G0704 CNC conversion

[ibuildstuff4u]

Santa brought me a new mill for Christmas, and last week I started making the parts for a CNC conversion. I just have two more parts to make and I will be ready to tare the mill apart and install everything. So far I'm really happy with how things are going and I think this is going to be a very accurate machine when done. I went with double nut ball screws to eliminate back lash and an installing thrust bearings on every axis.

The power supply came from Antek and is a 56 volt 1000W transformer with secondary taps for both 5vdc and 12vdc. Stepper drives are digital drives from Automotion Tech and are good for up to 80 volts. X and Y axis will have Nema 23 motors with 570 oz of torque and the Z axis will have a Nema 34 motor with 1200oz of torque.

Computer control will be with Mach 3 via a USB breakout board.

I'm hoping to have the mill up and running in a few more weeks!
Dale P.

 

[blighty]

its great when Santa brings you good stuff

USB BOB?? not really seen a lot of these. do you have any more details on it?

norm so far has been printer port BOB then a usb/ ethernet smoothstepper etc...and plug that into the BOB.

 

[ibuildstuff4u]

My CNC lathe runs off a parallel port, but last month I bought a new computer for the shop and had to get an ethernet smooth move board to connect it. To me it seems silly to have two boards to connect a machine to the computer so I decided to try one of these newer USB breakout boards. I'm surprised that manufactures are still making parallel port boards since they are no longer supported. ]

My brother used one of these USB breakout boards on his CNC router build and so far it's running great. He can surf the web and play videos while the router is working and it doesn't skip a beat. I figure if I have any issues I can swap it out for a parallel port board and use the second output on the smooth move board to connect it.

Dale P.

 

[RonGinger]

The parallel port is dead, go with ethernet connected motion control, and with Mach4. I have been using the ethernet smoothstepper, but they are not keeping it updated.

I am currently building a lathe, that will be offered as a build class at TheCNCworkshop.com in June. For that I am using a Pokey57CNC. This is less expensive that the smoothstepper and much better- it offers pendant functions as well as all motion and is very well supported by Mach4. They are stocked in the US by CNC4PC.com

The USBSmartBOB by PMDX.com is also an excellent choice. We used that last year in the mill build class, but it is not yet ready to support threading, which for a lathe is critical. I have a router running a SmartBob and it has been great.

I am also fully converted to Mach4. It is eons ahead of Mach3 in performance and stability.

 

[blighty]

when i first started this cnc lark, it was still under discussion if it was worth having a BOB or not. i went with not and my mill worked fine till i started adding things to it. finally i gave up, fitted a bob, Ethernet SS, redone all of the electrics and stuck it in an enclosure. had the mill running at 10m/min ( 250in/min) the other day with no signs of any problems.

as bob's and smothsteppers (and other buffers) do different things, i take it usb bobs are an all in one unit?

 

[benster]

I recently bought a G0704 and was going to look at CNCing it in the next year or so. The only control system I'm familiar with is using a breakout board to parallel, would you mind explaining what an ethernet smoothstepper is? Also wondering what kind of ballscrews you went with and what your backlash is at?

 

[blighty]

I recently bought a G0704 and was going to look at CNCing it in the next year or so. The only control system I'm familiar with is using a breakout board to parallel, would you mind explaining what an ethernet smoothstepper is? Also wondering what kind of ballscrews you went with and what your backlash is at?

there are two types of smoothstepper (SS), one that uses a usb and the other is with an ethernet cable. basically a SS and other types buff the pulses coming in from you controller (mach3 etc) they save these pulses up for a bit, then send them to the breakout board (bob) then onto the stepper/servo drives. this means the stepper/ servo drives get an uninterrupted stream of pulses.

end result.....smoother operation, more reliable, no lose of steps (hopefully) and a better machine all round.

 

[RonGinger]

there are two types of smoothstepper (SS), one that uses a usb and the other is with an ethernet cable. basically a SS and other types buff the pulses coming in from you controller (mach3 etc) they save these pulses up for a bit, then send them to the breakout board (bob) then onto the stepper/servo drives. this means the stepper/ servo drives get an uninterrupted stream of pulses.

end result.....smoother operation, more reliable, no lose of steps (hopefully) and a better machine all round.

Not quite right. Smoothsteppers, PoKeys and USBSMartBOB are really motion controllers. They actually generate the timing pulse, as directed by Mach3 or 4. Mach does the trajectory planning, the heavy math part, and the motion controller does the real time pulse generation. Either ethernet or USB can be used, with a slight edge to ethernet as being more robust or industrial strength.

