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Safety...
My view of it is that as the first layer goes down, it is tied to the bed and can't shrink. As subsequent layers go down further from the first layer, they do shrink. The bed heated to the glass transition temp. of the plastic allows the lower layers to relax and form an orderly transition from the unshrunk layers closer to the bed to the shrunken layers further from the bed. If the heated bed
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LoboCNC
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Looking forward to seeing test prints.
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LoboCNC
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Yes, these are, in fact, PIC-STEP boards which are still sold by JEFFREY KERR, LLC (although I'm not actually running the company myself anymore). They are functional, but pretty dated in their capabilities (only full/half stepping). They are still being used by companies that designed them into products years ago, but there are better and cheaper alternatives today.
And JamesK is right - the
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LoboCNC
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QuoteTangent1001
Can anyone give me a link where I can buy a pair of these?
Unfortunately, there was not a huge amount of interest in this so I've pretty much dropped the project.
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LoboCNC
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Regarding linear encoders vs motor shaft encoders, keep in mind that if there is any backlash or flexibility in the system, trying to servo-out the backlash can be difficult to do and often introduces hunting behavior or other instabilities. Industrial systems sometime will use two encoders - one on the motor to stabilize the position control and a second linear encoder to correct for backlash.
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LoboCNC
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The New Matter MOD-t printer (yes I know, closed-source) uses DC motors with optical encoders for all the reasons mentioned, and they are cheaper than NEMA steppers. They also eliminated the limit switches which always seem to be a nuisance.
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LoboCNC
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To throw my two-cents in: I just helped put together 4 FLSUN Prusa kits for the local high school. They were $220 ea with free shipping. There are decent pictorial instructions and when built as instructed, they actually do print OK. HOWEVER, I made about a half-dozen important mods to make them easier to use and print better, and maybe another half dozen minor tweaks. With that done, they ac
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LoboCNC
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One thing to note with ring-type blowers that attempt to blow air at the nozzle from all directions, by virtue of symmetry, the air velocity right at the nozzle tip must be zero. Of course, if the part itself occludes one side of the duct and the other side is unobstructed, you lose that symmetry and you do get air blowing on the critical outer edge of the part. But if you are printing somethin
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LoboCNC
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QuoteOrigamib
If you want awesome strength, consider annealing. Even PLA performs well with annealing.
I've tried annealing PLA, but have seen a significant amount of shrinkage. In particular, I tried annealing a CF/PLA guitar body and it distorted enough to render it useless. Has anyone else had this issue when annealing PLA?
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LoboCNC
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As a mechanical engineer thinking about almost any of the details of making this collapsing 3D printer, building something that works at all would be monumentally complex. Building one that works well, even more so. And then at what cost? And to what end? To save someone (sometimes) 8" of desk space? I'm afraid this is one I'll believe only when I see the sample prints.
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LoboCNC
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This looks like a solution in search of a problem.
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LoboCNC
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QuoteJamesK
QuoteJamesK
I'm pretty sure that last time I tried to order from them they declined to ship to Canada, but it sure looks like they can do it.
Ah, I remembered right:
QuoteDue to the cost and complexity of shipping our products to Canada, we are only able to accept orders from businesses and schools. We’ve canceled your order.
Why they can't make that clear on their website is beyon
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LoboCNC
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QuoteECJ
I was tested to remove epoxy from aluminum using acetone. I poured some acetone and covered with pvc film to not evaporate and let it act for 5 minutes. Acetone obviously does not dilute the epoxy, but it soften and lose grip ability! Then it is possible to scrape easily with a plastic spatula or even with the nails.
You can also use a heat gun to soften epoxy and then scrape it off.
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LoboCNC
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QuoteJamesK
QuoteLoboCNC
That's why I was wondering if it might be worth testing the McMaster PET/polyester adhesive backed film. If it works, the adhesive backing would be way more convenient than glue, and also, McMaster is pretty consistent with their sourcing.
For sure it's worth trying. A lot will depend on the temperature characteristics of the adhesive. I see some of the 3M transfer tape
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LoboCNC
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QuoteJamesK
For example, polyester is a family of chemicals that includes PET, and PET itself seems to come in multiple forms. I guess all you can do is test a particular product and hope that the manufacturer doesn't change the content.
That's why I was wondering if it might be worth testing the McMaster PET/polyester adhesive backed film. If it works, the adhesive backing would be way more co
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LoboCNC
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QuoteECJ
QuoteLoboCNC
Has anyone tried adhesive-backed polyester film from McMaster (https://www.mcmaster.com/#8689K42)?
