[Mmpie]

If you're getting those numbers and you're sure you're zeroed correctly then it looks like yeah, you need to calibrate the motors. Fortunately it's pretty easy to do, just time consuming. More likely to be caused by nonlinearity in the leadscrew.

Also bear in mind that the bed is quite flexible without reinforcement so you may be getting the tool pulling the job up into it.

Good point hadn't thought of that. I was climb milling pine on top of a chipboard spoilboard, although the part was clamped hard to the bed through a slot in the board.

Another thing I should have mentioned was I measured a few different Z moves with the DTI, there was absolutely no consistency. Sometimes a 1mm downwards move would be 0.93, next 0.87, then 0.96. Same in both directions. It's a well cared for genuine mitutoyo DTI justbto rule the tool out.

[cincron]

I slowed my referencing (zeroing) down to half of what it came with. Seems to be more repeatable from day to day. I've been using a vise with the same work coordinate. It appears to be the same everyday now that I slowed it down.


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[dharmic]

I seriously don't expect much more than 0.5mm repeatability out of these things, they are after all a cheap router not a big solid mill. For most of what I do that's plenty, so it doesn't bother me. I'm loathe to actually dial mine out in case I get to see how bad it is, become sad, and then start down the road of three phase to the shed and buying a bigger mill which I simply cannot justify for hobby work

Still, if that's the variance you're getting on repeats in the same X and Y position and spindle orientation (assuming you've chucked in the Mito) then it sounds like something's a bit sloppy. Be interested to hear where it's coming from.

[Mmpie]

I seriously don't expect much more than 0.5mm repeatability out of these things, they are after all a cheap router not a big solid mill. For most of what I do that's plenty, so it doesn't bother me. I'm loathe to actually dial mine out in case I get to see how bad it is, become sad, and then start down the road of three phase to the shed and buying a bigger mill which I simply cannot justify for hobby work

Still, if that's the variance you're getting on repeats in the same X and Y position and spindle orientation (assuming you've chucked in the Mito) then it sounds like something's a bit sloppy. Be interested to hear where it's coming from.

I had wondered. I had expected more to be honest, maybe not out the box, but my 3D printer is absolutely bang on and true to form - 10mm moves 10mm. That's on an ACME or trapezoidal screw as well.

[Mmpie]

I slowed my referencing (zeroing) down to half of what it came with. Seems to be more repeatable from day to day. I've been using a vise with the same work coordinate. It appears to be the same everyday now that I slowed it down.


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My vice has been on the drill since the day it arrived. Anything I've made would need flipping in a vice and I don't know where to start with that yet. Good tip on slowing the Z down though, I will try slow the Z down for everything and see if it helps.

[cincron]

My vice has been on the drill since the day it arrived. Anything I've made would need flipping in a vice and I don't know where to start with that yet. Good tip on slowing the Z down though, I will try slow the Z down for everything and see if it helps.

If you flip your part in the vice and use the same X and Y coordinate, you'd just have to set Z. Of course this all depends on what you're making.


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[RCaffin]

start down the road of three phase to the shed and buying a bigger mill

m o r e p o w e r , m o r e p o w e r

Cheers
Roger

[Mmpie]

Just a thought, has anyone tried filling the hollow channels in the bed with concrete/sand/resin?

[Mmpie]

If you flip your part in the vice and use the same X and Y coordinate, you'd just have to set Z. Of course this all depends on what you're making.


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The trouble is making sure you have put the part back in the vice at the correct X and Y.

It looks quite complicated and a bit of an acquired art to get right. An edge finder would help a lot but would be time consuming.

[dharmic]

Just a thought, has anyone tried filling the hollow channels in the bed with concrete/sand/resin?

Not sure I'd go that extreme. Someone back in this thread has removed the table, braced it with angle iron and replaced it. Happy.

[Mmpie]

It would be quite quick, easy and cheap to do. As the bed is made up of four hollow extrusions and the channels are where each extrusion meets the next, i think it would probably help turn those four separate pieces into one solid table and eliminate any flex at the join. I saw the bracing idea too, it's a good one. Will probably end up doing it myself too.


