- January 5, 2016 at 12:51 pm #5448
I guess it is time to start posting my progress on my MPCNC build. I decided that I am going to build it such that it has a 2’x3′ cutting area (X & Y lengths of 35″x47″ with Z length the same as in the recommended set up).
First, I built a worktable to use for the MPCNC out of 2×4’s, particleboard and a workbench kit.
All of my plastic parts are assembled, I just need to cut the EMT to size and then proceed with the assembly.
The question I am struggling with is this….How long should I cut the legs if I am planning on using a second piece of plywood on top of the table as my scrap board? Should I leave the legs the suggested 4″ in the recommended set up?January 5, 2016 at 4:10 pm #5454
Looks good, a giant one!
I know this doesn’t help too much but at that size I imagine you are planning on cutting a lot of thin sheets? I would cut the legs as short as possible, probably shorter than recommended. I’m not sure if you are too far into the table build but I made the bottom feet so the legs can pass through if you can drill some holes where the corners will mount. That way you can leave a little extra and move it up if you need too.January 5, 2016 at 4:32 pm #5455
Yes, I am hoping to be able to cut sheets of styrene for the most part. They are usually less than an inch in thickness.
Now, how about this. Instead of having shorter legs, why not add another 1/2″ or so on top of the table and make it the actual cutting surface?
The table is already build, so I do not think drilling holes or the legs is an option, but not certain.January 5, 2016 at 4:53 pm #5456
That’s how I do It. I stack material to get it as close to the gantry as possible. It is better for the legs to be shorter but I prefer the versatility of a taller machine and accept a little slower cuts.January 5, 2016 at 5:00 pm #5457
Great photos and build, all looks good to me.
My 2 cents about your leg heights. You say you are cutting sheets of styrene, mainly.
I know it has been stated to keep the Z height to a minimum, but the load against the
tooling for styrene would be very little, so you should be able to get away very comfortably
with 4″ of leg height.
The fact that you will be reducing the height with the 1/2″ waste board, only helps you.
So I would say that a 4″ height would be more then fine!
I use a 4″ (100mm) leg height and cut pine wood with a 6mm single bladed bit, at 4000rpm, 15mm/sec with no problem at 2.0mm depth passes.
Greg.January 9, 2016 at 7:47 pm #5690
Well, I got more work done on assembling my MPCNC as well as my first big screw up.
First, my son and I got the majority of the pipe cut for the frame. He was so excited to see what it looked like that I put the frame together for him. Had some issues getting some of the pipe to fit into the corner blocks as they were quite the tight fit. However, managed to “coerce” them into place.
And now the screw up. In tightening the lower corner blocks up this evening, I managed to split the screw hole on one and possibly a second. I was being quite careful in tightening the screws, I would turn one a couple times and then the other in order to get a more even compression of the pipe.
Not really sure what I can do at this point. Will cyanoacrylate work to secure the parts? My 3D printer isn’t able to print at the moment so making a couple new ones are not an option. Will the break have any adverse affect on the performance of the MPCNC? the pipe is already rather tight fitting so I do not think it will come loose.January 10, 2016 at 9:18 am #5713
Don’t worry too much about that crack, There is almost zero horizontal force on those they don’t even need screws.January 10, 2016 at 10:26 am #5715
Awesome! Thanks for confirming. I was worried there.
Now, onto attaching the legs!!!January 12, 2016 at 6:16 am #5781
More progress. Legs attached and gantry installed. Seems to work quite well.January 12, 2016 at 1:33 pm #5793
I cracked one of those same holes too. So far, no problems.
Since I didn’t read anything about actually screwing the corner blocks into the top part for the legs…I just CA glued them on since I’m using a laser with absolutely zero horizontal stress. So far so good on that too.January 15, 2016 at 7:54 am #5899
Hit a few snags last night as I proceeded to attempt to drill the holes in the pipe for the Z axis. First, I couldn’t find a pencil long enough to mark the pipe in the right spots. Then I couldn’t get the pipe to stay put (even w/ clamps) on the drill press so the bit traveled some. I need to go back and re-think my strategy.
Also, a question if someone can clear something up for me. On the Z-axis, how should I position the holes for the tool mount? Should the bottom most one be as close to the bottom of the pipe as possible?January 15, 2016 at 8:41 am #5903
Once I got a new set of drill bits this part has been very easy for me. I drill a small hole, then go back and then drill the over sized hole. I actually just put a foot on it and drill it on the floor. Nice bits are key.
The old way I did it was to use a dremel cutting disk and score an X where I want to drill the holes and do as above.
As for where to drill, use the nut trap part as your guide, short side down is best, backwards from how I originally designed it but slightly increases rigidity. Drill the holes over sized by a large margin so you can adjust the tool mounts a bit. You aren’t trying to screw into the metal just clamping to it. This is how I fix an odd tool angles when I switch tools.January 15, 2016 at 9:13 am #5907
So, I want there to be a space between the bottom of the pipe and the first hole (going from bottom up), correct?January 15, 2016 at 10:48 am #5909
Yup, right about 5-6mm upJanuary 20, 2016 at 6:10 am #6068
I finally got the holes drilled in the z tower pipes and now I am pretty much all assembled. Of course, the “final assembly” did not happen without its issues. When I went to remove the middle assembly so I could attach the Z-axis, I noticed a crack in one of the parts.
Well, I decided to use some super glue reinforced by some Steel putty to hold its strength.
It isn’t pretty, but it’s functional. And to be honest, I don’t remember tightening those screws that much. I try to keep things snug and not “put the uglies on it” as my wife would say. Worst case is I print up some replacement parts as needed. I am planning on printing and adding a vacuum holder to the CNC anyways.
