I have recently invested in a water cooled Chinese spindle for my MPCNC. This one specifically
I can tell you my ears love me for it. There were some issues with the install and use of the new spindle. First, the new spindle only spins at 24k max. This is considerably slower than the Dewalt 611 I was using which spins at 27k. Also the new spindle is heavier than the Dewalt 611. This baby weighs in at 3Kg (6.614 lbs), a full 2 lbs heavier. The cords and the water lines are more cumbersome to deal with and required a separate gantry to operate.
One annoying feature, because of the extra weight, the Z axis would spin down when the motor is disabled at the end of the run. Normally this wouldnāt be a big deal, but I cut mostly 2" foam with mine and I zero my bit to the top surface of the material and work down. I came up with a solution that I am in the process of completing. I bought some compression springs to mount around the conduit in the Z axis to help neutralize the weight of the spindle on the Z axis motor.
I have attached a CAD drawing of my intent. I ordered the springs from HERE. They were $11.77 ea, but there is a $40 minimum purchase, so I have an extra set. The nice thing is, they are stock springs. I expect them in next week and will update when I get them installed.
Interesting idea. Springs/conterweights/brakes/locks/etc. have all been kicked around as solutions to the ādropping Z problemā before but I donāt know if Iāve seen anyone actually implement any of those solutions so please keep us posted.
Just eyballing this, the spring rate of 7.2lbs/in (3.6lb/in x2) seems a bit stiff to me. If you set the spring heights to provide enough force to net out the Z axis weight at Z=0, you might not have 2" of travel left before bottoming out the springs. You only get 4.38 -0.71 = 3.67" total travel and if the Z axis weighs more than 2lbs (1.67 *7.2) you will run out of headroom. That being said, even offsetting som/most of the weight at Z=0 might be good enough to keep the axis up.
I liked that you caught that. I considered a single spring around the lead screw and keep the load at 6 lbsā¦ I put a scale under the bit in the spindle when it came to rest on the table with varying results, however, most times it was =/> 5lbs.
Thanks for the input, Ill get some pics and show results next week.
My newer build also has the z axis drop from the rather heavy weight of the Z axis. I had contemplated something to offset the weight but I would want a somewhat consistent force over the range of travel.
How much z travel do you have? If you have two springs in parallel like that the lifting force will increase by 7.3 lbs for each inch of movement. Lets say your z axis weighs 5 lbs, if you have no preload and zero lift at the top of your travel then you have net weight of 5 lbs, but descend by only 2 inches and you have 14.6 lbs of lift from the spring, or net of 9.6 lbs upward force on your lead screw.
I think you might do better by stacking the springs in series instead of parallel and then preload a bunch. If you stack your 4 springs on top of each other then the force changes by only 0.9 lbs for each inch of compression. If you preload with say 6 inches of compression then you will get 5.4 lbs of lift, and when you lower by 2 inches the force increases to only 7.2 lbs of lift, a very reasonable range compared to 0 to 14 lbs.
In my case I have a rather long Z travel so I had considered a spiral pulley, but so far thats just a concept.
You bring up excellent points, thank you for your feedback. I wanted to avoid a custom spring but i may have to resort to that. This was the closest "stock" spring they had to my parameters and i thought it worth the shot.
āIn my case I have a rather long Z travel " ā¦Now youāre just bragging. My Z axis is only 4.5ā currently. I would rather keep the Z axis motor energized between runs and just start from that point. I would think this would be the optimal way to overcome the problem. But alas, i am willing to try this solution.
How about a outside spring running from the motor clamp to the Z gantry. I have piano wire from 13ga(.031) to 18ga(.041) or I could order other sizes. I have numerous mandrels I made over the years. I could leave straight wire ends so the eyes could be made to fit the machine. Here is a link to piano wire string spring calculator. Or could trial/error R&D. Spring Making
So here is the final result. Well, not final, Iām reprinting the top Z axis pieces out of polycarbonite instead of PLA. However, the springs work like a charm. They have perfect amount of compression for the 90mm of travel ihave on the Z axis, yet the spindle doesnāt drop after deactivated.
Note: I am only cutting foam with this machine. (40mm thick foam with a 50mm long 9mm dia. router bit)
This is exactly what was needed. Let me know if you have questions
I also have two springs left if anyone needs them Cost+Shipping and Iāll forward to you.
What all is necessary for I installation of that spindle. I too am looking to upgrade and am wondering how the wiring, switching, and rpm control is handled on one. Iād hate to deplete my tiny budget on a spindle only to find out it needs a $300 controller and $500 of software to run it. Really love to find something plug and play. Thanks
The spindle comes with a VFD (variable speed drive) and the controller. The rpm is set manually on the VFD prior to starting the piece. There is also the consideration of the water cooling. The water cooling needs a somewhat larger reservoir because of the heat generation during cutting. If you are taxing your mill then the temperature will be higher. I got around the temperature issue by adding an air to water heat exchange (essentially a small radiator) I had lying around. (i work in processing).
Other than that, it is a fairly simple install. There is a method to turn the spindle on and off using the arduino control board, but i havenāt messed with that yet. My primary use of the machine is to cut foam sheets for packaging, and for that it works awesome.
I hope this helped, I will be happy to answer any other questions you may have.
