ok, so it's already built, and I use it every day in my workshop, but I thought at least put a few pics....
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ok, so it's already built, and I use it every day in my workshop, but I thought at least put a few pics....
working ok for me... are the pics on your pc or online? and have you got java enabled.... (if you recently installed a Java update you might need a reboot)
At the risk of teaching grandmothers etc....
Click insert image button
Attachment 6810
chose the image location on your PC, or select a URL, click upload...
Attachment 6809
ooh ... it seems I can paste a bit in the reply :)
Basicaly, about a year ago I started learning how to make a CNC machine.One day I went to visit my dad, and asked him if he had any pipe I could use for the rails. (he had a metal fab business ). "Come and have a look see - " he said, and started rummaging through a pile of junk ...
http://i121.photobucket.com/albums/o...K/DSC01948.jpg
http://i121.photobucket.com/albums/o...K/DSC01949.jpg
http://i121.photobucket.com/albums/o...K/DSC01950.jpg
http://i121.photobucket.com/albums/o...K/DSC01951.jpg
http://i121.photobucket.com/albums/o...K/DSC01979.jpg
http://i121.photobucket.com/albums/o...K/DSC01939.jpg
http://i121.photobucket.com/albums/o...K/DSC01941.jpg
http://i121.photobucket.com/albums/o...K/DSC01942.jpg
I thought for free, I'd take them !
VERY rusty, bearing balls missing ...Screw threads corroded etc etc... but at least I could start 'learning' how it all goes to gether.
Anyway... long story short (for now)
this is how it looks since it started working for me early this year.
It was only rigged up to test it, but it worked so well, it's been like this ever since. Cutting at least 2 or 3 hours every day !
\/ \/ \/ CLICK ON IMAGE BELOW, TO PLAY VID \/ \/ \/
http://i121.photobucket.com/albums/o...h_MOV00020.jpg
http://i121.photobucket.com/albums/o...K/IMG00113.jpg
It's still not finished. I plan to add a 4th axis over the end for a lathe attachment.
Cutting area is 25.5" x 24.5". I can get a 2x4 1/4 sheet on the bed with room to spare.
Construction is torsion box 12mm MDF
The most 'slop' in the build, is from those worn out hiwin type bearings on the X :(
But is works perfectly for what it was designed to do. I
t cuts at approx 150IPM at 1/8" passes. cant go faster at the mo, as my old router bearings are on the way out and squeel a bit !
But it's plenty fast enough for now.
I'll add some more details over time, and feel free to ask any questions.
Rich
video didn't work ?can
we embed video on here ?
LOL ! yes, sucking eggs :)
Thanks Irving, but my cursor dissapeared in the text box. It's happened before on this forum, which is why I never got to post my build here.
Seems ok in the reply box though :)
I've done it for you. Just went to the video on photobucket and copied the link called IMG code. This forum does not have HTML enabled, presumably to help avoid spam, so the html link you used wouldn't work.Quote:
Originally Posted by TrickyCNC
Can't say I'm not surprised it works smoothly with that amount of rust. Have you measured how much backlash you're getting and how much play there is in the X-axis bearings?
luckily no backlash, but it's a struggle to preload the play out of the bearings.
I later told my dad about them, and he said " Oh yeah ... I remember now, that's why they were in the skip ! " LOL
Anyway, all my parts come out the correct size, and no issues cutting profiles or V carving. the play translates to 'nodding' of the Z when cutting 3D stuff though, with the short stop/start accel's. I plan to add some angle and skate bearings to the outer edges to stop this. sort of additional X rails
Like I said, I built this just to test theory and see how things work. but it worked too well to start again, so I just used it as is.
I'm more than happy with the MDF bed , Z, and gantry. No movement / flex / twist at all . which was what I wanted to test.
http://i121.photobucket.com/albums/o...K/DSC01941.jpg
holy sh*te!!
thats a winner !
you have definately got some skill getting that lot to earn its keep :)
great stuff
Presumably you never used any of the spreadsheets for working out torsional stiffness and power of stepper motors required ? :barbershop_quartet_ :witless:
Well done that man, practice prevails over theory.
Ha Ha !
Thanks Both
I read and read, then over sized all the MDF sections, and all was good.
Yes, build it - try it , saves much time over spread sheets and theory :)
I did spend a few weeks of nights acid cleaning the rust, and ordered some 3mm ball bearings for the bearing bodies.
