Welding Tips and Tricks

This is what a 6500# + CNC knee mill looks like. I'm less than pleased to announce a series of miscalculations on this.

My original thought was that a CNC knee mill, on average, should not go over 4k#. I still stand by that thought as being logical. After more picture analysis....this is no average casting. More like 5k# plus another 1k# for the cnc bits. That killed the idea of using the available 7K# trailer to pick it up. That would have been a rough estimate of $500 personal transport cost.

I made the deal on it and hired a rigger that could do 6k#, no problem. Add an 8k# local forklift rental onto that. We made it to my shop and he went back to pick up a 6k# skid steer. The skid steer didn't want anything to do with it. I removed the ram and milling head assembly to lose what I estimate to be 750-1000#. The skid steer reluctantly moved it into where you see it. He is claiming that it is still over 6k# for the lower assembly and that may be true.

The rigger was slightly irritated after I carved out the most cash that I could muster for this move. I offered my shop time to cool down the situation and his demeanor changed quite a bit. I put the Hypertherm to work. There is a gross amount of plasma arc gouging on his trailer. There is several more hours of thinking, hammering, cleaning, welding, wire soldering, whatever. I don't have the immediate know-how to do double pivot point equipment ramps or we would have done those as well. Anyhow, I think both of us can agree that I'm now in the positive side of the deal.

I'd like to see a skid steer that can lift 6,000 lbs. 2500 is more like it for a skid steer.

aland wrote:I'd like to see a skid steer that can lift 6,000 lbs. 2500 is more like it for a skid steer.

You may be right on that. I remember it having tracks which would make it a track loader; not a skid steer as the guy was calling it. I think it was a Bobcat. I will get a picture if I ever make it back over to his place.

aland wrote:I'd like to see a skid steer that can lift 6,000 lbs. 2500 is more like it for a skid steer.

If I remember right, skid steer lift ratings typically are for at full lift height with movement. If you leave that sucker no more than a foot off the ground you can do a lot of work. Pallet forks may start to bend but that's a separate issue. I may have also heard the woeful rating thing wrong as well.

aland wrote:I'd like to see a skid steer that can lift 6,000 lbs. 2500 is more like it for a skid steer.

Bobcat s850
3950 lift and carry
7900 tip

MinnesotaDave wrote:

aland wrote:I'd like to see a skid steer that can lift 6,000 lbs. 2500 is more like it for a skid steer.

Bobcat s850
3950 lift and carry
7900 tip

Screenshot_2018-01-17-06-03-50.png

I wish our bobcat could 12.3 mph... And lift that much. Ours is an S205 so rated at 2050 lbs but I've lifted mini bulks with herbicide that are around 3000 lbs. the main thing is keeping the load tight to the loader as well. Ours wouldn't pick up our man lift because of the length of the man lift. Too much leverage in the front end. If it has fork holes on the side in sure I could have but too much weight 10 feet away from the loader it self wouldn't let it lift.

MinnesotaDave wrote:Bobcat s850
3950 lift and carry
7900 tip

Pretty familiar with the most skid steers, and although the s850 spec says that, I'd love to see it in action.

For reference, I own a Catapillar R-80 Rough Terriain forklift, it will lift 8,000 lbs, but it does that only on the 1st stage, so it lifts 8,000 lbs. to 10', not the full 30' with all 3 stages extended. Full height is more like 2,000 lbs to max height, and that is not tilted in any way.

Skid steers don't have multiple stages and are limited at the full extension of the lift, that would be no issues for a machine if you only need to live it a few inches, but to unload it you need to get higher as you need to get to the trailer bed.

Even still, let's just say the s850 will lift 4,000 lbs. to full dead lift. That is still quite a ways from a 6,500 lb. CNC mill.

Honestly, I wish a skid steer would lift more as I would trade my forklift for one, but I often lift logs with it that weigh 4,000 - 6,000 lbs. I don't think a skid steer can handle that and a good friend convinced me to give up on the idea. The other thing is the entire weigh of a skid steer, you need ballast when lifting. My forklift weighs 16,000 lbs. If you are not careful you can easily pull the entire lift over with a 3,000 lb. load if you tilt the mast too far forward. I have never lifted a machine that heavy, but my lathe weighs 4,000 lbs, and I've lifted it easily.

EDIT: Farmwelding you've got it right. Keep it low, keep it close, keep the weight down if you can.

Alan

I've done some checking and found that we used a Bobcat T870 to unload it. There was planning and a skilled operator to pull it off. That doesn't make it safe or right in any way. Don't do what we did. We used a Skytrak 8K# to load it and that handled it, no problem.

The moving costs ate the budget to convert it from 3ph to 1ph power. Another reason I'm still a bit cranky about the whole ordeal. I've also sold my manual machines. It is still a good deal and very much needed to move forward.


This is the early planning stages to get this running:

Aquire a name brand VFD to to convert the 5hp spindle to single phase.

Address shaft-pulley tolerance in the upper milling head. Replace 3 worn bearings. Remove worn spindle air brake components. The VFD will handle spindle braking. Add spindle encoder if necessary for rigid tapping.
I don't have the parts manual for the milling head. It is a Dah Lih brand and I would love to have one, but I can get by without it.

The CNC controller is a 1992 vintage Anilam 1400(M?). It is all single phase so no problems there. The electrolytic capacitors and old, dry heat sink compund will be freshened up. A LinuxCNC/Mesa controller may be in the future. I'm also liking the controller and conversational software package from Centroid. The prices can get way up there with Centroid however.

The power knee and coolant pump are 3 phase. I'm still undecided on what to do them until I can get the motor specs.

MFleet wrote:I've done some checking and found that we used a Bobcat T870 to unload it. There was planning and a skilled operator to pull it off. That doesn't make it safe or right in any way. Don't do what we did.

I agree, the operating weight on that steer is 5000 lbs., however the tipping load is 10000 lbs. so that seems within the spec.

Seems you got it moved and that is what counts. Thankfully nobody was hurt and the machine was not dropped in the process. I guess you can't argue with success, but it doesn't seem like a very smart move for a "skilled" operator, IMO. But my opinion means little. As I said, you got it moved and nobody was harmed.

http://www.ritchiespecs.com/specificati ... lid=108873

Alan

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

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

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.

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.

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. 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.

Good luck!

In my spare time (if I get any.. ) 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

Bye, Arno.

Arno wrote:Good luck!

In my spare time (if I get any.. ) 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

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

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

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.

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... 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...

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

Alan