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Goliath CNC knee mill

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Re: Goliath CNC knee mill

Postby aland » Sat Jan 27, 2018 7:50 pm

Homemade wrote:Would a 5 hp phase converter be cheaper then a single phase spindle motor and solve the 3phase coolant pump issue.


Do not swap the motor for a single phase, use an RPC, VFD or similar. Is your motor 5HP ? Some machines take quite a bit more on startup, but I don't think a mill is typically one of them, a lathe yes, but typically not a mill.

Normally you would want a 7-1/2HP RPC to power a 5HP machine, that is the general rule of thumb. But on a mill you might be able to start 5HP with a 5HP RPC, that I don't know.

Also, wire for the circuit, not the machine. IOW, wire for the max possible draw on the circuit rather than the max amps of the machine which can often be less. Using a 30 amp plug with 20 amp wire is not a good idea, as an example.

You can save some money by buying a complete RPC box, and hook your own idler motor up to it.

I use an Anderson 7-1/2HP RPC in my shop and have several 5HP machines as well as smaller machines I run off it. All are wired for the circuit.

HTH,
Alan
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Re: Goliath CNC knee mill

Postby noddybrian » Sun Jan 28, 2018 3:51 pm

Generally over here at least a VFD is sized so it will start the size motor it's rated for so no need to go over although I guess it can't hurt to have some leaway other than cost - the biggest issue is where people try running the motors direct online with the machines original switch gear which most VFD's are not intended to do - so long as you only use the machine switches to start the VFD & use it's ramp up time to allow machine motor to overcome any flywheel effect the nature of the machine won't matter - hence a lathe is not a problem even with a big heavy chuck / workpiece if you allow sufficient acceleration time in the setup menu.
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Re: Goliath CNC knee mill

Postby MFleet » Fri Feb 02, 2018 7:42 am

I'm not a fan of RPC. It's a stepping stone that I want to skip due to cost(detracting from a better solution), noise, and inefficiencies. It just doesn't fit my particular long-term goals. If I have no choice due to a variety of circumstances, that may still happen.

The coolant will be sorted with an auxiliary pump/tank that I already have. I like using the Noga mister too. The existing pump/tank is inside the casting and isn't worth dealing with. It's super puketastic in there and I only want to clean it once.

I'm still not sure about the knee motor. I need to remove more sheet metal to check. It may be ok with just a simple static converter circuit. I'm thinking that the worst case is a simple, tiny, VFD for the knee. Then again, leaving it unpowered would get me in stallion shape quick. The table likely weighs 750lbs without the knee casting.

noddybrian wrote:start the VFD & use it's ramp up time to allow machine motor to overcome any flywheel effect the nature of the machine won't matter - hence a lathe is not a problem even with a big heavy chuck / workpiece if you allow sufficient acceleration time in the setup menu.


This is the idea that I have. I'm definitely going to use a quality VFD with good support and documentation. Being generous with the ramp up and ramp down programming in the VFD is what I'm going with. I want reliable rigid tapping....at least as reliable as I can get. The VFD and a spindle encoder is key to doing this right.
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Re: Goliath CNC knee mill

Postby MFleet » Fri Feb 02, 2018 8:52 am

I confirmed that the machine was working on a very basic level before it was moved. I recently powered it back up to "run it through the paces" on the motion control. I wanted to do more visual evaluation and measurements to finalize a parts order. I did my due diligence and checked for any accessible leaking capacitors.

It didn't make it past 30 seconds before I had a small electrolytic campfire. I shut it down quick and realized that the most complex, and rare power supply it had, the supply to the motion control board has burned. The problem here is that the majority of the capacitors and board were hidden underneath a hooded heat sink. I've cleaned it up a bit and we will see if it makes it. I'm nearly settled on a Linuxcnc/Mesa, partial retrofit. That will address this particular power supply by default. It will also get rid of the ancient PC and ineffiecient motion control board. To all those that are interested in a ANY 90's cnc, pay attention! This is what you're in for.
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I've removed and evaluated all of what should be the top, failure prone items. Everything with an electrolytic capacitor. The electronic components are due to arrive on Monday. They were not much at ~$70. Thanks for the interest and input on the project. The moving costs were a huge hit. I'm slowly regrouping to bring in the VFD and late model motion contol parts.
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Re: Goliath CNC knee mill

Postby Arno » Mon Feb 05, 2018 2:43 am

Good luck!

