Thread: Time for mk2 upgrade!
I got the aluminium profile for free, as surplus to requirements. It was well used, but I selected the good bits to use on the machine.
To buy something similar would be about £40 per meter. E.g.
Good luck with casting parts. Another route to making bits, depending upon what you want to make, is posting a drawing on this site and getting a quote. Put RFQ in the title and see what happens.
If you are starting out on a new design, then you can always post a sketch on this site for constructive critism and comments. I would suggest adding as much detail about your intentions and limitations.
Oo. I know very little about CNC or anything else for that matter, but the Series 8 60x60 is doing wonders for my aluminium profile fetish.
ty for the link :)
14-07-2010 #14Oo. I know very little about CNC or anything else for that matter, but the Series 8 60x60 is doing wonders for my aluminium profile fetish.
ty for the link :)
This is one Extrusion site where a group buy would benefit as discount would be apparent on bulk buy.
Thing that also drew my attention was a 4% surcharge on the CC transaction,never known that to happen in any purchases over the net I've done and I have done many,most odd.
It's been a while, with bathroom projects and other distractions, but managed to do a bit more recently. Here are the updates with the some photos -
Re-wired all the stepper motors with 4 core shielded (let's not kick off that old debate!) from ebay. X and Y went well and the machine jogged around nicely. Went to wire the Z axis, and get a quick hum from the stepper then bam - all dead. Despite my checks I had managed to wire it up wrong. Very annoyed since it was the last step to get it all running around. I've blown the driver board (system3), probably the Z axis chip. Email to Roy asking about my options, he said if it was the chip he'd repair it for £10. What a nice man! Board will be posted tomorrow, will have to wait and see how it goes.
The microswitches are all in place on mounting brackets, ready for wiring. I bought some twin core shielded signal cable from my local cable shop (£0.30 a meter) and am intending to wire it different to mk1. Will put the home X,Y,Z on seperate pins, and the limits chained together with the e-stop on pin 13. All connections will be normally closed for safety reasons (plus I think this helps false triggers).
This is now all in place with the motor cables inside, and working well. I've split my wiring down the middle with the power on the left, and the signals on the right.
I finally decided on a cooling system, based on more research. It turns out that these spindles need very little flow and cooling. Pump spec is 5 gall/hr which is about 20 litre/hour. Windscreen washer pump is about 200 litre/hour and PC cooling pumps are about 500 litre/hour. No wonder a windscreen washer pump gets hot trying to force all that flow through the narrow cooling channels. The PC ones may be getting away with it because they are designed to run for long periods, and have ceramic bearings apparently. I bought a copper radiator rated for PCs of 300W (although the CPU is probably putting out 50-100W), which meant using a special coolant to reduce corrosion (spindle channels are probably ali). The pump I had lying around is around is 500 litre / hour so I'm thinking of using this one at a reduced voltage (5-6v) if it will run down there.
Some people are using a 6 gall / hour pump into a 5 litre steel bucket of water and running just fine, relying on the bucket of water to cool down without a radiator, so this is probably going to be a case of giving it a go.
I've got a 120mm fan (not pictured) somewhere which will bolt to the radiator. The whole cooling system will probably mount somewhere above the spindle. All for now. . .
Been away for a while, but here are some updates.
1. Water cooling system
Installed and working well. I went with a 12cm radiator, cooling fan, 12v pump, 3/8" hose and coolant used on PC CPU cooling systems. I bored out the small barbs on the spindle to help with flow, but having run the system for some time now it probably isn't required. Cutting wood barely raises the temperature (on the outer case anyway) and it is only very slightly warm to the touch after prolonged operation. In fact I recently ran it for 10 minutes cutting and forgot to start the pump. It was still barely warm to the touch.
2. 1.5kW water cooled spindle
This was a great upgrade from the router. Much, much quieter - you can easily hold a conversation next to the machine with an air cut. There is some noise from the cutter when actually cutting, but overall a great improvement and very smooth.
The other advantage is the lack of air blowing down over the work piece and throwing dust everywhere.
3. Power supply
Last year I had problems with glitching stepper motors. I had a 30-36v variable power supply turned down to 30v (switched mode), and found that replacing this with a 24v DC supply cured it. But this was not a long term solution so I bought another power supply, but this time 24v-30v. I tried various voltages and did not have a single glitch with it. Maybe the other supply was faulty. Anyway, sorted that one out.
4. X axis bearing arrangement
The X axis bearings run along the top, bottom and sides (for pre-loading) of the main aluminium sections. After maybe 10 hours of cutting there is a slight witness mark appearing on the profile where the bearings run. This was expected but the long axis is the most expensive to add linear rails to. I'm considering either adding a wear strip to the top surface, or adding supported rails.
5. Control panel
Made a new control panel with more inputs (option for touch probe etc), see photo.
6. Dust extractor
After several aborted ideas, I'm making a floating dust extractor foot. More photos when complete.
Overall I've cut out a number of items and been very pleased with the results. The machine is a massive improvement over mk1, which is progress.
Whilst this new machine performs very well, there were 2 features which were on the list to upgrade when time and finance allowed. First was to replace the x axis bearings running on the aluminium profile, and the second was to replace the wooden side members of the gantry.
So I'm planning my next moves. The X axis will be changed to 16mm supported rail and I have ordered the parts. The gantry sides will be RHS, probably 6" x 2" sort of size, with spacers inside where bolts pass through to avoid crushing the section and maintain the bolt torque. For the top and bottom gantry rails these spacers will be a slice of extrusion, just big enough to slide inside the RHS. For the bearing mount they will be some large turned tubes.
Whilst waiting from the rail to arrive I've been sketching some ideas, and settled on the ones attached. I've yet to see a really neat way of adding a rail connection to a full picture frame style gantry with single leadscrew drive. Anyone seen anything better?
So considering the forces acting I think this method will work ok. The only significant load on this cantilever is the weight of the main gantry and the z plunge of the spindle into the work. This is resisted by a 30mm thick ali block bolted to the RHS with 3off M12 bolts. The clamp load will therefore be very high, and since the block is full width across the RHS it will be able to transfer this load nicely into the stiff side walls of the RHS.
I could add corner brackets to add extra support, but I'm going to try it like this first and see what happens.
In the X direction there is no load because the bearing can slide, and in the Y direction the weak link will be at the top of the gantry side where it joins the horizontal part, so this stubby cantilever shouldn't make any difference.
That's the plan anyway, here are some preliminary sketches showing the current machine but with new RHS ali sides and 16mm supported X rail.
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