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Ajohn

Anyone have view on the Velleman K8200 3D

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I wonder if anyone is using one of these and has any comments. Having seen people mentioning switching to 3mm filament I wonder if it would be better to start that way. It can be converted / switched over to the thinner size but I wonder if there are any penalties.

Then there is the question of reliability and accuracy. It seems to be pretty light weight for it's size. Print area is about right for me but doubt if I would really need that much on z.

John

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I bought this kit several years ago and have done much work on it to get it to work, eventually modifying it almost beyond recognition.  The circuit board failed and after a couple of replacements which also failed, I gave up and bought a RepRap replacement set of electronics.  They may have improved things since then, of course, but there were several design faults in the version I bought.  I can find my threads on this if you like.

Edited by Gina
typos

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Thanks Gina. Sounds like buying one wouldn't be  a good idea. Any thoughts one 3mm filament against the smaller size. That is what attracted me in some respect but have also thought that 1kg of abs is 1kg of abs. Also the print area x y rather than z.

Price of the Velleman kit is around the max I would be prepared to spend. Less would be even better. There are so many it's hard to choose. I realise some may need a fair amount of careful setting up mechanically and parts seem to break so adding electronics to the list doesn't seem to be a good idea.

John

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In the low cost range I would be inclined to go for one of the many RepRap style printers and I'm sure others will have recommendations as to which.  The advantage of RepRap is that all the parts are readily available and relatively cheap.  The design is open source and a huge number of people are working on the design and using the printers. 

Apart from modifing the Velleman to RepRap and which I now call my Pilot printer I have built a RepRap style larger printer from scratch.  This one is called the GinaRep Titan and has a build volume of 290mm x 290mm x 350mm with a 300mm square heated print bed.  I also have a Giant printer under construction (though on hold ATM) with 600mm square heated print bed.  Whole thing is about a metre square and 600mm high.

As for which size of filament, I'm not sure.  I'm using 3mm on my DIY printers but my latest upgrade of the Pilot will take both sizes.  I have found I rarely used the available Z dimension other than on the little proprietry UP Plus 2 printer with about 130mm cube print volume.  That has been a good quality printer but expensive. It uses 1.75mm ABS filament.  Replacement parts are ridiculously expensive and non-standard, the problem with propreitry printers v open source RepRap.

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Thanks Gina.

Being impetuous I think I'm about to order ebay 181985013976. More than think. My son has just received a -20% discount offer off ebay and for some reason mounted on a decent base I like the look of it. :smile: 2kg of PLA to waste trying it out too.

Thanks

John

 

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Thanks Gina. My thoughts on the acrylic was that I could remake / strengthen that up pretty easily. I liked the look of the other components especially the guides and certain other aspects. It had a bowden feed too which I feel makes more sense that moving the stepper etc about. On the other hand I have no idea how well these work out. General thought was that it used parts I would be inclined to use for  a self build. I'd hope that the pictures in the listing were not misleading.

:hmh: Shortly after buying it I had a message - no uk stock but it's on it's way from China by boat. I doubt if there ever has been any. It seems that they will offer me another opportunity to buy at a discount but bang goes my 20% provided by ebay. There is also the announcement in the budget that said they were going to prevent companies from selling this way to avoid tax. That is likely to make all of my hobbies significantly more expensive.

Interesting thought John. I'll take a look but feel I would rather have bought the one I ordered and did further work on it if needed.

John

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There are pro's and con's to either method, and intuitively having less weight on top of the hot end should mean less weight=less intertia so should print faster. Ultimaker still uses the remote 3mm feed but most others use the combined extruder motor and hot end + thinner 1.7mm filament. You need to look closely at print examples to see what can be achieved with any particular printer because either system will work and the bottom line is how well that design has been implemented. User reviews will help for that. Not sure if you can print flexible filament that way as pushing the end of a long length of 3mm rubber band doesn't seem possible ;-)  Fine control over retraction would seem to be more difficult too.

ChrisH

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There seems to be mixed views on a bowden style feed. For instance

And

 I can see that if the filament fit in the tube is too loose it will have problems plus the person who reckons it's an improvement doesn't show any examples. I did realise that this aspect might have to go on the one I tried to order.

John

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I've gone for Bowden drive for my DIY printers as I was convinced that whipping all the weight of motor and extruder was not beneficial.  OTOH the little UP Plus 2 printer has the direct drive system though using smaller and lighter components - small NEMA14 motor with built-in small hobbed pulley directly driving 1.75mm filament.  My Bowden drives use NEMA17 motors with geared drive and 3mm filament.  I tried driving 3mm filament directly and couldn't get enough torque. 

I shall be trying Bowden drive with 1.75mm filament but I suspect the compression in something like half a metre of length might be a problem - we'll see.  There certainly are printers with 1.75mm filament and Bowden feed so it might be alright.  My Pilot printer is my test-bed for this with the idea of providing the best possible accuracy with a 200mm square print bed.

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With the Prusa I3 type you are also moving the entire bed + a potentially heavy print (of variable weight as the print builds up) print around, so the inertia issue is not all to do with moving the head plus motor. The gantry system of my Wanhao - which carries two NEMA17 motors - plus the fixed bed means the weight at the hot end stays the same and can be tuned for consistent results. So despite the disadvantage of the extra weight (which definitely reduces print speed) I still prefer that system. YMMV ;-)

ChrisH

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I'm wondering now after watching part of that first video if I might make an alternative X carriage for the Pilot printer using a NEMA14 stepper motor with small driect drive hobbed pulley and 1.75mm filament - emulating the UP Plus 2 as near as I can as that has given better results than either the Velleman direct drive system or my DIY Bowden system.