In my spare time (if I get any.. :lol: ) I like to work on and run old vintage computers of the 'refrigerator' size so I know some of the issues you're running into...

Dried-out capacitors are a common issue on these too. Once you know the smell they give off you can usually start to tell beforehand if something will need some (re)work before powering it up.

Small tip.. In some cases, mostly for smaller capacity ones, you can swap out the electrolytic caps for more modern polymer caps. The latter do not suffer from the same issues of drying out and going up in flames which is a nice bonus :roll:

Bye, Arno.
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Re: Goliath CNC knee mill

Postby MFleet » Tue Feb 06, 2018 5:28 am

Arno wrote:Good luck!

In my spare time (if I get any.. :lol: ) I like to work on and run old vintage computers of the 'refrigerator' size so I know some of the issues you're running into...

Dried-out capacitors are a common issue on these too. Once you know the smell they give off you can usually start to tell beforehand if something will need some (re)work before powering it up.

Small tip.. In some cases, mostly for smaller capacity ones, you can swap out the electrolytic caps for more modern polymer caps. The latter do not suffer from the same issues of drying out and going up in flames which is a nice bonus :roll:

Bye, Arno.


Hi Arno,

Didn't know anyone still worked on mainframes. I did run accross a video of a young un' that went through the trouble of moving an IBM into the basement. Cool to see the interest and what he was doing with it. They were a little before my time, but I do remember using logic probes and loading huge hard drives into the top of the cabinets. I would still like to know who made the call on putting those heavy things up there. I owe them a good whipping with some filler rod :evil: :D

I piggybacked this order onto $380 total worth of components for a market that I'm attempting to re-visit. As slow as things are, it may turn into a multi-day recapathon. And I'm with you using films where fit is reasonable and there is a guaranteed ROI. Panasonics and Wimas are the usuals. We know films can get quite large. We also know dimensions, weight, and vibrations can create serious stress on solder joints. I try to to stick with Japanese, high temp, long life lytics in power supply sections. Good circuit design permitting, I generally target 20+ years of function for these particular components.

Lesson learned on the hooded power supply that burned. Remove it or get the eyeballs way in there with lots of light and an inspection mirror. Triple 5v-6A/+15v-2A/-15v-2A. Obscure isn't the word. I do recall the nice, sweet smell followed by FIRE :D

The parts have arrived and I'm checking the invoices. There is plenty of China and Malaysia COO on there. Per part#, this was all Japanese not too long ago. I can only hope that the Japanese heads have dedicated the investment to vet the QA process at these locations. I've seen this type of transition fail first hand more than once. Parts picking is more difficult than ever now due to obscure lead spacing. The clientele may not know what it does, but none of them are blind to poor fit.
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Re: Goliath CNC knee mill

Postby aland » Wed Feb 07, 2018 6:19 am

MFleet wrote:I'm not a fan of RPC.


I'm not either, but it's not a bad solution if you have a bunch of different machines. I have a couple VFDs, but they're not too cheap when you start getting into larger ones that will run 5HP-7.5HP machines.

My lathe is probably the most demanding machine I have, with a 5HP motor, and lathes take more power to start up. I agree on the noise, ain't like anyone likes it... :roll: I also have a 7.5HP 24" wood planer (currently in storage), but it doesn't have the slow/demanding start like the lathe, or bandsaw, and CNCs are notorious for needing lots of power on startup.

In the best world we all have a Phase Perfect, or better yet just have 3 phase coming into the home/shop.

In the real world we need to sometimes do what we gotta do...:D

Any way, best of luck to you! A knee mill is a good tool to have in your shop, however it's powered.

Alan
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