[QUOTE=examorph;75595]I was planning on welding it direct to the gantry box section as its all going to be out of steel, would this be ok?
Sorry, missed that it was a steel gantry. Then end-on as originally drawn in post#7 would be slightly stiffer. Go easy on the welding to minimise the gantry warping.
CannonGuy - Thanks for spotting the upside down rails on the one side, it was me being lazy and mirroring everything along the mid plane!! Will probably leave it as a mirror as the feature tree on the SW assembly is already starting to get crowded.
routercnc - Thanks for confirming. I read on a few build logs that people have been keeping the temp below 60C to reduce warping, so will probably stick to this. I have a stick welder but can get a mig arranged if you guys recommend it?
Speaking of welding, do you guys recommend the epoxy leveling route on the x axis for a build this size? With the Y and Z axis do you normally not do this?
In principle epoxy levelling is worth-while on both the X (longest) and Y (across gantry) axes otherwise you are only getting some of the advantages.
In your case the Y axis will be difficult unless perhaps you epoxy the top rail, then when dry and the rail is fixed turn it upside down and use a DTI to dial in the other rail whilst it has a fast setting compound under it? I've not used them myself but I think Dean has talked about some kind of putty instead of shimming?
For the Z axis epoxy is not required as you would ideally use Aluminium EcoCast plate which should be pretty flat to start with. Alternatively you can use standard aluminium plate and skim it flat on a milling machine as the part is quite small.
With the welding MIG is nicer to use, but should be OK with stick/ARC for what you are doing.
I see a few things I'd look at. (I realise now why it looks strange.? You have drawn box section with square edges and normally they are radiused which makes the tubes look larger.1)
Gantry mounting is weak point. No end support will let it resonate with only lower bolts supporting the upper rectangle. You are using only fraction of the plate to sit it on and with only 4 bolts inline. You would be better extending gantry width to cover the whole bearing plate width and have square 4 bolt pattern.
Has I mentioned in reply to your PM I'd look at ways to protect the ballscrews from debris. The screws are a little high and funerable. I'd be looking to add gantry sides which drop down the sides to allow screws to be lower and drop on the inside of the screw so covers can be added without interference from bearing plates. The gantry side also strengthens the gantry.
Regards welding then you have a lot of tubes all intersecting at the same points which means a lot of heat will be generated there. Idealy you should try to offset any tubes so the don't all meet at the same points. This will reduce warping and stress.
You also have tubes you don't need the Centre vertical ones for instance. The diagonal ones are enough and it's less welding, less heat and distortion. (see pic)
Mig welder is far better than Arc when comes to heat so if you have access to one I'd use it.
I'd also extend the Top rail 100mm past the end this will allow spindle to pass end giving more flexabilty to machine.
Regards PMDX then you want 126 BOB not 122 it's far better. If you go with Belts then buy Cslabs IP-M.
Last edited by JAZZCNC; 09-01-2016 at 02:47 PM.
The Following User Says Thank You to JAZZCNC For This Useful Post:
routercnc - Thanks, will go down the epoxy route on the X and EcoCast plate on the Z.
JAZZCNC - Thanks for spending the time making the changes to the model to show me, this is much appreciated!
Any chance you could send me the SW files for this please or let me know what size rad it is and I will draw it up? Also, just to confirm as I haven't done much machining so not sure, what flexibility does the spindle overhanging extra 100mm give you? Is it normal to machine stuff which sits off the end of the table?
I will get a Mig welder arranged as suggested and also have a play about with the gantry sides and see if I can setup what you've recommended, should have some images up for comment soon.
Last edited by examorph; 09-01-2016 at 10:19 PM.
The changes to the model took 5mins. You need to learn how to use Weldments and structural members then frame design is simple, quick and accurate.
I'll send the model back to you with a few more changes and suggestions based on what you've drawn already. I haven't changed what you did at all just added a new configuration with my frame etc so you can flick back n forth and see the diffference.
You'll also see how I made the frame.!!
The extra 100mm doesn't affect the machine stiffness but does make it more versatile. Ie cutting dove tails on draw ends, cutting locks or hindges into doors. Machining over height parts that won't fit under gantry or using extra long reach tools. It also allows an easy way for a 4th axis without affecting the cutting area or having to fit or remove everytime use machine.
Got a habit of going back over emails and making them more formal at work, think I carried that through here too
Looking forward to seeing how you done the models and checking out Weldments and structural members on youtube now.
I made a few changes to the gantry sides as suggested:
Side plate is 10mm thick steel welded to gantry box section. Clearance between the frame and gantry sides is 10mm, so need to be sure that bolts which go into the ball nut bracket are only M5 so that the head doesn't stick out too far.
Images of X Axis carriage support plate also attached, thought it might be easier for access if I followed other designs on this forum and had bolts running into the side. If you think the 4 bolt square pattern on top face would be better, I could probably cut a slot in the gantry base 'L' to get access to them and have it that way instead?
If holes seem to close on the support plate, would it be worth going with the smaller width type carriages (without the flange) on the X also?
One thing I haven't really thought out yet for the frame is the bed. Will look back through some build logs and see how others have been doing it and get something up for comment soon.
Some things I am struggling with and hope you guys can help me with please:
1. Does using wider/flange type carriages on the X Axis have any benefit over the smaller width type carriages or am I OK going with the smaller ones?
2. Are there any cost effective ways of setting up a decent bed? I am seeing tool steel and aluminium beds on other build logs which I read can be >£300
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