Kiwi junk-box mini router...


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  1. #1
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    Default Kiwi junk-box mini router...

    OK....

    Only been on the site a wee while, but it would seem like a good idea to share my journey.

    Basically been dithering for aobut 5 years on making a router, never got around to it as I kept on designing things too complex to actually build at home. I got keen again about three weeks ago, did some googling, found the rockcliff design, which lead to this site.

    I've studied lots of photos, and a couple of the free plans, and decided if I studied too many more I'd never get started, and in five years time I'd still be collecting parts and dreaming of cutting bits of balsa wood.

    I'm a bit short to buy bits, but really wanted to get something going, so this is what I'm doing with stuff from the garage. (I collected lots of stuff over the last few years, so I've got a lot of bits in my garage!) It'll be too small for most of what I'd like to do, but I'm sure I'll learn lots along the way.

    The first pic is six of the ground shaft/bush pairs I've collected from old printers etc. Selected at random because I had pairs of them the same length/diameter with bushes. Yes the bushes should be longer for this type of use, I'm over it.

    Measuring those led to the second pic, which I drew up in qcad. Appologies for the metric measurements for those who don't live in france. Total travel going to be about 230x180x60 or there abouts. Going to swing my trusty old dremel tool on it, see if I can blow the bottom bearing out.

    Pic 3, the garage/workshop. after making one long cut I discovered that my skill saw blade has a wobble, so all of my cutting after that is/will be done with the drop saw, it's dead square, and makes a good tidy cut. The pile of recycled hardwood on the bench is a coffee table I should have been making for the wife. If anyone is talking to her, that's what the noise from the garage was last night, OK? Anyway, the basic frame parts are taking shape in front. All 18mm MDF unless otherwise noted on my un-dimensioned plan. I'll add dimensions as I need em. I have a 1:5 copy of the bench for reference, and I rounded all the measurements to 5mm increments to make it easy...

    Pic4, rod support bracket thingit, 1 of 4 for the base. Did them this way so I can retro-fit larger rod when I get some. The X rod (This is going to be X) is only 8mm, but with the short 230mm span it should be OK for light cuts. We'll see. block idea courtesy of this site (joes & jgro & others).

    Pic6, the only critical bit of the X axis, getting them vaguely parallel. I clamped, measured, re-clamped, measured and then cyno'd the edges of the 9mm MDF. Then I glued the bushes with a little cyno, super-screwed the 9mm down, and super screwed a wedge against each bush. The wedges can come out to put bigger bushes in at a later date. Got this right first time, it's as close as I can measure with my trusty steel rule to parallel.

    Pic 7, tada! 3 hours later and I've got an X. (an unknown value). Blocks screwed and glued with PVA, ends screwed & glued the same. The whole thing slides quite well, and is reasonably rigid. I've got some 'U' Channel aluminium I'll add to the base later to keep it all square and solid, and to provide a better mount for the gantry.

    last pic. Skip to the other shed (less dust, more electronics), and it's alive!

    I put a blacklash nut (not anti-backlash!) made of a bit of cutting board offcut screwed between two lumps of MDF on the bottom of the table, and mounted a stepper on the end.

    The stepper mount needs work, as I only had two M3 machine screws that fit the job, and my rod coupler is currently masking tape, leading to interesting amounts of whip and funny noises from the M6/1.0 threaded rod.

    I can get a reliable 720mm/m (28ipm) out of it, with a reasonable level of push left for cutting (Finger preasure push/pull test) stepper stalls jogging at around 900mm/m(35ipm). Steppers are old printer ones rated at 3A/1.8V driven by a knocked up L/R half stepping unipolar driver at about 2.5A from a 12V supply. (Yes, the resistors are running hot!)

    Software is EMC installed of the live Ubuntu build, on a junker celeron PC. Also tried it with turbocnc, which seems to 'glitch' while stepping a little on this PC, although it runs fine on an old laptop I have. Weird.

    Proper leadscrew coupling, a better nut and better drive should get me 1m/m (40ipm) or better. Looks promising so far.

    Total new bits purchased so far: small container of M6/30 machine screws and nuts for the rod supports ("gutter bolts"), and an M6 tap, as I couldn't find one in my box-o-taps, although I'm sure I have one somewhere, now I've got two!

    There'll be a bit of gap before I get anything more done, as I have a busy week ahead, next installment will be next sunday probably.