The motors are actually vastly over the top. I am probably driving them at about 20% of their potential. But they were free, and with a multi meter across the windings , I figured out how to wire them up to my 542's, and all is good there too.
I am thinking of re-using them to make an Aly mill after I build my bigger MDF machine.
I bought the 542 drivers as a 3 axis kit from Zap, and have been very pleased with them. I've had it up to 500IMP rapids with 180IPM cuts :) but keep it at 180IPM Rap and 150IPM cuts for trouble free day to day cutting.
Rich
Using a CNC to make money, doesn't have to be all pretty carvings ! Here, mine is cutting mortices in table legs .. (yes, I had the phone the wrong way up ! ) CLICK TO PLAY http://i121.photobucket.com/albums/o...h_MOV00023.jpg
a paste from my build thread on another site ...
the basic layout of the bed and X axis....
I've made the bed in the form of a torsion box out of 1/2" MDF.
Finished bed size is 36" x 27" x 4" - max working area will be about 26" x 26"
I've laid the screw and rails on top roughly in the position they will be in, except it will be the bottom when finished.
The gantry will be torsion box sections too , and fixed to the rails under the bed for a clean look.
The bed will be raised on legs when I figure out how high they need to be !
http://i121.photobucket.com/albums/o...K/DSC02026.jpg
http://i121.photobucket.com/albums/o...K/DSC02027.jpg
.......
,........................
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anyhoo,, today I spent a couple of hours on my build.
the rails I lined up on a bit of 3/4 ply, using a new ground level as a straight edge.
http://i121.photobucket.com/albums/o...K/IMG00030.jpg
I drilled through and counter bored underneath, before grinding off the bolts before tightening
http://i121.photobucket.com/albums/o...K/IMG00031.jpg
http://i121.photobucket.com/albums/o...K/IMG00034.jpg
http://i121.photobucket.com/albums/o...K/IMG00032.jpg
I must say, the mixed sets of machine screws / washers / nuts etc . are one of the most usefull buys I ever bought !
http://i121.photobucket.com/albums/o...K/IMG00033.jpg
I mounted the motor / screw assy on a bit of ply and shimmed it to be parallel
http://i121.photobucket.com/albums/o...K/IMG00036.jpg
and this is them all layed out .
http://i121.photobucket.com/albums/o...K/IMG00035.jpg
I now have to fix one to the bed and set the others in place of the 1st fixed bit.
I'm deciding whether to use the screw as the ref , or a rail .. but I don't suppose it matters much.
So, I fixed the screw in the center line under the bed.
Then I fixed one end of each rail.
I then fixed a temp gantry to tie the 3 together, and ran the screw to the other end of the bed.
Then fixed the far en of the rails.
Then ran the gantry back a couple of inches at a time and fixed the rails as I went.
Quick phone vid of the X moving... remember , this is upside down at the mo.
CLICK IMAGE TO VIEW
http://i121.photobucket.com/albums/o...h_MOV00003.jpg
I got it upto about 100IPM before it stalled, but I'm still running the drivers at minimum amps whilst testing. It's running at about 70IPM in the vid
Rich[/QUOTE]
Starting the gantry ..........
nothing impressive done
made a bracket from 1/4 plate for one of the bearings as I only had 3 out of 4.
Made the top and bottom gantry torsion boxes
http://i121.photobucket.com/albums/o...K/IMG00040.jpg
http://i121.photobucket.com/albums/o...K/IMG00042.jpg
Got to paint a dolls house tomorrow, so prob wont get much done here
Rich
........................
]got the under gantry mounted. Just bolted at the moment. If it moves at all, I'll glue it.
I added some temporary legs and got it right side up.
Played about with the settings, and upped the amps on the driver, got it upto 168IPM, with the acceleration almost instant
It moves pretty strong too, I can put a lot of force against the direction of movement and it keeps going.
I'm very happy so far.
it's moving about 20" back and forth in this video clip
<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid121.photobucket.co m%2Falbums%2Fo238%2FRichAAC-UK%2FMOV00004.mp4">
I made the gantry bridge tonight.
the top and bottom are 8 x 4, the uprights are then 9 x 3 .
It's just glued and pinned, so I'll have to wait till the morning to see how stiff it is, but being a bit gentle with it tonight I'm quite impressed !
