[Frankmali17]

I'm not the most experienced here but I think it sounds like some "Constant Velocity" settings.... I know that I ran into problems like that while V Carving, Basically it's like the machine moves and stops at every point... so while traveling to a certain destination.. there may be many points along the way....
Think of it like a GPS coordinate system....

Maybe Ahren can lead both of us a little on setting CV...
Let us know if that helped.

[ger21]

If you have Gecko drives, have you adjusted the trim pots?

[Frankmali17]

Also, what did you think of those steel legs? I am working on designing a bigger footprint 5x9ft PRO machine... I intend to work with CNCRP guys once I figure out how I want it... I'm going to request heavier extrusion...
So I was thinking of getting additional extrusion for the legs, and building cabinets underneath as well as plywood skins to make it ridgid and not sway as the machine moves.... Do you thinks this steel leg kit works well/ puts together well/ how are the bottom feet?

THank you

[ahren]

It is worth checking to make sure that your post-processor is outputting actual arcs -- some CAM software breaks arcs into tiny line segments. At higher speeds, the Mach CV settings actually smooth this out, but at lower speeds the machine will actually start and stop at the end of each line segment. I would check your g-code to make sure actual arcs are being output.

Best regards,

Ahren

[TerribleDamage]

The toolpath is a straight edge square spiraling outwards, so each move command takes several seconds to complete, and is a straight line. I will try ger21's suggestion...I have forgotten to adjust the trim pots on the geckos! I just read they're supposed to be adjusted at 2 revs/s, and since it's 1.5708 in / rev, I'll tune it at 188ipm. At that speed, the machine sounds okay already, but hopefully if I tune them, it'll solve the problem at lower speeds.

Frank, I have mixed feelings about the steel leg kit. On one hand, it was cheaper than me buying a decent miter saw and wood to build my own table, so that was the primary motivation for me buying the leg kit. The steel is heavy duty, no chance any of those beams will bend. But there are two main problems. First, (at least for the 4x4 foot router legs), for each side, there is only one horizontal (or diagonal) beam, not two. It can stand up on it's own if you tighten the bolts down hard, but it can never be sturdy on it's own. It really relies on the base of the machine to be fully defined and rigid.

Also, at first, I made the mistaken assumption that the steel beams should be flush. I spend hours squaring everything, making sure it was perfectly vertical for each leg, making sure they were just the right height for each leg, (my garage floor is not level) etc. But it turned out that making the steel beams flush caused the width of the legs to be inches too narrow to mount the base of the machine. Ouch, all that work for nothing. Also, at the top of each leg, there is a metal thing to connect the leg to the aluminum extrusion...but that is held onto the steel leg by a single bolt. So at the end of the day, my entire machine is resting on 4 lonely bolts. I'm definitely going to add a second bolt for each leg.

Also, at first, I assembled my base on the legs...it was frustrating and time consuming constructing up in the air like that. And when it was done, it wasn't perfectly square. I ended up taking the aluminum down, assembling it on a level floor carefully with a precision square, clamps, etc. Then I put that onto the steel legs. It was a serious challenge for me to lift and mount the 4x4 base and mount it myself...with 5x9 footprint, you will need friends to help. Anyway, that's my whole spiel about the legs. At the end of the day, they do work. But if I ever wanted to add shelving, I'd have to add another beam, since the two horizontal beams are not at the same height. I haven't run my machine over 300ipm yet, so I don't know how well they hold up with big forces yet.

[TerribleDamage]

Seems tuning the geckos was the problem. Had to tune them at around 25 -> 50 ipm, but now the machine sounds and feels much better at slower speeds. Getting ready to use loctite on the set screws and square the Y gantry tonight.

Quick question...I see most people use two layers of MDF on base of the table. What is the best way to secure that MDF to the table? Do they bolt it to the aluminum extrusion somehow? Also, do most people face the top of the MDF, or just leave it as is? I'd like to avoid a toxic dust cloud in the garage if I can. Thanks!

[ahren]

Terrible,

It's helpful to mount one piece of MDF to the extrusion more or less permanently, and then have a sacrificial board fastened to this that you can plane flat to the machine, and then discard if it gets too beat up. We use a Raptor composite nailer on our demo machines here (it's nice since you can machine through the nails), but you can also use recessed drywall screws to hold the two sheets together. You will want to come up with some sort of dust collection system at some point regardless.

To mount the bottom sheet to the extrusion, there are lots of ways to do this, but we find t-studs or t-nuts are the easiest. We sell these in our fasteners section here:

Fasteners and Brackets | CNCRouterParts

When it comes to squaring your gantry, while you can do this mechanically, I'd suggest getting some sort of switches so you can un-slave the axes and auto-square when you home. You don't have to get ours, but this feature is just really useful and Mach and the newest Smoothstepper plugin (which I believe is V10r2d1d) support it very well.

Best regards,

Ahren
CNCRouterParts

[TerribleDamage]

Alright, I may place an order for some brackets and bolts tonight.

I'm installing my home/limit/emergency switches tonight. I forgot to use clamps when installing the gantry risers, so I think my unsquareness is beyond what can be done with software. The left side (x-) only gets half an inch close to the bumper before the right gantry hits. Is the CRP4848 standard xml config file un-slaved by default? Or will I have to play around in mach3 settings to figure that all out?

