No longer a 'Wannabe'

[robinsoncr@naxs.net]

Howdy Everyone!

That's right! No more nights laying awake thinking about a Shopbot! No more tireless pacing, debating myself on the merits of a cnc that didn't cost more than my house!

We purchased Rick Adams' PRT60x120. It has one Z-axis, limit switches, z-zero plate, 15hp FPZ vac, 5hp Columbo spindle and an assortment of bits.

We've got the 3ph power supply ready and will set the machine in place this weekend. So, in preparation, I have a few questions. (In preface, I have read the archieves.)

My brother/partner has over 12 years experience as an Industrial Maintenance Engineer. From his experience, a few questions have come up.

1. Is there anyone that has located their PRT, then leveled with metal machine levelers and bolted the legs to the floor? He says it will significantly reduce vibration, reduce the potential for frame movement and reduce the chances that the machine will move over time. All of which contribute to inaccuracy.

2. We're going to add legs in the middle to reduce/eliminate sag. I read in the archives that someone had done this. Any advice?

3. I also read in the archives that the above person used gusseting on each let to further reduce racking. If you have done this, how did you attach from the leg to the frame?

4. Vac Pump noise reduction. I had the thought of locating the vac pump under the table and then building a sound enclosure around it. My thoughts were to take aluminum panels, bond noise reducing foam to the inside and bolting these panels to the outside of the machine, extending from the bottom of the table to the floor. We'd allow for motor cooling air circulation. Has anyone tried this? If so, how did it work for you?

Sorry for the long post. I've been building up for a while! Sorry I couldn't make it to the jamboree but I'm behind in work and couldn't get away.

Thanks,

Chris Robinson

[beacon14]

Chris,

Good luck, I can read the excitement in your voice.
I guess from the lack of response that you and I are the only ones who aren't at the jamboree this weekend.

1. Yes we did bolt the machine to the floor, with no regrets. (The landlord may regret the holes in the floor later, when we move out.)

2. We built a plywood table, doubling up 3/4" plywood for a 1 1/2" frame and rails, and it has center legs. It makes it less convenient for storing materials under the table, but I'm sure it makes the frame sturdier, especially with your 10' table.

3&4. Can't help you there.

Keep us posted,
David B.

[gerald_d]

My reason for lack of response is the fact that your brother/partner is advising you, and I am not going to start a family feud.

[robinsoncr@naxs.net]

Gerald, har, har! It doesn't hurt to ask for other people's opinion! No need to go through the whole ordeal to reinvent the wheel.

I wish I could've made the Jamboree...

Chris

[John S.]

Chris-
All of your brothers suggestions would help quite a bit. I have a PRT 120 and I didn't see any of those other posts and didn't have someone like your brother to advise me. Of course I see a lot of these problems now, but am too lazy to fix them. I guess I'll have to do it now that I see it's not just me that had to do a little tweaking.

The table does sag, so extra legs are a very good idea. Maybe a few more supports horizontally across the x axis that your legs can tie into?

The thing takes so long to square up, that I wish I thought of anchoring to the ground. I bumped the table a couple of times with a forklift and threw it out of square. The upsidedown carraige bolts on industrial slab concrete flooring tends to slide very easily, so even though the table hasn't been bumped, I am sure it has vibrated out of square again.

On the PRT 120, the Y car has a lot of bounce in it. You may consider adding some type of stiffiner to it. I thought of a 1x2 steel tube on the tops of each Y car rail. Drill holes that correspond with the holes on the rail, oversize the top holes (along the 2" wall) for the bolt heads, and a through holes just big enough for the bolts to pass through on the bottom.

I guess gussets can't hurt, but I don't think your machine can move fast enough for the gussets to make a difference. I could be totally wrong, but just my opinion.

[gerald_d]

Chris, if there is a potential for a John's forklift to bump into it, then don't bolt it to the floor. It is better that the machine can slide away, rather than crumple. And that would be the ONLY good reason for not fixing it to a concrete floor.

Gussets/cross-braces are always good, the longer the better. Try to go from a point on the legs near the solid floor. One bolt at each end of an angle iron cross-brace is enough.

Allowing for cooling/air circulation in a closed box under the table could be a problem. Out of sight, out of mind, and the cooling air channels get clogged with sawdust . . . . . . . .

And yes, I agree with John, you should probably look at your gantry first . . . . . .

[John S.]

Gerald-
As always, more very good points! I guess I was smart not to anchor my legs, right! ;-)

[robinsoncr@naxs.net]

John,

Timm is going to bolt the machine to the floor, pin the legs and gusset them. We have a forktruck but only Timm or I drive it. The truck won't be able to get into it because at the front, we'll have a scissor lift for raising sheetgoods up to the spoilboard.

We were looking at the y-carriage today. I was wondering about a frame made from 80-20 stock. Timm was thinking about welding up a thickwall aluminum carriage. (He likes to fabricate things anyway! You should see the Harley he bought in boxes and rebuilt!)

I'll keep you posted. I can't wait to fire this thing up!

Chris

[gerald_d]

For the gantry, the sketches at the bottom of this thread may give you some ideas.

[logical@gmi.net]

Well, I just made the plunge. I will pick up my new prt 96 the end of this month. I am anxious to get to work. Thanks again to all who gave me information at the jamboree.


Wes
Raleigh, MS