PM727MXL Y Axis Linear Rail Install
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- čas přidán 7. 09. 2024
- PM727MXL Y Axis Linear Rail Install, In this video I start to install the HIWIN linear rails on the Y axis.
I have tried to be as detailed as possible to the point of being informative but not boring. Please feel free to ask questions and leave comments
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I think you may dread the day you bolt the machine base to the floor, because those mounts will need to be adjusted within the same tolerances. Just tightening the base down will probably bend, twist, and skew the rails more than .010". I appreciate your tenacity, as I too, am a perfectionist in most everything I do. If anybody could make it work, you could. I just want you to keep in mind that these machines do not have rigid bases, and are not flat, and can easily twist the entire machine just by tightening the base mounting bolts.
Yes I anticipate there will be some movement. The plan is to not bolt the machine down hopefully that will help prevent some of the movement. The tolerances will most likely move I just want to start as close as possible.
@@CNC4XR7 or epoxy shim the base with the stand so bolting won't ruin this amazing work of patience!
Easy fix is to backfill the casting with epoxy granite/resin. We use a blend at work that is stout after it hardens. Every bench mill I’ve built gets EG and I’ve never seen any flexing at all sitting on the base. Just be sure your base is leveled but remember it’s a mill and not a bed lathe where you can see the twist, etc.. also the pm727 has a cast iron base if I recall right? If so that should help quite a bit. For my last build I was machining to .0003 accuracy with a fairly slow feed rate. I expect this current build to meet the same specs with 200ipm feed rates, light cuts, and excessively high rapids. Definitely needs to be fastened to the floor :-)
Great idea the hole in the bolt.... Never cross my mind...
Yeah the Idea of a bushing was borrowed. The bolt was just easy to turn to size.
Love this vid! Thanks for the rundown!
So if all those parameters are dialled in under the max tolerances how accurate will the machine be? (Repeatability accuracy?)
Cheap cncs are approx 0.02mm
Decent quality is approx 0.01mm (10microns)
And precision machines (kern, etc) are under 0.005mm
The kerns with hydrostatic bearings and temperature control to prevent thermal expansion have 0.002 - 0.003mm repeatability (2 - 3 micron!!)
That's fkn crazy!!! Lol
I need to build one for making watch parts, I need at least 0.008 repeatability for watch parts that will be flawless.
It'd be great to know where your cheat sheet would put us at?
I suspect if you get on those numbers we'd be talking a very precise machine similar to the Haas quality if not better.
I'd love to hear some opinions!!
well if I ever get the machine finished I'll post the results. but this is a retrofitted machine not originally meant for CNC.
but hoping for pretty good results.
Don’t forget the granite table has errors so don’t worry too much about the odd reading but piece of advice, never shim a rail as that leaves a weak joint enabling the rail to move easily in the event of a machine bump/crash. Keep up the good work.
Yes this is true, I'm just trying to get as close as possible. without machining the mounting surfaces I have no choice but to shim. unfortunately there are drawbacks.
Thanks for the tip and comment
CNC4XR7 Hand scraping is the answer. I’ve over 45 years experience in building cnc machine tools with blisters to prove it 😩 😄👍
Yes
! something i'm terrified of doing.
@@CNC4XR7 glad I'm not the only one!
@@CNC4XR7 If you're putting shims in that are like 5 microns thick? couldn't you just run a stone or some abrasive over the highest spots, which it looks like are only a few cm in length based on your tape marks, and grind off a few microns to get the same leveling effect as you're doing with these shims? Seems like that would not take a huge amount of elbow grease since you're removing such a small amount of material and you can do it very slowly so as not to overshoot.
Excellent work, it seems very daunting to get to that precision level though. I'm not sure yet if I should attempt that mod on my machine.
Well in the end it can only be as good as you can get but the tighter tolerances should yield better results.
Find a buddy with an industrial cnc and you will get as perfect as you need regarding accuracy. I have both industrial and hobby machines and currently building a pm833 with linear rails. The column is probably most challenging and without proper tools or another machine of decent accuracy you would struggle to do a job well. For myself I can grab the forklift and load the castings onto a 4020 and simply machine them to tolerance then take a grinding stone to smooth any burrs or inconsistencies. You need to machine a reference stop or install pins for the rails to butt against and make sure you indicate everything as accurately as possible. I had to machine my column backside because the casting was lightly rounded in order to get it to lay flat without screwing around with shimming and time involved. About a week to do the column with proper equipment including installing servo brackets, etc... not my first time and the saddle usually takes me a few days and another 3-4 days to get it back together so factor about two weeks time as if it were a full time job or 120 man hours.
veru helpful for my upcoming project. Where did You purchuse those "datum" plate that You used?
I made it
the word is gone back
thanks
Love the work! Excited to see the finished product. One question on your method though. You are verifying that the two rails are the same height by comparing their top height to the top height of your surface plate. That certainly confirms that the rail is the same height from the bottom of the base casting, but how do you know that the bottom of the base is flat? If one side of the casting was 3 thou lower than the other, wouldn’t your method just offset the rails by that amount?
I suppose that would be a good assumption, The machine will be resting on the base and the rails need to be within specs. I found this to be the best way to ensure they stay this way. of course when I do put the mill in place I need to sit it on a surface that is also flat.
@@CNC4XR7 Would it be worth it to just use another (maybe used) surface plate for the machine base, to avoid the time and energy of re-doing any alignment issues?
Base should be irrelevant. As long as it’s flat and the point of rest is where you want the only concern is what’s above it. If you’re using a new casting or fresh mill tear down you have decent surfaces to start with. I’ve found that the precision Mathews castings are accurate to around .0005 to .001 (inches) and if you take your time and have good equipment you can make it better. My current build the specifications are near or exact to the industrial machine I’m machining it with. If you don’t do something to improve rigidity then that’s your weakest point. Best I could recommend is find an old machine to practice on so you can learn what you need to do so you’re not risking the beloved you eventually want to build.
Why you're not measuring the rails in relation to each other? Most machines have leveling feet to "level" the machine. Isn't it possible your rails were already flat in relation to each other to begin with and just not level with the surface plate? I guess it would be nice if they were both flat in relation to each other as well as the bottom of the machine...
The problem is now that you've leveled them (changed them) to the surface plate you might have to do a lot of extra adjusting on the Z axis.
Most people just put the indicator on 1 of the rail carriages and then slide it to measure the other rail.
Yes there are many different ways to go about it. I'm not sure my way will give the best results However Many who convert to Rails use Balls type blocks which have larger room for error on the Side to side and Height discrepancies. The RG series Roller Blocks do not. I wanted to make every effort to get then as close as possible.
The column regardless will need to be trammed in so i don't see that being a Issue. In the End you have to be satisfied with the process you use . So far I feel pretty good.
I didn’t see the rail reference edge? Did you machine into the surface? Or pin the rails so they don’t shift under load? It’s hard to hear I’m watching in the middle of a machine shop where it’s a bit noisy. My current build I went with HGR25HA for the table and saddle and hgr30 for the column. Using a 30mm screw for z and 25mm for the remainder. 2.6kw AC servo and brake for the column (no need for counterweight) and 750w ac servos for the remainder axis and 600w for the 4th axis of I don’t use my Haas 5c 4th axis instead. May have both option. I wish I had the longer pm727 base. The 833 is a smidgen shorter.
I used datums
what if the tool is applied to a conventional lathe, is it strong enough to withstand tool pressure?
yes
Whats the macmaster carr part number for this precision ground bars ?
www.mcmaster.com/9516K46