Results 11 to 20 of 51
-
09-25-2019, 09:16 PM #11
- Join Date
- Jul 2017
- Posts
- 184
It's not really a "frequency", it's switching fully on/off at a specified threshold. It has nothing to do with frequency it's always either full on, or full off depending on what side of the threshold your sensor is measuring. There is no regular, repeated pulse of varying width (or duty cycle) which makes PWM. This bang-band control how most ovens, hot water cylinders etc work. The time between switching is not pre-determined (unlike PWM, where each pulse is a fixed duration, just with varying on time) and the time between switching is measured in minutes if not longer. Even if the switching time was regular, if your period is measured in minutes or even seconds I don't think anyone will call that PWM. Have a look at the wikipedia page for bang-bang control.
https://en.wikipedia.org/wiki/Bang%E2%80%93bang_control
-
09-26-2019, 01:07 AM #12
- Join Date
- Sep 2019
- Posts
- 18
Thanks, but i will probably just go with a mosfet because its more suited for the job. When i say I'm on a budget i just mean that I don't have an unlimited budget and if I wanted to spend a ton on a printer i would just buy one already made. I have several printers already so i don't want a cheap crappy printer that can just print. I want a really nice quality print and a large print volume and am willing to spend the money on things that make a difference like linear rails and maybe even genuine Hiwin or equivalent as I have heard they are worth the money. Its sometimes a challenge figuring out what will really be worth spending on but there are certain things I know will help. anything that makes it run smoother basically so belts, bearings, pulleys, stepper drivers, linkages etc will not be where i will look to save.
I just want to be smart about where i spend the money. A perfect example is the SKR board. It was like $30 CAD compared to a duet or others for $150-$300. I bought a clone E3D V6 but bought the genuine block sock and thermistor kit and hope to replace the heat break soon as well. I may stick to the 24V heatbed just to keep the costs down but may buy the 120v depending on how the budget is doing.
Power stuff I will stick to what is safe and made for the purpose. life span of electronics is related to proper power regulation as well as heat dissipation and duty load etc. I always use decent power supplies and components as it saves a lot of time and money in the long run.
-
09-26-2019, 01:46 AM #13
- Join Date
- Jul 2017
- Posts
- 184
Linear rails aren't bad, but I feel like it's a bit of a sledgehammer to swat a fly scenario. Lots of printers with round rails produce great results, even ones that are indistinguishable from those made on printers with linear rails. It's up to you, but I feel that many people go for linear rails because for the same reason they like to buy fancy cars. At the end of the day you're squirting molten plastic from a 0.4mm bore, and 0.2 is considered a good fitting tolerance, if your round rail can't hold that tolerance it's bent. The biggest practical advantage linear rails have on a 3D printer is that they can be fully supported, so on longer spans there isn't the bendy and flexible bit in the middle that can wobble under inertial forces (or sag if its not appropriated sized, but the rails on a delta are vertical so they wont sag).
This is even more so the case with idlers, pulleys and belts, the cheap stuff from china works fine and is manufactured to much higher tolerances than your printer will be outputting. Belts can sometimes cause problems from what I've heard with the rubber wearing off the belt, or not having fibre reinforcement but I've never run into these issues myself. Any difference someone claims between a chinese idler bearing and a name brand one is entirely in their head.
I don't know how much money, if any, you'll save buying a 24V bed vs line voltage, but at that size/power requirement I can virtually guarantee you'll spend more money than you saved on a 24V power supply that can handle that much current.Last edited by Trakyan; 09-26-2019 at 01:56 AM.
-
09-26-2019, 11:13 AM #14
Man you are chock full of great advice. The linear rails get bolted to the frame every inch or so whereas the rods mount through holes only at the very ends of the rods and the entire length of rod can flex and the holes can get loose and then the rods themselves can move not the bearing against the rod. That is why we all upgrade to the linear rails. Because it stops the z wobble completely even with less than perfect leadscrews. You should just read more on this forum and try to limit the amount of advice you are giving here.
Last edited by AutoWiz; 09-26-2019 at 11:20 AM.
-
09-26-2019, 02:06 PM #15
- Join Date
- Sep 2019
- Posts
- 18
The reason for the linear rails has been gone over but it's also to enable a speed increase basically. The more sturdy and less flex the faster you can print without losing resolution.
