[ghostlx]

The X is rack and pinion, one on each side. So I can check all that.

also check your back lash that is what it appears to be if you are running mach3 I think you can compensate for it .
ghostlx

[Arbo]

I was trying to twist and force the mechanicals, and found that my gantry, spanning the two x rails, could be twisted. Must have worked itself loose. Loosened the bolts, clamped everything together tight, got it straight and retightened and it seems to be working.. Re surfacing the work top so I can put down a piece of corian and cut a litho to verify...

[Arbo]

Finished with the coroplast stuff. After the picture I caulked around the edges. Keeps chips up on the table, so cleanup is easier.

Main reason for this was the table is close to a wall, so getting back there to clean is a pain.

[Arbo]

For those using the cncrouterparts stuff, how often are you changing bearings and other bits? I thought I had got rid of the problem I was having, but noticed it creaping back.

So I had ordered new bearings, as well as an anti-backlash nut for my Y. Just got done ripping the machine down and replacing stuff, and getting it back together and lined up.

Had to replace the bearings on the bottom y carriage, as they were all pretty shot. Seems everything else was good. With new bearings and adjusted, the y moves much more smoothly. Also, the anti-backlash nut for the Y obviously had far too much play in it, I guess it just wears in time, or I have beat on it a bit hard. I would guess there was about 1/64 motion back and forth. New one on, very tight, no movement.

Just wondering how often others replace the little bits like that? I'd guess over the past month, the machine has been running at least 4 hours a day on average (some days none, some days 12 hours)...

Thanks
Paul

[Drools]

How many hours of use on the bearings? What type of usage, heavy cuts or easy stuff?
I'm using the cncrouterparts carriages but only light use in wood and plastic on a small 20x30 inch machine. I have not noticed any issues so far, but I sure would like to know what to expect from the carriages. The bearings Ahren uses are from VXB and are not very expensive. Maybe a better quality bearing would be a good idea?

[Arbo]

I'd have to estimate there is about 300 hours of run time on the machine so far. Mostly easy cutting... but when I first started with it I banged it around pretty hard while learning and getting things set right.

Using Ahren's bearings.. All the rest seemed to be in good shape, perhaps just the bottom Y carriage went first as it see's the bulk of dust and chips and such...

[ahren]

Hi all,

On rails that are in good condition (no chips or divots out of them) with a light to moderate preload, the carriages should last for miles of travel. I have a couple of customers using them in a production setting who have gone for over a year running 8 hours a day on one set of bearings.

There are two things these bearings don't deal that well with. One is severe overtightening -- if the carriages are difficult to roll, they are likely too tight, and continuing to push them in this state risks damaging them. The other issue is dust. I've seen some creative ideas adding paint brushes and leather flaps to machines.

I am trying to find a good way to integrate some sort of wiper into the carriages themselves, but collecting dust at the source is always the best policy. I'd also welcome forum member ideas on the best way to add a wiper to the design!

As to the quality of the bearings used, the bearings we use are ABEC 7 bearings, and are more than adequate for an equally abusive mechanical environment (roller blading). Really, keeping local stress-risers (like dust or dings in the rails) out from between the bearings and rails is important for any bearing, regardless of how much it costs.

Ahren
www.cncrouterparts.com

[ghostlx]

Hi all,

On rails that are in good condition (no chips or divots out of them) with a light to moderate preload, the carriages should last for miles of travel. I have a couple of customers using them in a production setting who have gone for over a year running 8 hours a day on one set of bearings.

There are two things these bearings don't deal that well with. One is severe overtightening -- if the carriages are difficult to roll, they are likely too tight, and continuing to push them in this state risks damaging them. The other issue is dust. I've seen some creative ideas adding paint brushes and leather flaps to machines.

I am trying to find a good way to integrate some sort of wiper into the carriages themselves, but collecting dust at the source is always the best policy. I'd also welcome forum member ideas on the best way to add a wiper to the design!

As to the quality of the bearings used, the bearings we use are ABEC 7 bearings, and are more than adequate for an equally abusive mechanical environment (roller blading). Really, keeping local stress-risers (like dust or dings in the rails) out from between the bearings and rails is important for any bearing, regardless of how much it costs.

Ahren
www.cncrouterparts.com

ahren
what do you mean by a light to moderate preload.will you explain more .
( I tightned up the bolt that goes thru the bearing untill snug ( colapsing the lock washer.) after mounting the skate to the machine and rail i then tightned the set screw lightly is this correct ) if not will you post the proper procedure I think it will help every one to know how to do this
thanks for your time
hh

[marzetti]

My experience with the bearings has been good. They are in good condition after approximately 200 hours of use. The anti-backlash nuts are another story though. My y-axis nut has about 0.01 backlash. The x and z are fine so I'm assuming the wear accumulated mostly on the y because I've done quite a few lithophanes with the major movement in the y axis. I'm thinking I may try to add another o-ring to tighten it up and perhaps I'll get a little more life out of it. Anyone have an opinion on that idea?

[Drools]

I will share my experience with the install of the carriages.
I tightened and locked down all except for the one with the set screw. For this one I left the set screw at the point where it just touched the bolt then I tightened the bolt and checked for movement. If I felt it was too tight/loose I loosened off the bolt and turned the set-screw out/in a 1/4 to 1/2 turn then tightened up the bolt again. I must have repeated this a half dozen times for each carriage (4). Once the axis was installed without the Lead-Screw I made sure it rolled freely before I went any further. I’m pretty sure that is what the instructions say to do.

