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Messages - Stonemull

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1
Mini CNC / Re: Waiting for my mill
« on: February 25, 2019, 07:57:09 AM »
Is worth printing a 20mm calibration cube. Mine comes in within 0.1mm. x and Y more acccurate than Z due to a little squish onto the bed, could probably more accurately get the bed height spot on and increase first layer extrusion to compensate, instead I tend to run less clearance.

Have added these rails to my cart currently as half the price of the sbr12 or regular 12mm rail and I have seen them used in much larger mills.
The 12H version of the bearings has some pretty good torque specs it appears.

Look what I found on AliExpress
http://s.aliexpress.com/JzEbyM7F


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2
Mini CNC / Re: Waiting for my mill
« on: February 25, 2019, 06:46:50 AM »
i had a quick look. you might have printed the different parts on a different axis on your printer ?
not all printers have the steps correct even, mine came with a default of 81 steps/mm on X and Y, which is wrong and I changed to 80. (3200 steps per rev/ 1 rev  = 40mm, 3200/40 = 80)

I forgot to mention a couple of things earlier, firstly I printed 19.00mm holes for the the 19.00mm bushes despite knowing it would be too tight as I noticed the latest cura has a new option under "shell" called "horizontal expansion" .. you can apply an increase/decrease in size to all polygons on a sliced layer. if set to +.1mm then a 3mm hole will print at 2.9 (or 2.8?), so its the opposite polarity to what i would expect.
The other thing is that PLA shrinks by around .3% after printing, so in theory a 19mm hole should be modelled at 19.057mm (19 * 1.003) ABS is double that at around 0.6%.
A vertical hole is smaller again unless settings are spot on as the the extruder pulls the molten material into the hole while doing a lap, single degrees in temperature can make a difference here. So yeh, I should have printed at 19.1mm probably, I had intended to try the shell offset but totally forgot about it.





3
Mini CNC / Re: Waiting for my mill
« on: February 24, 2019, 08:43:03 PM »
Thats why on the one I designed I have holes for optional locking bolts for the bearings and the fixed bush.

I need to redesign the damn one I printed,  I measured the distance between the holes on the aluminium bracket I got with my motor and made sure the 8mm rods on the Z would fit inside them if I used through bolts .. except I forgot about the 16mm bearings. so my bolts impinge on the bearing space.

this has made me look into buying SBR10 or SBR12 rod for the x and maybe upgrade the small Z distance with a longer version, except I am trying to find data on the graphite bearings instead of the usual linear bearings.

picture is with the supplied aluminium bracket, the bolt holes from that hit the larger hole for the z linear bearing though (looking at making that brown piece currently, the green piece I already have)




4
Laser Parts / Re: tapped rails for sale and rotary setup?
« on: February 24, 2019, 07:51:27 AM »
Maybe try a metal scraper and open up the slot a little bit, or a file, only need to open it up a small part of a mm each side.
I have a little hole scraper deburrer that would make short work of it. Like the first one in this video, also used on the straight edge portion. You can get them from Banggood or Aliexpress for a couple of bucks though I think I got mine from a local auto shop.


https://youtu.be/1HISXiKvmgE



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5
Mini CNC / Re: Waiting for my mill
« on: February 24, 2019, 07:35:46 AM »
I just used a punch and pushed it all the way through the block, there is a lip stopping it for about  2mm the 'short' direction.

To insert I used the threaded rod to make sure it went in straight, just gently tapped it in.



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6
Mini CNC / Waiting for my mill
« on: February 19, 2019, 11:25:41 PM »
I was going to suggest a few posts back that optical isolation would be a good thing and possibly necessary, these controllers rectify the mains so there is no mains isolation to the actual motor, there is a small transformer in the control section but I don't believe it is a mains isolation transformer, I am yet to fully check it out but I was intending to make a spindle controller using an optical mosfet (I forget the part number but I have a few).
I wrote a review up somewhere here with some internal photos.

Edit: found it, looks like I decided it was isolated and opto coupled,

Spindle motor arrived .. now to assemble a machine around it
 https://r.tapatalk.com/shareLink?share_fid=2012650&share_tid=2842&url=http%3A%2F%2Fwww%2EBenboxLaser%2Eus%2Findex%2Ephp%3Ftopic%3D2842&share_type=t

I will double check my findings but if that is the case then a couple of resistors is likely all that is needed.


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7
Mini CNC / Waiting for my mill
« on: February 19, 2019, 07:05:39 AM »
Made it from scratch, it's pretty basic really, I will stick it up on thingiverse when its been finished and tested.
Sucks that I end up with the prototype, find the annoying little bugs, improve the model and publish it and everyone gets a better version than me cause I don't bother reprinting it, not at 12 hour print time Lol.
Its a little tight around the spring for the antilash bush and I forgot to add some extra top bracing around the stepper to stop flex there, 2 of the bushes in my original one were moving in the holes to, so I added bolt holes to pin them in place but mine are so damn tight they aren't going anywhere, bushes were 19mm so I modelled 19mm holes. I reckon 50-100kg to push them in place, was expecting the carriage to explode and split the layers but it didn't.