I also like the video my el cheapo phone can produce ... perfect for this kind of thing !
so, some more :)
<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid121.photobucket.co m%2Falbums%2Fo238%2FRichAAC-UK%2FMOV00005.mp4">
I'll fix the video links so they work in this forum when I get a chance :)
Starting the Y movement parts..................
so, I very quickly realised that the clearance will be reduces when the Z assy goes in ! oh well, I'll try and design it to be as thin as poss under the Y.
I had some precision supported rail (without the support ) from the skip (dumpster) stuff.
I cut it in half with an angle grinder, and made some supports from angle iron I have knocking about.
That's about it for today. I bought some M8 threaded rod / bolts / nuts / and washers, so will start on the bearing trucks tomorrow
http://i121.photobucket.com/albums/o...K/IMG00049.jpg
http://i121.photobucket.com/albums/o...K/IMG00050.jpg
http://i121.photobucket.com/albums/o...K/IMG00053.jpg
http://i121.photobucket.com/albums/o...K/IMG00051.jpg
http://i121.photobucket.com/albums/o...K/IMG00052.jpg[/QUOTE]
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So, not much done today to show.
I got the Y rails more or less aligned (good enough for now)
Simple setup with a set square and clamp, 1st I got the height from the bed equal along the length of each rail, and both rails equal to each other.
Then I checked the distance from the outer edge rail to rial along the length.
http://i121.photobucket.com/albums/o...K/IMG00056.jpg
http://i121.photobucket.com/albums/o...K/IMG00057.jpg
http://i121.photobucket.com/albums/o...K/IMG00054.jpg
http://i121.photobucket.com/albums/o...K/IMG00055.jpg
then I got to making some skate bearing trucks.
the rails are 31" long, my travel will be about 25" long, so I cut some angle iron to 7" and drilled the holes 1/2" in for the bolts for the skate bearings. spaced with nuts, and cut to length after with the angle grinder.
http://i121.photobucket.com/albums/o...K/IMG00060.jpg
http://i121.photobucket.com/albums/o...K/IMG00061.jpg
next to figure the best way to atatch the trucks to the Z carriage ???
I'll be asking that in another thread :)
so, today I had to clear the CNC project to one side to do some paid work
I cut this stack of MDF to make 2 house shaped bookcases, which is the kind of thing I make most of my living off
This is the stack
http://i121.photobucket.com/albums/o...K/IMG00065.jpg
it's one of the things I want to cut by CNC
the finished item looks like this
http://i121.photobucket.com/albums/o...K/IMG00046.jpg
this one was ordered with rainbows for a children's therapy room.
anyway, I'll assemble them tomorrow.
I got the Y carriage mostly built later today
I dado'd out for the bearing trucks, based on Ger's answer to my other post. Thanks Ger
http://i121.photobucket.com/albums/o...K/IMG00069.jpg
The bolt head were a little proud, so I ground them on the belt sander
http://i121.photobucket.com/albums/o...K/IMG00067.jpg
http://i121.photobucket.com/albums/o...K/IMG00068.jpg
for a nice fit
http://i121.photobucket.com/albums/o...K/IMG00070.jpg
I made a torsion box at the top, and a removable bottom plate for dissassembly.
A threaded rod just above the bearings for the pre load adjustment
I might make a fitted side plate if it needs stiffening (to stop nodding), will know more tomorrow when the glue has dried
http://i121.photobucket.com/albums/o...K/IMG00071.jpg
it rolls pretty well
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I'll connect the screw assy tomorrow, then to start on the Z
I hope to make some sort of 1st cut by the end of this week :wee:
]Spent today beefing up the carriage.
I filled in the sides, and added a mini torsion skin the the front. I'll do that back at a later date. Lined up for the screw to be bolted up.
http://i121.photobucket.com/albums/o...K/IMG00077.jpg
Now it's just the Z to make and I can test it :D
so, tonight, I'll mostly be looking at everyones Z's and choosing how to do mine.[/
:) finally got started on the Z today
I'm still making it up as I go along, depending on what I can find to make it out of !
Today, it was 1/2" birch ply.
the bearing trucks and rail are quite wide, and as I dont want to build out any more than I need, towards the front, the Z plate ended up quite a bit narrower than I imagined. It's still 4", so should be ok.