    Thanks to this site for the bit of inspiration that got me off my chuff after so long.

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  2. #2
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    Interesting , keep up the flow of pictures , Along the lines I was considering before I decided to cnc my existing mill/drill ( Still in the "gunna" stage :-( )



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    Default Good Job!

    I actually have 22 old printers now that my son gets $5us for each one he disassembles and sticks all the parts into a bag (one for each printer) and 2 copiers to do also.

    I am encouraged by the bushing solution more now for the small ones.

    Keep up the pics and let me see if I can match your build (although I may stick to HDPE instead)

    Coog

    Building Stage:[xxxxxxxxxxxxxxxxxxxx] 105%
    Finishing Stage:[xxxxxxxxxxxxxxxxxxx-] 95%


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    Default Looks Good

    I would like to know if you made your own driver or board and what about the power supply.I am geting some old HP printers model # 3 that has 100oz motors that I plan on using, keep up the good work, and keep us up to date.
    Dan



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    kiwichris: do you have CAD drawing od machine.



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    Hi-ho,

    Dan:

    The controller I'll be using is a simple Unipolar mosfet job, with resistor current limit... Yes, I've built it myself as I'm trying to do this out of the junk box as much as possible. Although my electronics junk box is fairly substantial as I used to run a part time business doing electrical/electronic design work... I'll post some pics of the controller later on when I update my progress on the machine itself. I don't have a circuit diagram, although I can scribble one and scan it if you're interested. I have used three PIC16C84's as the stepper translators, and can provide the source if you're keen on that as well, although you could use one larger (more pins needed) processor for all three axes if you're not lazy like me. :-).

    For the power supply I'm using an old PC power supply, 12V rail for logic (Using a 7805 regulator to get 5V) and 5V rail for the steppers... When you're using a resistor limited driver anything more than around 2x the rated voltage of the steppers is really just waste heat, and my steppers are rated at 1.8V. I'm not too worried about performance with this one obviously... If it turns out that it dosn't work well enough I'll design a unipolar chopper driver for it, but based on my simple testing so far I think it'll be fine for light cuts in wood/plastic which is all i want from this machine.

    Tonev8: Yup, I'll post a DXF later on, it's a bit vague as I've been winging it to some extent, but the basic layout and dimensions are mostly correct. I've been editing the cad file as I go to reflect the machine. :-) They are 2d only though, and don't show fasteners etc. As I don't currently use a 3d package, as I found I was wasting too much time drawing things!

    I got some more work done on the machine yesterday, I'll post progress pics and descriptions tonight.

    Cheers, Chris H.



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    Hi-ho,

    Some progress from the weekend….

    Pic 1:

    I decided that the masking tape lead screw couplings had to go, so got out the wee lathe, and started to turn up a M6 to 1/4 stepped coupling.. This is as far as I got before the belt In the lathe shredded itself. Hmmmm.

    I bodged up a belt from a couple of large O rings plastic welded together, and managed to finish one coupler, but will have to get a belt to finish the other two.

    With the coupler installed in the X from last week there is now almost no whip at all, and the odd ‘whop whop whop’ sound as the screw whacks against the wood is gone. I was kinda liking that sound..

    Pic 2:

    Some fabricated bits for the Z axis, and stepper mount/offset bits. Made much MDF dust and noise to get to this point.

    Pic 3:

    The Y carriage. (The flat bit of MDF will be known as the Y carriage from now on, OK?) Notice the three ‘saddle’ bush holders and the one offset one. I found out pretty quickly after I tightened the M5 machine screws that getting things lined up perfectly in MDF with the ‘through hole’ mounts for the bushes was going to be near on impossible, and it made the entire thing very tight to move.

    I simply trimmed off one side of the bush mounts with a scroll saw and re-mounted them with the bush hard against the Y carriage (The flat bit, remember?). I understand now how folks have arrived at solutions using routed slots in the ‘carriage’ to align the bushes, but I don’t have a table router or table saw, so I might CNC up a better carriage with this machine when it’s finished!

    The machine screws are too long because I only wanted to buy one length of them, being a tight wad.

    Pic 4:

    Skip forward a wee bit and we have a finished Z. Here you can just see the nice shiny aluminium coupler. I stuck two M3 grub screws through it, and if they don’t hold I’ll add another couple and some red loctite.