You are correct that the result is much smother motion, usually fast motion and all around better control.

A Breakout Board, or BOB is generally just an amplifier, or buffer. Originally they were designed to protect the PC and its on board parallel port from any possible electrical problem in the CNC machine. Now devices like the USBSmartBOB and Pokeys handle the buffering internally and BOBs are not usually needed.

I think the G0704 is an excellent choice for a conversion. I have one as a manual mill, alongside my Jet knee mill that is CNC converted.

 

[DICKEYBIRD]

....redone all of the electrics and stuck it in an enclosure.

Fantastic job on the enclosure! A very good example of how to tidy things up. I'll bet you shop looks the same. Kudos!

Question, where do you guys get your smoothing caps? Like most all of us, I'm sure you have your favorite place to get good parts as cheaply as possible. I have a big 36 volt toroid & a rectifier; just need a cap. I found a website with the formula to approximate the cap value but the it's written down at home.

 

[blighty]

They actually generate the timing pulse, as directed by Mach3 or 4. Mach does the trajectory planning

buff the pulses coming in from you controller (mach3 etc)

same thing really

 

[blighty]

Fantastic job on the enclosure! A very good example of how to tidy things up. I'll bet you shop looks the same. Kudos!

Question, where do you guys get your smoothing caps? Like most all of us, I'm sure you have your favorite place to get good parts as cheaply as possible. I have a big 36 volt toroid & a rectifier; just need a cap. I found a website with the formula to approximate the cap value but the it's written down at home.

my shop looks like a bombs hit it. i had a clean up the other week and found some cups i don't remember owning. there was some interesting stuff in the bottom of some of them, think one of the cups had reached the stone age.

cant help with the cap.sorry

 

[ibuildstuff4u]

Your absolutely right about Parallel ports being dead. I don't know why breakout board manufactures still make them for parallel ports as they should all be ethernet or USB based.

I have a Sound logic combo breakout board in my lathe and went with the smooth move controller because it was the easiest way to hook the lathe up to my new computer with out having to re wire anything. I just plug the smooth move controller into my ethernet port and then the lathe into the card.

As for the mill, I looked at a lot of breakout board options and love the PDMX stuff, but I'm not ready to up grade to Mach 4 so their motion controllers were out. I ended up picking up this USB all in one board off E bay for $75.00 and figured I would give it a try. My brother is using one right now on a router and it's working great. It offers a ton of inputs and outputs and everything is optically isolated. Some day when I move up to Mach 4 I will up grade the breakout board to a PDMX controller.

The ball screws are C7 from a retailer on E bay. They cost me just under $200 with custom machining on the ends and double ball nuts. With the double ball nuts i expect less than .0005 back lash. I'm using the Hoss plans for the conversion, but I think you can find better ones for free on the internet. I don't like they way he designed some of the parts and will end up re making them after the retrofit is done. As for the mill I love it and have found it really accurate. I just wish they would have put a better spindle motor on it. The motor is pretty weak and will get replaced some time soon.

Dale P.

 

[RonGinger]

As for the mill I love it and have found it really accurate. I just wish they would have put a better spindle motor on it. The motor is pretty weak and will get replaced some time soon.

I agree with this. My spindle is some how magnetized- it hold chips to the tool. I frequently demagnetize it with an old audio tape demagnetizer but in just a few minutes its back. I think the motor is somehow responsible. I see the end cap of the motor appears to be aluminum, so I wonder if the motors field is leaking out.

I have looked around the net for new motors, but so far all I have found seem to heavy. Id like about 1/2hp three phase and a VFD. The brushless DC motor used on the LittleMachineShop.com high torque mini mill looks nice, but its to expensive when bought as spare parts. I am going to look closer at the various servomotors offered for CNC, I could make a simple arduino pulse generator to drive it.

 

[ibuildstuff4u]

My original plan was to convert this one to CNC and then get the G0759 to use as a manual mill for squaring off stock and doing secondary operations, but there are two things that I don't like with this machine. The largest problem is that the spindle motor is too weak, and the second problem is cranking the head up and down is a work out when working on projects with a lot of tool changes. I thought about adding a motor to the Z axis as well as a power feed to the X axis, but when you add in the cost for a different spindle motor too it gets quite expensive. Im now thinking that the G0755 would be a better choice for a second mill. I don't really need a full DRO, and would just have to add a small readout to the quill.

