Dah Lih DL-VHR-GIF mill - a journey of discovery

[Wizard69]

Whenever I come across discusions on VFD and their associated costs I wonder why no one has explored the DC option,there's heaps of DC treadmill motors from 1.5HP -4.0 HP out there,enough power to rip your bloody arms of as" Aunty Jack" would say, a very easy conversion with full speed control,check out You Tube on treadmill motors.I've converted my pedestal drill using a 1.5 HP DC motor,geared 2:1 works fantastically,next project my Lathe with a 2.0HP DC motor

VFD’s are very cost effective for converting ex industrial equipment that already has a 3ph motor. In some cases taking only minutes to get a machine running of single phase.

In the home shop I can’t imagine that there is a stand out advantage to one type or the other. The biggest disadvantage to treadmill motors is that they often don’t conform to industry standard frames or lack mounting feet. This is nothing that can’t be addressed by a home shop machinist.

Also there are as many 3ph motors in the waste stream as there are DC treadmill motors. Used motors can be surprisingly cheap.

Now in an industrial setting I’d prefer 3ph motors every time simply due to the reduced maintenance. In a home shop you would likely not wear out the brushes and if you did you would effect a repair before the commutator is chewed up.

 

[joco-nz]

VFD's turned up today. These are neat little units that take 230V input and provide 380V output. Just right for dealing with single voltage 3 phase motors. I've done a temporary connection after checking and tweaking ever so slightly the VFD settings. These videos show me mucking about really, just trying a couple of different ways to run the motor and see how it went.

At the moment I do not have DC braking on. Once I get that setup it should stop stop much faster. I do need to determine if I can and should use a braking resistor. Given this is a mill I don't see a lot of built up energy in the spinning parts, at least not like a lathe with a spinning work piece on it.

Starting at 25Hz, using the dial to push to 60Hz then hit the stop button.
[youtube1]

Starting at 25Hz then using the forward/reverse button and finally stop button.
[youtube1]

Starting at 0Hz and using the dial to bring the Hz up to about 49Hz then back down to 0Hz.
[youtube1]

 

[joco-nz]

Some further testing and a significant improvement in the start and stop speeds. Half the battle is deciphering the unclear manual. The next signifncant stage will be expanding the existing electronics housing to accomodate the VFDs (one for vertical spindle and one for the horizontal) as well as the static converter electronics. Hopefully some progress pics from that after this weekends efforts.

Anyway, very short video of how quickly things spin up and down under VFD control.

 

[joco-nz]

I’ve made some progress but it’s really temporary as I’m waiting on a number of parts to arrive before I can make things final. I made a little video just to show what I had gotten working and setup. I dont clam to be videographer so bear with.

I also did some tramming on the head using a DTI with 0.01mm markings. Front to back is bang on. No movement. Left to right i got to under 0.01. Given the level of movement in the needle I would estimate slightly less than 0.005. Pretty happy with that.

I did do a review of the wiring after this video amd fix a few bugs. Where things should have been running slower than they were in the video. But you’ll get the gist of things.

Cheers,
J.

 

[joco-nz]

Some more fettling and improvements.

I was finding the Z axis really stiff on going up and when letting it down it would "judder". I had thought i had too much slop and it was locking on the way down. Actually it is much simpler than that, the gib screws were too tight. It was the first time I had looked at them. After a little tweaking the Z axis is nice and smooth.

Next challenge was Y axis. Quite a bit of excessive slop here, about a 1/4 turn of the wheel and when milling with heavy cuts I could feel the give when the end mill grabbed and moved the table a little. Definitely not ideal. So I went hunting for the adjustment (oh please let there be adjustment). And I found this arrangement:

Now this image is post adjustment. Imagine this with only the top M6 screw and with no clamping washer. So first off another M6 screw and two custom clamping washers whipped up on the lathe. Then some tweaking by backing this nut off then re-clamping the M6 screws to drive a little loading on to the leadscrew. Net effect is a really smooth wheel action and a backlash of 0.04mm. I think I can live with that.

