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Re: Build volume vs extruder travel limit - 8 years ago

Quotethe_digital_dentist How about printing a big cube and seeing how big the printer can actually print? That would be a powerful sales tool (assuming the cube was actually big). I think I saw something like that in a recent Prusa video. Again, not really looking for a "sales tool", but yes if I was going to claim a build volume for a printer I'd built I'd say that a big cube that size would

Re: Build volume vs extruder travel limit - 8 years ago

Quotethe_digital_dentist The standard is and the thing do is to say whatever it takes to sell the printer. If you ask the marketing department build area will be the bed plate size even though very few printers can really print from edge to edge. Actual build area is hard to predict because it is a function of flatness, leveling, temperature, and size as well as the limits of motion of the extr

Build volume vs extruder travel limit - 8 years ago

May seem a dumb question, but what is considered an "honest" build volume? I mean if I want a 300x300 XY build volume, is that considered the limit of how far the nozzle will reach at extremities, or should it travel an extra 10-15mm in all directions to allow for rafts, brims, etc? What is the standard or considered the done thing?

Re: Rugged CoreXY - 8 years ago

QuoteLarsK On that printer the idlers on the Y axis are cantilevered. That is, they are not supported from both top an bottom. You see the screw comes through what looks like a 5mm plate and that and the clamping should hold the idlers in place. I have come to believe that The Digital Dentist is right in his proposal where he supports all the idlers both top and bottom. It does make installation

Re: Rugged CoreXY - 8 years ago

Don't like the jukebox look cosmetically, but quite a few similarities in my gantry design here.

Re: Atfer Hbot, go to CoreXY. - 8 years ago

QuoteZerginator I am working on a customised version of jands printer since some time. Here are some pictures of the current status: I see you've got the top of the leadscrews fixed in bearings. Aren't they supposed to be fixed at the bottom and on the build plate platform but unattached at the top?

Re: Is there any "rule of thumb" to know how much would a 6mm GT2 belt creep/stretch when tensioned? - 8 years ago

Quotethe_digital_dentist I don't know how much 6 mm wide belt will stretch, but for the same tension, 9 mm wide belt will stretch less. It is a minor change in design to use 9 mm vs 6 mm belt, and cost difference is minimal, so I'm going to use 9 mm wide belt. When numbers aren't available, I tend to err on the side of overbuilding and it has worked well for me so far. That's what I've done, b

Re: Is there any "rule of thumb" to know how much would a 6mm GT2 belt creep/stretch when tensioned? - 8 years ago

Quotethe_digital_dentist Spring loaded idlers are best applied on the low tension side of the belt loop. If the belt reverses direction, the idler alternately operates on the high and low tension sides of the loop. Since it doesn't work well on the high tension side, it's best to use only on belts that don't reverse direction, and only on the low tension side of those belt loops. It's similar

Re: Is there any "rule of thumb" to know how much would a 6mm GT2 belt creep/stretch when tensioned? - 8 years ago

Quotethe_digital_dentist Um, if the belt turns in one direction you can't use a spring tensioner because it will run into the pulleys. Not one of those little spring clips, I meant a spring loaded idler pulley. I didn't mention a car motor either.

Re: Is there any "rule of thumb" to know how much would a 6mm GT2 belt creep/elongate when tensioned? - 8 years ago

Don't know about the stretching, but read one of those engineers manuals somewhere that said that spring loaded tensioners were no good of the belt was running back and forwards. They should only be used on belts that turn in one direction apparently.

Re: Z axis configuration - 8 years ago

Ended up going with 3x (supposedly) genuine TBI Motion 1204 ballscrews off alibaba. I went with a 600mm length overall with the 4mm pitch as it was a standard off the shelf size...sort of, and would suit my need for 450-550mm Z travel. Both this guy and the Australian distributor said exactly the same thing, it came in plain lengths and had to be ground to suit. Difference was that the Aussi

Re: Z axis configuration - 8 years ago

I'd really like to go with 12mm screws, as I agree that 16mm is just too big and heavy. 1204 is a fairly common size in the cheapy chinese's, but I can get any pitch I want from Hiwin. It's one area where I might use the no name brand to save money, as I've got to get 3 of them. I'll see what the prices for Hiwin are like first. Smallest layer height I'd EVER bother with would be 0.05, and to

Re: Rugged CoreXY - 8 years ago

QuoteJamesK I think it's reasonable to be sceptical, the general consensus is that it's at best a very big compromise to combine printing with milling. It's an attractive idea to re-use the 3d motion platform, but anything but the lightest milling is so far removed from the requirements of printing that the compromises don't make sense. It's bad enough trying to design a printer only mechanism ba

Re: Rugged CoreXY - 8 years ago

It would be awesome if the sniping at each other could cease....seriously there's some clever cookies among you, let's match that with with some tolerance of opinions other than your own and some maturity? Please? Back on track.... I realize my design here is massively overdone, and part of that was because I wanted the possibility of using it as an engraver etc off in the future. Then I see t

Re: Rugged CoreXY - 8 years ago

Quotethe_digital_dentist I had some experience with standing pulleys on bolts before and found that the tension on the belt was enough to cause some flex in the bolt and/or the 1/4" aluminum plate it was screwed into and the belt would try to walk off the pulley. I'm still working final details of my CoreXY design out, but trying to avoid that problem which will be multiplied because I'm using t

