[phomann]

This is the start of a journey. I've had a Taig CNC mill for over 10 years now and it is a fabulous machine. I was after a larger machine and the Grizzley G0704, BF20 or Sieg X3 seemed popular choices.

If all turns out well I'll should be able to provide a nice controller kit for this type and size machine.

The G0704 is not available in Australia. The X3, is as are a number of BF20 style machines. In the end, I chose a TM20VL from Titan Machinery. It looks similar to the G0704 and the BF20L but does have some differences. I could have got a BF20L for less, but I was not sure of the quality. Also I wanted an R8 spindle so I could use TTS tooling.

I'm planning to do the conversion following the CNC Conversion DVD by Hoss. Obviously it depends on how closethe machine is to the G0704.


The TM20VL has the following Specifications:

• Spindle taper R8
• Spindle travel 50mm
• Quill diameter 60mm
• Table size 700mm x 180mm
• Table travel (longitudinal) 550mm
• Table travel (cross) 180mm
• Max. dist. spindle to table 360mm
• Max. dist. spindle to column 185mm
• Machine depth 580mm (to front handle)
• Machine height 930mm(head fully extended)
• Machine height incl stand 1730mm
• Head tilt 90º both ways
• T-slots 3 slots, 10mm studs
• Range of speeds 0-2500 RPM
• Motor 800W BRUSHLESS DC, single- 240v single -phase

[phomann]

I picked up the machine from the shipping depot. I ended up using a scissor jack trolley to get it off the trailer. I raised the trolley to the height of trailer and shoved, pulled etc.

A few pics below.

[phomann]

The first thing I noticed is that the TM20VL Z axis is different from the G0704. The latter have a plate with the bearing to support the Z-axis screw. The TM20VL just has a sheet metal cover.

I popped the cover off and it is quite different. The screw support is beneath the crown and pinion gear

The bearing support is on a plate that also has the z-axis handle. You can see the setup in the photos.

Cheers,

Peter.

[pippin88]

The first thing I noticed is that the TM20VL Z axis is different from the G0704. The latter have a plate with the bearing to support the Z-axis screw. The TM20VL just has a sheet metal cover.

I popped the cover off and it is quite different. The screw support is beneath the crown and pinion gear

The bearing support is on a plate that also has the z-axis handle. You can see the setup in the photos.

Cheers,

Peter.

Someone might find the following of use if converting this mill:

I spent the afternoon pulling apart the Z axis. Head and carriage came off fine.

Then I tried to get the side plate out that holds everything in place.

Peter's photo is of interest:
http://www.cnczone.com/forums/attach...ion-z-axis-jpg

Mainly because my mill only had 3 bolts, with no bolt in the top left area (and no hole).... or so I thought.
The three screws came out fine, but I couldn't get the alignment pins out. They are threaded for a removal tool, I was using a bolt and pulling on it - nothing.
I then proceeded to remove all the bondo and paint between the column and this plate, which is quite a large amount - big gaps. I tried a bit of hammering from the back (through the top of the column) - nothing. Then I proceeded to drill the alignment pins out as deep as I could but couldn't drill the quite the full depth of the plate.

With some more hammering I got one edge to open up, drove a wedge in all around. Got a far bit of separation on the right side and lower left, but the upper left still seemed to be attached. By this time, with all the hammering and wedging, I've broken some of the cast iron plate edges and a small round shape becomes visible in the top right of the plate. There is a bolt in there. The sneaky ******** bondo-ed and painted over a bolt, that is a bit lower and not in line (not in the square pattern) with where it should be (and where the one in the photo above is). There is a tapped hole in the column where you would expect a bolt, and where Peter's has one. Not sure what they were doing...

Hopefully haven't done any damage to the column with all the hammering etc...

[hoss2006]

Yeah that's different, looks like a new top plate with the bearing mount for a ballscrew might be in order.
Hoss

[phomann]

Hi Hoss,

Yes, I think that will be the way to go. I took a few photos of the X/Y ballscrews. They are 25mm diameter. The X screw nut mounts differently to the G0704 ones. You can see that in the photo. Hopefully there will be enough room

I also took of the left endplate from the X-axis. There is no bearing race, just a hole as a sleeve. A bit disappointing.

I'll make new endplates and I think I'll use this style of ballscrew supports.
1 set Fixed Side FK12 and Floated Side FF12 Ballscrew end supports CNC DIY | eBay

Cheers,

Peter.

[phomann]

Ok, I removed the table to see what is underneath. Below is what I've found.

The X Nut is quite interesting. It is low profile which is not good. The screw is 25mm diameter so there is only about 35mm clearance.

The nut has backlash adjustment. There is a 3mm ball bearing sitting in the nut. As the backlash adjustment screw is tightened the ball is forced against the screw.

Cheers,

Peter

[phomann]

Removing the saddle to look at the Y nut was next.

You can see the nut mounted to the back edge of the saddle. You can also see the bolt that holds the nut to the saddle.

With the saddle removed, you can see the gap through the base. Lots of room for the Y-Axis.

The Y-nut is interesting and has the same ball bearing backlash adjuster. The hole for the screw seems off centre but preliminary measurements indicate that it is on the centreline of the mounting boss.

Cheers,

Peter

[phomann]

So, now I need some help on how to do the X-axis ball nut.

I plan to make new end plates for the table which will hold the ball-screw end mounts. At this stage I'm planning to use 1605 ballscrews and use the FK12 and FF12 style ball screw supports.
FK12 16mm BALLSCREW END SUPPORT BEARING BALL SCREW CNC | eBay

I also plan to use a FK12 on the Y-axis as well.