Cheers,
J.

 

[joco-nz]

Okay I'm getting lazy in my old age and doing these videos shows way more than a set of static pictures.

What we have here is ...

[1] Video showing the new chinese sourced digital tachometer in operation against the high gear. If anyones interested I can take some photo's of how I have the sensor and magnet setup in the head.


[2] showing the tapping speeds and the speed of stopping and reversing when under VFD control. I've used this setup to power tap M10 into 6mm steel with no worries at all. I suspect it will do a lot thicker and at some point I'll dig out some 12mm scrap and try it on that.


Cheers,
James.

 

[joco-nz]

The learning continues both in how to set up the VFD but also in how to use the mill. I setup on Gear 2 which had a name plate top RPM of 700. It was actually spinning out about 800 rpm. For drilling with a 6mm pilot hole and then to dialling it back a little for the M10 tapping drill size. Then pulling things back to the low gear belt and running at 25% of max frequency (15Hz) for the tapping. Which gave about 140 rpm. Once I have everything setup with the final parts I should be able to get down to between 5-7 Hz, so about 60-70rpm.

The key learning with the current setup I have which is 8 preset speeds from 100% down to 12.5% is that I can have custom ramp up and ramp down rates. So for the two bottom settings I have it decelerating at 60Hz/sec. This means the spindle stops FAST, or for that matter moves from forward to reverse pretty dang fast as well. Where as for the higher speeds I have a more leisurely 30Hz/sec rate which just keeps things less stressed on the motor. It still stops in ~2 secs.

Have a look at the video of power taping for M10 x 1.5 into 16mm steel. Pretty cool and quite fast.

 

[joco-nz]

In the process of building a tailstock support for a rotary table i got to power tap M10 x 1.5 holes through 30mm of mild steel. This 1HP motor on low gear (not a back gear) under VFD control just munched trhough it at about 80-100 rpm.Not single sign/sound of strain.

 

[joco-nz]

I thought I would post some pics showing how I had setup the digital tacho on the mill. It's not particularly special I guess but just in case someone finds it useful. It seems to be working well and in the end allowed me to mount all the parts without having to glue anything to something that would require destructive removal when wanting to get back into the spindle assembly.

Overall view looking down into the belt housing. You can see the collar that I made from aluminium to hold the magnet. The hall effect sensor and the bracket its on. On the collar you can see the M4 screw used to clamp the collar onto the top nut on pulleys.

Just turned around to show the magnet. Press fit into the collar. I don't think its going anywhere.

Looking at the side of the housing and you can see the bracket clamped on to the side grill.

 

[bruedney]

That washer is a bit rough

 

[joco-nz]

Its what i had about. At some point I need to get some washers for M5 and M6. All i had was M8. But it works so ... *shrug*
But now the voices in my head have started ... Get OUT Stefan!!

 

[joco-nz]

Some progress today on finally getting the new buttons and speed potentiometer (POT) working. I had been having issues with the external POT not being recognised on powerup. It all came down to having to use shielded cable. I was using Cat5 UTP and while this worked fine for the buttons the POT was being problimatic. I did a test with some 3 core shielded cable and it started working correct from startup. So since I had to have about 6 wires for to one of two VFDs I shifted to Cat 6 STP (actually SFTP) and we have a nice tidy run, fully shielded and working correctly.


The buttons are
Top row from left: Stop, Forward, Reverse, Speed Dial
Bottom row from left: Table feed On/Off toggle, Pump on/off toggle, eStop that kills table and spindle. Once I get the CNC BF20 built I'll engrave the lables on this plate.

The POT is an interesting on I got from Banggood. Its a 10k ohm multiturn POT with a neat dial that shows the turns and the graduation in a turn. Want to get to about 50% speed, turn to the outer number is 5. Then adjust from there to get the rpm that works best.