Re: Z axis configuration - 8 years ago

No they have an 8mm section at the bottom that the pulley will slip onto. Id never clamp a pulley onto a threaded part

Re: Rugged CoreXY - 8 years ago

There's ebay links above for all the pulleys I'm using, and Im using both flat and toothed idlers depending on the side of the belt Im touching. Im not twisting the belt because I dont need to and I would also just rather not. Im not sure about the bearings as I havent seen them yet, but they are off ebay so seeing is believing. As it goes Id like to mount the idlers on 8mm unbrako shoulder bo

Re: Rugged CoreXY - 8 years ago

Quotedeckingman Quotehobbymods I wont be twisting belts or having them run hard against flanges. I will extend the shaft on each stepper so that the drive pulley will be on the correct plane for each of the 2 circuits, and do some sort of pedestal bearing mount to support that extension. I've got toothed idlers coming for where it turns on the toothed side and plain idlers for the other, I'm no

Re: Rugged CoreXY - 8 years ago

I wont be twisting belts or having them run hard against flanges. I will extend the shaft on each stepper so that the drive pulley will be on the correct plane for each of the 2 circuits, and do some sort of pedestal bearing mount to support that extension. I've got toothed idlers coming for where it turns on the toothed side and plain idlers for the other, I'm not going to all this trouble to

Re: Z axis configuration - 8 years ago

Quotedeckingman Quotehobbymods I must have got it wrong about the 1mm pitch being the norm....thought I'd done my homework. I'm looking again at the Hiwin range: And if I'm using a Duet which seems likely, I'd probably be looking at 0.9 deg steppers? The simple/standard internal recirculating screws they have seem to come in a range with all sorts of pitches starting at 1mm, so maybe 4mm wit

Re: Rugged CoreXY - 8 years ago

I think we're getting our wires crossed a little bit again. He said it was important to use the same diameter idler pulleys, 90 deg angles, the same length of belt (obviously) and even tension in both belts (already discussed) for best balance of torque throughout the thing. I also read that any kind of spring loaded tensioner might be an issue in a belt driven system that changes direction qui

Re: Rugged CoreXY - 8 years ago

For Aussies I used these guys for 20T pulleys and 10mm wide GT2 belt. They are reasonably well known and have a reasonable reputation. I'm considering configuring the pulleys with the staggered pulleys on the X axis, like the Fabotum design without the belts crossed. The Gates guy seemed to lose interest, but he did mention that even using different idler sizes for staggering pulley

Re: Z axis configuration - 8 years ago

I must have got it wrong about the 1mm pitch being the norm....thought I'd done my homework. I'm looking again at the Hiwin range: And if I'm using a Duet which seems likely, I'd probably be looking at 0.9 deg steppers? The simple/standard internal recirculating screws they have seem to come in a range with all sorts of pitches starting at 1mm, so maybe 4mm with 2:1 pulley ration would be go

Z axis configuration - 8 years ago

Hi All, I'll need a Z axis with my gantry, thought I'd discuss that separately. Did a lot of research on the belt driven triple lead screw configuration, and despite it all looking diabolical it seems very popular. I'm looking for a 450mm build height on a 300x300 platform, and was looking at using 2x 15mm linear rails at the back with one lead screw in the middle, then a lead screw on either

Re: Rugged CoreXY - 8 years ago

Quotethe_digital_dentist Is your dog bone part intended to impart some extra rigidity to the X axis? If so, you might get much more stiffness without a lot of increased weight by using a piece of rectangular tubing instead of a flat plate. Thing with that is that it needs to have a flat surface with reference shoulder about 3mm deep ground into it. I'll trim it up before the laser cut mockup.

Re: Rugged CoreXY - 8 years ago

Yes it's true the internet can be a pain, but I like to think that things can be clarified. For example I sent this to the Hiwin Australia office: Hi xxxxx, I’m hoping to use a single long carriage (EG15) across the X axis, mounted on the “dog bone” shaped plate as in the picture. The mounting plate will be checked/machined for flatness, and the axis’ will all be trammed properly with a dial g

Re: Rugged CoreXY - 8 years ago

QuoteKoko76 I'm not touchy or annoyed. It's your money, your design, your printer. You asked for help and input, you keep applying value judgements like "better" without being able to quantify them. I've made a couple suggestions to help you be able to better qualify and quantify "better" for yourself. It does not appear to me from your replies that you understand what I'm saying. Perhaps it

Re: Rugged CoreXY - 8 years ago

QuoteKoko76 I guess I thought when you said "I'm well aware of moment loads" earlier in the thread that you were familiar with them. It's not "x amount of kilos", it's force at a distance, in SI expressed as newton meter (Nm). You have static moment loads when a torque is exerted in on an axis such as mounting the rail to a vertical surface and hanging the carriage off of that, in that case the

Re: Rugged CoreXY - 8 years ago

Re: Rugged CoreXY - 8 years ago

QuoteKoko76 Quotehobbymods QuoteJamesK QuoteThe point Koko is making I feel is that our pissy little extruders weigh and exert forces MILES under the extremes these precision rails are made to take continuously Yes, looks like you are right. A quick back of the envelope calculation suggests that the static rated moment specs for mgn 15 in all 3 axis are ~2 orders of magnitude over anything the p