El Beast - Initial design phase, comments and critique welcomed!

**Voicecoil** · 03-11-2018

Originally Posted by Zeeflyboy

Interesting. Just to be clear the part of the gantry that is actually doing the work is 65 x 200 mm made up of a heavy 40mm extrusion and a 25mm tooling plate, not just the 25mm tooling plate on it's own. The span is 620mm... it also has 6mm plate top and bottom which will be screwed down to the extrusion and the tooling plate. Given the relatively short span I don't think it should have much flex?

Yes, I got that, the extrusion will help, but I suspect it would need to be bolted to the plate at a lot of points to get it to work " as one": if they're not joined seriously rigidly, you won't get the full benefit of the extra thickness as they can slide over each other. If you want to stick with your current arrangement, I suspect that splitting your plate into 2 and having some in front and some behind the extrusion would also be of benefit.
OK your gantry isn't overly long, but if you're machining metal you need all the stiffness you can get. And as the rest of your machine is so beautifully made it would be a shame to compromise this surely?

**jarjar** · 03-11-2018

Originally Posted by Zeeflyboy

Interesting. Just to be clear the part of the gantry that is actually doing the work is 65 x 200 mm made up of a heavy 40mm extrusion and a 25mm tooling plate, not just the 25mm tooling plate on it's own. The span is 620mm... it also has 6mm plate top and bottom which will be screwed down to the extrusion and the tooling plate. Given the relatively short span I don't think it should have much flex?

The 25mm plate may not stiffen much the alu profile. The top and bottom 6mm plates probably won't do anything. Each bolted joint is a potential weak link when the contact surfaces aren't perfect.

Now all we are doing here is guessing. A very stiff gantry won't be very useful if the weakest link is your gantry arms.

**Zeeflyboy** · 03-11-2018

problem is finding somewhere to buy it in UK.

Cheers guys, I'll have a think - 80mm would be easier to work into the design than 100mm but 100mm is easily available at misumi where I need to buy some profile anyway.

**Zeeflyboy** · 03-11-2018

I believe I could make the 80mm work, although it would need new plate ordered for the side arms as the stock I have isn't big enough). Problem will be finding somewhere to buy it - have sent an enquiry to ITEM and to another place, will see what comes back. In the mean time I can continue to work on the design as it only really changes the side arms... will run both ideas and maybe look into simulations to get an idea of differences if I can wrap my head around it sufficiently well to simulate a fairly complex construction.

Oh and just printed out a shield belt clasp to see how it would come out - seems to be good, can pull on both ends pretty hard and no give

**Voicecoil** · 03-11-2018

Originally Posted by Zeeflyboy

problem is finding somewhere to buy it in UK.

Talk to Pamela at MBS <[email protected].> they're the UK agents for Item stuff, seem to be able to get most stuff within a week or so. Not cheap, but then quality rarely is I guess, and they seem to be a good source of heavyweight profiles.

BTW, how does your tramming plate work please? is the back of it machined to a very gentle radius so you can tilt it?

**Zeeflyboy** · 03-11-2018

Thanks - they are actually the other one I sent an enquiry to but from the look of their website was not sure they sell to plebs.

Tramming plate only trams in one axis (left/right as you look at the machine head on), the entire gantry will be able to be trammed fore/aft (the Z-axis can also be trammed left/right independent of the tramming plate) to make sure the axis of movements are correct. Plan for spindle is to tram fore/aft with shim stock then left/right using the tramming plate. The issue I always had tramming just with shim stock is that you would get one axis in, then the other would be out... this way should work well for me.

**Zeeflyboy** · 05-11-2018

Originally Posted by Voicecoil

Talk to Pamela at MBS <[email protected].> they're the UK agents for Item stuff, seem to be able to get most stuff within a week or so. Not cheap, but then quality rarely is I guess, and they seem to be a good source of heavyweight profiles.

BTW, how does your tramming plate work please? is the back of it machined to a very gentle radius so you can tilt it?

MBS got back to me very quickly with a quote - not a cheap piece of extrusion, comes to around £200 with cut and delivery... in for a penny in for a pound though I guess!

**Voicecoil** · 05-11-2018

Originally Posted by Zeeflyboy

MBS got back to me very quickly with a quote - not a cheap piece of extrusion, comes to around £200 with cut and delivery... in for a penny in for a pound though I guess!

That doesn't altogether suprise me

- I got them to quote on a ~1.3m length of the 120x120 profile and that was the neck end of £200 + VAT. On the subject of the tramming plate, I assume the thing at the top LHS corner is an eccentric bolt of some kind?

**Zeeflyboy** · 05-11-2018

Nevermind, it's done. Thought I'd go for it before I had time to think and change my mind!

**Zeeflyboy** · 07-11-2018

Want to give a big thumbs up to machine building systems - extrusion arrived already and it was incredibly well packed (much better than the misumi ones were!) with a good wrapping of cardboard and wooden end blocks.

Quick pic comparing it to current machine, it's a beasty extrusion to be sure - thanks for prompting me to "upgrade", think it'll be worth it.