In fact, it ended up just like an idea I had the other day of making your own Hiwin type rails and bearings.
I have it mostly assembled and glued under preload from a clamp. It moves really nicely.
Tomorrow, when the glue is set, I'll be adding more glue block support to the outside edges, behind the bearings. the pipe is not attached yet, so I can shim under it if needed.
Also, not shown in the photos, I block planed the rail housing edges so the pipe fits in it's slot snugly and seats on the bottom.
http://i121.photobucket.com/albums/o...K/IMG00085.jpg
http://i121.photobucket.com/albums/o...K/IMG00086.jpg
http://i121.photobucket.com/albums/o...K/IMG00087.jpg
http://i121.photobucket.com/albums/o...K/IMG00088.jpg
http://i121.photobucket.com/albums/o...K/IMG00090.jpg
CLICK TO PLAY
http://i121.photobucket.com/albums/o...h_MOV00010.jpg
T
I got a bit done today.
Screw and nuts sorted.
I'm going to mount the motor to the Z plate, and was looking at the space I had to mount the nut(s) for the allthread screw.
I have just enough room for the nut, but not much more. so this ruled out a nut surround.
My 1st thought was to weld the nuts to a small bit of 1" x 1/8" flat bar, but my welder is well packed in under a load of "stuff" in the corner of the shop. So I'm wondering how to hold the nuts in posistion without using any space around them. The nuts are quite meaty, so I had the idea to drill and tap through the side of the nut, and hold it in place with a bolt, through the bottom of the bearing carriage . I didn't know if it would work, or what the nuts were made of ? could I drill them ? would they be too hard ?
Anyway, it seemed to work OK. I tried a bit of spray can to mark the bolt that protruded through, but it didn't stay on when I removed it, so a bit of fussing, and I had the bolt ground down to the correct length where they wont foul the leadscrew, but have maximum purchase on the nuts.
I didn't really take the time to have the nuts alighned, instead, I left them slightly loose, threaded the leadscrew through both, set the leadcrew in the correct posistion and 5 min epoxy'd the nuts in place. once that had set, I tighten the bolts that hold the nut. Time will tell, but I see this as a temporary setup until I get a better screw and antibacklash nut.
So, onto the screw. I wasn't sure how the end should be, so I made it look like pictures I'd seen on here and online CNC shops.
It's the 1st time I've used a lathe, so was happy how it came out.
It's M12 allthread rod, skate bearing, M8 nut, and 1/4" coupling bit on the end.
The lathe cost me about £100 UK pounds and is about 100 yrs+ old !
I think it will pay for itself very quickly :)
So, I still have the bearing blocks and couplings to make, they'll be next.
Still not cutting, but getting there ! It seems to be taking longer to make the Z than the rest put together ...
http://i121.photobucket.com/albums/o...K/IMG00092.jpg
http://i121.photobucket.com/albums/o...K/IMG00093.jpg
http://i121.photobucket.com/albums/o...K/IMG00094.jpg
http://i121.photobucket.com/albums/o...K/IMG00095.jpg
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http://i121.photobucket.com/albums/o...K/IMG00098.jpg
http://i121.photobucket.com/albums/o...K/IMG00099.jpg
http://i121.photobucket.com/albums/o...K/IMG00100.jpg[
so, not go much done today. I have designed my bearing block and motor mount (in my head) using what I have lying around.
the skate bearings OD just happens to be 22mm, which I have that size in a spade bit. 22mm counter bore in two bits of MDF, with 16mm through bore for the nut and screw clearance, and I have two halves of a fully encapsulated bearing block ... simples :)
I'll make the real one from birch ply. One half I will mount to my Z plate, the other half to my motor mount. They will be bolted together, so they can be split any time, to get at the bearing if I need to.
That's the general idea anyhow :)
http://i121.photobucket.com/albums/o...K/IMG00103.jpg
http://i121.photobucket.com/albums/o...K/IMG00104.jpg
I'll try and get that together over the weekend. Then it's just a router mount I guess, and then some cutting :D
[Z attatched.
I made the coupling out of wood, so I'm not sure it will grip. but it's progress for now
http://i121.photobucket.com/albums/o...K/IMG00107.jpg[/
]router mount made ....
just got to wire up the Z, and I can test it :D
Maybe today is the day ?
http://i121.photobucket.com/albums/o...K/IMG00108.jpg
]Got the router mounted. (I know I should have waited until tomorrow for the glue to set .... )
Got the Z wired up, only to find it moving in the opposite direction. ???
