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RepRapPro's Ormerod http://reprap.org/wiki/Ormerod
Re: Fixed, non-mechanical probe idea: Inductive Proximity Sensors - 10 years ago
Hi The CNC guys seem to have abandoned them for probes and just use them for limit / out of range sensors. I played with a couple of the parts you mentioned. They don't seem to trigger as reliably as a microswtich. Bobby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Hi Early on thrust bearings were discussed, and rejected (I think) based on cost. Do not appear to be overly expensive if you can use a bunch of them. They do not fit nicely on an arbitrary metric bolt ..... Bobby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Hi I thought (and maybe wrongly) that taking the play out of cheap bearings with some axial tension was part of the design..... Bobby uncle_bob - Delta Machines
Re: Fixed, non-mechanical probe idea: Inductive Proximity Sensors - 10 years ago
Hi Another thing to consider - they are temperature sensitive. Get them close to a heated bed and the sense distance will change. Bobby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Hi At this point I"m not even sure that a change in the arm joint *would* impact my layout. The one thing I want to make very sure of is that a change would not mean moving the pipes. Switching from one joint to the other is pretty cheap / simple. Chopping all new plywood - not quite so easy. Bobby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Hi As I rotate the "column triangle" relative to the "screw triangle" (yes I have an angle specified in the model for each relative to the base) I eventually hit the point where getting the printed part out of the beast is a bit difficult. I'm well away from there right now. I'm also *guessing* that having the pipes and shafts close to each other is a good thing in terms of keeping it all rigidby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Hi The arm being offset from the drive screw gives me about an inch or so of clearance around the support pipe that's not there with a centered arm. Put another way - the arm moves over towards the pipe by the width of the arm when you center it. The arm hitting the pipe when you are at max rotation is one of the constraints on how close in you can push the support pipe. Depending on a whole bunby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Hi A straight arm joint does not allow the arm to "sneak around" the support pipe quite as well. Time to do some more modeling.... Bobby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
If you look at some of my shaft placement sketches, they do result in a full use of the rods and a part that can be lifted out of the printer. If you drop the arm junctions on center, the hot end and mount structure comes up further into the "empty space" at the top. That's not to say you *should* do that. Put another way, having the arm pivot points almost hit the build plate uses up more ofby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
QuoteSheldonE Quoteuncle_bob What is the advantage of the racks over the lead screws? I was thinking about the issue of not using the whole length of the lead screw for the Z height. The suggestion to use rack and pinion was just a "throw it out there" comment. It seems to have more problems than it solves. I don't know that it creates more issues, it simply has some follow on impact on the dby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
If the racks move and are as short as you describe, then they would need to be much more rigid than the lead screws. The screws are terminated at both ends to keep everything lined up. With your proposed design, one end of the rack is "floating". To retain the captivated ends, the racks would need to extend 1X past both ends of the printer. What is the advantage of the racks over the lead screwby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Do the motors move or are they stationary? If the motors are stationary, the moving racks get pretty crazy. If the motors move keeping things attached without further structure gets a bit interesting. Either way having the system rotate like the LISA does would be difficult. Once you drop rotation at the arms it's not really a LISA.by uncle_bob - Delta Machines
Re: The minimum angle between rods and tower? - 10 years ago
The rods can go to "negative" angles (past vertical) in some designs. As long as nothing hits, there's no magic maximum angle. Look very carefully at what's going on for interference.by uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
My base has morphed a bit: It still fits through the ever famous door. It's optimized for motors and electronics above the mid plate. More or less - no more bottom plate.by uncle_bob - Delta Machines
Re: Stepper motors clicking while printing - 10 years ago
Have you checked the tightness of the set screws on the belt drive gears?by uncle_bob - Delta Machines
Re: Prusa i3 Plate stabilizer? - 10 years ago
There's not a lot of rod in the second approach. It's a bit dated, but it might fit the printer you have. There isn't going to be a better / cheaper approach than that one.by uncle_bob - General Mendel Topics
Re: LISA Simpson - 10 years ago
So now that we have some very nice drawings to look at - back to the calibration. I made a comment about starting with a flat print and never explained why. Here's what I'm thinking: 1) Make a simple stick and use it to get all the lead screws spaced the same. Do this on the top and bottom plates. 2) Check your other parts to make sure they all are the same. 3) Check your support pipes to beby uncle_bob - Delta Machines
