Hi, I have had my MPCNC built for a while now as per Ryans design exactly then with a slight modification, changing from open legs to an enclosed base.
Any issues I have had and have are all due to poorly printed parts on my part, including some of the flexing issues you demonstrate above.
I lived with these issues for a while cutting MDF parts up to 25mm and its had no bearing on the actual cutting and accuracy of this machine in the Z axis, however a poorly printed and assembled Gantry had huge issues on my accuracy in the X and Y which I had to quickly fix by reprinting parts and better assembly.
My machine is 1200mm x 900mm total with a Z travel of 80mm and so far I have no issues with stability using the 25mm galvanized tubes I have, no supports added along the tube lengths and no tube infills.
I have cut MDF, Plywood, acrylic and some test cuts in Aluminum.
I do have issues with Aluminum but that’s more to do with not getting all settings dialed in for Aluminum.
My accuracy with my spindle is about +/- 0.5mm and my laser is about +/- 0.2mm
Any issues with stability were always down to trying to cut too fast or too deep, especially depth for me depending on what I was cutting.
I do, all listed on the parts page. Other things you find on TV are either for a specific use, or I prefer my design for one reason or another. If I like something I ask the creator if I can use it in the official parts.
I bought mine at Alcoa, thickness is on the parts page and FAQ’s, but is very easy to use any size really.
I found the cheapest tubes to be from a local place (which is a national chain) called “metal supermarket”. There is almost certainly a metal supplier in any medium to large city.
I seem to remember having an issue with the roller plate due to using rectilinear infill. For whatever reason there was more flex on one side then on the other.
Of this is the case I may have enough pieces to reprint to warrant upgrading to the s.s. tubing if I can find a good price on it.
In any case adding the 6/32 support system seemed to help.
Dude. I can only ask nicely so many different ways. This statement right here, do you know what that is? That is a rumor that will grow. You just said your part was better, even after I asked you to prove it many many times.
You can very easily prove it with a scale or an actual improvement in your cuts. Nope. You very boldly said you improved the design. No one other than me cares if you prove it or if it actually does anything. Now anyone that sees that one little sentence will ask for your better parts.
The roller plate, it has zero structural functionality, it holds and endstop and prevents the belts from falling off of a poor build. The part isn’t actually needed.
I’ll update when I get back home. It’s been a few months since I printed out the parts. Obviously that part will have no function in the rigidity of the z axis. You can see which part I’m trying to stabilize in the picture.M
Mystatement of it helps, is in regards to the fact that one of my parts, whatever it’s name is, may be of poor quality.
It’s the part that holds the z axis bearings. One side has quite a bit more flex than the other side. So yes. Adding the support helped.
Yes, it helped.
Yes, his comments helped. You must be miss interpreting me here. He ended by stating I hope this helps. His comments made me remember that I was curious as to why one side of that part flexed more than the other. My conclusion is it's an issue with my infill.
Thus, I realize if I’m going to need to reprint many parts, I may as well upgrade my rails, provided I can find some at a reasonable price. Where did you purchase yours from for so cheap, Ryan? Did you quote 42 dollars?
I haven’t been using a weight scale to measure deflection. You can do it with a known static weight and measure actual deflection, so doing that side ways isn’t as easy. Pulling at the z axis with my fingers a pound or so caused a bit of flex( in the part I’m saying may be a bad print) I could visually see.
Again, no reflection on your design, just noticing this on my build. Again, I may need to reprint a few parts.
Can’t seem to post. I hope this doesn’t get posted double
Lets go with this real quick. At what Z distance? Torque=force * distance, hence the half the length twice as strong statement I keep making. You had all the figures and links earlier if you want to discuss this you need to still with complete information. F=ma, think 1lb, concentrated down to the surface area of the bit that is in contact with the surface of the material about 1mm squared and a majority of that energy is kinetic rotational. What would one pound balanced on the tip of a pencil feel like? So maybe just stop with the over analyzing until you try it, at this point I feel like you will not see the complete picture and just keep focusing on one tiny aspect and missing the complete picture. This is not a math problem in a book this is a real world system. Every part depends on another part. FEA can not even be accurately modeled because 3D printed parts are to variable.
This thread is a very negative one. Too many assumptions, no evidence, no numbers, all guesses.
People are trying to help you improve a build that you have not tried to even use yet. You can see this might be an issue. You say your part flexes unevenly, it shouldn’t it is a symmetrical part as is infill, but how do you know that it flexes too much? You are blindly stating you have too much flex but have not proved that. Use the machine. If you can not mill pine wood at 4mm DOC, at 8mm/s, with Dewalt 600W DC motor, single flute up cut bit you have a major problem. You are using a belt driven brush less motor that will be belt driving a collet system with some ratio. We will have nothing to compare it to.
You go through explaining what you quoted and that I mistook it, and then reinforced your own assumption. So now your rumor is here twice.