In the description says it's PET. I already tested PET film and the result is not good. The adhesion of ABS to PET is worse than that of glass.
Do you know what type of polyester is in the transparency film you are using? 3M transparencies claim to be made of PET. Maybe a d
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LoboCNC
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Has anyone tried adhesive-backed polyester film from McMaster (https://www.mcmaster.com/#8689K42)?
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LoboCNC
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Quoteobelisk79
Fair enough, being the manufacturer I'd lean towards believing their numbers as well. I am going to be switching from mxl belts to gt2 in a couple of weeks hopefully. But it will be coming along with a redesign of my mechanical motion as I frankenstein my CubeX into a CoreXY machine I've dubbed the CubeXY Project. I'm not sure if it would really be useful as a direct comparison bet
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LoboCNC
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Quoteobelisk79
Given the same materials used for production, there should be little to no difference in equal width/length belts. Any difference at that point would come down to quality control or amount of embedded fiberglass which I imagine would vary based on factory it was produced in. The real difference would be in looking at other core materials as mentioned above.
Yes, you would think.
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LoboCNC
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QuoteDragonFire
The resistance to stretching is mostly down to what sort of stiffener a belt has embedded in it. Some have steel or carbon fiber embedded.
There is wide variation between the different variations, even within the GT2 range, let alone comparing it to other types of belt.
I'm just looking for an apples-to-apples comparison of MXL vs GT2 (2mm) - standard neoprene belts with fibergl
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LoboCNC
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I ran across this a little while ago:
Apparently MXL belts are about 25% stiffer than GT2 (2mm pitch) belts. I use MXL belts because they are a little more available, but I know most people are using GT2 belts because they theoretically have less backlash. Does anybody have experience comparing the two in the same machine?
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LoboCNC
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Quotedc42
QuoteLoboCNC
1. If the nozzle hits a bump (some errant bit of filament) the X or Y motor will be pushed out of position. With open-loop control if it gets pushed out by more than 1 full-step, then you'll never recover and forever have shifted print layers.
Actually it needs to slip by 4 full steps, although something that blocks motion for just 2 full steps or more will cause that t
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LoboCNC
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Quotekr_
1 - Missed steps when the nozzle hits a bump that sometimes appears when doing top infill (I don't want to lift the nozzle or slow down both the travel and the top infill speeds for the whole part so I currently edit the Gcode to reduce the feedrate for the problematic layers only...)
2 - Missed steps when fast solid infill moves hit a natural frequency (resonance) of the Y axis.
Both
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LoboCNC
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Quoteo_lampe
My above mentioned question was also related to geared steppers and the chance to eliminate backlash with an encoder on the output side.
When using a geared stepper for your extruder, the backlash isn't really important because you can always add a fixed increment to the retraction distance to compensate for the backlash.
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LoboCNC
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Quoteo_lampe
I see the biggest benefit of closed loop steppers in the possibility to use smaller/lighter steppers for direct drive extruders with gears ( say you want to build a mini-E3d Titan with even smaller stepper )
Can you confirm this?
As mentioned earlier in this thread, you might be able to use a slightly smaller stepper, but without gearing and running faster, you aren't going to get m
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LoboCNC
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Quotetrampas
I was confused over what you were calling phase advance, I think I understand now. I do not do this currently as my goal was not maximum motor speed, but rather positional accuracy.
Is there a need for such speeds? I had figured most people would be happy with full stepping speed, and microstepping accuracy.
You don't get a lot of torque at the higher speeds, but it can be handy fo
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LoboCNC
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QuoteMechaBits
Is this a similar solution?
Yes, this project looks more like the standard commutation + PID control. And then there's this ,a discussion of my earlier effort at a closed-loop stepper controller.
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LoboCNC
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Quotetrampas
LoboCNC,
I am changing the current on the Vref1 and Vref2 pins such that I have 256x microstepping at the A4954 driver level. Thus I can can adjust the motor for very small errors, less than 0.01 degrees, the A4954 driver also lets me change the current (torque) (ie magnatude) going to motor. So I can move with a lot of current one microstep or a small amount of current one micros
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LoboCNC
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Quotetrampas
The code does implement phase advancement which in simple terms, allows dynamic step size on the stepper motor. That is the driver code for the A4954 implements 256x microstepping, while I have normally been running the external interface at 16x microstepping. So what happens is when a user requests a step internally the firmware calculates what the desired angle is, then it measure
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LoboCNC
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Trampas, Great work! Does your version of the code implement phase advance in the motor commutation? This can dramatically increase the top speed of the motor.
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LoboCNC
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