The ball nut mount is more problematic. The ball nut mounts are 25mm apart so I could use them . The centreline of the lead-screw is 15 mm above the base and this is where the problem is going to be I fear.

I have a Taig CNC mill, and the TM20VL saddle will fit if machining is necessary.

The dimension of the Ballnut from CNCShop is attached.

The diameter of the ballnut is 28mm excluding the mounting flange. This gives me a 1mm clearance to the 15mm centreline. I could mill a clearance slot in the saddle for the flange. I would then have to mill the top of the flange so that it does not interfere with the bottom of the table.

I could also mill the top and bottom of the flange which is my preferred plan at this moment.

Any ideas welcome.

Cheers,

Peter.

[691175002]

You will not be able to machine the nuts on a taig. You can use some form of abrasive cutter (dremel stuff) if you have a high speed spindle in the taig, or you can just attach the dremel to the taig.

You could also use a bench/angle grinder and do it by hand.

[phomann]

Thanks, I should have realised it would be hardened. I'll see if I can get linearmotion2008 to do it when I order them.

Cheers,

Peter

[phomann]

Still sorting out how to do the conversion.

Both the X and Y nuts are screwed in place. The Y even has a boss that fits into the saddle so no adjustment can be made at all.

The X and Y end pates also have locating pins so there is no adjustment available there. I wonder if the threads are cut in place using a special tap that uses the end plates as an alignment jig. Anyway, it doesn't help me.

The G0704 mill retains the nuts by having the nut holder sit in a slot and two screw jam it in the slot once everything is assembled.

On my mill, the x nut is mounted with 2 screws that can't be adjust once assembled as the table sit over it. The only was I can see to adjust it would be to not fully tighten the screws, assemble the axis and allow the nut to self align then take the table off and fully tighten the nut screws. This sounds unlikely to work or be very easy to do.

The alternative may be to cut a slot into the saddle and change the mounting method similar to the G0704.

Whichever way it goes, I don't think it will be simple.



Cheers,

Peter.

[phomann]

I went out to the shed and had a better look at the saddle. It appears to be too low profile to use the G0704 nut holder mounting method.

The current X axis mount screws into 2 threaded holes in the saddle. one possibility will be to drill 2 new mounting holes (so as not to destroy the old ones) with the nut holder having matching threaded holes. The 2 holes in the saddle could be oversize to allow adjustment.

The X-axis could then be assembled onto the saddle, without the saddle being mounted onto the base.The assembly could be flipped upside down and the X-nut mounting adjusted and tightened.

Cheers,

Peter.

[phomann]

The Y-axis mount is located via a boss. There is no alignment adjustment in that method.

I could get some alignment capability in where the nut mounts to the nut holder by using smaller mounting bolts or enlarging the mounting holes. Sounds like a hack though.

Initially I'll just try to make an accurate mount and see how I go.

The nut is mounted at the rear of the saddle. The screw is only fixed at the front of the machine so at the closest point the nut is some 6" from the screw mounting point. so a minuscule od misalignment may be tolerated.

Cheers,

Peter

[691175002]

I'd personally skip the pins. You will have to realign every time you assemble though.

[phomann]

I'd personally skip the pins. You will have to realign every time you assemble though.

Yes, that's what I was thinking. Hopefully it wouldn't be too often.

Cheers,

Peter.

[Bubba]

Peter,
On my RF31, there are no alignment pins. Never has been and like you say, it has to be aligned each time. However in ten years or so, I haven't had to do that more than a couple of times. Also, the original lead screw nuts look exactly the same as my RF31 did. When I made my X axis one I kept having a problem with the two bolts not holding the nut mount tight enough and it would work loose causing backlash. For the nut mount, I used a couple of alignment pins and haven't had a problem since.

[phomann]

Peter,
On my RF31, there are no alignment pins. Never has been and like you say, it has to be aligned each time. However in ten years or so, I haven't had to do that more than a couple of times. Also, the original lead screw nuts look exactly the same as my RF31 did. When I made my X axis one I kept having a problem with the two bolts not holding the nut mount tight enough and it would work loose causing backlash. For the nut mount, I used a couple of alignment pins and haven't had a problem since.

Hi Art,

I was thinking that there was not much "meat" on the mounting flanges and wondered whether it would be a problem.

How did you align the nut onto the saddle since it can't be adjusted once the table in put on. Is it a matter of tightening it so that there is a little movement, fit the table, get it aligned then remove the table and fully tighten the nut?

Then once it is all aligned, drill and insert the pins?

I am also considering having clearance holes in the saddle for mounting and threading the nut holder. That way, I could tighten the bolts from underneath.
The saddle would be mounted to the upside down table on a bench.



Cheers,

Peter

[SCzEngrgGroup]

I fail to see how the alignment pins save any significant amount of time on re-assembly. You simply leave the bolts loose, run the axis so the ballnut is as close as can get to the bearing support, then tighten up the bolts. It takes no time at all.

Regards,
Ray L.

[Bubba]

Peter,
On the X axis, I followed some instructions that was on the old IH site. I made the nut mount and loosely bolted it to the saddle. Then using my highly calibrated :}) digital caliper, made the lead screw parallel to the dovetails as I could. At this point, I tightened down the bolts for the mount. Next, I drilled the holes for the roll pins that I used to anchor the mount in one place ( see picture on my old web site:
My CNC Homepage ). Then the table was placed on the saddle, the gib strip put in and snugged down. At this point, the end plates were loosely mounted and using a socket wrench, we moved the table to one end of max movement and that end plate was tightened down. Then we moved the table to the opposite extreme and the procedure repeated.
The Y axis was done in a similar manner except there are bearings on only one end.

HTH