Swapped a and b coils, and all is good now..
http://i121.photobucket.com/albums/o...K/IMG00109.jpg
sorry - held my phone the wrong way up without thinking for these
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<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid121.photobucket.co m%2Falbums%2Fo238%2FRichAAC-UK%2FMOV00012.mp4">
Not done any tuning on the Z yet, but it carves :D
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It carved deeper one end than the other, but I only had it clamped at the edge - off the bed, and I did notice it was lifted towards the other end.
I'll investigate tomorrow, (It's night time here now )
but
http://i121.photobucket.com/albums/o...K/IMG00112.jpg
:D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D :D
:wee:
]so, been playing with some free software.
Inkscape with gcodetools can do pathcutting and V-Carving.
I surfaced a spoilboard (did I say that already ? ) and recut the EMC demo
http://i121.photobucket.com/albums/o...K/IMG00113.jpg
http://i121.photobucket.com/albums/o...K/IMG00115.jpg
that turned out pretty good.
I worked out how to do V-Carving with inkscape, and cut a Pet Cross, with the name MAX on it. The biggest problem I had, was figuring out where to position the pre made cross, to get the carving in the correct place. It ended up being low of center, but the carving itself was quite neat. It did look very 'machine cut' though, and I do prefer the hand carved look. I'll have to change the wording in my sales pitch !
http://i121.photobucket.com/albums/o...K/IMG00117.jpg
<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid121.photobucket.co m%2Falbums%2Fo238%2FRichAAC-UK%2FMOV00015.mp4">
http://i121.photobucket.com/albums/o...K/IMG00119.jpg
then I tried a tile pattern on a scrap of MDF. It was about an hour to cut, and I noticed it start cutting deeper in the lower left corner. I suspected the Z motor coupling, so marked it, and marked the top motor shaft corispondingly. Sure enough, the coupling was slipping. I tightened it up and continued cutting, which seemed fine to the end.
http://i121.photobucket.com/albums/o...K/IMG00120.jpg
<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid121.photobucket.co m%2Falbums%2Fo238%2FRichAAC-UK%2FMOV00016.mp4">
the end result was pretty good for a test. I used just plain path cutting. I think V-Carving would have been better.
http://i121.photobucket.com/albums/o...K/IMG00121.jpg
I need to start tidying up the wiring, and locktighting the nuts and bolts. The odd one is coming loose already !.
This is the machine as it stands today.
http://i121.photobucket.com/albums/o...K/IMG00124.jpg
I had to switch off, and do some paying work, so no more playing for a bit :(
Thanks for looking
Rich[
And that's about it.
I've painted a few more bits and added a new spoil board and fence, but I've been using it like this now, every day for about 6 monthsI'll tidy
up the broken links over the next week or so, but this just about covered my 1st CNC build from scrap and bits of wood :)
I'm happy !
looks awesome.. do you think it's going to stay in mdf or do u think over time you will recut pieces in to alu to add strength?
Thanks Wilfy
I think this one will stay MDF. I'll fix/change the sloppy bearings, which is where I get most of the movement, and then see if the MDF is moving / flexing at all. But at the moment, I cant see any movment in the gantry or risers. Remember, it's intended to cut wood ! If I want to cut metal, I'll build one to suit.
I'm saving for another driver/motor kit and I'll be building a 8' x 4' working area machine. I'll be making that in MDF or PLY too, as this "test" build has proved it to be sufficient.
Rich what a great job. There is a lot on this site about the merits of mdf v ally v steel. Its the old horses for course and if mdf is what you are cutting then it will do you well. And soooo much quicker than my build now into its 9th month.:neglected:
While i agree that you are saying your machine works well as it is in mdf and does the job that you want it to do, I'm sure there is more reason behind everyone's arguments to use metal than just do it as that's the only way, fact is mdf bends a lot. Now the only downside I can see to this flex is that your pieces will run out by a certain amount, this is quite obviously within your tolerances so great for you. I think you may get even more play from your 8 x 4 machine but again if your happy with it then super.