Okay, now onto the good stuff. I got the Z-Axis installed as well as the motors mounted and the belts installed. I used the belt clamps from GeoDave to secure the belts on so I can easily tension the belts as needed. I also left a good bit extra on the various belts for added sanity in the event further tensioning is needed.
I also managed to get the X & Y motors wired up and attempted to get them moving via the RAMPs . Well, that was a huge flop as my laptop would not fully install the drivers needed to talk to the RAMPs . However, I managed to figure out the issue this morning and I can connect to the RAMPs just fine now. I will reconnect the motors later tonight and give it a test run.January 20, 2016 at 6:11 am #6069
Oh, and one more thing. Would this be the correct sizing to replace the printed Rigid Coupler with?January 20, 2016 at 6:34 am #6070
That looks like the right thing to me. Here’s the one I ordered: http://www.amazon.com/gp/offer-listing/B00H1LNX5A/ref=dp_olp_new?ie=UTF8&condition=new.January 20, 2016 at 6:43 am #6071
Flexible coupler will pretty sure give you vibrations problem, I think is best to buy an rigid.January 20, 2016 at 6:55 am #6073
Interesting. I didn’t realize there was a choice of rigid or flexible. I have been using my flexible one for two months without issue. What kind of problems would you anticipate using the flexible one?January 20, 2016 at 7:45 am #6074
Well, i do not have any experience with cnc, I still building my own and first cnc. But i have build 3d printers and used both flexible and rigid couplers in the past.
The flexible coupler are great to use where the z axis have little weight and the threaded rod is upper and the motor in lower position (in an prusa printer for exemple). The flexible coupler will allow to have a more “fluid” movement and reduce the shock of abrupt movements.
In the case of the cnc you need to have very rigid axis and the use of the flexible coupler can give you the next problems:
– allow an unwanted movement of several mm up and down. When you try to make an precise hole of 10mm for example, pretty sure the flexible Z will go up 1 or 2 mm when you will start to make the hole, was final result the hole will not have an precise 10mm deep.
– if the z axis move a lot, this will up and down movements and create vibrations.
-imprecise deep cuts, sometime it will cut less deep, other it will compensate and cut more.
But you can correct some of this problems by simply have the 5mm motor shaft and 8mm rod all inside the flexible coupler and touching.January 20, 2016 at 7:47 am #6075
Thanks for the explanation – I will order a rigid coupling.January 20, 2016 at 8:27 am #6078
I agree with all that. Those a basically springs. If I could find a cheap source for the right sized couplers I would include them in a heart beat, but at about $8 in bulk I’ll stick with a printed one.
Rigid is better, spider couplers would be best. The one you listed is not good, it is an 8mm, we use a 5/16″ I know they are close but they are not close enough in my opinion. You will need to shim it with something like a soda can piece of metal. I have wrapped literally hundreds of these for a previous company I worked for to get rid of the wobbles that the off center clamp creates.
“the uglies” your wife sounds awesome! Next time I break something I am sure that will pop in my head. hahahaJanuary 20, 2016 at 8:43 am #6079
Does anyone have a link for 5mm to 5/16 inch rigid couplers? I already ordered the one Dave C. linked to, so I guess I can shim it like Ryan says, but I’m curious, because I haven’t been able to find the exact size.January 20, 2016 at 9:04 am #6084
I order this one from china, is an 5mm to 8mm coupler
5/16 inch = 7.9375mm, the coupler use 2 screw for each shaft, it will work for the 5/16 inch rod.
price 2.7euro = 3 dollars…January 20, 2016 at 12:05 pm #6106
LOL!! It’s quite catchy, isn’t it??January 23, 2016 at 6:33 pm #6280
Was able to get all 3 axis running via computer control. Sorry, no video just yet.
One question though…on the Z axis should down be a negative value and up positive? I know on my delta printer up is positive. Just not sure if this is the same way.
I will take a video tomorrow and post of it in operation.January 23, 2016 at 6:43 pm #6282
Yup towards your waste board is negative.January 24, 2016 at 6:35 pm #6335
Finally got to the fun part of this build and got my MPCNC to actually move. Had a few mis-steps at first, but after some tinkering it worked out in the end.
My first hiccup was that the upper connector for the Dewalt does not seem to want to close completely. So, in an effort to prevent it from breaking I have one of the bolts just holding in there by itself w/ no nut on the end.
Next, I could not seem to get the correct GCode generated in EstlCam. I followed the walkthrough and still got nothing. The time in Repetier said 45 seconds to complete. I downloaded a Celtic knot to carve. All that I would get is the bit drilled a hole down in the same spot and that is it.
Finally, after downloading GCode from the walktrough, I was able to get the MPCNC to do its thing. When I did so, the carving was a mirror image of what it was supposed to be. In addition to that, there was a part of the carving missing. It was as if that section of the wood was lower than the other.
Turns out, I had the X-axis reversed. Once I switched it all around the carving came out perfect.
Here is a link to the video of the third and final “first cut”.January 24, 2016 at 7:10 pm #6342
The cut looks great! Good Job.
As for the mount I couldn’t see the top mount but try turning it over. I don’t have mine on right now but I think the top one gets put on flipped over. It effects the angle as well.
I actually have the 3rd prototype printed of the new mount, but I haven’t had free time to measure the angle or test it yet (taxes, boring). The 2nd proto had a 0.45 degree angle on it not much but I really want to get it perfect now that I found and easy way to measure the tool angle.January 24, 2016 at 7:32 pm #6348
I might have missed it, but what bit/endmill did you use in your test cut?
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