Need Some Advice on Making a New Solenoid for Bridgeport

[Doozer]

... Heck, thinking about it, maybe getting rid of the back gear is ok too, unless you are tapping. ...

Throw a 1" drill bit in there and then talk to me about your plan.
Why would you intentionally make your machines less capable ?

-D

[Sparky_NY]

Sounds like a nice machine Sparky. I have seen a few machines that eliminated the varidrive- it seems like a good idea. Good thing nowadays is that you don't need to use slow RPM's. With modern coated carbide cutters you can happily cut with a surface speed of 450 SFM. I might do that once all my stock of HSS cutters is used up.... Heck, thinking about it, maybe getting rid of the back gear is ok too, unless you are tapping. You have a spindle encoder, is there a reason why you can't or don't do rigid tapping?

No real reason for not rigid tapping. The few holes I need to tap I just prefer to do it by hand.

[Sparky_NY]

Throw a 1" drill bit in there and then talk to me about your plan.
Why would you intentionally make your machines less capable ?

-D

For me, gaining the much higher rpm capability (6500) made the machine much MORE capable for the uses it routinely sees. I retained the backgear on mine so drilling larger holes isn't a issue. Being a cnc, large holes unless very deep are done much more accurately, quicker, and with a better finish by circular interpolation.

On a manual machine I would agree that it might make the machine less capable in some respects, especially if the backgear is eliminated. (bad idea in my book)

Even big VMC's don't have variable speed belt drives anymore, just the VFD and a two speed transmission. I can attest that the method is MUCH smoother and quieter which no doubt will show in the surface finish as well.

It is worth noting that the low rpm torque roll off, using a vfd for speed control, may not be as big a issue as one would think. Sensorless vector type VFD's have a much wider (read lower) rpm capability than non-sensorless types. With a spindle encoder and closed loop spindle control the torque roll off becomes even less apparent. A electric motor can take a quite large momentary overload, low rpm high torque conditions can be handled unless they are prolonged in duration, even the example 1" drill bit might well be done with a peck cycle in a cnc making the torque peaks very short duration.

BTW A series one Bridgeport's specs say a max drilling capability of 3/4"

[Doozer]

...BTW A series one Bridgeport's specs say a max drilling capability of 3/4"

Yes I believe that.
But any sensible machinist would drill a 1/4" pilot hole first,
to accommodate the web thickness of the drill bit,
then drill with a 1" size. Makes for easy like eating cake
drilling of a 1" hole with a twist drill.

-Doozer

[polaraligned]

Sparky, I am with you. I can mill out any hole I will ever need. I have a 40k RPM 30 taper inline spindle for really tiny endmills. In reality, speeding up the spindle saves cutting time because you can use higher feed rates. I have been pretty happy thus far going down to 1/8" endmills with the varidrive cranked up to 4200 RPM, but like you said, it is a bit noisy. In steel, I still have use for dropping the speed down to the high teens. I almost never go into the low range.

In regards to your spindle drive, the encoder goes back to the VFD and LinuxCNC gets a motor power reading from the VFD? Or is LinuxCNC playing more of a role in your spindle control? What VFD are you using? My Hitachi 200 is about 8 years old now and does not accept feedback.

[Sparky_NY]

Sparky, I am with you. I can mill out any hole I will ever need. I have a 40k RPM 30 taper inline spindle for really tiny endmills. In reality, speeding up the spindle saves cutting time because you can use higher feed rates. I have been pretty happy thus far going down to 1/8" endmills with the varidrive cranked up to 4200 RPM, but like you said, it is a bit noisy. In steel, I still have use for dropping the speed down to the high teens. I almost never go into the low range.

In regards to your spindle drive, the encoder goes back to the VFD and LinuxCNC gets a motor power reading from the VFD? Or is LinuxCNC playing more of a role in your spindle control? What VFD are you using? My Hitachi 200 is about 8 years old now and does not accept feedback.

The encoder feeds into the linuxcnc interface board. Pretty much any VFD would work. The closed loop is done in linuxcnc with a PID loop comparing the commanded speed to the actual and the output is via the common 0-10V line to the VFD. Load variation response is extremely fast and commanded vs actual rpm is always less than 10rpm apart (usually around 2 rpm)

Linuxcnc is extremely powerful, I am still amazed at what is capable with it. The learning curve is quite a bit steeper than the average retrofit control but its well worth the effort. You can do some pretty wild things, for example some have it send a text message to their phone when the job is completed or if a fault happens. Its also one of the cheapest retrofits out there.

[jdunmyer]

Back to the original problem: is it possible that those solenoids are supposed to be run on AC? They'll pull way more current on DC than they're meant to, and will probably have a short life.

OTOH: knowing this, you can often run an AC solenoid or relay on a lower voltage DC source if you need to. For instance, I've run 120 VAC solenoids on 36 VDC

[polaraligned]

The encoder feeds into the linuxcnc interface board. Pretty much any VFD would work. The closed loop is done in linuxcnc with a PID loop comparing the commanded speed to the actual and the output is via the common 0-10V line to the VFD. Load variation response is extremely fast and commanded vs actual rpm is always less than 10rpm apart (usually around 2 rpm)

Linuxcnc is extremely powerful, I am still amazed at what is capable with it. The learning curve is quite a bit steeper than the average retrofit control but its well worth the effort. You can do some pretty wild things, for example some have it send a text message to their phone when the job is completed or if a fault happens. Its also one of the cheapest retrofits out there.

Thanks Sparky. I wasn't sure if your VFD was using the encoder to maintain programmed speed and then relaying the info to your controller. Yes, I know that Linuxcnc is very powerful. It is one of the oldest, if not the oldest controllers out there. It's roots go back to NIST. I saw a EMC2 retrofitted machine at Cabin Fever probably 12 years ago. It seemed unnecessarily complicated. There were tachs on the servos and other stuff that really was not necessary given the processing power that was available, though I guess it was just this builder who decided to use tachs on the axis.

I love the Centroid. Even though it does not do silly things like send text messages, it is a top line controller. It has extra encoder inputs that can be used for the spindle, extra axis, or glass scales on any axis. I use one input for a glass scale on my knee which I use as my W axis, which is servo driven. The glass scale gives me high accuracy. The idea is to use the knee for tool length offsets....and the knee is one reason why it is not worth getting rid of my air brake and speed control as I need air for the knee as it is air assisted. And yes, a spindle encoder with the Centroid will give a bar graph of the power being used by the spindle as it already does for each axis motor.

As for your question jdunmyer. The solenoids are clearly marked for DC.

[polaraligned]

I ordered, received and installed the solenoid that Doozer pointed out on Ebay. Totally different model number, but it fits and works perfect.
Thanks Doozer!!!