Constructing Janus, by Dirk

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Constructing Janus, by Dirk

Postby dirktheeng » Sat May 07, 2011 1:47 pm

Well... I finally broke down and parted with the money to build a laser. I actually designed one myself, but decided against building it after seeing the 2.X laser system here and adding up the costs of each. Bart's laser is smaller than I would have liked to have, but I also figured out how to make strong items that are much larger than the table (actually I am workign on a design for a 4'x'8 CNC router where all the parts can be cut out from this system. It will be very competative with the BlackToe router, and probably better actually). So far, I have ordered the parts from Misumi and gotten all the kits from Bart. I got them 3 days ago and have been carefully putting stuff together. I am up to the point of completing the gantry now and will post some pictures when my wife gets home with the camera. I have made several changes/improvements to the system already and will post them as I go. I have several more in store, but they will have to wait until I finish the build becuase I need to cut new parts for them. In general, this has turned out to be a good system, but I have found some room for improvements.
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Fixing a V-Rail that got glued up wrong

Postby dirktheeng » Sat May 07, 2011 2:22 pm

So far the only thing that happened that was almost tragic (ok that may be a bit of an overstatement, but hey I'll take my literary freedoms here. After all it is my buildlog) was when I accidently glued up the longest V-rail on the X axis in the wrong position. I don't know how it happened still, but when my wife and I finished setting the rail, there was a gap between the the overhanging lip and the side of the extrusion on one side. It was supstancial too, enouth that the car would bind. Also, I have to mention that super glue is incredibly strong. Even after just 30 seconds of set, I could not move the rail with even a clamp or vice. There should be no concern about these rails moving or failing. I could hardly believe it. Anyhow, after the proper ammount of freek out and pannic, I realized that this was completely fixable. Fortunately we had used super glue and not epoxy (though if we had used epoxy, I probably would not have made this mistake as I would have been able to adjust it with time to spare). Being a chemical engineer, I quickly realized the solubility of sodium acrilimide in acetone and put together a rescue plan. I made a trough our of aluminum foil and went and got my trusty quart of acetone. The trough was made to closely fit the shape of the extrusion with the rails on it so I didn't need a lot of acetone. I took it outside on the deck, put the part in the trough and filled it with acetone. I used about 2-3 cups of acetone by the time it was all said and done between spills leaks and evaporation. I let it sit in there for about 4 hours or so (by the way, after about 20 minutes any excess glue sitting on the surface was dissolved or softened to the point that it could be wiped away with a rag). After letting it sit for most of the afternoon, I pulled it out and was able to pop it off with a clamp. No damage what-so-ever. I think if I had left it in all night, they probably would have fallen off by themselves, but I wasnt' that patient. The only side effect was a white residue left on any part that was submerged. I figured this was what was left of the glue as it came off with a wipe of an acetone soaked rag. I was actually planning on trying to remove both rails, but the other one didn't have a substancial gap and couldn't be budged with a clamp after the short soak. I actually found a product that is supposed to "debond" super glue in unter a minute. It's a solution of dimethylformamide. the DMF will strongly bond to the acrilimide and solubilize it. Check out ... =jndqrpgrc. If the acetone trick hadn't worked, I was going to try that. The DMF is known to be a much stronger solvent than acetone. However, given enough time, the acetone will work. The tigther the gap, the longer it will take as the acetone has to diffuse in through the narrow super glue layer. If you want to un-glue tight rails, I suggest finding a metal pipe or some sealable contaitner to hold the part under the liquid level and letting is sit for a day or so.
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Advice for new builders

Postby dirktheeng » Sat May 07, 2011 4:33 pm

Just thought I would give some helpful advice for people wanting to build the 2.x laser based on my experience:

1) study the drawings in addition to or in preference of the google instructions. The biggest challange is getting the correct number of t-nuts in the rails at the right time. I have had to take things appart repeatedly because I missed a t-nut or put them in the wrong position relative to other parts. It is not enough to just slide them in the track in some cases, they need to go in the right order relative to other parts.

2) Buy at least 1 pack of 50 HNTP5-5 t-nuts (the spring loaded ones as apposed to the HNKK5-5, the ones you have to slide in from the end) when you order from Misumi. They are more expensive, but you will wish you had a pack when you forget to put the KK5 in from the end and everything is assembled already. The TP5's don't need to slide in from the end, they are shaped right to go in anywhere along the t-slot and they have the advantage of saying where you put them due to the spring. The build probably would have taken a several hours less if I had those. Plus, when you want to modify the laser later, you will want to have these on hand so you don't have to take it appart to add anything.