I originally planned to use mdf for my machine but I wouldn't want to make it and it to have play in it, so I've decided on steel box section as I see this as the next step up from mdf/ply
Quote:
Originally Posted by wilfy
Sheep :) you know , one bleats, and the others follow.
there are plenty of other sources of info and forums on the net, with many many working, and accurate, CNC machines made from wood or wood products. Quite a few cutting ally well too.
oh and - the fact is , steel bends a lot too ;) in fact, a lot more than you would imagine !
most of the ally builds on here, you will see them being beefed up /boxed / braced ..., and talk of too much flex and twist etc. etc. "oh , you need bigger/thicker sections/thicknes" ... and so on.
same goes for MDF. It can be made to not bend.
One of the longest standing moderators on the CNCZONE (Ger21 - he's on here too) has decided to build his new 8x4 machine from .... err ... oh yes ... MDF ! He knows his stuff .
There is nothing wrong with steel or Ally. Just don't dismiss MDF . or birch ply . or phenolic ply ..... bamboo ply !
Rich
calling me a sheep is a little immature,i happen to be able to make my own mind up about things and have read lots of forum posts given here, with lots of very technical workings out, things people didn't have to do as it shouldn't make any difference to their own life other than the happiness of helping others... its not like the advice here is going to make people money.
as i saw jazz post in another thread which you are also commenting.. in fact it's my thread.. a sheet of 25mm MDF which i have just bought recently cost me something like 26 quid i think and as jazz had said you could buy enough 50mm box section for £26 to build the same size machine.. i have a welder, yes i bought it to help with my cnc machine but over the past few years it's something i've felt i could have done with and i have no problem buying a tool to tap threads where needed.
so comparing the raw cost of the materials there is no way a 25mm sheet of mdf will produce the same stiff machine that steel box section machine will, thats not me following like a sheep.. thats me not being stupid and realising the difference between steel and bendy mdf.
for the record i have complemented you on this machine and i think it's great that you have made it work the way you want it to.. i just dont think it's as accurate as it could be, but thankfully the work you do obviously doesnt need this level of accuracy
I didn't mean YOU were a sheep - sorry.
I meant forums like this in general, people tend to post like sheep. If they've read it, it must be true, so they repeat what they have read... and so it goes on. Even though most have never actually tried it themselves.
I know you complemented my machine, I said thanks :) but then you say it can't be that accurate ! when in fact you have no idea how accurate it is. It's almost as if you are implying that I don't work with any accuracy, which is kind of insulting to me ;)
My parts come out the correct size, and square, with no noticeable backlash or carving errors when doing small circles or fine engraving.
That is my test of accuracy.
I have said I have play in my X bearings, and I know not to have short fast accel's for it not to show up. That is something I will be fixing. but it's nothing to do with the MDF
We are cutting wood here remember, not aerospace engineering LOL I have 1 thou (imperial) resolution, but you could never measure wood to that degree, as the fibers compress etc.
Steel is good. I said that (I think) MDF can also be good, don't knock it till you try it, that's all . (I'm not even saying you should try it, just don't dismiss it because you THINK it's bendy ! )
I don't want to get on the wrong side of anyone here. but text on a screen can make it look like that (both ways) sometimes.
! PEACE n HUGS ! n all that :wink: and good luck with your build
Rich
Thanks MOTOXY :)
Attachment 6876
Approx a 4 Ft span.
Bloke weighs around 200Lb
Metal bar for visual straight edge reference
Yer but that picture has been photoshopped Richard, that's really a steel beam you have made look like wood lol
Quote:
Originally Posted by martin54
LOL !
it's not my photo, I googled for an example to show that thin sheets of wood can be made to be 'not bendy'.
Before starting my design, I made a few test torsion boxes with hardboard skins . it's amazing how they work !
for them to bend, they have to curve. now everyone knows, the outside of a curve, is longer than the inside. So the only way for it to bend, is for the skins to stretch !
the further apart you keep the skins , the stronger the end result.
The only problem you have to solve is how to fix parts to each other, so I chose not to use harboard. With MDF, you can use cheap super glue to 'harden' any fixing holes, which greately increases their strength. washers are good for spreading the load too.
Another trick is to use a rot treatment/wood hardener over the whole part. it's basically liquid plastic, and soaks into the MDF stiffening it and waterproofing it.
The use of ply instead of MDF, is also a good option, as it takes screw fixings a lot better.