This will hopefully be a build log for my laser cutter rebuild.
I have some sketches and ideas I would like to discuss with the forum, I will try to upload soon and start roughing things out in cad
Budget for rebuild £1000
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This will hopefully be a build log for my laser cutter rebuild.
I have some sketches and ideas I would like to discuss with the forum, I will try to upload soon and start roughing things out in cad
Budget for rebuild £1000
This is a sketch of my new cantilever designhttp://i59.photobucket.com/albums/g2...psqgyk9pcq.jpg
http://i59.photobucket.com/albums/g2...pst24jasms.jpg
Build attempt number 1.
Lots of errors on this build.
Pvc plastic mounts
Mdf mounting board
The Y axis motor shaft coupler rods were too small in diameter.
Lots of backlash...
Basicly the 40w laser is way too small for the large bed size I made, so either I get a new laser or I rebuild it smaller. As im not keen to sink more cash into this project and I also need the space and want a compact unit im going to rebuild smaller.
Im thinking about a steel frame to mount a ballscrew driven y axis (moving table) and then a cantilever x axis with either ballscrews again or belt drive. The X axis needs to be faster for raster engraving but the best laser results I have seen are from Tweekie cnc little router/mill/laser contraption and his great machine uses screws or ballscrews?
The cantilever x-axis can move up and down in the Z to allow for different work heights and then laser head optics will also be adjustable for fine tuning.
Have you considered putting the laser at the end of the X axis and then moving the target material in the Y.
That removes 2 mirrors and one entire Y axis from the beam length.
You could do the fast engrave motion in X and the slow stuff in Y.
Thought about it and decided I didn't want the laser tube hanging out over the machine. The plan is too mount it on the fixed gantry, I guess I could mount it 90 degrees to the gantry, that would get rid of one mirror and still keep the laser roughly within the footprint of the machine.
There are plenty of angles you can use apart from 90, with a bit of jiggery pokery it can mount along the fixed axis with just one mirror and still be fairly compact.
That's a good point Robin, I'm so used to thinking in 90 degree angles for the moving gantry, it didn't occur to me to point the laser to the first mirror at a strange angle.
I have been thinking about how to lower and raise the cantilever gantry on the laser.
A couple of linear rails with a lead screw down the middle that can be turned via a hand wheel is one way. This would be locked off with a clamp of some sort. I am missing an easier and cheaper way of doing this.
If I went with profiled rails I could get away with using a set of second hand rails as accuracy is not too important.
Would it be worth contacting a local machine servicing company I imagine they must throw away any linear rails that need replaced?
I have a drum sander in the workshop now I think about it which does exactly what Im after here will take a look at that and see how its done.
Scavanged this scrap z axis off another router. It has a single linear rail sliding inside two 35mm bearing block, seems pretty solid. This is going to hold the cantilever. This is going to give me 200mm of adjustment.
http://i59.photobucket.com/albums/g2...ps5821cdb8.gif
Adding in some more specs for the machine.
Needs to be moveable by two men or forklift/pallet truck. Forklift needs space for tines
Welded steel frame with self leveling epoxy mounts for the rails and ballscrew bearings.
£1000 rebuild cost.
40w laser tube.
belt driven X axis, ballscrew driven y axis (single )
Thinking about using igus drylin for the fast moving X axis.
There needs to be some way of tramming the X axis so it is level and square to the table.
Servos would be nice but they would blow the budget so I'm thinking about using a hybrid stepper with encoder for the X axis as this would be the axis to most likely lose position when rastering an image.
shields for the laser, the gantry design makes it difficult to fully enclose the machine.
Attachment 12588
Simple 3d layout
Found these nice modular parts for laser cutters. Thought it was worth a share as they look very well designed, the only neagtive would be the high mass of the laser cutting head.
http://www.buyneto.com/?ua=ncG1vJloZ...a21qZpipuq0%3D
I ended up buying the setup advertised on Aliexpress. It arrived today and I very pleased with the quality of the parts. It certainly beats the build quality of the countless cheap lasers I have used in various fablab around the UK, not as nice as the American stuff as I would say the parts on the mjunit stuff are a little heavy, I think a laser should be fast and light but I hope this will do me just fine, time will tell.