[ahren]

Terrible,

In that case, your best bet may be to place a small shim on the inside edge (only) of the gantry riser, between the riser and the gantry extrusion, on the side that is furthest off the back bumper. This effectively "levers" the gantry forward by the ratio of the width of the riser to the length of the gantry (about a 25:1 ratio, so a 1/2" delta should take about a 0.020" shim). The R&P units can take out quite a bit of skew if you auto-square, so it doesn't need to be mechanically perfect.

The XML file we provide on our site has the X and A slaved by default, but if you set up homing with both an X and an A home switch, they will un-slave automatically during homing. You are welcome to give us a call tomorrow if you'd like help with any of this.

Ahren
CNCRouterParts

[TerribleDamage]

I've got it pretty square. Just in case others read this thread, the brackets for sale on your side are for the metric extrusions for the PRO machines, not standard machines. I ordered them, but soon got a phone call warning me that they'd be 1mm proud for the standard CNC machines which use fractional instead of metric like the pros. That's no good. Instead of brackets and screwing in the bed from below the table, I have another plan. I will use the CNC machine to drill holes in my bed, (1/2 MDF, screwed on top of 3/4 MDF....no way I'm going to unscrew them now), so I'll be able to drop the t-nuts right through the bed into the aluminum extrusion, and use a hex flange nut to secure it. It'll be a shame the table will have a bunch of holes in it, but I'll get over it, I'm sure.

[BuckNaked31]

Faztek has those brackets and you can order them online.

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[TerribleDamage]

Yup, I was able to locate them on apex industrial supply yesterday also. But for those prices, I think I'd rather have some cosmetic holes through the MDF bed, and not have any brackets.

[BuckNaked31]

You'll be better off that way. I have one layer of plywood, then 2 layers of MDF on mine. Since my frame is made of welded steel tube, I just bolted the bottom layer of plywood to it and screwed the MDF layer and glued and screwed the top layer. I also have 5/16-18 square nuts, 72 of them, embedded (72 pockets with an 1/8" cutter, took about half an hour) in the first MDF layer, then I have 3/8" holes cut down to the nuts. I can clamp or index in these holes. They will also accept a 3/8" shoulder bolt since the threads are 5/16... I also have a pocket cut in the corner that accepts a 123 block lined up to the matrix of holes. I use my 123 block as a touch plate, so it's wired to the probe input. Once you have your scripts written, you can located to edges and bolt holes quickly. Anyway, this gives me plenty of thickness on the top board for leveling it later after I screw it up. I've only replaced it twice in 6 or 7 years. I've been thinking of engraving a ruler into the edge just for convenience

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[CYoung]

Bucknaked
Can you send some pics of your table? It sounds very interesting. I am trying to figure out how to build out my table and yours sounds perfect.

[BuckNaked31]

Sure, I'll snap a couple tomorrow...

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[nlancaster]

I actually Tapped the Aluminum extrusion 1/4-20 to hold the base of the table down 18mm baltic birch fills the entire table side to side, front to back. And I am then going to insert 290 1/4-20 Thread inserts from the bottom of that. then 1 layer of 3/4 MDF on top for a spoil board. I will then pocket the spoolboard 1/2inch diameter down to the baltic birch after surfacing. So that I can use 1/2inch pins to align parts on the table.

[BuckNaked31]

I use the inserts for individual tooling plates that I attach to my spoil board. I found that MDF dimples really bad when I use them, and they are expensive as all get out when you need a boatload of them. 100 of the square nuts was $7 Also, the 5/16 size is compatible with all my rockler clamps and bolts. Shoulder bolts with 5/16 threads are 3/8" at the shoulder, which is also a standard shank size for router collets and I could do most of the drilling with a stub length 3/8" drill bit (I don't have an ER type collet, I'm on a PC router with the precise bits collets)

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[TerribleDamage]

Man, now I'm worried I'm underbuilding my bed! I just used 3/4" MDF under 1/2" MDF, and secured the two together with 48 brass screws. It seems pretty solid, and when I do cut wood, I'll use a sacrificial board and secure it to the table with brass screws. Later, I plan to secure the MDF to the aluminum extrusion using 32 t-bolts...hopefully that will be enough. I read things like 290, that's like 9x as much!

On a positive note, I have drag chains installed, and all the limit/home switches wired and tested...securing the bed and confirming the machine cuts square are the last two items on my checklist.

[BuckNaked31]

You're probably OK, it depends on how you use your machine. Almost everything I cut is double sided, so all my holes are for indexing, I try to clamp in the same holes when I can so there are lots. I only have a 30" x 54" cutting area. I'm not cutting sheet goods like you guys are.

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[BuckNaked31]

Ok, here's some pics with the screenshots from my cad files, I didn't take any pics putting it together. I think you'll get the gist of it. It works very well and didn't cost squat. I don't locate with home switches, I locate with a 123 block wired to the computer. I also made my own Mach screen that has everything I need in normal operation on the main screen done in some colors that are pleasing to my eyes. This includes circle finding and edge finding scripts and autozero for the Z.
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