Knee Mills | picking the right one for retrofit

[citterly]

Hi All,
I'm really enjoying the Acorn platform and learning a lot.
As much as I like my proLIGHT, it's just too small and light duty to handle everything I want to make.
The work envelop is quite small and it struggles with steel more than I'd like.

I'd like to get an older CNC knee mill with a full size table and do another Acorn retrofit, something pre-2000.
The bigger 3 phase machines are a bit intimidating for me, so I want to be sure I know what I'm getting into and plan it right.

I'm not really clear on the limitation of Acorn with one of these machines and when stepping up to an AllInOne is necessary.
I really want to stay at the Acorn level due to cost.

From what I've seen on this forum, AC servos are a must, and the older machines are typically DC servos?
I'm wondering if there are more ideal candidates than others for retrofit.

Thanks for sharing your insights.
Chris

PS, the attached photo is a Hurco KM5P we have at the Kzoo Makers, makerspace. It's fully operational, but we don't have the right power to run it. It was a donation, as the business is a non-profit. I've considered converting it to Acorn, for the makerspace, but my gut says it would be an expensive project. We could probably sell it and use the money to get a machine better suited for the conversion.
It's too big for what I would want in my garage, but this path could be a good way to learn upgrading an industrial grade piece of equipment, if the business will fund it. Then I can more quickly do something for myself....

[converterking]

That is just a basic cnc knee mill and could easily be run on single phase. I would suggest you take a few courses at your community college on basic electricity, motor controls and plc programming. I think you would enjoy it and it would help you in future projects.

[cnckeith]

lots of good oldie knee mills out there. just make sure they are not worn out!

http://www.centroidcnc.com//bridgeport_ ... dx-32.html
http://www.centroidcnc.com/sharnoa_CNC_ ... rofit.html
http://www.centroidcnc.com/shizuoka_retrofit.html
http://www.centroidcnc.com/bridgeport_boss.htm

[citterly]

That is just a basic cnc knee mill and could easily be run on single phase. I would suggest you take a few courses at your community college on basic electricity, motor controls and plc programming. I think you would enjoy it and it would help you in future projects.

It's a good suggestion, maybe in the fall, I forgot about the CC....
It's been about 10 years since I did learning there, got started with welding and auto repair there.

I'm sure it would be enjoyable.

[citterly]

lots of good oldie knee mills out there. just make sure they are not worn out!

http://www.centroidcnc.com//bridgeport_ ... dx-32.html
http://www.centroidcnc.com/sharnoa_CNC_ ... rofit.html
http://www.centroidcnc.com/shizuoka_retrofit.html
http://www.centroidcnc.com/bridgeport_boss.htm

Thanks Keith, is Acorn able to work with these older systems or would they require upgrades to more current drives and motors?
I feel moderately comfortable believing that running the spindle is not a problem.
Thanks!!

[cnckeith]

with the old DC axis motor knee mills you have two choices, 1.) upgrade the encoders on the old motors (if the motor is in good conidtion) and use Allin1DC as the cnc controller.. OR..2.) sell the old DC axis motors and drives on EBAY..(there is always someone out there trying to keep the old control alive) and use that money to buy new AC brushless motors (like the Estuns 750 watt units we sell which are perfect size for a knee mill.) and use Acorn as the CNC controller.

and yes using the existing spindle motor with a modern VFD is fine. (this might open heated discussion:-))

[converterking]

You say you don't have the right power for that Hurco. What power do you have?

[citterly]

Thanks Keith, I appreciate the guidance.
Your options are clear as described and confirm some of what I was gathering from reading other threads.
Additionally, encoder replacement is something I didn't understand / consider.
Although, migrating to a newer style motor seems like the path of least resistance for those wanting to make chips versus do electronics.

This helps me move forward more comfortably, thx.

You say you don't have the right power for that Hurco. What power do you have?

I'm still learning, so my apologies if this is a bit off.
My understanding is that the Hurco requires 480v 3 phase power.

I believe we have "low voltage" 3 phase, which is 230v-250v, somewhere in there.
I'm just repeating what I've been told by a friend.
I appreciate your continued participation.
Thanks!!

[cnckeith]

fyi...details on encoder replacement on DC servos is here.
http://www.centroidcnc.com/sem_dc_servo ... rofit.html
this will "modernize" a DC servo that was originally equipped with either a low res encoder and or a Tach and or resolver so that it is compatible with Allin1DC and improves the performance of the motor at the same time.
step by step photo album of the process.
https://get.google.com/albumarchive/106 ... source=pwa

[martyscncgarage]

It can be done with Acorn, but yes, you have to upgrade the servos. Estun is a good choice as is DMM. The advantage to DMM is they have NEMA 42 frame AC brush servos. If you measure the mounting bolt pattern and shaft of your current servo motors, that will tell you what you have.
Estun does not make a NEMA motor frame that I know of. (Metric) you might have to make adapter plates and get or modify the servo pulley.

Marty