etc. in other posts. It is a more expensive proposition at 5 Hp and above, but I think you will be very pleased at the end of the day. Otherwise, buy a static converter as a band-aide to get you started, or add a motor to get you to an RPC and then go from there.
 
Last edited:
Mksj, I appreciate your comment about loss of power. I have to say that I have never seen an instance when I thought the lathe was lacking power. However, this lathe is so much more powerful and stable than I have used before, perhaps I am being too conservative. Anyone have any guidelines for what a 3HP 14” lathe ought to be able to do? If so, I’ll give it a try.
 
Winegrower, with a 14" lathe and a 3 Hp motor, with a static inverter you might be realizing maybe 2 Hp from the motor. In essence you are running off of 2 out of 3 coils, and you would also expect some imbalance. Heavier machines, may not show as much surface issues due to the momentum of the system/mass of the machine. You also loose torque. Cutting power wise, unless you are pushing really hard, 2 Hp is more than enough and you are not loosing Hp when gearing down. One could do comparisons to see how much of an effect this would have vs. an RPC, can't recall seeing this. But certainly single phase to 3 phase with a VFD, I have seen pretty dramatic differences in surface finish/motor performance. I also recently participated in a few discussions in surface grinder conversions and there was a number comments of poorer surface finish/performance running 3 phase surface grinder with a static converter. They work, some maybe better than others, but an RPC is not much more and more flexible for different machines. Use a low speed RPC motor, more of a faint hum as opposed to a roar. There is some power consumption penalty, but the few I have seen worked very well/quiet (like the AMP cube and a few larger systems). There are additional costs if running a shop with multiple machines and adding a 3 phase sub-panel.

On 2 speed motors things become a bit more complicated as to their performance with static converts and to some degree RPC's. See some threads below. I have also seen this in some home machine shops and other people I have worked with. My take on this is static converter for a 2 speed motor is not a good choice, and even an RPC may not always work. I do feel these days that for a single 3 phase machine, 3 Hp and below, VFD's are a very competitive option if you can keep the control system simple. There is a learning curve, and I was a bit overwhelmed working with my first VFD. After that it gets easier.
 
Mksj I always appreciate your thoughtful analysis. A net 2 hp with the simple phase converter works fine so far. For my wood lathe, the VFD was an easy add...there are really no electrical controls to worry about, so running everything from the VFD front panel was straightforward. For the Takisawa, with the foot break, direction switch, coolant pump, etc., it just seemed like too much of my remaining life would be squandered. A local friend who surprisingly also has the same TSL-800 uses a RPC. Man, his whole shop seems to fill with the noise, and he had that professionally installed some way. The low noise option would be a huge plus, if they tend to be that noisy.
 
Update. On mksj advise I returned my Invertek vfd and bought Yaskawa VFD (like to use Yaskawa for Takisawa ;-)
Yestreday, I, with help of friend, connected the VFD to my lathe and get it running. Get it working.
Now, I need to design whole control system. I like Marks design and will take it as base for my system.
 
Last edited:
Back
Top