One thing that annoyed me was the customs guys slashing open one of my boxes and then just making a crap job of sealing it back up. Cutting the box destroyed its strength and the delivery guy had it slung over one of his shoulders and it was bent like a banana, I feared the worst but the rails look straight.
http://i59.photobucket.com/albums/g2...ps02c7b4cc.jpg
http://i59.photobucket.com/albums/g2...ps0c9b527a.jpg
http://i59.photobucket.com/albums/g2...ps35c81619.jpg
Next job is to weld up a frame to hold the rails and mount the electronics onto. Then I need to source some nema 23 steppers or servos. What do you think about these chinese servos
http://www.aliexpress.com/item/Leads...989514984.html
http://www.aliexpress.com/item/Leads...854636877.html
The reason I was thinking about servos or closed loop steppers is mainly for the faster rastering axis. At fast engraving speeds the quick change of direction may cause a stepper to lose position. These chinese servos look cheap but are they any good, I haven't seen anyone use them before?
Rebuild costs so far £750 leaving me £750 to complete.
One turn of the linear actuator shaft moves the carriage roughly 70mm
There is a reduction of 3:1 on the motor so one spin of the motor will move the carriage 70/3 = 23.33 mm
The advertised top speed for the units is 1.5 m/s to achieve this the motor will have to spin at what rpm?
Change 1.5m/s to mm/min = 90,000mm/min
90,000/23.33 = 3857.69 rpm
I have been looking at the leadshine closed loop stepper units. In particular the nema 23 2nm unit. They advertise the ability to run at 3,000rpm but the torque seen at these high rpms is very low just like most steppers in fact the torque curve stops at 2000rpm?. I guess this is why the high end laser cutters use small servo motors. Leadshine also make a nema 23 frame servo which is almost the same price as their closed loop steppers, for some reason I haven't seen a sole use them on any project. The same could be said for the steppers.
Why do you think you want 1.5m/s?
If you wanted speed why are you planning to reduce the motor rpm 3:1?
Robin I do not necessarily need 1.5m/s. A decent laser like a trotec will run higher at 3m/s. Speed is important when rastering an image with the laser, not so important when cutting.Quote:
Originally Posted by Robin Hewitt
The manufacture of the slides suggest a max speed of 1.5m/s so I was just looking to see what rpm I would need to hit the max. In reality I think the laser head is too heavy to run at 1.5/ms so I would be backing off the speed until it looks about right.
The 3:1 reducer is part of the kit so I prefer to leave it in, I think the reduction also helps with the sudden changes in direction the xy is subject too.
Is it possible to keep everything static and just move a mirror accurately to reflect the beam around the tool path ? the strength of the beam would need to be continuously adjusted to compensate for distance changes I think ?
Presumably you would only go for engraving speed on the lightest axis, call it X? Making it fast will make it heavy so you will need a different motor and much lower target speed for the Y. In my day if you wanted enormous speed and acceleration then you used a pancake motor, is that what the Trotec uses?
I think the Trotec uses a small dc motor and everything mechanical is kept very light.
May just go with the closed loop stepper motors for now and then maybe upgrade to a servo motor (on just the x axis) in the future if need be. Going to buy the stepper sets from Aliexpress and hope for a similer good experience. I don't think they will come till after christmas, so I can get to work on the frame in the meantime.
Im thinking box section construction, which I will level with epoxy to mount all the components on a flat plane. I could use shims but id like to give the epoxy method a try.
Interesting. About the Mjunit. Looks Well thought. Could you tell us some more info please?
-What is the sliding element? I can not figure that from the photos.
- v or u bearings ? balls like Hiwin?
-size/type timing belt?
-What the price for the setup you bought? Looking at aliexpress but all say same price, may be the price of an element
-Does it seem precise, i mean move smoothly and without play?
Hi Silyavski,
I paid £600 for the 900 by 600mm laser kit, import tax brought the total up to £750. You contact the seller and he/she will send you a quote.
The sliding element is 4 U bearings. The extrusion is Alu alloy but the tracks that the U bearings slide on is not, I guess stainless steel or chrome plated steel? I will take some pictures to show you.
