My New Gantry mill project

[Stevie]

Ok here we go for real this time
Here are the 3 x 3 x 1/4 wall 6061 extruded way carriers with the original design channel between them; spacers are cut for the end; but they still need to be mill sq on the ends; these will be spaced between and 2 threaded rod draw screws will clamp them

The difference in the design will be a massive increase in travel for the X axis; from 23" to 33" or the max of the ball screw shown; to make this possible I'm going to be doing something many may frown on; the rails will be bolted to the underside of a 5000 grade Aluminum table top 1 1/2" thick 39.5" long and 15" wide; cast tooling plate is as some may know milled flat both sides; it has no internal stresses caused by rolling; so is a great medium for a table
The table with it's slides (THK SR35mm) will actually slide out of 2 blocks once a distance from center is reached; but as the slides will be still supported by 4 blocks I feel it will be acceptable; the rails will not be unsupported at the extreme limits by just 4 blocks alone; but 2 additional needle roller bearings per side will also help stop table droop; these will be placed at the correct distance so as the rail leaves the 3rd block it will already be started onto the needle roller
This way I can use a 39.37 (1 meter) rail to move 33"
The rail will be radiused for the wipers to allow the rail to enter the block as it once again moves to center position; all this might be something THK do not normally think is good for their products; but I want to try it; blocks are cheaper than long rails

Here is the rough assembly I posted earlier; the channel with the 1 meter SR25 rails can be seen; the gantry will most likely be higher and the 3/4 plate holding the verticals will have to be cut now; new supports made for the bases or if I can find longer stock; I'll replace the verticals; the SR25 rails for the Y axis have already been replaced by HSR25; and the Z axis is also using HSR25

Here is the Z axis once again 5000 Aluminum for the main plate to carry the motor/spindle etc

[ViperTX]

Good move on mounting the y-axis rails on top and bottom to minimize the z-axis stackup.

[Stevie]

it also allowed me to pre-load the setup to help control chatter

[Jason Marsha]

That Zaxis looks like a monster. How much does it weigh so far? What is your estimate for the finished Zaxis weight inclusive of spindle etc?

Jason

[Stevie]

Z is about 25 lbs now; there is a 20lb 3/4HP Baldor going on it; the spindle will be massive too; it might be made from a Dodge half shaft I got the other day; we could not fix it so the customer simply got a new one from the dealer; I was about to pitch it when the idea of just how good a steel is this

I'll of course have to re-profile and shorten it up; but I think it might be useable; depends on the biggest diameter right behind the drive flange (thats also the area damaged) theflange of course will be removed
Even if I don't use it; the spindle design I'll be using is going to be a bit of out of the box thinking anyways; there will be pulleys for low speed and high speed (16,000 max once again) but also a VFD
The design will use both fixed length front loading/locking tooling and ER25 collets in the same nose; just the front lock ring will change for the change to ER25
This will be a test bed for this design; if it works good; me and Catch might offer to build custom spindles based on it

Back to the Z; I'll counter balance it like the mini mill

[Stevie]

Hereis the cross spacer bolted in; the other end is the same; I'm also chking the clearances for both stepper drives and servos; of course the actual location will not be down there; but much higher as more cross webs still have to be added inside the channel; the old rail mounting holes will come in real handy

[santiniuk]

Stevie,

Can I ask a 'daft' question.

Is there an advantage mounting your rails top and bottom on your Z design ?

I'm in the planning stages on a machine and I'm just laying out the Z axis support etc.

I normally see the rails mounted on the front. As per attached pic.

Thanks for your input. (I have sooo much to learn !)

Cheers

[Stevie]

You mean the Y axis rails
I did this for 2 reasons; first to let me preload the axis as my rails are not preloaded
2nd reason; it spreads the centerlines of the rails apart more; which gives better stablity

[jimbo]

It will be interesting with the 3 block x axis setup. I am curious as to how it will work out as well. I wonder if it may be wise to slow down prior to contact with the block so as to ease the transition, esp if there is any preload in the blocks. As always I enjoy watching your progress through your pictures.

[gotis]

Hereis the cross spacer bolted in; the other end is the same; I'm also chking the clearances for both stepper drives and servos; of course the actual location will not be down there; but much higher as more cross webs still have to be added inside the channel; the old rail mounting holes will come in real handy

I would mount the rails on the base and the bearings on the table, would probably be more stable.

I´m planning a similar project so this thread will be in my subscribe folder

What size Steppers and spindelmotor are you using?

Best regards,
Gotis

[Stevie]

The difference in the design will be a massive increase in travel for the X axis; from 23" to 33" or the max of the ball screw shown; to make this possible I'm going to be doing something many may frown on; the rails will be bolted to the underside of a 5000 grade Aluminum table top 1 1/2" thick 39.5" long and 15" wide; cast tooling plate is as some may know milled flat both sides; it has no internal stresses caused by rolling; so is a great medium for a table
The table with it's slides (THK SR35mm) will actually slide out of 2 blocks once a distance from center is reached; but as the slides will be still supported by 4 blocks I feel it will be acceptable; the rails will not be unsupported at the extreme limits by just 4 blocks alone; but 2 additional needle roller bearings per side will also help stop table droop; these will be placed at the correct distance so as the rail leaves the 3rd block it will already be started onto the needle roller
This way I can use a 39.37 (1 meter) rail to move 33"
The rail will be radiused for the wipers to allow the rail to enter the block as it once again moves to center position; all this might be something THK do not normally think is good for their products; but I want to try it; blocks are cheaper than long rails

3/4 HP

[Stevie]

My $400 slab of 5000 Alum
Just before drilling the rail holes



Ok before anyone says "hey thats not square etc" nothing is bolted down yet as far as the table blocks/uprights/upright supports basically it's all just sitting there while i figure it all out