3) Those #4 screws and nylon nuts that hold the belts in place on the x axis are a real pain. I recognize the need for some sort of resistance to thread motion there, but getting them in after the gantry is in place is hard. My little philips head screw driver was too long so I had to go get another one. I couldn't get on the head strait. I got a short #1 philips (about 2" long). It was still a royal pain to try and get them in. I ended up taking the nuts, threading them on just a little bit and holding the nut in a lighter flame for about 10 seconds and then quickly doucing them in cold water. This melted the plastic into the threads just a little bit and made them slightly easier to turn (still not going anywhere after install). I would have prefered to have nuts that were not nylon locking so I could use threadlock on it or something like that. You can use threadlock in a nifty way to keep from really figting to get it off. Put the nut on all the way and just coat the back with a very small drop (use a q-tip to apply). This keeps the nut from unscrewing, but doesn't lock the threads so hard that you can't get delicate parts off again if you have to later. (that comes from my model aircraft building)
Last edited by dirktheeng on Sat May 07, 2011 9:50 pm, edited 1 time in total.
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Re: Constructing Janus, by Dirk

Postby bdring » Sat May 07, 2011 4:57 pm

The nuts can be frustrating. Tim did a great job of listing the nuts in the build instructions, but you will miss some. Regardless, you will probably want to add your own mods later and the post assembly nuts will be needed.

We almost need the instructions to go step by step on each piece where it says put 5 nuts in front of you. Install piece x. If you still have nuts in front of you, you screwed up. Stop, and go back a step. :)

Dirk, if you want access to edit the build instructions, please let me know.

I have said before.... While the post nuts are more expensive, you will be more than happy to drop $5 bills into the slots rather than take apart at some point.
"If you didn't build it, you will never own it."
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Re: Constructing Janus, by Dirk

Postby Enraged » Sat May 07, 2011 5:37 pm

if you buy 3 of the bags of 100 nuts you will have a lot extra, so why not drop a few extra into each rail during assembly?
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Re: Constructing Janus, by Dirk

Postby naPS » Sat May 07, 2011 6:59 pm

I dropped several extra nuts in each rail of the extrusion that would have a concealed channel. The issue comes in with when the nuts are trapped between two pieces, and you need to move them to the other side of one of those pieces. It's not that hard to do, usually, as the pieces that are trapping them are typically the angle brackets and can be un-bolted temporarily, but it's still a pain. The post-assembly nuts are pretty awesome to have in that situation. Much faster than trying to move pre-assembly nuts around. The only issue is that if you are trying to place one close to a corner, you have to be very cognizant of the direction you place them, as the threaded hole is not centered on the nut, but pushed over to one side.
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Re: Constructing Janus, by Dirk

Postby dirktheeng » Sat May 07, 2011 9:53 pm

I am going to be modifying the z axis to give it more stability (I want to have a positive stop on the table that I don't have to worry about moving when the table moves up and down). I am definatly going to be ordering post assembly nuts then and keeping them around. No doubt they are more expensive, but it is a royal pain to have to disassemble frequently
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Modifications to get a full 13" of X travel

Postby dirktheeng » Sun May 08, 2011 5:26 pm

I got the camera from my wife and I have a few pics of my machine, Janus. She's quite an eye catcher, if I don't mind saying myself :lol:

So here is the first pic. I've made a lot of progress to get to this point and I'm quite proud of her so far.


As you can see, I have gotten the main frame assembled as well as the gantry and have it all alligned. If you study this picture, you will find that it is not quite the same as other 2.X builds because I made several changes to maximize the travel in the X axis. Some of the projects I have planned could really benefit from this extra space. I can get about 12 7/8" of usable space on the X axis with things arranged this way.

Here are the pics of the mods necessary to get that space.

First, you have to move the contact switch and post on the Y axis to the other side.

Contact Switch
Y Axis Post

You also have to flip the bolt upside down on the back side of the laser car or trim the blot (I flipped it because it was easier).

Bolt Flip

Next, you have to trim the laser mounts to give clearance for the laser car wheel and deck. This was really easy to do with a dremmel. It was far easier than cutting a blolt. The plastic cuts really well. If you notice, I cut a 2 step notch in the laser mount. I DO NOT RECCOMEND DOING IT THIS WAY. I chose to cut the plastic to move the bold head down and give just a little extra clearance between the car deck and the top of the bolt. However, this created a problem in that it put the edge of the bolt in line with the top of the vgroove bearing. I actually didn't need to do that as there was about 1mm clearance between the deck and the bolt in the first place, but I didn't want it to get caught. If you have clearance problems, grind down the top of the bolt or repace it with a pan head. I had to grind down the side of the bolt to make enough clearance for the car to pass freely. It all works fine now, but I wouldn't do it this way again.