So after this success and while I happen to have the vice off I decided to do a more accurate tramming of the head from left/right to the table. I had done this previously on the vice and had to pretty good but felt it could be done better. So I setup my 0.01mm DTI to trace an approx 430mm diameter circle. Given that size circle this should provide some pretty good sensitivity. So after a few sweeps and some nudging on the spanner we got ourselves to this position:

I think over 430mm we can call this good. To do any better I'm going to need a 0.002mm DTI.

Cheers,
J.

 

[joco-nz]

A little more progress today. The plan to be able to run the horiztonal and vertical spindles off the same VFD is starting to come together with the arrival of this big ass changeover switch.

The two motors are VERY similar with all the VFD parameters being the same plus the change over wont be done without powering off the VFD. Given that moving to horizontal milling is quite an exercise this depowering process shouldn't be an issue.

So taking the eletronics box door off and mounting on the table so as to thin the 6mm aluminum down a little, in the same way as the existing power switch has been seated. Used a HSS 12mm 4-flute end mill running at 1700 rpm. A bit of WD40 and a robuts feed rate and things were cutting very nicely with nice tight chips.

The resulting switch mounted and the door back in place. The intention is the left-hand switch will be Master Power and the right hand swicth will be Spindle Drive Selection. Once I have things a bit more sorted I'll be taking the old signage off and replacing with something else. Ideally carved on a yet to be completed CNC'd BF20.

Cheers,
J.

 

[Cogsy]

Will there be any issue if you switch the spindle drive selection with the master switch on? I only ask because definitely at some point I would reach out blindly while thinking about something else and flip the wrong switch. Might just be me though.

 

[joco-nz]

Cogsy - I had thought of that possibility. Its why the master power is the first switch twoard the front of the mill and thus the easiest to reach.

Obviously there is some risk but I would have to have the VFD in Run Mode (i.e trying to drive the motor) AND swicth the VFD to the other motor to be really likely to fry something. And the risk of doing that is VERY VERY low. The control box is on the side of the mill main body so I have to walk around it to get at it. Very very unlikely to do that when its running.

The more likely scenario is to have the VFD in Stopped mode, so no frequency being sent to the motor and to switch motor feeds instead of powering off. Not ideal but shouldn’t cause things to get upset.

I have been pondering putting a clear perspex cover over the switch so as to force some thinking before mucking about with it.

Cheers,
James.

 

[BIGTREV]

All very nice

 

[joco-nz]

It's been a bit quiet over the holidays while I waited for some more parts to turn up. So I mucked about a bit and did the following.

[1] Changed the buttons a litte on the control panel. I wanted a more overt STOP look to the red button and a different colour between the table power feed and coolant. Here's the result. Of course I still need to sort out the labeling. I also got the wiring for the eStop fully sorted out. So that now it prevents the spindle and table power feed from running when triggerered.

[2] Made a "speed handle" for the mill vice. Been wanting to do one of these for a while and I had made the hex holed part a while ago, just never gotten my "a" into "g" to finish it until now. The tappered handle is 6061 ali and it feels really nice to hold. The rest is all mild steel.

The fit on the vice hex is excellent. A nice sliding fit, not tight and not sloppy. The handle spins freely but is not sloppy on the retaining "screw".

I might polish up the main parts edges but at the end of the day this is a functional tool that is going to get a bit dinged. So I'm not too fussed about going OTT on the finish. I did have fun practicing draw filing on the front and back face to get a really nice smooth finish. That was more for learning than anything else.

Anyway, a nice and useful addition to the tools supporting the new mill.

Cheers,
J.

 

[joco-nz]

Here are the drawings for the speed handle for anyone interested. You will see from the drawings that I did the handle differently (i.e. only tapered for 25mm not the whole length). This was so I could more easily mount the part in the collet chuck after cutting it from the stock bar.

Note this design is not mine or unique. There are a number of people on the net who have done similar things and these types of handles are available commercially.

Cheers,
J.