As for the idlers/pulleys and belts, belts are important because the cheaper the belt the less fiber and more elasticity which is bad for accuracy and print resolution. The idlers and pulleys themselves are fine buying cheap but its the bearings that make the difference. I bought a bunch of cheap ones and all the bearings were crunchy and not smooth. They would be better to just use bushings than terrible bearings. I ended up going to the hobby store and buying good RC car bearings and fixed the issue but its a pain. better to just buy decent ones with better bearings.
While these things all seem like small details, they add up and end up compounding to cause problems that can be avoided.
For the heated bed, I completely agree it would probably be cheaper to buy the mosfet than to buy a 24V power supply that would do the job. I'll probably do that.
-
09-26-2019, 03:54 PM #16
- Join Date
- Jul 2017
- Posts
- 184
Again, I already mentioned the bending, and that the rails can be fully supported which prevents that. My point was just that there are plenty of printers that get good results with rods. You can't say "we all upgrade to linear rails", we don't all do that because cost is a concern, and there are a lot of other ways to get rid of z wobble. Plus, the OP is building a delta with belts so the the z wobble you get from a bent screw is irrelevant.
@reefsider
As for crunchy bearings, it wont influence your print unless it takes you a cheater bar to turn the bearing. Cleaning and re-oiling the bearings will make them run a bit smoother if really bothers you, but your printer wont care. If you're worried about belt stretch you should go for steel core belts not name brand aramid or glass fibre ones. In that case even the cheapest Chinese belt that might skimp on the reinforcement will do fine. For such a big delta with long belts steel core might be well worth considering, just make sure you pick the right pulleys and idlers so you don't end up with broken reinforcement in a few weeks.Last edited by Trakyan; 09-26-2019 at 04:03 PM.
-
09-26-2019, 04:55 PM #17
Drag on the drive belt will most certainly impact print quality buddy. And crunchy bearings are not steady drag. They roll free then get tight then roll free then get tight and you will most definitely see that in your print. And with that I am gonna tap out of this. The OP seems to have a good working knowledge and I think he will do just fine on his build. I just hope he shares a whole mess of pictures of the build with us along the way. I for one would love to see a home made large format delta. Godspeed OP. Don't let us down with the build thread.
-
09-26-2019, 05:04 PM #18
- Join Date
- Sep 2019
- Posts
- 18
Thanks very much for the input and encouragement! I think it will be a pretty cool looking printer that will be really sturdy when I'm done with it. I will keep the post updated with pictures as I go. It may take me a while to do things as its a side project but it will get done eventually.
I plan to take the parts to the machinist in the next week or two to have the parts squared and cut to the same length. I'll take pics and then start the build. I just got the rim and will cut that in half tomorrow so i can model it in fusion and get on the assembly file and start some simulations.
Cheers!!
-
09-26-2019, 08:52 PM #19
-
09-27-2019, 07:18 AM #20
honestly the linear rails will make absolutely no difference whatsoever on a delta.
A 4 wheel carriage, properly fitted, will run smoother and faster with less potential vibration.
As far as belts go - get decent ones but also use a tension based belt tensioner.
They look like the middle of a cloths peg.
Bascially they keep the belts at exactly the same tension, no matter what.
One of the first things I did to my delta was add 2 to each belt.
It also means you don't need complicated belt tensioning apparatus. https://www.amazon.co.uk/HALJIA-Timi...gateway&sr=8-5
One thing you probably haven't considered is a kit from this chap. They'd used one on the duet3d stand at tct this week.
http://www.zatsit.fr/english-summary.html
Dunno if you can buy them yet or not, the guy who builds the duet machines is a certified mechanical genius. So he probably got some ahead of the launch.
But worth considering. On checking the kickstarter. It's a full delta kit and hasn't started shipping the kickstarter items yet.
So worth a look, but it woupd need to be a diy setup. Magnets and carbonfibre rods probably a better bet.
Unless i missed something and you're using the linears for the arms - I can see that working, lol
***
Oh yeah (puts his mod hat on), autowiz and trakyan - play nice, there's a couple of good lads :-)Last edited by curious aardvark; 09-27-2019 at 07:30 AM.
Ender 3v2 poor printing quality
10-28-2024, 09:08 AM in Tips, Tricks and Tech Help