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There is an interesting DIY build on youtube aimed at a larger printer. He's thinking it out as he builds it which makes it more interesting but they are long video's.

The way he has done tt meant that he had to raise and lower a rather heavy platform. He went for a bowden feed and from one trial print didn't seem to see it as a problem. Looks like there are other things still to sort out. This link may go to all 11 of them. I've found it interesting as it shows potential problems.

"

Doh  I had hoped to just post a link. The first one in the series is unlikely to be of much interest but they do get "better" eventually. Lots of chat.

John

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I used linear bearings for my printers at first as that was what was supplied with the Velleman kit but I found these didn't last long and the rubber seals soon gave out and then tiny bits of filament would cause the bearings to jam.  So I went for a more up-market approach of V groove aluminium extrusion and special ball bearing wheels to run on it.  These are much more free running and don't jam.  The extrusion is also readily available in greater lengths than the polished stainless steel rods as used with linear bearings.

My Titan printer uses nozzle motion for the X and Y axes and bed for Z as in the video whereas the Pilot still retains the bed motion for Y that the Velleman kit used.  I did however change the X motion from bed to nozzle.  My Giant printer is designed to move the nozzle in all three directions and have a fixed bed.  This is because the bed being 600mm square x 4mm aluminium plate plus a number of large cartridge heaters and their mountings could weigh several Kg whereas the frame holding the XY rails is much lighter.

Another change from the traditional Reprap design was to use cord, pulleys and drive drums instead of timing belts and pulleys.  This gives much smoother motion.  The cord is sold as fishing line and has negligible stretch - it is also rated at 100lb breaking strain.  Much cheaper than timing belting too.

Edited by Gina

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Been scanning through those videos - far too long winded to watch straight through.  Got up to part 5 and need a break :D  All very well making a 3D printer from scratch if you've got a fully equipped workshop like he has!!  Even a CNC laser cutter :eek:

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He has some one helpful as well. Looks like they made the extruder for him so not sure how complete his workshop is. Workshops don't cost anywhere near as much as they did thanks to China. It does need some caution purchasing though.

I  assume the fishing line is braid? I'm surprised it doesn't slip. Did you post any photo's of the set up?

The aluminium guide rail and bearings have been mentioned before. I couldn't find them. Does anyone have an ebay number or link to a supplier?

John

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Edited by Ajohn
Note about workshops

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I'll sort out the links shortly but I can answer some of your questions...  The fishing line is braid and is either anchored to the drums or wound round several times and arranged so that turns can't ride up on each other.  In some cases ends are fixed.  This will be clearer when I give links to my builds to follow - complete with photos.  I'll post links for the V-slot extrusion and V-slot wheels plus other parts.

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Thanks Gina. I didn't think to search extrusion.  :hippy2: I think I am going to have a vision.

I've looked at various kits and it seems to be a good frame and by the look of it missing parts on the electronic side, and may not be in the uk really or so so simple flat aluminium plate frame with everything that looks like it may be made by a UK company with all of the fittings printed. So in some ways making one up appeals.

I found some details on how the braid is handled - clockwise and anticlockwise around a drum. I sea fish a lot at times so am bound to have some braid about. I've seen comments about it stretching but would have thought that would be pretty slight once the filaments in it have settled down. As timing belt is likely to have something similar in that may stretch a bit anyway.

In some ways I would be inclined to use a typical router style set up for the z axis and also do all of the movements at the top. Trouble is that this wouldn't minimise the weights being moved about and the front back movement would need driving on both side really.

Needs some thought but I feel I would only really need 100mm or so Z axis. The other axis are more of a problem as I don't really know but more than 200mm in one direction would probably be best.

I've cross posted with you but will still submit this one. Whoops seems I didn't but the forum thought I had

John

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Edited by Ajohn

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I was editing a post ready to print - maybe the software picked that up :D

Here a link to my latest mods on what was the Velleman kit printer and it still uses the frame.  It has been converted to V-slot extrusion in place of round SS bars and linear bearings.  It also used braid string with drums and pulleys.

GinaRep "Pilot" 3D Printer - Description and Further Enhancements

Again this is the whole development thread with "blind alleys".

Edited by Gina
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The cord/line I got was Spectra Extreme Braid - 100m reel cost just a few pounds.  Elasticity is very low but it does stretch a bit in time so a method of adjustment is needed.  Guitar tuning pegs work well - see my Pilot build.

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:grin: I'm bleary eyed from reading the Pilot thread.

A useful thread Gina. I'm worried. I now know I can buy some things such as borosilicate sheet etc. The braid is very abrasive so can understand why you switched to the V groove bearings.

One of the interesting aspects was different masses on the x and y axis. I wonder if different motor powers might help - crazy thought. Good thoughts on the reasons for problems as well. I had forgot something that I actually spent some time using long ago. A drawing board. My excuse is that it was a different type but the x arrangement might prove useful. Not so sure about the clever twin axis one.

Dose of optrex and a rest and I'll take in the other one.

John

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