    You can also see my fabulous ‘Backlash nut’ solution. (not anti-backlash). I figure it will get things going, and if the machine shows promise of actually doing real cutting of something harder than sponge cake I’ll splash out on some ptfe or acetyl to make some better nuts from. Probably acetyl as it’s quite a bit cheaper here in NZ from the calling around I did last week.

    The Z axis is a bit stiffer to move than I would liked, as the bushes are a little tight, and I think there might be a slight bow in the Y carriage. It moves fine in testing though.

    Holding on to the carriage it moves up and down without stalling at 400mm/min (15ipm) with a 1.5kg weight hanging on the bottom plate. (The motor and end plates will travel up and down with the spindle).

    Spent a little time playing with EMC settings as well, to see how the acceleration figures change performance etc.

    Pic 5:

    Another delay and we have the ‘Y’ rods and bushes mounted on the other side of the carriage, and the front plate of the Z axis mounted. Not to forget another fabulous cutting-board lead nut assembly.

    Here the Z is resting on X, showing Y. (This is draft for the beginning of a Dr Suess book…)

    The lead screw protrudes through the left end so that I can add a bearing to that end if stepper end-float becomes an issue. Not sure if it will for the speeds and materials I want to work with, but it gives me the option without changing too much.

    Pic 6:

    For Dan, a picture of the home brew controller. I’m using three separate pic 16C84’s (16F84 replaced them, these are old) as stepper translators, driving into some LM324 opamps I’m using as level shifters for the standard mosfet gate drive.

    Logic level mosfets wouldn’t require the op-amp, but I didn’t have 12 logic level ones I wanted to use in this project. The fets are BUK 456-60A’s. A bonus advantage of using the LM324’s is that they have a slowish rise time, and protect against Dv-Dt failiure of the mosfets, so no series resistor is needed for the fet gate.

    I’ll be using a separate board for the six current limit resistors (1Ohm 10W). I’m using the 5V rail from an old PC power supply for the motors, and running the logic from the 12V rail of the same supply via the LM7805 on the board shown. I’m only using 5V at this stage to reduce heat loss, and anything much more than 2x the rated voltage on a LR controller is just wasted as heat anyway. The small steppers I’m using are rated at 1.8V 3A.

    I’ll also add a buffer board for limit/home switches and estop. The whole thing (Three bits of strip board and the PC power supply) will get screwed into a case if I can find one in the garage, or more than likely a bit of MDF as I have lots of that.

    Software in the pic is pretty simple half step code. I’m might add an ‘enable’ input that I’ll drive off EMC to reduce static heat build up.

    I almost fell into the trap of re-inventing the wheel and creating a microstepping chopper circuit for this, but in reality kits like the hobbycnc one are cheaper than I can buy the components, so I’ll save my pennies and buy something like that for my next attempt. Either that or I’ll get brain fade and design something anyway, just for the sake of it!

    Also attached is the DXF file. The drawing is a work in progress, so don’t expect high art… I’ve been updating the drawing as I go, so it’s currently got some vague in the area of the Z/Y carriage, and some dimensions may be patently incorrect and/or different from what I’ve built.

    Total new bits purchased so far: M6/30 machine screws and nuts, M6 tap, M5/50 machine screws & nuts/washers.

    Lessons learned this week:

    It is better to drill/tap MDF than use wood screws for such small bits when going into the ‘end grain’. The threads hold pretty well, and you wont split both end plates for your Z axis and have to re-make them. (Ahem)

    Pretty bush supports made of a (very slightly) compressible material like MDF are not much good, doing up the screws distorted them enough to misalign things.

    ‘O’ rings can be used as a lathe drive belt in a pinch with application of soldering iron to weld them together!

    Next steps: Alloy bracing bits underneath the bed, and gantry. Finish up the controller so it's usable off the bench. More lead screw couplings.

    Cheers Chris.

    Attached Thumbnails Attached Thumbnails Kiwi junk-box mini router...-2-0-jpg   Kiwi junk-box mini router...-2-1-jpg   Kiwi junk-box mini router...-2-2-jpg   Kiwi junk-box mini router...-2-3-jpg  

    Kiwi junk-box mini router...-2-4-jpg   Kiwi junk-box mini router...-2-5-jpg  
    Attached Files Attached Files
    Last edited by kiwichris; 03-04-2007 at 06:17 PM. Reason: Add images... Doh. & Typos


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    kiwichris: thanks for CAD drawing.

