In upgrading my control box, I have had the MR-1 in pieces. This includes the spindle so I could do some bench testing. I would really like to keep the servo and replace the spindle cartridge with something that can be changed faster and/or more reliably. Runout on the probe when using the collets, even using a dedicated collet, seems to be a constant battle.
The spindle taper is 16*. Has anyone looked at using different tool holders and releasing them from the top rather than at the collet? If that is not viable, is replacing the spindle cartridge an option? I remember seeing an old post where they had a BT30 holder in a prototype. BT30 is obviously too large, but ISO20 seems more reasonable and wouldn’t dig into Z too much - maybe I am wrong.
I don’t think the stock spindle is hollow, right? If I remember correctly the top of the spindle is closed and has a fitting for the belt drive cog to fit on it?
I switched spindles completely to get faster tool changing, and a few others have too. It would be cool to see someone figure out how to do it without changing spindles.
One other big advantage with changing spindles is that you can get much higher spindle speeds, which I think the machine is well suited to. When I had the stock spindle I was running at 8k all the time, now I have a spindle that goes up to 15k (but I did give up low speed torque for this) and often run at 12-15k.
I am not sure if the spindle is hollow. I saw some posts that indicate it might be, but they were early on in machine development. I was hoping someone might have taken it apart to see so I don’t have to
Langmuir put out a blog post detailing why they went the route they did and agree with them. Also, the all in one spindles are almost half the cost of the machine. I could probably have a spindle cartridge machined for less - which is something I might investigate.
@AlexW did you ever disassemble the entire spindle assembly to see what is going on in there?
I never took the spindle out of the bearing block, but I did look at it pretty closely.
To do this I think you need to solve 3 problems:
What’s the biggest tool holder that you can fit into the existing bearings? ISO20 is probably a reasonable guess.
Re-engineering the top of the spindle to support a drawbar or puller.
Making room above the spindle for a pneumatic drawbar. The current setup has the servo motor overlapping with a lot of the spindle. You want to do this while keeping the motor weight as close to the centerline of the Z axis as possible.
There are BT30 spindles all over AliExpress and eBay that don’t have a motor and require an additional pneumatic drawbar that probably make this a lot easier. You might be able to build an adapter to make this work with the existing servo spindle motor. Quality seems pretty low from what I’ve seen on YouTube though, and they typically have a max speed of 6-8k.
Personally I wish that Langmuir followed in AvidCNC’s footsteps and sold the machine as a mechanical kit only for $1000-1500 less and allowed the buyer to supply their own spindle, steppers/servos, and electronics. I do understand why they want to sell a turnkey product though.