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[Mmpie]

You all must be fed up of hearing from me now and my questions

Sorry there's another one.

How are you tramming and keeping the spindle straight effectively without it just moving? My spindle mount has a lot of play for the spindle to move around inside but not much potential to align the mount against the z plate as the bolt holes are very close fitting. I noticed today my tramming was no longer straight parallel to the X and when I measured it it wasn't far off 1mm out over a 70mm swing. The only way to get any meaningful adjustment more than a few hundredths of a mm is by having the spindle slightly lopsided in the mount, but it's so easy to knock straight back out, even cranking on the collet nut to change a tool knocks it out of alignment. I dread to think what's happening when it's actually making a cut.

Front to back is fine as that's shimmed with precision tin foil.

Dharmic I remember you posting about moving the spindle up and down in its mount a lot, do you have to realign it every time?

[extent]

if you can slip the spindle off axis in the mount with it all tightened down you must have a bad mount. For x alignment you need to twist the mount, and it's bolt pattern may get in the way of that. I took it off and filed the holes that were getting in the way wider in the direction I needed to twist until I could move it enough to get it tram, trying for maybe a thou or two over about 150mm at worst, which was much better than the maybe 15-20 thou it was off originally. Also try using the mount upsidown, I was able to get closer to tram to start by flipping it and then had to shim much less.

[Mmpie]

if you can slip the spindle off axis in the mount with it all tightened down you must have a bad mount. For x alignment you need to twist the mount, and it's bolt pattern may get in the way of that. I took it off and filed the holes that were getting in the way wider in the direction I needed to twist until I could move it enough to get it tram, trying for maybe a thou or two over about 150mm at worst, which was much better than the maybe 15-20 thou it was off originally. Also try using the mount upsidown, I was able to get closer to tram to start by flipping it and then had to shim much less.

I think the flex is probably in the mount itself although as I mentioned I can get the spindle in slightly lopsided. I took the mount off and drilled all the holes out to 8.5mm today which has given me the ability to tram X properly. I only have a 70mm diameter circle (so 35mm radius) around the centre of the spindle to tram on, I've got nothing lying around to make a strong longer bracket out of so just 3D printed an attachment for now. I'm now .01mm in each axis, let's see how long it lasts.

I think a brace for the spindle/mount would be a very worthwhile addition to these machines as it doesn't take a great deal of force to see movement.

My original Y tram wasn't so bad at all, 1 piece of tin foil in the bottom got it as good as I can with my current readings. A second piece takes it .01mm out the other way. It's good enough to give me a nice smooth flat feeling finish on top of wood.


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[dharmic]

You all must be fed up of hearing from me now and my questions

Sorry there's another one.

How are you tramming and keeping the spindle straight effectively without it just moving? My spindle mount has a lot of play for the spindle to move around inside but not much potential to align the mount against the z plate as the bolt holes are very close fitting. I noticed today my tramming was no longer straight parallel to the X and when I measured it it wasn't far off 1mm out over a 70mm swing. The only way to get any meaningful adjustment more than a few hundredths of a mm is by having the spindle slightly lopsided in the mount, but it's so easy to knock straight back out, even cranking on the collet nut to change a tool knocks it out of alignment. I dread to think what's happening when it's actually making a cut.

Front to back is fine as that's shimmed with precision tin foil.

Dharmic I remember you posting about moving the spindle up and down in its mount a lot, do you have to realign it every time?

To be very clear: I've just used the thing. I've not measured how level the bed is beyond an initial couple of tests where I found the bed flex rendered any attempts to get anything else square pretty much useless. At that point I stopped dicking with it and just used it because I know I was just going to get sad if I kept going. My vice is crap and won't hold anything particularly square. My requirements aren't for any huge precision. The stuff I'm doing with it is generally pretty small so variances across the part don't stack up much and I use small (usually max 12mm for facing, 6 / 4 / 3 / 2 for milling) cutters so tramming errors don't make a big difference.

If I'm cutting through I make my tabs about 0.75mm thick and I set up to go past the bottom of the part by about 0.5-1.0mm - I have a lot of pretty patterns on scrap pieces for spoilboards.