Who cares if it helped some sort of flex you may or may not have. Does it do anything to a real cut? Please be more considerate.
Early on in this thread you felt the need to tell me solid rod is stronger than tube. You did not complete the statement by adding the increase in weight that comes with that 2.8x’s increase in rigidity and the reduction in accelerations this causes, the price increase, the difficulty in cutting that material, as well as difficulty in finding it. You keep doing this. Cherry picking information you like and not completing the system. I keep filling in your gaps.
How different would this thread be if you would have built a machine with your braced tube or solid rod, made some cuts and shared your findings. Side note here, there are several build that incorporate solid rod, and/or braced tubes in the forums.
I feel your right about this being a very negative thread. Not my intentions but I don’t feel it’s entirely my doing.
All I wanted to do was strengthen the outer rods. What’s so different from doing that than Douglas Bell’s enclosed build or using 1" tube? 3/4 emt is pretty flimsy in comparison. It was expressed early on that a 2’ x 3’ cutting area was too big. I gathered that by your comment suggesting I build the low rider.
In the examples given other who built a machine of comparable size built with thicker pipe.
You quoted me saying one side of one of my parts had more flex. I openly said I believe it to be a poorly printed part. I’d return your request here to be more considerate.
Because they all tried it and told us how it went, there was no second guessing every single aspect of the machines design. Actual real numbers, and usually an odd use case to go with it. Totally awesome!
Dude, stop it. Unsubstantiated claims on inadequacy. There are thousands, literally, of 3/4" builds. There is no reason to build something out of carbon fiber and titanium if $4 EMT is enough. If a spaghetti noodle worked and was cheaper I would use it.
You are making me defend my design. I will. Always. This is my actual full time job, for years, my income depends on it. I take it very seriously. When you make statements that are false, or untested, I will be here to correct or point it out.
I think it’s the perfect time to just forgive everything that has happened so far in this thread. I think you both understand each other much more, and if you still wanted to have this conversation starting tomorrow, ideas would flow much easier, and with less conflict.
No one said 3/4 emt wouldn’t be adequate in a machine. I’m not attacking your machine. Your jumping to conclusions and being a jerk. You quote me outta context. Thanks
Yikes, I am sorry it came across that way, obviously I am better at CAD than putting the right words together. I assure you no ill feelings were meant. I’ll just stay out of your thread.
I will share this with you guys. The original parts I printed we’re in standard abs. Everything was a little tight, and besides these parts I’ve had issues with layer bonding and warping occasionally.
I changed to esun abs+, and after messing with it for awhile, my parts come out fitting like they are supposed to. When I first started using it, I treated it like abs, but it didn’t seem as strong. Slowing the print speed down made a huge difference. This may be the case with standard abs as well, but slowing it down usually resulted in curling.
I didn’t print a hook and load test it, or anything, but it seems a little stronger overall. Maybe one day I’ll test it to be definitive.
Anyway, it’s been a while since I bought my steel for my low rider, but I do remember it being way cheaper offline (even at metal supermarket). Just calling a local shop and asking them is worth it. Asking for smaller pieces could also help.
Sorry if me contributing to this thread has exasperated the situation a little.
My goal was just to let @Jason know that I followed the plans as described using the size chart to make my machine the size I wanted, and that any issues I had were not with the design but my poor construction / printing.
My cheap 25mm Galvanised tubes cost me about £8 for 3 meter lengths, I didnt think they would be up to the task, but even at 1200mm long I have no issue with them, yes they flex if I push down on them but I am putting a lot more force downwards than my machine will ever do.
As my comment on an enclosed base this one done a long time after using my machine and was more that I was fed up hoovering my floor as I don’t have a vacuum system on my machine.
Hi Douglas. I didn’t mean to drag your name in, in the way it came out.
I realize I must be the umteenth person to try an “fix” the emt. I’d like to say though, I never said there was an issue with the machine as it’s designed. Like you said, the rails do flex under pressure. I saw that and wanted to stiffen it up. Whether or not it will help the machine is another question.
This morning I pulled off the new xyz part ( this is the correct name for it) from my printer. It does not flex like the old one. I believe infill patern is to blame.
For the weak part, adding something to stabilize it did exactly that. I didn’t realize how weak it actually was in comparison with this new part, until I held them both in my hand. I assumed once I bolted it all together it would be fine, but there’s no substitute for a properly printed part. With this new part I don’t see a need to resupport it.
@heffe
That’s where I started, but locally they are using internet prices to model their prices. They cater to big industrial companies and can get away with it. Bummer.
Just thinking out loud, but I bent 3/4 emt and 1" emt daily for a few years out of high school, and 1" was pretty tough in comparison. I wonder if the o.d. would work. This is just thinking out loud. Nobody has to go look it up, I’ll check later.