    Does it z axis move only 50mm, whay dont you make at least 80mm.



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    Quote Originally Posted by toneV8 View Post
    kiwichris: thanks for CAD drawing.

    Does it z axis move only 50mm, whay dont you make at least 80mm.
    Hi-ho,

    Your english is fine...

    The drawing has 80mm of travel, as per the image, the blue is the fixed carriage and the pink slidesup and down with stepper motor/spindle attached. On the real machine I'll get about 70mm due to the stepper mount screws sticking down from the top plate of the motor support / Z axis assembly.

    Cheers, Me.

    Attached Thumbnails Attached Thumbnails Kiwi junk-box mini router...-z-travel-jpg  
    Last edited by kiwichris; 03-05-2007 at 02:16 AM. Reason: typo


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    Default boards and power supplies

    I am going to attemp to build a board like the one you are using, Will get my printers taken apart this week and see what size motors I can find, and may need more help to get mine going, I really like what you are building and the fact that you are keeping it simple without all the high dollar items that most are talking about.
    Thanks for showing others that it can be done.
    Dan



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    U'r welcome. . I enjoy giving back to sites like this, as I get so much out of them..

    For what it's worth, the steppers I'm using here are line feed motors from a Sekoshia BP5420 printer, the 9mm rails I'm using for Y were from a couple of Brother 1409's and I think the 8mm ones came from OKi microline 84's. (what a great printer.) I got two of the dead BP5420's from my old work in the 90's (used to service them, their controller boards were a nightmare discrete design which failed when you looked at it) and another from a recycling place that strips down computer gear for metals etc, so I got two for free, and one for $10.

    I also have some larger Nema 23 double stack motors that were the carriage motors from the Sekoshia printers. The Sekoshia was a large dot matrix, an excelent source of bits . Also has some good 20mm shafting, and the power supply transformer is a mother of a thing I'll probably use in my next machine with the nema 23 double stack motors, and microstepping chopper controllers (Probably my own design, but we'll see how silly I feel on that count, re-inventing wheel and all that).

    For what it's worth, if you have to buy all the components individually to make your controller board it may be cheaper to get one of the kits around, especially if you value your time at all. I have a fairly good stock of components, so building the controllers for me is a matter of picking components I have and making a circuit to fit what's in stock.

    Good luck with your junk box build.



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    Default A little bit more...

    Spent some time in the shed yesterday, got a bit more done. :-).

    Made up one more lead screw coupler, and did some work on the controller..

    Pic 1 is the controller powered up with all three motors for the first time, and the current limit resistors I intend to use temporarily mounted in the terminal strips. You can also just make out the lead screw coupler on the X motor...

    I'm getting a measured 2.7A per winding, but the static voltage is a little higher than rated, so the motor that wasn't moving much (Y in this case) was getting really hot.... Almost too hot to touch after 10 minutes.

    The 10Ohm load resistor is to get the powersupply to start, these old PC switchmodes wont run without a load. Should use a higher resistance, but I only have 1Ohm and 10Ohm 10W resistors to had... Will change that before I complete the job.

    This is the first time I've used these steppers near their rated 3A. I've messed about with them a bit at lower current levels, and never had any heating problems. I might have a bit of a re-think on the voltage/current decision, and go to a lower current, but higher supply voltage, which should give me less heating due to less static voltage on the steppers.

    Pic 2, A screenshot of emc2, the reason the 'Y' motor got so hot. This code is a simple jpeg to gcode conversion I wrote in a shell script, the X is constantly moving, so was only just warm, Z was moving a bit, so was warmer, and Y only moves at the end of every horizontal line, roughly every 15s, so got toasty warm.

    With some basic number crunching, with a 1Ohm resistor I'm getting 2.7A, therefore 0.8Ohm in the stepper winding, which is a higher resistance than the implied spec of 3A at 1.8V printed on the stepper, which would give 0.6 Ohm. Either way, the 2.3V across the stepper when it's not moving is getting it nicely warm. Disipating 11.6W of heat in there somewhere, which dosn't sound too bad. Hmm, might post something over in the stepper forum on this one..

    Watch this space..... :-)

    Attached Thumbnails Attached Thumbnails Kiwi junk-box mini router...-controller-test-jpg   Kiwi junk-box mini router...-facecut-jpg  
    Last edited by kiwichris; 03-07-2007 at 04:27 AM. Reason: missed a bit.


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