Building a new table, any tips?...

[SeanP]

Yes 3m vhb tape, I see it's listed on ebay.

[davek0974]

Found it, on the way

[davek0974]

Reclaiming some motion distance....


After building the base frame and motion, I decided to build a new floating head using Hiwin and a single carriage - pretty much a standard design. However, this moved my torch 30mm closer to the front of the table than I had planned which left very little over-travel on a full 1250mm sheet - not good.

The first pic is a cross-section of the average torch mount with the Hiwin at the bottom and the circle being the torch clamp.

THC New.png

Now, as I am using wide/stable Hiwin rail, could this idea work?? It regains a valuable 30mm of spare travel on the Y axis.

THC New 2.png

[acourtjester]

On the lower one if you rotated the part the holds the torch 90 degrees you could save more

[davek0974]

Yep, or i could simply mill the bottom off and make it shorter

[SeanP]

Looks like a good idea to me, have you some sort of mag breakaway incorporated into that as well? are you using these brackets they are a perfect fit on the 45 torch.

Funnily enough I was looking at my machine this morning thinking I had wasted a good bit of my table after seeing how you sat the gantry back with the side rail brackets, I still can cut a full sheet, but if I don't watch what I'm doing I have been known to run up against the stops at the far end mid cut!!! then the verbal starts

[davek0974]

Yep, its a standard round-rail support 25mm, I can easily mill the base off and some of the body then drill/tap directly into it for mounting.

No mag breakaway (yet), my floating head design has two microswitches not one, the first to trip is the probe switch as normal, a couple of mm more trips a limit switch and stops the machine - any jams or serious dives just trip the limit and stops it.

Yes, I was a bit worried about how the space was eaten up with the Hiwin style float, my existing one was going to be used and its very compact, but I decided to get all new bits and went with the standard design. Now I can modify it and regain my travel.

I use the soft-limits in Mach to stop me running into the limit switches, works well but with the 20mm spare travel I had left it would not work, now it should be ok.

Should be able to get the torch mount fitted this week.

[davek0974]

Here we go, down to 27mm distance now, thats a little less than my existing unit

Screen Shot 2015-07-28 at 15.29.42.png

The side effect is that to get the torch back on centre, I have to shift the Hiwin carriage to the left a fair bit, luckily this will be over the machine side beams and will not affect anything at all - perfect

[SeanP]

It's a 35mm dia torch on mine Dave

[davek0974]

Hmm, ok, will check that, I have it fitted in the 30XP holder now, odd.

No biggy, I have a 35mm mount as well and the space to fit it

[davek0974]

Just checked the manual - definitely 25mm / 1" torch

[SeanP]

Sorry I forgot you are using the hand torch

[davek0974]

That would explain it

[davek0974]

Got the floating head mount fitted to the Z-axis, probably work better when i fit a means to stop the carriage and torch falling off the bottom

IMG_0963s.jpg

[SeanP]

You are making good progress!
How did you end up fastening the rack on the gantry?

[davek0974]

I used the 3M VHB tape for metal-metal fixing, seems pretty firm

Time will tell but I'm all for trying modern solutions, just cleaned up with strong solvent, fixed a few alignment blocks with clamps, stuck the rack on and left it clamped up for 24hrs as the instructions said

Time will tell.

[SeanP]

Good stuff, a bit more weight saved as well

I used the 3M VHB tape for metal-metal fixing, seems pretty firm

[davek0974]

I don't think the gantry weight is going to be any issue at all, it moves so easily that you can push it around with the tip of your little finger

Its rigid enough to move both sides within 5mm of each other just by pushing one side.

[davek0974]

Little bit slower now, onto the small fiddly bits....

Got the Axis hard-stops and beam end-covers designed, cut and fitted..

IMG_0966s.jpg

Fitted the floating head, torch mount and probe/limit switches...

IMG_0965s.jpg

The front Y & A axis limit/home switches...

IMG_0967s.jpg

And the Y far-end limit switch...

IMG_0968s.jpg

Started work on fitting the cable chain to the X axis now.

[davek0974]

Another slow day today, had a few orders to make then fitted the cable tracks and trunking and started planning out the bed support frame.

[tcaudle]

I don't think the gantry weight is going to be any issue at all, it moves so easily that you can push it around with the tip of your little finger

Its rigid enough to move both sides within 5mm of each other just by pushing one side.

You are measuring FRICTION not weight. Weight is MASS. Physics says on order to ACCELERATE a MASS you have to have enough force to over come the INERTIA plus the frictional forces. While low friction is good it is part of the over all EFFICIENCY (how much of the force is converted to motion versus heat).

[davek0974]

Thanks Tom, my fault for not being scientific

What I was trying to convey was that the overall effort needed to move the mass of the gantry and overcome the sliding friction appeared very low.

In reality I estimate it will weigh around 10kg or so, if I remember i will put it on the scales next time I have it off the table for an accurate assessment.

[acourtjester]

moving an object sideways takes less force then lifting the same object.

[davek0974]

Yes but knowing the mass/weight will allow some sums to be done regarding the torque required to get it moving in a specific time and at a specific speed i.e acceleration.

[davek0974]

had a couple of hours today, fitted the last of the limit switches and started on the slat support frame.

I thought a seperate frame would be best to avoid putting any heat into the side frames and make replacement easy.

50 40 x 5mm angle fitted into bed opening and a strip fitted to its bottom edge to support the slats vertically.

IMG_0969s.jpg

Quite disappointingly when i did the heavy tacks to secure the bottom return strips, the angle warped and is now 4mm high in the middle

Not good, not sure what to do about it - ignore it and let the THC tackle it, maybe slit the angles vertically in two or three places, press it flat and weld up or something else.

I didn't think angle that heavy would warp!

Apart from that it s all going to plan