Im not sure about the timing belt will need to measure.
It seems quite precise and smooth with no play. Time will tell how it really performs.
After buying this kit I recently spotted a second company selling smiler items. http://www.ccmmade.com/ I think the mjunit laser stuff looks better, but this other company has videos on their website and facebook page you can check out. Their prices are also cheaper.
Thanks.
At the second link they seem they have also slightly bigger 60x60mm.
i figured why the 3:1 ratio, they build it for time lapse photography, where a resolution is needed.
Its also common for lasers to have a 3:1 reduction ratio. I think it is to help the motor overcome the inertia due to the high acceleration and quick changes in direction?Quote:
i figured why the 3:1 ratio, they build it for time lapse photography, where a resolution is needed.
Need your brains!!!
I've got a cheapo laser cutter and am having problems with it....anyone around Derbyshire /Manchester way I could pay to help fix it? Or even a few miles out I'll cove cover travel of course. Please help me :(
Started making the frame today out of 100mm box section. Not much else to say.
http://i59.photobucket.com/albums/g2...psjxugbm4i.jpg
http://i59.photobucket.com/albums/g2...ps5tbhtcrs.jpg
http://i59.photobucket.com/albums/g2...psma5rjzl6.jpg
http://i59.photobucket.com/albums/g2...pschffln9v.jpg
http://i59.photobucket.com/albums/g2...ps5eghzmhl.jpg
Little update on the laser build. Finished welding the basic frame and have made a start on the movable table/z-axis. My laser will be a little different as usually a laser table is raised and lowered via four screws, one in each corner. My design is more like a knee mill with one large linear bearing and screw. I am relying on the mech being stiff enough to resist twisting. The large linear bearing was originally a secondary z-axis carrying a 5hp router on a big cnc router so it should be up to the job. There is only one bearing in the picture, but I have two to prevent twisting.
http://i59.photobucket.com/albums/g2...psghaxddjc.jpg
http://i59.photobucket.com/albums/g2...pshp0bidhc.jpg
http://i59.photobucket.com/albums/g2...psghaxddjc.jpg
Nice, cant wait to see that finished. So you are making it a kind of like 3d printer? The bed i mean. But whats the purpose behind that? Different height, big entire objects for cutting or engraving?
Exactly that yes, if you want to laser thick foam or engrave a deep box you can drop the table. Some machines also have a fixed focus lens so you use the bed to focus the laser at the right height. My laser has an adjustable head but the table will be handy for larger items.Quote:
Originally Posted by silyavski
I am trying to simplify the z-axis/table cause the normal way of doing it looks complicated. Google it to see what I mean. Mine is more like a knee mill, I plan to use a car sissor jack to move the knee/table.
Laser cutter z axis linear bearing mount - After drilling the holes on the bridgeport mill I used this metric tap guide and a m8 tap to thread the holes in the plate. I am a little disappointed in how well the tap guide works, there is way too much slop in the guide to hold the tap straight. The guide itself is very well made just not snug enough. I guess this is due to most taps from different manufactures being a slightly different size, so it would be difficult to make a system like this that works with them all?
http://i59.photobucket.com/albums/g2...psdliyus2q.jpg
http://i59.photobucket.com/albums/g2...psbyndgj4b.jpg
http://i59.photobucket.com/albums/g2...ps8xe2syny.jpg
IF you have a lathe, next time make a sleeve with a hole a nice fit on your desired tap, and a nice fit in one of your bigger holes in the jig.
As a rule i usually centre /drill & tap all @ the same setting, ie without moving the setup but you could use your dial or digital readout to do the same, after your holes are drilled put a centre in your spindle to locate in the end of your tap and everything should be square, if you have a digital readout, much more better.
Regards
Mike
Good ideas thanks for the tips mike.
Any news for this project?
typed a response, then realised how old the post was... please delete this comment..
Hi Palmar, I should be getting back on it soon. Will update with some pics. Just thinking of a neat way to enclose the work area for projection and to help create an enclosure from which I can draw air.
Have your mjunit rails arrived yet?
Yes, the mjunit rails just arrived today :) They was well packed. Will update my post soon :D