It's getting my job done. If I need to do something precise where the errors in the unit cause problems, well, I'll have to look at options. Tidying up the machine, maybe. Or getting a baby mill. Or, if it's just one piece, talking to the guys at work about running it on their Haas EC1600 or one of their Bridgeport machines.

[Mmpie]

Ok, I get that. I got this machine for occasional modification of aluminium parts (make new or modify existing bolt holes, shave off a few mm off a side etc) the very odd one off aluminium part, cutting foam inserts for equipment boxes (big one, huge money saver), cutting mould positives to take silicone molds from, maybe dick about engraving graphics into wood etc and the usual stuff a machine like this will come in handy for. But above all else it's a decent starting point for learning about CNC and different materials.

For the aluminium tight dimensional tolerance isn't particularly important but a decent smooth finish is. The mold positives obviously need some tight tolerances but they will be cut out of some sort of soft material, not sure what yet. I don't think any of these are unreasonable expectations for the X6.

Still not a word from Omio CNC, I've sent two emails to grace and contactus... I know they're had Chinese New Year but should have been back at work for a week now. They replied instantly when they were keen to take my money, now they've got it...

The problem seems to be getting worse with use as well. I've stopped using it now til I figure out what's causing the jamming and get it fixed.


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[zeeflyboy]

You can really forget tramming in the x-axis - its not going to happen with any precision.

If surface finish is important I'd suggest building a tramming plate to sit between the spindle mount and mount plate... fairly easy to do - just one corner with a shoulder bolt as your fixed pivot, and then an eccentric bushing on the other side. Few more bolt holes with a bit of wiggle room to then clamp the plate in place once trammed.

It would also be worth then looking at replacing the extruded spindle mount with something machined from a solid block - that'll give more reliable spindle position.

Be sure to calibrate your steps per unit too if you are after accuracy. Mine was way further out than even c7 ball screws spec should allow.

I'm currently designing a new CNC machine for myself, you can see how you could adapt the tramming plate I've designed for it on to the X6 easily enough (the only problem is the spindle would move even further forward of the gantry). You can take a look at the design here http://www.cnczone.com/forums/diy-cn...28752-cnc.html


re Chinese new year, a lot of companies are only getting back this week - I imagine they have a huge backlog of emails too. Generally they are quite good at responding so I would consider either just waiting a bit longer before sending another email.

If it's got to the point that you have stopped using the machine, perhaps try removing the gantry and loosening the bolts to see if the rails then become smooth. It could perhaps be an alignment issue?

[Mmpie]

Bloody flaming Nora Zee that's some machine you're building, wouldn't like to imagine the cost. Can you pinch much stuff such as the rails, ball screws etc off your x6?

Yes I came to that conclusion myself. I've seen a few ideas such as yours, I'm just having a think about it for the time being, I'm only farting about cutting random things out of wood whilst I get a grip on it all (or was til my machine started jamming constantly even at lower speeds) so it's not a priority for now.

I actually thought about making a height adjustable bracket to support the bottom of the spindle, that way the forces would be countered closer to the source and prevent the spindle acting as a lever to produce a lot more force higher up at the mount.

I did however trace the tabs getting cut to the tramming working it's way awfully out, the cutter was catching under the part on the final cut through and lifting the whole lot up with the retract.


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[zeeflyboy]

No it'll have to be all new as the travel is longer (395mm in X, 750mm in Y and 165mm in Z), I'll probably put the X6 back to stock and then sell it to re-coup some costs.

Sorry if I missed it but I assume you've machined a level spoil board for you to work from? The bed is massively out of level on mine, and that would show some of the same symptoms as ****ty tramming.

[Mmpie]

No it'll have to be all new as the travel is longer (395mm in X, 750mm in Y and 165mm in Z), I'll probably put the X6 back to stock and then sell it to re-coup some costs.

Sorry if I missed it but I assume you've machined a level spoil board for you to work from? The bed is massively out of level on mine, and that would show some of the same symptoms as ****ty tramming.

Yes was the first thing I did. Cut some out, tram the head, then cut again for a nice smooth surface. Cut slots in it too so I could still use the t slots, don't fancy clamping to a piece of wood.


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