Now Cutting! - Auckland NZ

[KenC]

60V rated caps is enough but if you feel unsecured, 100V rated cap is only double the price. 400V rated cap are also available, only cost a few times more than 100V caps.
for me, I pick the cheapest cap with the lowest ESR with voltage rating higher than my running condition. Which ended up with a 20,000uf @100V rating. & it happened to be a stud mount... which made me a happy man.

[litemover]

Just a small update, received my laser cut parts from a cutter outside the city at a reasonable price. Everyone in Auckland wanted waay too much. They were cut really well, and bending seems to be good quality with exception of a large bending radii on one of the smaller pieces (spring tension). Hopefully, it won't be too much trouble. The 3mm to 6mm pieces I had cut in G350 steel, as they don't have 300MPa, just G250 and G350. 2mm and 3mm parts were cut in G250, hope that works ok.



I'm looking at used steel for the 67mm crossbeams, have found some used 3m&6m scrap 62mm C Channel for that purpose at $72NZD/$120NZD ea, wondering if that will work ok without compromising the machine stability too much? Steel here is very expensive. 1x 9M 180mm C Channel for main beams costs $580.00NZD.

That's all for now. Working on my control box drawings next.
Chris

[domino11]

It also looks like they forgot to bend the small tabs on the spider plate. Look at the dwgs and you can fix that with a vise and a hammer.

[litemover]

While waiting for the next few pieces to come in, I've decided to build the machine in 3d to gain a better understanding of how everything goes together and make some shop plans. Here is the render from that. Haven't put bearings or screws/bolts on yet, but it's given me some very good perspective of what goes where.


photo sharing

[litemover]

One more of Z and Y car closer. Still need to find bearings in 3d ,and gas shock.

[Gerald D]

The ends of the gantry at the top of the picture are suspect.

[litemover]

You mean where the near/far carrier plates meet the tubing? I wrongly mated a motor plate to the inside of the gantry on the right side, but corrected that on the later rendering. I'll put the angle pieces on later tonight.

A friend has some 75mm x75mm x3mm tubing, was thinking of using it for legs and cross braces, would it be ok?

Here's a closeup of the other side of the gantry.

[Gerald D]

You seem to call the y-car the gantry? The gantry is the big thing that straddles the whole table.

CNC_5.gif

[litemover]

Ahh, yes thanks for pointing that out Gerald. For some reason that side became misaligned. Will clean it up when I do the rails. It's a fantastic design BTW, and the gantry with y car is well conceived with a low centre of gravity. If I can get the bearings worked out in the model, I can sim the machine to play with motion and moments. Can't wait to start putting it all together. Very happy I've gone with this machine.

Thanks,
Chris

[Red_boards]

Can't see the cable chain support, but I assume it's on the RHS of the topmost X-axis?

[KenC]

Don't overlook the cable chain support like I did....

[litemover]

Just two quick stupid questions anyone.

1. I'm about to purchase a welder, and I've seen in the plans that a tig is required, would mig be ok?

2. Can one put 2x z slides in the machine simultaneously, one with router, and one with laser optics using an extra PK296-7.2 for the other slide, and will the weight be ok if I am using the PK296B2a-7.2sg on the gantry and Y car?

Thanks in advance for advise.
Chris

[darren salyer]

I didn't use a tig.
Stick and mig here.

[domino11]

There have been a couple of dual z slide machines built.
Should be no problem.

[Gerald D]

Originally Posted by litemover

. . . . . I've seen in the plans that a tig is required. . . . .

That was definitely not the intention behind the plans!

I think TIG was mentioned only for very fine welding of the gears? The message there was that other types of welding would likely not be successful for THAT application. Stick and MIG are definitely the first choice for a person new to welding. You would scrap the project if you tried to start out with TIG!

[litemover]

Great thanks! That's good news.

[Zouave]

I do not have a MIG welder. Entirely stick welding over here. Worked out fine so far!

[litemover]

Has anyone ever cut their own racks using a fly cutter by chance? Thinking of doing that as racks here are $70NZD per meter. Which is about $60 USD per meter. I found a video on how to do it here: http://www.youtube.com/watch?v=ma6kdIHwrFI

[smreish]

Chris,
If you have access to a vertical or horizontal mill that could step properly, you could probably save money - but take a bit of time. The racks are not usually hardened, so mild steel would be mostly fine.

I don't personally feel that 70 dollars / meter is that expensive.

Good luck with your choices.

[KenC]

Fly cutting looks like a lot of maths...
How about using a chop saw, or a band saw or a hand grinder with a cutting disk?
BTW, cutting the rack straight isn't the end of the rack joining, you still need to do some grinding to prepare for the welding join.

