Mill Spindle Direct Drive Conversion

Looking good so far.

As to the brake drum, I'd model it on SW and do a quick FEA using your loading value. For a quick check the standard FEA that comes with the software would give you a ballpark number that would either make you feel good or raise concerns. If your cad doesn't have this capability I can model it for you and run it. I like to use it as a gut check but you have to be careful when using the absolute numbers as with any FEA analysis. Let me know if you are home tomorrow, I can come by with my laptop. I need to see your shop anyway.

Dan
 
Why do you need a drum brake with a VFD? With electronic braking it will probably be just as effective, if not work better. On my new mill with a digital head, they do away with the mechanical brake all together, and the fans that are normally incorporated in the mechanical varispeed head are eliminated. You could also program two braking rates, so the default is 2-3 seconds, E-Stop or brake lever would revert to single stage which could be something like 1/2-1 second. You would need a braking resistor. You would need to interlock the brake lever so it also deactivates the run command when activated and requires a restart. They also have a similar switch for the back gear.
 
mksj said:
Why do you need a drum brake with a VFD?
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I really don't, the only time the brake gets used is to lock the spindle for tool changes. Dropping it into low speed should give enough resistance to do a tool change. If not, I can always design a mechanical lock. I have the VFD set for a 2.5 second stop. We'll see how the new VFD reacts, I'll set it at the minimum that it will take without tripping out. I do have a braking resistor for it.
 
No brake on my bench top mill was the main reason I went with an ER32 collet system. Made tool changes much easier than using the R8 collets.
 
I should have read your earlier post more carefully, I assumed you had a power drawbar and it wouldn't take much friction to use it for collet changes. Like Dan, I mostly use and ER system, but I am putting a power drawbar on my new mill so that may change. I have seen a number of spindle locks that use a spring loaded pin to lock the spindle, if you want to get fancy you could use an interlock switch to make sure it is fully disengaged when the run signal is activated. I would think that would be an easier and safer approach then using the cast iron brake system, and maybe less vibration. Looking good otherwise, look forward to it up and running and your final thoughts on the conversion.:cool:
 
mksj said:
I should have read your earlier post more carefully, I assumed you had a power drawbar and it wouldn't take much friction to use it for collet changes.
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My spindle is an Erickson NMBT30 QuickChange, no drawbar at all. You loosen the nut with a special spanner wrench.

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mksj said:
I would think that would be an easier and safer approach then using the cast iron brake system, and maybe less vibration.
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I agree. I have decided that the brake drum is going away. I'm just going to build a spacer to take up the space where it used to be. I will build a lock pin system if it needs it.
 
The Erickson quick change system is not all that quick, that's why installed a power drawbar.
My mill had a solid spindle, so I removed it and gun drilled it for a 1/2-13 drawbar. I never use the spindle brake to change tools. But on the other hand, I still have the lower pulley on my conversion and have run it up to 6200 rpm. If I were to do it over, I'd eliminate it and use a disc brake.
I had the same problem with that bearing retainer, and ended up making one from steel.
 
sanddan said:
Looking good so far.

As to the brake drum, I'd model it on SW and do a quick FEA using your loading value. For a quick check the standard FEA that comes with the software would give you a ballpark number that would either make you feel good or raise concerns. If your cad doesn't have this capability I can model it for you and run it. I like to use it as a gut check but you have to be careful when using the absolute numbers as with any FEA analysis. Let me know if you are home tomorrow, I can come by with my laptop. I need to see your shop anyway.

Dan
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Dan did you get my PM?
 
I like the poly v belt your using. The one on the Kent (single small 1/2" V belt) slips under even a medium load at low RPM. I would love to convert it over to the different style belt.

I don't like having a nice heavy 3HP mill that I can't use the full power on. But, it's still light years better than my Bridgeport.

Is the Shizouka ready to go?
 
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