Re: LISA Simpson Take 2 - 10 years ago
Here's an alternative to sinking the build plate. I'm not claiming it's a *better* alternative in all cases... Make up a C shaped structure to elevate the bearing that holds the lead screw above the mid plate. Have the open part of the C towards the build plate. There is a flat plate on the top of the C shape that the bearing mounts under. Think of it as a pipe supporting the bearing mounting plby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Since the main impact is from the tan function, the question becomes - are we in a "cute" region where there's a math shortcut that saves xx% of the cycles? Probably not.....by uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Quotenicholas.seward @Hazer: Real quick. The prepocessor I have made breaks movement in 1mm or smaller chunks. (Actually whatever size you want but 1mm doesn't show any artifacts.) At that scale a straight line in one coordinate system is approximately straight in the other. All the math is the same between the Rostock and LISA (LISA enjoys the same simplifications that the Rostock does.) exby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
More to the point, if you are doing this on what's basically an 8 bit machine, precision costs even more compute cycles. Something like an ARM with an FPU would run major circles around a Mega in this regard. I can get that sort of chip for < $10 from any of a dozen vendors and multiple flavors from each vendor. A full board costs more than the chip on it. Even after markup the board isn't allby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Most of the Delts'a out there have universal joints in them. The tolerance / wear / wobble issues with them are well documented. Going from the fancy bearings in a LISA back to the universal joints would not improve the accuracy. None of the Delta printers print perfect parts right out of the box. The same is true of cartesian printers. My i3 did not print perfect cubes right out of the box. Ifby uncle_bob - Delta Machines
Re: Head rises when moving towards the centre? - 10 years ago
What you have is backlash. Since it repeats every time, it's not a skip. Look at things like belt tension and play in the rod ends. One classic is the belt drive gears slipping back and forth on the stepper shaft because they aren't quite tight enough. If your steppers have flats on the shafts they will slip over a very narrow range. The result will be what you are seeing. If it was a measurby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Motors: Speed got me back to looking at the steppers that came in a while back. What came in isn't quite what the listing said it would be (welcome to auction sites ...). The motors in the listing did not have any torque vs speed curves on them. The motors I got (3A motors) *do* have torque vs speed curves. Sounds like good news.... The motors pretty much die (torque wise) at 300 rpm. Judginby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Math: I was going over the spread sheet back and forth figuring I'd made a really basic error. They are the ones that are very hard to spot (you missed the existence of a third arm segment). New improved smaller fits through door drawings coming soon. Thanks! SumPod Math: All delta robots have the same basic issues with shape. When you want a straight line or a circle, you move all three axiby uncle_bob - Delta Machines
Re: LISA Simpson - 10 years ago
Math Question: If I look at the ever popular: 1) The point that the largest circle hits the build envelope appears to be half way between the two drive shafts. 2) That's where the arm from the third drive shaft is horizontal. 3) The distance from the shaft to the hot end should be arm + hub offset + shoulder offset (unless I have those terms wrong) 4) That's 200 + 50 + 37.5 = 287.5 from tby uncle_bob - Delta Machines
Re: LISA Simpson Take 2 - 10 years ago
Warp: My concern is mainly the warp being humidity / time dependent and messing up your bed level. Three pivot: Darn that physics stuff .... I had been looking at it only at the edges. The center does indeed create an issue. I'm wondering if a heavy center would seek the lowest point . I don't think I would want to depend on that. To much chance of it turning in to a very cool looking rotaryby uncle_bob - Delta Machines
Re: LISA Simpson Take 2 - 10 years ago
If you are going to the effort of putting the leveling probe on the head, you might as well use it to its fullest. Plywood does change as it dries out. Variable warp with time is not at all an unusual thing. The biggest issue for probing is space in the middle of the printer. Here's a possible solution: 1) Right now all the arms meet at a single vertical pivot point directly over the hot end. Thby uncle_bob - Delta Machines
Re: Has anybody tried 3mm filament in airtrippers filament drive for rostock? - 10 years ago
One limit case is trying to push filament with close spacing against a glass print surface. Nothing's ever flat / level so you get variable back pressure as you hit the bumps ...by uncle_bob - Delta Machines
Re: LISA Simpson Take 2 - 10 years ago
I've done the auto bed leveling stuff on other printers. It does work, but you need to do it right. The probe and mount need to be more rigid that you might at first think. Getting a top mounted probe past the arms is a bit exciting in terms of getting the problem past the arms. Mounting the probe on an arm is a clearance issue with arms bumping each other. If you have the arms low to give you maby uncle_bob - Delta Machines