Thread: Homann Designs TM20LV CNC conversion

Well, the Z-Axis brackets are finally done. That's the last of the axis conversions.

The drive is a 1:1 belt drive. I chose the pulleys and belt from what I had on hand to match the stepper /ballscrew centre distance. All the drives are set up as 1:1 but I'm using 3 different pulley sizes.

Still so much work to be done. I think I'll jury rig up the motors and give it a run to see how it goes.

A couple of photos are attached.

Cheers,

PeterZ-axis1.jpgZ-axis2.jpg

Hi All,

I finally got around to wiring up the motors on the mill.

I'm using my 570 oz.in 5A stepper motors on the mill. The pulleys are set up for a 1:1 ratio.

I have a G540 based controller for my Taig milling machine and it was always one of my goals with this conversion was to determine how well a machine of this size would run of a G540 controller that is limited to 48V and 3.5A/ph. This was also part of the reason that I used a pulley drive setup so that I could try different ratios if need be.It must be said that the main reason for the pulleys is to tuck the motors out of the way which has worked out very well.

I set the current for the motors at the maximum 3.5A and started to tune them up in Mach3, not sure what could be achieved. To my surprise I was getting 6 meters a minute (236in/min) out of the X and Y axis. I left the Z at 4meters/min. That seemed like more than enough speed for rapids on a machine this size.

I then wrote a small G-Code file to rapid the X and Y to the extent of their travel. I'm getting 470mm travel out of the X axis and 190mm out of the Y.

A short video of the machine running this program is here;

http://youtu.be/caZ6F5MT8FA


I then loaded the road runner program as it is a good test to check for motor stalling and it ran fine, albeit a lot of rocking and shaking. I put the head on table to add some extra weight. The video is here;

http://youtu.be/AjfhQUBjBjI

I'll end up reducing the rapids to no more than 5m/min (200in/min). I still have to test the Z-axis but I'm sure that it will be fine running of the G540.


If anyone is considering converting one of these machines, a G0704, BF20 or similar sized machine I's suggest you seriously look at the Gecko G540 as an option. I don't believe that a larger driver will provide better or useable performance.

At this stage I'm not going to bother about looking at larger stepper drives for this machine. I could try using the 387 oz.in motors but they only have a 1/4" shaft and my pulleys have a bore of 3/8"

Cheers,

Peter

Hi Peter

I would not have thought that you could use 5 amp motors with a gecko 540. Is it just limiting the current to 3.5 amps that allows you to do this?

The pedestal drill height limitations could possibly be overcome by raising the base of the pedestal say 200mm and then swinging the drilling head around to the side of the drill. I have done this when faced with a similar problem.

Hi Peter,
Good to see the mill build revived.
The rapids are more than you will need for a mill unless you intend to install a high speed spindle. I do wonder how tight your jibs are though as the table seems to travels quite freely.
Good progress and keep it going.

Originally Posted by Bob Willson

Hi Peter

I would not have thought that you could use 5 amp motors with a gecko 540. Is it just limiting the current to 3.5 amps that allows you to do this?

The pedestal drill height limitations could possibly be overcome by raising the base of the pedestal say 200mm and then swinging the drilling head around to the side of the drill. I have done this when faced with a similar problem.

Hi Bob,

You can use a larger motor but it won't be producing it's full torque. If I get time, I might measure the torque it develops at 3.5A.

Thanks for the tip on the pedestal drill. I had not thought of that.

Cheers,

Peter

Originally Posted by rodm

Hi Peter,
Good to see the mill build revived.
The rapids are more than you will need for a mill unless you intend to install a high speed spindle. I do wonder how tight your jibs are though as the table seems to travels quite freely.
Good progress and keep it going.

Hi Rod,

Yes, I will be reducing the rapids as running it this fast will only wear thing out. I was just seeing what speeds I could wring out of it.

I tightened the jibs up so there was no movement. I haven't checks themafter the tests, so they may have loosened up I guess.

One of the next jobs is to put a belt conversion on the head. Then do a power drawbar for the Tormach tooling system tool holders.

On that note I need to get a 3" diameter pancake, 3 or 4 stage pneumatic cylinder to generate about 1800lbs of force. I have Hoss's plans on how to build one, but my 7x14 lathe won't be up to the job. I've seen single stages on ebay but nothing that will suit what I need.

At the moment my option appears to be to purchase it new from the USA for around $400.00. So if anyone knows of a cheaper alternative I'm all ears. Or if someone has the capability to build one and earn some money I'd be interested in that too.

Cheers,

Peter

Hi Guys,

I had a bit of time on Saturday to start the spindle belt-drive conversion. I'm using using the kit from Scott at Bench Top Precision

The kits are beautifully made. They are almost too good to put on a Chinese mill. In fact I'm so impressed with the quality I'm going to stock them, along with a few of Scott's other offerings. The kit just bolted cleanly onto the head and motor. It also comes with a belt cover for the front of the mill.


I've just ordered some new bearings, a Set for the spindle and another for the intermediate shaft(not sure what to call it) I've figured that since I've completely dismantled the head I might as well replace the bearings.

Below are a few images of the belt kit.

Cheers,

Peter

Originally Posted by phomann

Hi Rod,

Yes, I will be reducing the rapids as running it this fast will only wear thing out. I was just seeing what speeds I could wring out of it.

I tightened the jibs up so there was no movement. I haven't checks themafter the tests, so they may have loosened up I guess.

One of the next jobs is to put a belt conversion on the head. Then do a power drawbar for the Tormach tooling system tool holders.

On that note I need to get a 3" diameter pancake, 3 or 4 stage pneumatic cylinder to generate about 1800lbs of force. I have Hoss's plans on how to build one, but my 7x14 lathe won't be up to the job. I've seen single stages on ebay but nothing that will suit what I need.

At the moment my option appears to be to purchase it new from the USA for around $400.00. So if anyone knows of a cheaper alternative I'm all ears. Or if someone has the capability to build one and earn some money I'd be interested in that too.

Cheers,

Peter

So you have drawings? Rough idea how much work in it? I might be able to help, only if you are not in a hurry.
Cheers

Hi,

At the moment Scott who makes the belt kits agreed to make one so I'll see what he can do.

Thanks very much for the offer though.

Cheers,

Peter

Hi Im replying to an old thread hoping to get some help.
I'm looking for a driver for a motor that came of a TM20LV. The seller said it was '750w 4 pole 3 phase brushless 240V DC '. Im zero in electronics. Can you please let me know if these are the right specs or if I need more info to buy a driver for it. I bought this a few years ago and now need use for it. Thanks.