Laser Mount Mod 1

This picture kindof shows the clearance you need... it is at an angle so it doesn't look that close, but it is You don't need to trim back the plastic as far as I did to make room for the wheel, but you definately need to cut some of it off.

Laser Mount Mod 2

You also have to put the z axis top ilder bearings upside down and adjust the threaded rods os they don't stick up at all.

Z axis idler bearing

I also put the z axis motor mount on the botom level. I will use standoffs to mount the motor just like the Y axis motor.

Moved Motor Mount

Note: I am oing to move the pullys to the underside of the bearings. I just thought of that when I was sitting here looking at Janus and saw that I had room to do that.

I also had to countersink this bolt on the LHS idler pully. I used a 5/16" spiral bit and it worked very well. The plastic cuts very well. I used the other bolt hole to bolt the fixture to the top of the frame and that worked very well to hold it in place while drilling (I don't have a shop set up yet, but that will come soon enough). The 5/16" hole was perfect size for the bolt head. It fit very snugly and acted like a nylon bolt. It couldn't have been "engineered" more perfectly.

Countersunk bolt

The last thing to do is notch out the left side gantry car as shown below. This side is longer than the other. I cut this out to make clearance for the idler pulley. You can also see that I am just bairly on the rail with the lower wheel when my contact switch is thrown. This is fine for homing, but I would set my zero point a couple milimeters in from the contact switch.

Notch LS gantry car

So far, this project has been very fun and challenging. It is very freeing not to have to worry about messing something up that would void a warenty. It is my project and I can do what I wish with it and I really like that freedom. Plus if I build it I know how to fix it.

Edit on 5/9/2010:
I found that you also have to remove the RHS cover catch as the RHS gantry car hits it. I don't think that should be a problem as only 1 catch is needed to hold the lid open.
Last edited by dirktheeng on Mon May 09, 2011 8:30 pm, edited 7 times in total.
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Re: Constructing Janus, by Dirk

Postby bdring » Sun May 08, 2011 5:56 pm

No, there is no warranty. Actually there is an anti warranty. If you destroy something while trying to void the warranty there is a warranty. In other words, I'll gladly support innovative hacking gone bad with replacement parts. :D

My motto "If you didn't build it, you will never own it." is a hack on the "Makers Manifesto"... If you can't open it, you don't own it. I read "open it" as "hack it"

Good work Dirk. I actually have a few similar things in the works to release if and when MakeSlide is available.

PS: Z pulleys do go underneath per the drawing.
"If you didn't build it, you will never own it."
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13" x axis continued

Postby dirktheeng » Sun May 08, 2011 8:41 pm

I didn't see the notice that we can only uplode 10 pics per post, so I am continuing the post below

here is the pic of the x axis at the front of the machine with the contact switch tripped. I put a ruler in the photo to measure travel.

x axis at zero

Here is a pic with the x axis at the limit at the back (it is hitting the z axis pulley blocks). At this end, the bottom pulleys are just barely off the bottom guides, but it doesn't seem to affect the motion or the level of the car when they come off. I have the gantry cars set so they only just contact the rail without putting much pressure on it. I actually think that gravity would be enough to hold this gantry in place as long as the motion doesn't get too crazy. I wish the kit came with lower rails that were about 1/2" longer. I could actually move the rails towards the front and pick up about 1/16" more and not have them come off on the back (it only comes off on one side as I had a misalignment by about 1mm on the left side). If you get it in the right spot, then there is nothing to worry about. The lower rails are 13 1/16" long.

x axis at end

I also moded the z axis pulley system from what was shown above, this way the pulleys are beneath the z axis idler bearings. We can put the motor on the top with the big pulley on the top.

Revized Z-Axis pulley system

As bart pointed out they go on the bottom. I was actually thinking about cutting off the length on the bottom before I thought about this. But I learned enough building this thing that I don't want to do anything that makes it hard to undo until I have it all set. I'm really glad that I didn't or I'd have to go to lowes and buy new ones.
Last edited by dirktheeng on Sun May 08, 2011 9:15 pm, edited 2 times in total.
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