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8
Mini CNC / Re: Waiting for my mill
« on: February 19, 2019, 05:44:00 AM »
Redesigned the carriage, 12 hour print at 4 layers and 70% infill, old one weighs 126g and mine weighs 196g, less flex. Everything fits but it's freaking tight, had to push the bushes in with a vice, the first one I hammered in and released one bearing.
I can bolt bits onto the rear of this one when I decide what I need.

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9
Mini CNC / Re: Waiting for my mill
« on: February 18, 2019, 08:30:22 AM »
cause thats no fun ?
Like I said and like you, I have no real reason for one currently, but I like improving and modifying things and 3D modelling and stuff, plus its not far off being able to do aluminium I don't think, so curious to see if I can improve it. its a hobby :)

I pulled the carriage of mine apart tonight and modelled up a new carriage for the larger spindle motor.
Uses the X rods a bit further apart and I add 8 x 5mm mounting screws on the rear so I can play with added bearings.
It also places the Z rods further apart and the bushes on the x rods have more distance between them.

About to start a thin low density print to see if it works ok.

10
Mini CNC / Re: Waiting for my mill
« on: February 18, 2019, 02:53:02 AM »
ok link works on PC, yeh those rails would be a good upgrade, I would still be tempted to got the 12mm version still.
I found a 2x400mm length of 12mm linear with bearings and end supports for $42 AUD delivered, I think from czech republic, same from china is $62.


found this spindle upgrade for the 52mm diameter motor, just measured my 500W motor and its 52mm.

https://www.thingiverse.com/thing:2719169

I might do some further mods to the carriage, I was thinking if the rods were further apart then less twisting moment and flex, only about 20mm easy movement though without major mods.
secondly, perhaps a carriage upgrade to run bearings from the moving part to the X braces.


11
Mini CNC / Re: Waiting for my mill
« on: February 17, 2019, 09:44:50 PM »
Link doesn't work for me, just takes me to front page of Banggood after a redirect somewhere. You will have zero issues with balsa and foam imo, even aluminium is sort of doable with sharp tools and enough care, it's just a long way from ideal.

A mate bought a larger mill to batch cut out slots in plastic boxes (manufacture), one of these
http://s.aliexpress.com/ma2qYj2a

He has not really used it yet, comes with Mach 3 and uses a usb-centronics port, but I had to pick some hardware up from him today so I went a tested it's flex like I did mine, much better, it uses 12mm rails for the X and there might be 0.5mm if that, the bed itself rides on 4 12mm rails. The sides look like marine ply but closer inspection it is like a nylon and had been cut at about 7 depths, looks just like ply layers.
So I am thinking I might get 4 400mm lengths of 12mm linear real and perhaps upgrade it to use both the 10 and 12mm rails, I reckon.. Or just leave this one for wood, not decided yet, I just like buying/making tools, I rarely use them Lol.



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12
Mini CNC / Re: Waiting for my mill
« on: February 15, 2019, 09:23:25 PM »
If it's the same build as my 3018 don't expect to do aluminium, climb milling is no chance as flex in the tower will allow the tool to pull into the work, conventional milling is the only choice but tool chatter is substantial.

https://www.harveyperformance.com/in-the-loupe/conventional-vs-climb-milling/

Is not actually flex in the frame that is the main issue, I added a 1/2 thick mdf base around mine to capture dross and improve rigidity and reduce noise, it's the twisting torque on the tool twists and bends the x axis rails allows 3 or 4 mm of tool movement. Been considering a 12mm rail upgrade but I figure the same would need to be done on the y as well.. Then again there is zero movement there in comparison despite being longer and the same 10mm so why is it more rigid?
Good question I will have to think about..

Here's a quick vid I just did.

https://youtu.be/Ixc6rcPByog




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13
General Discussion / Maple veneer & leather etching
« on: February 14, 2019, 08:23:25 AM »
I did some test burns on leather including wetting it a few months back, I did it for the purpose of seeing if it made any difference to the mark made but since then I have been wondering a few other things I am yet to check, firstly if you burn leather hard it stains the area surrounding the burn with smoke, secondly, it stinks.
I will have to try it again and check both of the above.
I was also wondering if coating the leather with beeswax before a burn would make a difference.

I also have a leather post on here (projects?) that could go into a new section.


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14
General Discussion / ESP32
« on: February 14, 2019, 08:13:48 AM »
Grbl has a queue but some commands like jogging and I would assume stops are acted upon immediately.
Not looked at how is done code wise off sd card, I run off sd card on my plasma cutter but I installed a mill/laser version of marlin on that  I expect is much the same, it knows gcode data is coming from sd but it also listening on a serial port for immediate commands as well as monitoring ports for things like end stops, safety covers or jog buttons.



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15
Mini CNC / Re: Waiting for my mill
« on: February 14, 2019, 08:05:42 AM »
I have that one I think, yet to actually fit it to my mill as I am not happy with the chassis strength as it stands so I wanted to toughen it up first.

https://youtu.be/lMeD_B1UVCM

One warning, treat the wires to the motor as if they are live mains, it runs rectified mains to one side of the motor, so capable of killing you.



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