My shop is in the basement so the only real draw back to getting the G0755 is that the machine would have to be taken apart to get it down the steps.

Dale P.

 

[ibuildstuff4u]

Blighty,

I love your control box! Looks great and everything is easy to work on. I wan't going to get wire ducts for my build, but after seeing your system I'm going to order some tonight.

Thanks for sharing the picture!
Dale P.

 

[Wizard69]

I agree with this. My spindle is some how magnetized- it hold chips to the tool. I frequently demagnetize it with an old audio tape demagnetizer but in just a few minutes its back. I think the motor is somehow responsible. I see the end cap of the motor appears to be aluminum, so I wonder if the motors field is leaking out.

I have looked around the net for new motors, but so far all I have found seem to heavy. Id like about 1/2hp three phase and a VFD. The brushless DC motor used on the LittleMachineShop.com high torque mini mill looks nice, but its to expensive when bought as spare parts. I am going to look closer at the various servomotors offered for CNC, I could make a simple arduino pulse generator to drive it.

I'd suggest a bit more than 1/2hp AC induction simply to maintain power at lower speeds. They do get big pretty fast so maybe buying a Bushless DC is a better upgrade.

 

[kvom]

250 ipm on a small mill like that sounds scary. Good work on the electronics enclosure - very neat.

 

[ibuildstuff4u]

I would love to go with a brushless motor but they cost too much so I'm probably going to pick up a 1 to 1.5hp three phase motor and VFD. I found this one for sale locally on Craig's list, what do you think?

http://madison.craigslist.org/tls/5384143178.html


Here is the spec sheet on the VFD. I'm still trying to find specs for the motor but I think its only 1715 rpm from what I can read on the motor plate.

http://attachments.temcoindustrialpower.com/Data_sheet/Minarik-VFD05-D230-PCM.pdf

Let me know any thoughts as I would be purchasing it in the next day or two! Thanks!
Dale P.

 

[ibuildstuff4u]

Just talked to the guy on the phone about the motor and drive for sale and he said he works for Tormach and this combo was used on their machines for several years before they moved up to digital drives. So I'm glad to hear it's been proven for use on milling machines with hours of continuous use.

Guess the only thing I worry about is the motors RPM. I see some people are going with 3000 RPM motors but this one is only 1715 RPM. With the VFD I should be able to get a lot more RPM since it can be turned up to a higher frequency??? I wonder what pulley ratio are guys between the motor and spindle?

Dam, too many questions to find answers to. I just want to build the machine, not engineer it.

Dale P.

 

[blighty]

Just talked to the guy on the phone about the motor and drive for sale and he said he works for Tormach and this combo was used on their machines for several years before they moved up to digital drives. So I'm glad to hear it's been proven for use on milling machines with hours of continuous use.

Guess the only thing I worry about is the motors RPM. I see some people are going with 3000 RPM motors but this one is only 1715 RPM. With the VFD I should be able to get a lot more RPM since it can be turned up to a higher frequency??? I wonder what pulley ratio are guys between the motor and spindle?

Dam, too many questions to find answers to. I just want to build the machine, not engineer it.

Dale P.

i think getting the right motor is the hard bit, there are so many options out there and they all sort of work, but that depends on what the application is. you wouldnt put a 1hp 40'000rpm water cooled spindle on your mill but it would be fine on a small router.

then you have AC or DC, servo drive motor and now it seems treadmill motors are all the rage. then you might have to think about gearing. ac motors loos power at low rpm so you need to gear them down. dc is fine with this,but,but,but the list goes on.

when i did the belt mod on my mill i went with a 3hp AC 1400rpm @50Hz running from VFD. i can run from 35Hz up to 80Hz. @1 to1drive this gives me a speed range of 980rpm/2240rpm. 1 to 2.2 gives 2150/4920 but now i have 1.2hp. i could of gone for a 2800rpm motor @50Hz but would cure the high rpm torque problem but now your screwed for low rpm for steel etc. unless you have a 5to1 gear for e.g.

the perfect motor in my book for my mill is this one. all i know from the vid is the motor is 3hp does 11'000rpm, geared down to 6'500rpm and can be controlled by step and direct, but i cant find out any other information about it.

[ame]https://www.youtube.com/watch?v=ISzkthutKnA[/ame]