Y-axis help

[Heywood]

Greetings, it's been a while since I've been around but I've run into an issue with the Y axis on my PM-45 (think RongFu 45 clone) and could use some expertise and collective wisdom in diagnosing.
It's been a while since I used the mill (was working fine at that time) but now I notice that there is excessive friction with the Y-axis (that wasn't there from the last use), so much so the DRO can jump up to .002 increments with just the smallest turn and the table will continue to move when tension is released from the lead screw and I start to go the other way on the wheel. I have cleaned the ways and re-oiled, removed and loosened the gib as much as I can with little change. I have noticed a slight increase in friction when the table is moving in the -Y direction vs the +Y. I also removed the Y-axis lead screw, cleaned, checked and re-installed, I cannot detect any movement where the nut/arm connects with the table to cause misalignment. What else should I be looking at? Suggestions? I'm thinking I'm at that point where I have to pull the table and both axis apart?
The X-axis works just fine...

Thanks!

[wsippola]

I'm not familiar with your mill, but does it have tapered gibs on the Y axis? If so, it sounds like they are moving a bit with the table. If they are straight gibs (and I would guess they are) I suspect you missed an adjustment screw - one could even be broken so it seems loose on the outside.

What you've done so far should have solved it - you could try loosening the leadscrew nut's mount in case it's slightly off center and causing it to bind. Does the leadscrew itself feel tight when you turn it back and forth taking up the backlash? It shouldn't be of course. That's all I can think of off the top of my head,

Wayne

[spro]

Good advise above. Time turns oil exposed to sticky and the gibs were adjusted a certain way before. There is a channel in the gib for adjustment screw. The channel may be oversized (many are) so when the ways are sticky it pulls the gib to tighten.

[Heywood]

Just a quick follow up. Life got in the way but I finally got around to pulling the table apart. Spro hit the nail on the head, old sticky oil. A thorough cleaning of the the ways and gib and re-lubing with some Vactra solved my issue. Ahhh like new....

As an incentive to get me back out in the shop I added a y-axis power feed. Enco was kind enough to send a 30% w/ free shipping coupon code to my email. Who am I to say no to a good deal like that. It's noisier than I thought it would be and even disengaged the y-axis feels like it clicks tooth-by-tooth when turned manually. Can this be adjusted out? Of course being from China there was no documentation.

Spro, I sent you a pm. But I'll throw this out to the populace... I'm turning my attention to a power feed for the z-axis. I HATE that hand crank. What am I looking for in a motor? Is a servo the best option? I was planning on direct drive with a coupler. Ideally this will be controlled from a box mounted on the head having the controls of on/off, up/down and a rheostat for speed. Possibly driving this with an arduino board as a driver. I would prefer to power w/ 120vac. I was planning on converting to a ball screw as well. What am I getting into? Lol

Thanks for the help!
ETA: after some better research it looks like I'm looking for a DC gear drive motor controlled with a PWM. It looks like people are using this from eBay with good results. What rpm range should I be looking for, assuming 5mm/1 for ball screw.

[stevec]

Heywood, Here's a pic of my answer to cranking the head up and down by the "Armstrong" method.

The little gear motor is a Baldor GP 3001.
It's a 90 VDC perm. magnet gearmotor the output rpm is 173.
The drive sprocket is 24teeh and the driven (crank) sprocket is 60 teeth and it's just No. 25 roller chain.
The DC supply is just 110V through a full wave rectifier.

full wave rectifier.jpg (3.15 KiB) Viewed 3894 times

Switching is done via 2pole double throw momentary contact center off switch.
Has worked well for me for years (except when I forget to slack the Head locking bolts LOL).

[Heywood]

Thanks Steve!
Here's a link to a motor I found but they sure are proud of it. Maybe I need to adjust my price expectations? Seems expensive but then again I can be cheap . It's probably the easies to install tho'. Saw a few 130vdc motors as well but converting from 110/220vac to 130vdc seems more of a hassle and $$ Bodine seems to be the mfgr that I see most of on eBay.

[Mr Ron]

Here is an example of some 12VDC gear motors available from Surplus Center. They have some up to 1.5 HP.
http://www.surpluscenter.com/Electric-M ... 1667-I.axd

[mfletch]

I'm going to use a old wiper motor there already geared and cheap

[Heywood]

I'm going to use a old wiper motor there already geared and cheap

I saw that people were using those. I'm not sure it has enough "umph" to move a square column gear head up and down, probably fine for x-y axis if DOC isn't too much. The other issue I saw posted about those is that they aren't constant duty and may burn up quickly but if you have a cheap, stable supply it would be ok if they went south.

[stevec]

Heywood, I wouldn't hesitate to run a 130VDC motor on rectified 120V.
The reasons I didn't use a 12VDC motor such as a wiper or power window motor are, you'd have to have a step down transformer before the bridge rectifier, and some wiper motors may not lend themselves to reversing with a double pole center off switch (the body/mounting plate of the motor may be the neg. connection).

I've noticed you haven't indicated you general whereabouts in your profile, It's a good idea to do so, it can help responders if they have an idea where you are.

[Heywood]

Thanks Steve, I've updated my location.
So is this what I'm looking for to do the voltage conversion?

I took a look at the z-axis yesterday and it looks like I can do a direct drive to the existing lead screw. The end is 20mm. I'll need to machine off a small section to give the set screws a good purchase assuming thats how couplers work?

Ok, so are all dc motors reversible and variable speed? What sort of torque rating am I looking for, in# or ft#?

Thanks for all the help and patience with the 20 questions.

[stevec]

Thanks Steve, I've updated my location.
So is this what I'm looking for to do the voltage conversion?

I took a look at the z-axis yesterday and it looks like I can do a direct drive to the existing lead screw. The end is 20mm. I'll need to machine off a small section to give the set screws a good purchase assuming thats how couplers work?

Ok, so are all dc motors reversible and variable speed? What sort of torque rating am I looking for, in# or ft#?

Thanks for all the help and patience with the 20 questions.

Heywood, that Bodine motor control looks like overkill for your needs (and pocket book). You don't need variable speed control for your head lift.

I suspect direct drive of the leadscrew will require a slower speed gear motor than one to drive the hand crank shaft. But you can easily determine your leadscrew speed requirement by turning the crank by hand.

I'd venture to say all dc motors are reversible but a windshield wiper motor may be difficult to reverse the polarity because most I've come across are negative ground through their body (as mentioned before).

I have no way of knowing what sort of torque would be required for your machine, sorry.