[litemover]

Hi Guys,

Just about finished with plans to order steel cuts and am having a small problem. With all dimensions related to gantry and table being accurate, I'm not able to square the gantry V-rollers with the Table X rails. If I square the left side up, on the right side it is about 4-5mm over . Am I doing something wrong, or should I just adjust the table width/gantry tubing length?

Many thanks,
Chris


picture hosting

[bradm]

If you think about the consquences of being 1mm too small as opposed to 4mm too long, I think you'll agree that this is a conservative approach to the measurements. You can add 2mm of shim to each v-roller, or more or less depending on exactly how the gantry turns out.

However, in that picture above, how accurate is your model of the motor (actually, gearbox) shaft length? Did you shorten it in the drawing? Double check that your pinion gears can meet the rack. Also, I'd expect to see a little more space between the gantry plate and the motor mount plate due to a slippery plastic washer of some kind between them.

[Gerald D]

Chris, have you actually built any hardware or are you just playing on the computer?

[litemover]

I've done laser parts, have drivers, motors, and electronics, bearings arrived a few days ago.. I just haven't ordered the table/gantry steel yet or cut rails, blocks, and prox sensors.

The motor drawings were taken off OM site so I didn't shorten anything. I've just done a mock up drawing to accommodate my size table and make sure I've got a proper list of steel cuts using some spare pieces that my friend has but the x rails and Gantry steel is the same. I'll go over the whole thing again tonight see where I might have forgotten a washer or something in my drawings. Just out of curiosity, how far on each end in the Mechmate CAD drawings does the end of gantry tubing overhang off the table on each side to the X rails outside faces?

Thanks,
Chris

[Gerald D]

If you want to play with this on the computer, try the following:

1. Use the centerline of the table as the reference point. Don't double the dimensions of concern by aligning everything on one side and then looking at the other.

2. Plot the main longitudnals wider apart than what is shown in the drawings. Why?....because the reality of welding is that things move. How much?....well, that depends on your welding experience, but 2mm per side is not too shocking.

3. Plot a 16mm wide rack against the longitudnal (not 0.5inch) because that is a very commonly available size. Then move the rack 1mm away to have some clearance so that the pinion gear doesn't rub on the beam.

4. Your gantry cross-tube: Plot the length as per drawing, but cut the end skew by 1mm, tapering narrower at the bottom....the drawing allows this because all saws don't cut square.

5. Put the x-rail on top of the rack, and put the roller on top of the rail.

6. Put part 1020451/452 inside the gantry-tube end

How thick a spacer do you need behind the roller now?

I had to juggle with all these variables and make a call on the sawn length of the gantry tube. You are welcome to shorten the tubes.

[smreish]

Gerald is the expert on this one, but from practical experience building a few of these, the 4mm you mention is easily taken up by the build averages.

Quickly looking at that measurement you point to as 4mm. My rails had a 1.5mm gap between the 1/2" 20 pitch rack for rail overhang. Then I had usually about 2 shim washers on the vee bearings, which as .060 " thickness. ; then my pinions I shifted about .050 past the shaft for rack engagement. Added together on my machines you are at roughly 3.37 mm. Pretty darn close to your "calculated" distance. Sounds like your just fine.

[litemover]

Thank you Gerald,

I understand what you're saying with the table changing from welding, but I'm needing to bolt mine together on the Y table channel beams, so I can disassemble it if need be, so wouldn't expect too much pull inward I suppose in that regard, would I? Is bolting the crossbeams to the Main Longitudinal not advisable?

[Alan_c]

At some point you will have to weld something, even if its the bolt on legs - and it WILL move! Mine is a bolted assembly and I had to to use straps and a come along to correct for some welding movement.

[smreish]

#5 was bolt, #28 was fully welded. I didn't change one thing with my cut list between both tables.

-The cross members were bolted. 1/2" bolts in 5/8" holes. Thus, collectively 1/4" slop (7mm)
-Rails bolted on....1/2" hole with 5/16" hardware - 3/16" adjustment (5mm)

End result, the cutting, welding, assembly tolerances are in spec with either method.

[KenC]

Gerald did gave great instructions on how to do the welding job correctly in various sticky threads.
As summery of what I learnt from him. (Gotta follow these good practices religiously unless you have more time to waste then I do)
1) Weld as little as you can live with (I keep my weld around 12~15mm longest)
2) stagger weld, don't be lazy , you gotta move around. You gotta spread the heat as evenly as possible,
3) don't weld across the cross-section of the beam.
4) try welding on the thickest part of the SHS & Channel, i.e. along the longitudinal corners.

FYI, my Channel only deform less than 2mm diagonally; Error not measurable with measuring tape on length & width not measurable with measuring tape. I'm very impressed with how it turned out .