VFD for Bridgeport Knee Mill

[bigguns69]

Enclosed are pictures of my knee mill with a CFW Variable Frequency Drive that I installed. I have also included a wiring diagram of the setup shown. The Mill was purchased from a College Engineering department several years ago. It has a 3 H.P. 3 phase electric motor as a driver. It has digital readout and power feed on the X-axis. It is a variable speed unit on the spindle.

I choose to go with a VFD versus a phase converter because the VFD does allow for speed control of the motor. The VFD can also be programed to control startup and slowdown speeds, but in my case that doesn't matter to me. I can control the rotation direction of the motor via a grounding toggle switch input to the VFD. My VFD, I had upgraded with a rheostat knob, to dial up or down rotation speed. The combination of the adjustable speed of the VFD and mill spindle gives me some very fiine tuning of the spindle speed whether in low or high spindle speed, and I get full power out to to the spindle. The one thing that is interesting is that the spindle speed change of the mill, series II, does cause for a direction change so the direction change from the VFD was necessary to get it to function the way I wanted it.

The VFD was about double the price for a static phase converter. I put a 20amp 220v breaker box on the back of the mill as I will be plugging into my 50amp welders outlets. The Phase converter cost about $310 and another $240 for other items and I am set on go. I went with the CFW brand VFD just because they had good information on the internet. There are others that are a little cheaper and I did go with a bigger unit then I really needed.

I would recommend a VFD install on any 3 Phase piece equipment, (auction bargains) that may come from a factory environment. It was pretty easy to do and you get variable speed output. No more belt and pulley changes.

Enjoy.....

 

[toolchaser]

Don't you already have speed changes without belt/ pulley changes? It's a variable speed mill.

 

[gorilla]

One thing to consider before deciding to run a motor with a VFD is that when you reduce the frequency from the nameplate frequency then the motor is derated to a lower horsepower rating. If the load stays the same the motor will overheat. This may not matter for some things but it should be part of the thought process when selecting a 3 phase power supply.

 

[saabman]

+1 on the VFD. You can find them on Ebay all the time for little money. I run a 3 phase Mill and drill press with VFDs. Above 3 HP capacity they can get a bit pricey though

 

[hammertime1]

It's a buyer beware with eBay and some places for VFD's, static and rotary phase converters. If it ruins your motor it isn't a bargain.
When I was looking for how to power my mill n grinder on a budget. I passed on buying the seller's Anderson's statics. He said new price was about $50.00 when he bought them. He forgot to mention that was ten years ago. So I had sticker shock and was all set to buy cheapest no name brand I could.
I ended up with Wyn static phase converters with intention of making em rotary if I can ever find some discarded motors in range I need. He got a love on one of the machining forums and early on worked with people on the forum to improve or upgrade his designs.
I read numerous stories about hooks ups being done right, start up and motors smoking right of bat or getting super hot to touch almost instantly. It came down to wrong wiring, defective parts or incorrect parts used by manufacture. If those people had not been alert it would have been a very expensive disaster. Is the manufacture going to replace your damaged parts or take blame when it is due them ? It's a big If. Even with my statics I got an email mine were being delayed in shipment because his old vendor for a part was suddenly having quality control issues. He stopped all orders until the new parts from a new vendor came in and he could swap em out. Food for thought. I went in thinking oh converters no problem to damn its simple but buyer beware since their can be negative consequences.
I love the VFD'S set up you did. I read and viewed a pictorial a guy who did the VFD on his M head plus before and afters. It's enough to make a handle cranker drool.
Saweet looking machine you have there!!!!

 

[Slick111]

I have a 5 hp from American Rotary running my 2 hp Bridgeport veri speed series 1 mill have over 300 hours on it totaly happy with it cost around 450 bucks 3 years ago.