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Discussion in 'CNC Mills/Routers' started by HuguesP, Apr 27, 2018.
Yet Another Chinese Linear Rail CNC, my first one, doing this mainly for the fun of building it more than using it.
HuguesP published a new build:
Read more about this build...
Since I am new the the world of CNC, I have a lot of questions that come to my mind.
- Can a limit switch be used as homing switch. I dont understand the requirement for both. Unless you really require some drastic precision over the homing position.
- if you see any major flaws in the design, please raise a flag.
- I f someone have experience with the RNR controller using a digital jog handler, please help me i cannot configure my jog handler to work properly.
"doing this mainly for the fun of building it more than using it"
once it works...believe me, U want to use it (learn to use it)
i'm also new, (using 3 limit switches)
Yes you can use the limit switch as homing , but it depends on the software u use i think.
haha, thanks for the info, ill be using mach3
Excellent your design, congratulations! Do you plan to share the entire project? (The shared Fusion file is just an image)
yes the goal was to share the model, i did not took the time to verify everything was right at the time but i will change this as soon as i can
I just change the Fusion link, you shall have access to the 360 file. please remember, 95% finished, it is still a work in progress
Just updated the build log, also uploaded a video of my carriers not working very well ( issue with carriers.mp4), i feel the rails are problematic, because if I switch the carriers on the small rails, the seem to all work relatively OK. if someone have an idea on how to improve the smoothness of the carriers over the rails, please tell me what to do because as it is by now, i am really disappointed of those china made linear rails and i believe this is so bad, it can even prevent the build from being usable.
here is the video also available in the build log
Have you tried cleaning them and re-oiling them? The come with a lot of garbage from packaging and shipping. But they are also hit and miss on quality....
I have tried brake cleaner and re-oil them, i think i did more bad than good, i should get my hand on a grease gun, it might help!
Hey Hugues I told you I bought used THK linear rails & carriages but a couple of the carriages had a sticking sensation with rough movement. I think the main culprit is the ball bearings inside. This is of course if you inspected the rail itself for scratches. You can disassemble the carriages (one at a time, don't mix balls from different carriages) and soak all the METAL parts in mineral spirits. Wipe down the end caps with a non corrosive cleaner like WD40. Reassemble the carriage by installing one end cap, filling the balls and when you fit all you can, fill the remaining end cap and squish some grease in the ball tracks of the cap to keep the balls in while you flip it over to install it.
While you have it apart for cleaning, take your clean ball bearings and inspect them for flat spots.
Also, how is your enclosure coming along? I am very sorry to hear about your PSU and motherboard.
Make sure if you do disassemble them that you do only one at a time and over some sort of tray to catch any runaway balls. You may even be able to measure the diameter of the balls with a micrometer and source some replacements.
Yeah after watching the video, I think you need to take them apart. Please no more brake clean because this will damage the soft wipers and plastic parts. It sounds to me like you have either junk in the carraige or you have balls with flats.
Thanks for your help Michael. It is really strange because i have tested all the carriers with different rails and at some point I had a rail where all my carriers would slide relatively well. but I also feel more play on this rail. Chinese rails may not not have the same quality control / tolerances than those Hiwin or Misumi. Some rail might be tighter and therefore all the junk /flat spots are more perceivable. The way you said it, it doesn't seem much complicated to do a complete clean.I might do this in a near future.
Before that, I ll wait for my enclosure to be made, will assemble / wire all the electronic, hopefully the cnc will fire up. I will do some pen testing and might even do some machining testing. ( For this I will need to educate myself a little because I have no knowledge about the type of bits / feed rate / DOC / etc. if someone one have a good cheat-sheet for that, point me out.
Then I will take it apart to clean the carriers. this way if something else need to be serviced/modified, i will be able to do it at the same time.
The ebay seller i bought mine from ended up sending me two replacement carriages free of charge so if you figure out what is wrong I would at least try contacting the seller. You've got nothing to loose at this point. Maybe they will send you replacement balls? It's worth a shot!
i don’t have much time right now, but i can say that today we reached a goal, making our first cut without issue. after breaking a 20$ carbide bit and at least 5 limit switches, the last engraving went no issue!
Well done on this design. I have 3 linear Ball screws and a few linear rails, some C Beam... I guess most of the stuff to build this. What size linear MGN rails did you use?
What did it cost on plates to be cut?
Another question, but how will you face your spoil boar exactly? It doesn't look like your spindle gets to all the sides and front and back.
Thank you CMW,
my rail are H20 ( 20mm) all axis , not MGN, much stronger.
I had to outsource the plate, they are 3/8 for axis and feets are 1/4, 6061. it cost me 800$ CAD for all the plates. but this is a rob. all my plates are made to be cut into 8" wide plate. I Just bought 2 plates of 33" x 8.25" , 1/2" thick plates, it cost me 100$ CAD. or course you have to machine them yourself, but since you have a C beam...
For the spoilboard, i milled only the portion it can reach. it is actually not a problem because I cut my blank so they fit in the space. Next time, i will use the router manually and mill down, 6mm-8mm of the portion that can not be reached by the router when it is on the CNC. the spoil board is 25mm thick, so it should not be an issue.
you can see that my spoilboard is way down on the right side, after investigation, I found out that the linear rail on the gantry, ( x axis) are slope down to the right. I will have to realign them.
I still have a lot to learn about all this. i have failed many tries.
hopefully i will figure this out.
Those aluminum chips look good but you're definitely taking too deep of cuts. Something isn't right though because of the rolled edge the end mill is creating. I would try a more shallow depth of cut combined with a higher speed. The max depth of cut I intentionally took with my Sphinx was .5mm. I did take deeper cuts when using adaptive clearing but I wouldn't worry about that method just yet. The type of end mill I would us is a 2 flute un-coated carbide end mill with .5" flute length and just start with .2mm DOC, 500mm/min feed rate and just adjust up from there. Also, make sure to spray a little WD40 on the aluminum to prevent chip build up.
What size power supplies are those you're using? I read your post about 24v & 36v psu. My Sphinx only used a single 24v psu for controller AND steppers! Well, that's the lower end of the spectrun so I bought 2 x 36v psu's for my new machine. I figure each 36v psu can supply two drivers. The drivers do have a range of 24-48v but I read that it's risky to run this type of driver a top of voltage range.
1x XKTTSUEERCRR 24V 15A 360W Switching Power Supply Driver Converter Adapter
2x LETOUR 36V Power Supply 9.7A 350W AC 110V/220V Converter DC 36Volt 9.7Amp 350Watt Adapter Aluminum Shell LED Power Supply
both from amazon.ca,
they usually supply under voltage under load. 28-30 volts. 1 power supply for the dual Y axis and 1 power supply for the X and Z. I didn't have any issue yet, but on the long run they can tun hot. i would not use 1 for all. What I have read is that it is best to run your steppers at the maximum voltage the controller is allowing you to performance wise. IF I could i would have used the 48 volts power supply, but it was not available. I believe that using the cheap TB6xxx stepper driver might be an issue but the 542 at 36 is perfectly fine if everything is perfectly grounded. No issue yet.