5 HP Colombo

[terry]

(You "anti-spindle" guys will love this)

I bought a used 48x144 Bot a month ago, 2002 model, and from the look of it and talking to the original owner, used less than 250 hours. The original owner is a very meticulous man, and all his tools were clean and well taken care of though obviously used regularly, so I don't think he misused the machine at all. But, after using the machine less than 15 hours, the spindle starts squealing and evidently, from talking to the people at Precision Drive Systems, needs an 800.00 bearing replacement.

Now, that said, the past is an unknown factor, (although it purred like a kitten, such a sweet machine), but I can say what I was doing with it. (Although, as I was informed by the "friendly" folk at ShopBot, being an new user I am "in no position to say with any authority what factors may have contributed to the failure" of the spindle. And while that may be true, I anticipate a different tact from you guys that will leave me at least a little dignty.) I figure that for about four hours we were just playing with it, cutting out little 3D objects, Ron Brown's stars and the like. Then we got started on our first real project which was cutting out parts for a bunk bed out of pine 2x material. We were cutting pockets and sizeing the outside dimensions: 1/2" end mill, 3" per second, 22,000 RPM, 2 passes to cut the outside cuts. It had been cutting about 5 hours when it started to make noise and we shut it down at once. It was very hot. Every time we used the spindle, without exception, we warmed it up for at least 10 min at 6000 RPM before bringing it up to speed.

What caused the falure? I'm sure I was at fault, that's always how it works out, but I don't want to have another failure at 800.00, plus freight two ways, plus down time, etc. I can see the value of having the spindle, especially since I am going to be doing a lot of cutting in solid oak with it (5 peice arched cab doors). Thanks in advance for your help. (By the way, I made a bracket to hold a 3 hp Hatachi router, used the same bit, 1.5 inch per second, for 18 hours, no problem, no noise, no heat.)

On a different note, I want to express how impressed I am with this forum. Not only is there help with practical things but their is also input from those with very technical approches. Back ground doesn't seem to be an issue and every one gets the answers they need (except the "King", and I guess he got the answer he needed too!) be they novice or experienced, with out complaint about spelling! (Thank goodness!!) As has been said many times by others, this forum is the reason I bought a ShopBot and not another brand. So this is a big pat on the back, keep up the good work to all of you!!!

Thanks again,
Terry

[richards]

Hi Terry,

Sorry about the spindle. It looks like you're running the spindle way too fast for the move speed that you're using. The chip load calculator indicates a speed of about 9,000 RPM, 1-flute cutter, 3-ips, for a 0.020 chip load. A 2-flute cutter would run at about 4,500 RPM, but you'd lose a lot of torque at that speed.

Running the spindle that fast with that large a cutter would really build up the heat in a hurry, especially if the pine had a lot of pitch. I don't remember the last time I used a 1/2-inch cutter. The 3/8-inch works great for the majority of my work.

You might want to buy an infared thermometer to monitor the spindle's heat. You can get one for $45 at your local Checker Auto Store. My 3hp spindle runs at about 120-degrees (6-ips, 12,000 RPM, 2-flute 3/8-inch cutter, MDF and particle board - for a chip load of about 0.015). I don't have the specs in front of me right now, but I believe that 140-degrees is as hot as you'd want to run the spindle.

[elcruisr]

Terry,
the maximum RPM for the Colombo spindle, unless you have ceramic bearings, is 18,000 rpm. If you were running at 22,000 rpm with steel bearings that's what did it in.

Eric

[bleeth]

Terry: I have found that 2ips works a lot better for me on solid 8/4 stock with a 1/2" end mill. It also could have been that your collett was shot and the wobble caused by this toasted the bearings. Pine covers such a broad area of densities that a more precise response to cause may be difficult. I wouldn't beat myself up over personal responsibility though. Probably you were just grinding the chips too fine and not evacuating enough heat. Check out the Onsrud cutting tools site and/or catalog for an excellent overview of appropriate speeds of spindle and distance to determine the right load. Your Hitachi was undoubtedly actually spinning quite a bit slower when faced with the resistance whereas the spindle will spin much closer to advertised speed. I have found cleaner cutting and better chip load with a lower RPM. (I have just finished a huge load of 3/4 virola parts and double sided veneered wheatboard parts with a 1/2" compression bit and did it all at 2ips and 15k w/no problems other than needing to keep a close eye on the holdown bearings on the car.) Notice that the shopbot reccomended default settings for the 1/2" end mill in PW is 1.6ips at 15k with a 1/2" stepdown. Although this is a little conservative on the step and speed of cut it is not a bad place to start until you are more used to your tool.

With so many tools a month going out the door and shop-bot's policy of customer service forever they may be getting a little overloaded and that could explain your less than favorable impression of their response.

Dave

[bleeth]

WOW-Three cross posts-could be a record-Must be Friday afternoon.

D

[terry]

WOW is right! Thanks for all the input. As normal, I asked my questions a little late. I can see that what you have mentioned here is probably right on point. I can see I need to learn a lot about bits and feed speeds. The sawdust in the grove was very fine and hot to the touch. I'm not positive the speed was 22000, but is was as fast as it would go, and the guy at Precision said it had metal bearings. So there is another mistake.

So, in line with the above, where can I get educated? Dave mentioned Onsrud and I will go there. I have a themomoter that has a wire to stick to the window for outside temp that I bought to mount on the Y-car that would give a continual read-out. Will that work? I don't minde buying the infared themometer, but would rather not have to check it manually all the time. And where can I find more info on the spindle. The manual I got is probably great for and electrical engineer but it's Greek to me. Doing a search on this forum would probably net a huge amount of information. I'll start there.

Thanks,
Terry

[harold_weber]

Terry, you really need to get a copy of the manual for the VFD and learn how to program in the maximum speed it will drive the spindle. Depending on the brand of VFD, this might be available for download from the internet.

Precision Drive Systems has a web site that lists the maximum speed for the models they offer. They also have a few application guidelines in some downloadable brochures.

[richards]

I agree with Harold. Go to the www.pdscolombo.com (http://www.pdscolombo.com) site and visit their Engineering Support section. Pay particular attention to the section on Cutter Entry Angle (showing the need to ramp into a cut). They also have a chip load chart in their Spindle Speed section that will help you select reasonable speeds for the type of material that you're cutting.

As far as using your outdoor type thermometer, I'm afraid that I have no opinion based on no experience with that type of thermometer.