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View Full Version : VFD on a Bridgeport Basics?



glenj
02-25-2004, 03:59 PM
I've been reading a bit about using a VFD drive on pulley head Bridgeport but don't have a good grasp on the basics yet. Could someone provide a link or a basic explanation of what is required to use one with a mill? The BP clone (First) I have coming this weekend is a pulley head model and I'd like to have speed control without messing around with the pulleys and belt all the time. It already has a 1-1/2hp motor mounted on it that runs on 220v single phase. Should I ask for the original 3 phase motor in the package? Is it required for using the VFD?

Thanks for any information..

Glen

Bruce Griffing
02-25-2004, 04:01 PM
A three phase motor is required for use with a VFD. I would run the machine as is for a while before making the jump to VFD. You may find that your initial dollars are better spent on tooling than a VFD.

Forrest Addy
02-25-2004, 06:21 PM
A VFD requires a three phase motor. If the three phase motor comes for free, get it. You can always find a buyer for the single phase motor when you change it out. Now or later.

Your best choices depend on circumstances.

If dollars are short and you have no milling accessories, Bruce's suggestion to spend the money on tooling is excellent. The price of a budget VFD from a discount source will still buy the one of the import BP tooling kits you see advertized in Enco and other catalog supply houses.

If you have some money to spare and you have single phase power you might be well advised to get a VFD to run your 3 phase motor at infinitely variable speeds from the get-go.

Adding: here's a link to a tutortial:

http://www.practicalmachinist.com/ubb/Forum3/HTML/000002.html

[This message has been edited by Forrest Addy (edited 02-25-2004).]

glenj
02-25-2004, 09:11 PM
Thanks for the information and the link.

I already have a bit of tooling I can use that I've collected over the last 5 years for my Standard Modern lathe. In addition I have about 15 endmills in a range of sizes from 1/8 to 1-1/2" (3/4" shank) mostly 2 flute, a mill vice, drill chuck, an R8 collet set, large drill index with drills up to 1" and a fly cutting set.

I still need a parallel set, edge and center finder set and a boring head to get started. Later I plan on a set of reamers, an ER collet set, 10" H/V turntable etc etc. The mill has encoder style DRO on X and Y so I can wait a while to upgrade to a glass slide 3-Axis unit (unless a good used one come along).

I've spent the last 8-10 months building a 510sqft shop building in the back yard. It's a slab on grade foundation with well insulated walls and roof and has radiant floor heating tube set in the concrete ready to hook up. I put in 60amp 220V single phase service and two sets of double 4' wide doors. Can't wait to get the lathe and mill in and running, the boom truck is booked for Friday.

Glen

JimH
02-26-2004, 04:03 PM
I put a VFD on my mill and set the VFD to read 1725 at the normal motor operating speed. I then put together an excel spreadsheet that shows what the spindle RPM is based on the VFD display and the belt position (5 on my mill). Note that you loose alot of torque when you get down to 40 or less percent of normal speed. I mostly run in belt position 2 because it gives the widest range of commonly used speeds, but occassionaly need the higher speed of Position 1 or the low speed (and torque) of Position 5.

I too agree that as nice as the VFD is, you can't use it much if yuo don't have tooling.

Jim