# VFD for 2x72 Belt Grinder



## jbolt (May 31, 2018)

I'm slowly collecting material and parts to build a 2 x 72 belt grinder. I have a 3 hp 3 phase inverter duty motor to use and I'm looking at VFD's. I see a lot of diy and commercial units use the KB VFD's since they are simple to setup and in sealed enclosures. Their 3 hp unit, KBAC-29, is only rated at 3 hp with 3 phase input. I will be running single phase input which they only rate the VFD at 2 hp. I have a Hitachi WJ-200 on the 3 hp motor on my lathe and it works great. The Hitachi is less expensive than the KB but it would need an enclosure and I assume venting which is not desirable for the environment of a grinder. I also don't want a huge enclosure either. Any thoughts on a suitable VFD and/or enclosure or just taking a chance on the KB unit?


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## ttabbal (May 31, 2018)

I would use one rated for the 3HP. I don't know how well they limit themselves. The sealed units are great, but it's not like the others don't work. I use a cheap one, as I can go through 4 of them for the price of the KB. I just remote mount it in a cabinet for now. I would like to put it in something with a filtered vent, but I'm distracted with other things. 

90% of the grinding dust goes straight down to the floor. Easy to clean up with a shop vac or even a broom.


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## Alan H. (Jun 1, 2018)

I have a 2 hp KMG set up with a KB unit.  Some of the advantages from my viewpoint of the KB unit:

Has an enclosure built for dust with heat transfer surfaces built in
Easy to mount on the machine and puts controls in a usable spot
Switching - on/off; run; reverse/forward - all there
Speed knob
Eazy Peezy to configure vs. other VFDs
Made for this service and ready to go
So from my perspective, for a grinder the KB is the way to go.  BTW, I have several other VFDs - Hitachi on a PM lathe included.

Here's a photo of mine when it was being put together.   Not the best for detail but you see the layout.


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## Bob Korves (Jun 1, 2018)

Can a 2" sanding/grinding belt actually pull down a 2 HP motor to near it's capacity?  I see a lot of people putting lots of HP on their belt sander/grinders, but cannot get my head around why.  Please enlighten me...


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## ttabbal (Jun 1, 2018)

I can't bog down my 2HP. I wasn't planning on this big, but got a great deal. The guys that use these a lot say 2HP is the sweet spot and 1HP and smaller do tend to bog down. There is also some torque loss when using speed controls, the bigger motors make up for that to some degree.


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## jbolt (Jun 1, 2018)

Alan H said:


> I have a 2 hp KMG set up with a KB unit.  Some of the advantages from my viewpoint of the KB unit:
> 
> Has an enclosure built for dust with heat transfer surfaces built in
> Easy to mount on the machine and puts controls in a usable spot
> ...




Thanks Alan, I like the setup of the KB vfd but concerned it would not work with a 3 hp motor.


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## jbolt (Jun 1, 2018)

ttabbal said:


> I would use one rated for the 3HP. I don't know how well they limit themselves. The sealed units are great, but it's not like the others don't work. I use a cheap one, as I can go through 4 of them for the price of the KB. I just remote mount it in a cabinet for now. I would like to put it in something with a filtered vent, but I'm distracted with other things.
> 
> 90% of the grinding dust goes straight down to the floor. Easy to clean up with a shop vac or even a broom.



 What brand of VFD are you using? Due to space limitations I cannot remote mount anything so the VFD and controls need to sit in front of the motor.


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## jbolt (Jun 1, 2018)

Bob Korves said:


> Can a 2" sanding/grinding belt actually pull down a 2 HP motor to near it's capacity?  I see a lot of people putting lots of HP on their belt sander/grinders, but cannot get my head around why.  Please enlighten me...



I'm still learning the ins and outs of the modern belt grinder but from what I have gathered the modern ceramic belts work best under pressure. With the large surface area of a platen it acts as a brake so more hp helps keep the belt speed consistent for optimal material removal and increases belt life. There seems to be a split on 2-pole vs 4-pole motors, 1725 vs 3450.


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## mksj (Jun 1, 2018)

I would look for a NEMA-4X/IP-65 Enclosed/sealed VFD, KB is the most common one I see on these types of grinders. Works well for basic installs where you will directly be using the control pad. Teco also makes a series called the E510. Theare are other manufactures that also have sealed and fanless units,, like Yasakawa. All 3Hp single phase input.
http://www.electricmotorwholesale.com/10001-KBAC-29D/
http://www.electricmotorwholesale.com/KBDA-29D-10003.html
https://www.wolfautomation.com/products/ac-drives/ac-drive-indoor-medium-duty-230v-3-hp


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## jbolt (Jun 1, 2018)

mksj said:


> I would look for a NEMA-4X/IP-65 Enclosed/sealed VFD, KB is the most common one I see on these types of grinders. Works well for basic installs where you will directly be using the control pad. Teco also makes a series called the E510. Theare are other manufactures that also have sealed and fanless units,, like Yasakawa. All 3Hp single phase input.
> http://www.electricmotorwholesale.com/10001-KBAC-29D/
> http://www.electricmotorwholesale.com/KBDA-29D-10003.html
> https://www.wolfautomation.com/products/ac-drives/ac-drive-indoor-medium-duty-230v-3-hp



Ah! Thanks Mark,  I missed the single phase input only version of the KB units (10001). I was looking at the single or three phase input unit. Looks like the digital KB unit comes out to the same price with the added switches.


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## ttabbal (Jun 1, 2018)

jbolt said:


> What brand of VFD are you using? Due to space limitations I cannot remote mount anything so the VFD and controls need to sit in front of the motor.



Mine are the ebay el cheapo units. About $70. If you need the VFD right by the motor, I don't recommend them on a grinder unless you put them in an enclosure. I put mine in a cabinet and use a little control box next to the motor. They will get grinding dust in them and blow. I have about 10ft of cord which gets the job done for me.


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## TonyRV2 (Jun 10, 2018)

As a knife maker, I also own a 272 grinder...an Esteem with a KB VFD.  Very easy to use and sealed like others have said.  But what I wanted to talk about is dust and let you know what I did, not because of the VFD but I just hate a dusty messy work environment. First, I just mounted a heat vent, just like you have in your floors with forced air heating/cooling, on my bench right underneath the belt with some round heat duct bring it down to a bucket in which I leave a few inches of water to catch the hotter bits.  A lot of folks do this if you check out some youtube videos on setting these things up.  Secondly, I have one of those 3 magnet parts trays which I set on top of the bench right next to the grinding belt.  This tray catches 90% of the dust that swirls past the ductwork.  Between the two, I get very little dust in my shop from the grinder.


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