940 mill models

Phazertwo the 833t does look very interesting, why would you have choose that instead?
 
My friend has a true RF machine, made in Taiwan. There is no question, it is a few notches above the machines made in China proper. The fit and finish is very nice. I have inspected the pictures of the 833t very closely and it looks very comparable to his RF machine, including the scraped ways. The "Main High Quality Features" section of the 833t page is pretty much a list of reasons that I wish I had it.

When I got into this, it was because I switched jobs when I just started seriously learning CNC. I decided that it was a skill that I wanted to have, so I considered getting a manual machine and converting it, but in the end decided I was less interested in the conversion and more interested in the machining. However now, I wish I would had got a manual machine and CNCed it myself... Considering how much I have already changed my on 940 and how much more I plan to change, it would have made more sense to start with a manual machine for sure. Live and learn...

Don't get me wrong, the 940 is a killer machine, the travel cannot be matched which is the reason I bought it. With only changing the controller and tuning I've been able to hold ±0.002" with out really trying and I can do better than that if I take my time. Bang for buck, it's tough to beat.

PZ
 
I was just looking at your thread about the 940 I see what you mean about all the work you are doing. It’s a shame you had to do it.

What are your plans for increasing the spindle speeds? Are to going to eliminate the gear box altogether? I always hated how loud the gears sounded on the RF45. I also upgraded my spindle bearings and installed a 3 phase motor. I ran mine as high 3000 rpm with a vfd. Talk about noise.
 
I have the 940-CNC-VS, so it's a VFD controlled motor with 3200rpm max speed. I'm ditching the gear box all together, it just won't be able to get to the speed that I want, and I'm tired of listening to the damn thing.

I'm going to attempt a two speed belt drive that will be controlled by the CNC controller. It'll be similar to Fadal's Pozi Drive, time will tell if it will actually work.

PZ
 
There doesn’t seem to be much information on the 833t out there, is it a new machine? Nothing on YouTube at all.

Can you direct me to information on the belt drive system, that would probably be my first upgrade if I decide on this machine.

Thanks
 
There are a few guys on this board that have an 833t, and pictures are trickling in. Here are a few threads:

https://www.hobby-machinist.com/threads/new-pm-833t-in-the-shop.56111/#post-566729
https://www.hobby-machinist.com/threads/pictures-of-the-pm-833t.65776/
https://www.hobby-machinist.com/thr...-machine-and-how-i-got-to-the-pm-833-t.65200/

I don't really have much information on the belt drive setup. Take a look at Jake's 940 thread, it's where I got most of my inspiration.

https://www.hobby-machinist.com/threads/my-pm-940-cnc-modifications.57976/

Basically it comes down to a 2.089:1 motor to spindle ratio (I think Jack got 2.000 on the dot). That should get us a top speed of ~7200rpm at 120hz and -600rpm at 10hz. The sweet spot for roughing will likely be about 3600rpm and 60hz. As for the dual speed belt setup, I have no details, and haven't found anything about anyone trying it. Fadal made it work, so I figure it's possible.

PZ
 
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