[Dylwad]

I gave up on the O-rings on my AB nuts from the start, and use zip ties instead for the time being, until I go the Dumpstercnc route~which look fun to install to say the least.

My main problem with backlash now is the helical motor couplings, with the backlash out of the nuts, theres enough drag to slightly twist the couplers .002" or so, My next move is to CA some sheet rubber around the couplers, and wrap that in heat shrink, the other option is Disc type couplers, at $100+ a set.

BTW I found a neat cheap trick for keeping dust out of the slots in the 8020, 1/2" caulk backing rod from Lowes or HD slips right in, and looks good too, and MUCH cheaper than the covers from 8020.

[ahren]

All,

Sorry to be absent from this thread for a while. Things have been very busy. Drools, thanks for your post on the carriages! This is the correct procedure, and I'll move it to the FAQ on my site this weekend. The one thing I'll add is that for final adjustment, you probably want to be turning the set screw in 1/16 revolution increments to get things dialed in more easily.

Interesting discussion on backlash. Marzetti, are you certain the backlash is in your nut? 0.01" sounds like quite a bit, and to me either speaks to the axis being misaligned, causing excessive wear, or perhaps backlash from another source, like the thrust bearings being loose. If you like, I can send you another nut to see if the problem goes away -- they really should last much longer than 200 hours.

Dylwad, without the orings, you have effectively disabled the anti-backlash compensating mechanism. Our nuts and Dumpster's work on the same principle of compressing the threads in towards the minor diameter of the screw, and using the 29 degree threadform to "wedge" the threads of the nut so they are touching both the left and right adjoining threads on the screw. We do it with an O-ring, Dumpster has a sexier (but bulkier) mechanism with a spring and taper. You actually don't need a lot of force to accomplish this since the threadform is so close to square. However, you do need to keep tension radially inward, and allow some flex back out for local high spots on the screw, and a zip tie does not provide this. I would guess the backlash you are seeing is not from the helical coupler, but from your nut. I could be wrong though -- how are you checking this?

Ahren
www.cncrouterparts.com

[Arbo]

never heard of calk backing rod. I'll have to swing by the home depot and look for it. Far better than cleaning out all the stuff that builds up in there.

[Dylwad]

@ Ahren, the zip ties are used to get more clamping force on the threads, With the O-rings I was measuring .005" on the X and Y after a few weeks of use, and .010" of backlash on the Z, I tried beefier O-rings Which helped, except they started cracking in just a few days.

Not wanting to go through the trouble of removing the leadscrews again I used Zip ties, which take all of the lash out of the threads. I have no issues with lost steps with the extra drag, even at 500 IPM rapids. I check for lost steps using a G-27 command, which homes to Optical home switches, and tells me how far home was from the last 0 point. My home switches have many times the accuracy than the steps per inch on the machine. The zip ties are loose enough you can work them off of the nuts with the screws in place. The backlash almost disappears when I wrap tape around the helical couplers. (but the tape doesnt last very long) Before I could rack the axis' on the nuts by hand and see the lash in the indicator. you can see and hear .010" on the Z. There is no play in the leadscrews, they are under tension between AC bearings at both ends, except on the Z where both AC bearings are pre-loaded at the top of the screw.

I check backlash with a Mititoyo .001" dial indicator in a Noga magnetic base.

Your's and dumpsters/Kerks nuts use the same principle, but the main difference is the dumpster and Kerk nuts have much more thread area clamping the screws. I think that having a longer "collet" section and double or triple O-rings, as well as using silicone or similiar O-rings may help.

I'm not so much looking for 0 backlash, as this is an impossible feat, I want the same backlash regardless of wear on the nuts, I ran Dumpster's on our last machine, and after 5 years of 4+ hour a day cutting the backlash was the same as day 1~small enough to not need any compensation in software. We used modified (for 0 lash) lovejoy couplers.

When I have backlash comp set right, I get very good results, a 3" wide piece of .375" 6061 cut with a .25" 2 flute carbide, 40IPM and .02" Z steps, leaving .005" for a full deptch finish pass at 8 IPM leaves me with a part that measures 3.0005" measured with a mititoyo dial caliper. Circles however have spots on the quadrant points that software compensation just can't deal with.

@ Arbo, the caulk backing rod is in with the weatherstripping.

[Drools]

Dylwad, where did you source your ACME screws? I'm just wondering if the issue might be with the screws and not the nuts...
Just a thought.

[Dylwad]

Screws are from McMaster, the nuts were tight when new, screws are polished and straight. The 1/2-10 5 start screws from Mcmaster are much higher quality than the 1/2-8 2 start from MSC we used on the last machine with dumpster nuts.

[Drools]

I have been looking at the McMaster 5 start screws myself, the coated ones to be specific. Please let me know which nuts work best for you.

[Dylwad]

Mine are uncoated, I keep them lubed with silicone spray. the 6' rod was perfectly straight, the 3 footer needed very minor work to get it straight. the Z axis looks to be the exact same rod, but I purchased it from Fineline automation.

I have a Haydon Kerk leadscrew assembly coming for the Z, 1/2-10 single start, coated, with their A/B nut.

[Arbo]

Dylwad, thanks for the info on the caulk backing. Picked some up today. Works great.

[Arbo]

Finally managed to make a vacuum hold down (that works) ... I've been cutting a lot of balsa, and was using 3M-77 spray glue (a light mist) to hold down the parts. But that always seem to be problematic. So I did a quick draw up and cut some MDF. Need to make a fixture to hook my dust collector to it (It seems getting a 4" to bigger adapter and cutting the bigger part off will work).

Can not slide the wood by hand without smashing it when it's on.