Question 840 Table - Stiffening and Leveling

After owning my 840 for a few months and been pretty amazed what it will do, I ventured into cutting longer parts and then realised I had a problem with the flatness of the table. This can be seen with this image where you can clearly see the difference in cut hight (about 1.5mm from one end to the other).



I also felt that there was a bit of flex in the table which I guess is not helping with the torsional stiffness of the machine. So to help with this I made a support support frame to fit inside the chassis of the machine (12mm MDF). If you would like the Vcarve files (can I export as dxf?) let me know - you'll have add your own stop cable holes!


These were cut on the Steppi (see photo 1) but with all that care I still forgot to put holes in for the emergency stop cable ! This has made the table much more solid, and to that I added jvalencia's elastic solution to control the cable conduit. This job would have been much quicker on a table saw but not as much fun.



The table is improved but I still have a problem with what I think must be twist, I've attached a DTI to the Z axis and will do some proper tests today. I'm building a heavy duty spoil board (about 30mm) with T Slots which I will level with a cutter once made, visit Peter Passuello's Youtube page www.youtube.com/user/cncnutz for stacks of useful info. The next stage will be to build a solid base for the machine to sit on.


Without doubt my rush to build and use the Steppi probably didn't help in the accuracy of the build and now after playing making a lot of things, it's time to set the machine up properly, which actually is a lot of fun.

By definition a CNC router is a precision machine and considering it's a kit, the Steppi is really quite amazing, but for me it has been vital I bought the machine though a UK based supplier with years of CNC knowledge and not just a company selling boxes. I really think without the support I have received from Stoney CNC I would have not got this far.

Oh remember, cutters are sharp

Amazing work! The problem is the entire table is on the air, and the metal plate is not enough rigid for that.

Your solution is solving this by 50%.

The other 50% would be removing the legs and sitting the entire machine on a board (and giving enough vertical space for the Y axis travel).

That way it would be rock solid!

Continuing with improving my table here is the first half of my spoil board.

Notice the cleverly designed 6mm tabs for the Stepcraft clamping system to clamp down to the work surface - which you can't fit without taking off either the front or back cross beam

But then I thought never mind, I'll just screw it to the original top, that will save time!!



Why drill one hole through the Y stepper motor when you can drill two !

Once again thanks to the great service of Rory at Stoney CNC, he has sent me a replacement motor before I stopped banging my head against the wall and didn't even laugh (well not when he was on the phone).

More to follow unless I drill through anything else.

Hi hale2160,

as I use a 420v1 I've probably less problems with the stiffness of the table, but still i'd like to measure the level. Would you be so kind and post the dxf of DTI-holder?

Hi Daniel

Please find attached files, dxf and Vcarve.

I set the job up for 12mm MDF and used a 1/4inch cutter/6.35mm cutter. Hope you find it useful.

Hal


Can't seen to send a Vcarve file

Continuing on I have now made the T slotted spoil board. This is definitely MK 1 with several errors. The good thing to come of it was spending time tuning the Y axis. I now have pretty much full travel on the X and Y. The weight of the spoil board is also helping with the flatness of the machine.



The first error was to do with the poor setup of the Y axis, only myself to blame. On the above photo you can see the failed attempts of the first slots for the bolt heads of the T slots.


The second error was I reduced the size of the board to fit the poor Y performance which led to me milling a couple of screws I would have missed if the table was full size! An expensive error, I haven't looked but I think it's time for a new 1/4 end mill

On the plus, I'm really pleased with the accuracy after i tuned the Y. I fixed another 12mm board over the base and then milled the slots for the bolt studs, they matched perfectly with the head slots and the clamping bolts slide really well in the slots.

I think I will hack this spoil board around for a bit and then remake it.

Very pleased with the results of my T slot spoil board, works a treat!




I made these clamp supports out of some scrap 6mm MDF and will also make some 12mm versions


A very useful attachment is Peter Passuello's parallel rule, great for re-setting jobs to the X axis.

Finally, I'll have to wait to level the bed - my one and only 1/4 end mill didn't like hitting a screw at 20000 revs!

Wow, I feel sorry for your end mill.

Hi

thats an interesting way to make a T slot table. If I got that right you use three layers, one as base, then the wide part of the T and on top the narrow part? What thickness of MDF did you use? I'm surprised that MDF can be used for clamping because normally that stuff is quite brittle...

I wanted to make a vacuum table with MDF but I might just go your way. Or maybe just make both and use whatever fits the job better

Regards Andi

Hi, sorry for the late reply, I've been tied up building a new workshop.

I used a 6mm MR MDF base thinking I could quickly remove the table if I wanted. On version 2 I will not bother with this but I may use 18mm for the first layer. The main table is made from 2 sheets of 12mm MR MDF. The first sheet was glued and screwed to the base board and then had the slots for bolt heads (m6 bolts) milled. The second sheet was them glued and screwed (screws were well counter bored) on to the first 12 mm sheet and the slots for the studs were cut.

Finally the completed table was machined to size (see above).

I have used this pretty much constantly since making it without any problems, I do only clamp finger tight. MR (moisture resistant) MDF does seem to be harder and machine better than standard (mind the dust!!).

Version 2 will have another slot.

Here are some closeups of the T-Slots and my nylon clamp nuts and packing pieces.

Hi,

I'm having the same issue with the bed of my S-840. Your solution seems like it worked perfectly. Could you please share your Vcarve files with me. Thank you!!

Thank you very much for the info! Would it be possible to have the vcarve or dxf or any other format files? Regards

I have a stepcraft 840 cnc machine which has a z-axis leveling problem. Please suggest me how to measure and correct it.

Dear sanjaykviswas,

I wrote a guide to level the Z axis on this thread:

www.stepcraft-systems.com/en/forum/assembly-and-maintenance/3367-spindle-bed-tramming-840-supports#42414