[adam_m]

It makes me want to think about some type of counter weight to offset the 3/4 plate not to mention the weight of the router in addition to..

I think the ACME nut is just going to prematurely wear and develop backlash or quite frankly fail.

Adam,

[roundrocktom]

My Z plate is 4" x 15" x .25" thick. So 15 cubic inches x .283 pounds per cubic inch is about 4 Pounds. Add the The weight of the Aluminum (1530 x 15") is about 3 pounds. I'm not sure on the router, maybe 12 pounds (guess).

So in the scheme of things, going from a 4" plate to one 8" wide, means going from 19 pounds to 23 pounds total. Not a huge increase, but reduces the margin on the Z bearing. Simple solution is to keep a spare Z nut handy.

In my case trying to engrave 0.2" letters means a lot of weight shifting back and forth. Hind sight, I attach the Z drive like I do aircraft building, lots of lightening holes in the 1/4" steel plate and aluminum 1530.

At thing point your machine is pretty close to being finished, so just finish it and get to town. [I suspect no one uses "Get to Town" any more, but phrase from my farm boy father when he would tell me to get to work and finish my chores. Oh my]

[adam_m]

I think my Z will weigh in around 23lbs...

10 x 11 x .75 = 82.50 X .283 = 23.35 ouch!

[adam_m]

I was thinking about going with a linear ball slide Z-axis and was curious about some experiences from the users on the forum with regard to usage and durability.

My initial thought is a 20mm unit with 2 pillow blocks per rail and an approximate length of about 20". Something similar to theses (20mm Linear Shaft 55" Long 2 Slide Units 2 Shaft Supports Linear Motion Kit: VXB.com Ball Bearings)

What can I expect with regard to side-play and backlash?

Are bronze bushings a better choice?

Anything I'm overlooking that might tell me to look elsewhere?

Thanks as always for your input.

Adam,

[CarveOne]

Design the Z axis so that most of the heavier parts are fixed to the non-moving part of the assembly. Only the bearing blocks, ACME nuts, router, and router mount would move up and down.

My PC7518 router weighs 11 pounds by itself. If and when I install it on a machine it will have two anti-backlash nuts on one ACME screw, or rack and pinion. The two tandem anti-backlash nuts would be the lowest cost and will handle the weight better. Keep them lubricated and they should last a long time.

[adam_m]

C1, do any of your machines utilize linear bearings on them?

My largest concern is that the bearings do not have any adjustments for any type of backlash which can translate into inaccuracies, etc.

I may post this as a new thread to get it un-burried from my build... I'm sure other peeps are using linear slides..


Adam,

[harryn]

If you have linear bearing questions, there is an excellent section for that in the mechanical engineering section, just above the wood router area.

[adam_m]

Ah great, thanks harryn.

[EDIT}

Thanks Admin for moving the post.

[adam_m]

I landed on some THK HSR 25's and 400 mm length rails, I think this will do the job nicely..

[LeeWay]

I use those in both my mill and lathe. They are very heavy duty. Excellent score.

You won't see any play in those. Also, slop in a bearing slide isn't really considered backlash. Backlash is associated with the drive parts and not the ways.

[CarveOne]

C1, do any of your machines utilize linear bearings on them?

My largest concern is that the bearings do not have any adjustments for any type of backlash which can translate into inaccuracies, etc.

I may post this as a new thread to get it un-burried from my build... I'm sure other peeps are using linear slides..


Adam,

No. They both use CNCRP bearing carriages. After looking closely at three really nice Camaster CNC machines on display over the past three days at an Aspire Camp in Columbia, SC I may give the THK style a try on whatever I decide on for my next machine build. Or buy a Camaster ATC 508 on a 30 year loan plan.

[LeeWay]

Those linear ways are pretty much install them and forget them. Except for periodic greasing. I grease mine once a year. I don't think they need it that often and I use mine daily.

On my roller skate bearing machines, I don't have to grease them, but do need to check it for adjustment. I generally do that between summer and winter and vice versa.

[adam_m]

Admin, please delete this thread.

[adam_m]

Well I've finally had a little time the last few weekends to make some progress on the remodel of the Z-Axis and thought I would snap a few pics and post them in the thread.

It would have been nice to have been able to cut this plate on a cnc as I had to slot the bottom holes for adjustment, fun with a hand router...

I'm still waiting on the top plate to arrive but essentially I went with a 3/8" plate for the back and 1/2" for the front - it will have about 6 1/2" of total movement which should be more than enough for any job I can think of.

Enjoy,

[roundrocktom]

Progress is looking good. Love the slotting method, it is 'geterdone' nicely done. -- Tom

[adam_m]

Thanks Tom.

I'm finally getting some traction on the project again... hoping to be up and running soon.

Adam,

[adam_m]

Making some solid progress this past week with the Z axis, just about finished, I need to start the wiring and get the limit switches in place.

Ahren, at CNC Router parts was kind enough to swap out my original 5 start Acme nut (plus the difference in price) which was way too tight upon trial fitting with one of their new designs, much smoother and was a bolt in replacement for the old one.

Since I don't have a CNC to cut mounts with I had to fabricate them from MDF, I think they'll work for a short time but plan on milling some ASAP.. I used a drawing from CarveOne to get started on the mounts and then had to do a little redrawing to make them fit my Z plate... printed off some template guides and glued them down for fabricating, made the job much easier.

Mounted the PC in the case, need some ventilation and mounting plate for the G540 and power supply... etc... etc...

Anyway enjoy the pics..

[CarveOne]

Whatever it takes to get it going is a step or two closer to the big day that cutter meets material, right? Glad the drawing was useful to you.

[adam_m]

Thanks C1, I've plenty of learnings yet to come my way.. I hope that some of the design implementations don't hinder the performance.. We'll see.

Adam,

[adam_m]

Finally figured out the configuration for the echain.. I need to make the connections permanent and then install the limit switches, wire it up and turn it on???

Can I really be that close... hmmm....


Adam,