MechMate CNC Router Forum

Go Back   MechMate CNC Router Forum > After Building the Beast - Operating , Troubleshooting and Maintenance > The Show Room
Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Reply
 
Thread Tools
  #1  
Old Thu 09 December 2010, 16:39
Alan_c
Just call me: Alan (#11)
 
Grabouw (Western Cape)
South Africa
Send a message via Skype™ to Alan_c
More Chairs! - this time serious production

Here are some chairs that we produce for the local pre school and primary school market. Previously these were made with conventional solid pine timbers, mostly butt jointed and screwed - not meant as a high standard furniture item - very utalitarian but they got the job done for reasonable cost. Since we have had a few return issues I decided to re-look at the design taking into consideration what is now within my scope having a MechMate at my disposal. They are super strong and should last well in a demanding environment - I can sit on them and rock on the back legs with no flexing that I am aware of and I think I weigh a bit more than the average 5 to 7 year old!

ply chair 2 sizes.jpg
These are made from 18mm shutterply (I soooooo wish we could get decent quality reasonably affordable ply in this country - its either hight cost Marine grade or really crappy shutterply ) The smaller size (320mm seat height) is the standard size we make and I am able to get 5 complete units from one 8'x4' sheet (2440 x 1220) Cutting time with three passes using an 8mm slot drill at 2000mm/min is about 1hr 35min per sheet.

seat back.jpg

The larger size (400mm seat height) takes about 1.25 sheets to produce 4 with a bit more waste, not really an issue as these are only ever custom made for special order so I can charge a bit more!

branding.jpg
Of course having the CNC enables me to brand all my products easily.

joint detail before assy.jpg joint detail.jpg
The first batch had very tight clearances on the slots and tabs and held together very well on their own, but the screws are added as we are talking about kids here and if anybody can test items to destruction, its kids! The second batch had larger clearances, but this time a little too big so the third batch was just right - a bit like Goldilocks

production.jpg

The ply is a very nominal 18mm so on some of the chairs I have had to trim the protruding tabs with a bearing guided cutter in a router - this can be a bit frustrating - see point about ply quality above.

Last edited by Alan_c; Thu 09 December 2010 at 16:42..
Reply With Quote
  #2  
Old Thu 09 December 2010, 18:04
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
Cool Chairs. Do you leave them raw wood? Or do you paint them?
Reply With Quote
  #3  
Old Thu 09 December 2010, 19:38
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Allan,

Have you thought of creating cut files for different thickness and measuring the wood before you start?
Reply With Quote
  #4  
Old Thu 09 December 2010, 20:47
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Good job Alan. That pic with the text engraving; is the ply above the text really that bad? The thicknesses of the layers appear to be badly uneven?
Reply With Quote
  #5  
Old Thu 09 December 2010, 21:58
CAM Craft
Just call me: Sean D
 
Cape Town
South Africa
all pine ply in SA varies from sheet to sheet or within the sheet the ply varies +-0.5mm. we have had "18mm" ply that ranges from 16.5mm-17.5mm. fun and games for interlocking components
Reply With Quote
  #6  
Old Fri 10 December 2010, 00:28
Alan_c
Just call me: Alan (#11)
 
Grabouw (Western Cape)
South Africa
Send a message via Skype™ to Alan_c
The chairs, in fact all our products get 2 coats of gloss clear polyurethane, cost effective and durable.

The varience within one sheet can be so bad that when I run the engraving, depending on where exactly I zero the cutter, in some places it will cut too deep and in others the tip will barely scratch the surface. I now have to run the engraving as 5 seperate files, one for each area of the board with a local Z-zero in each area.
Reply With Quote
  #7  
Old Fri 10 December 2010, 00:34
CAM Craft
Just call me: Sean D
 
Cape Town
South Africa
what a mission, why not just brand it after cnc. therefore there is no tool changes per sheet of ply. or use a 2mm str bit set at 2mm deep. ie doesn't really matter on ply thickness
Reply With Quote
  #8  
Old Fri 10 December 2010, 08:46
Greg J
Just call me: Greg #13
 
Hagerman, New Mexico
United States of America
Nice work Alan.
Reply With Quote
  #9  
Old Fri 10 December 2010, 09:59
PEU
Just call me: Pablo
 
Buenos Aires
Argentina
very nice, edges are rounded? can't tell from photos.
Reply With Quote
  #10  
Old Fri 10 December 2010, 10:42
Alan_c
Just call me: Alan (#11)
 
Grabouw (Western Cape)
South Africa
Send a message via Skype™ to Alan_c
All edges are rounded with 3.2mm radius round over bit, see 5th image - joint assembly.
Reply With Quote
  #11  
Old Fri 10 December 2010, 11:58
Kobus_Joubert
Just call me: Kobus #6
 
Dalview
South Africa
Send a message via Yahoo to Kobus_Joubert Send a message via Skype™ to Kobus_Joubert
Nice simple and strong...Would like to see those oakies trying to break them.
Reply With Quote
  #12  
Old Fri 10 December 2010, 22:20
hennie
Just call me: Hennie #23
 
Roodepoort JHB
South Africa
Nice Alan, I have the issue with ply also real crap that we get.I ordered 6 mm ply and after measured it was 8.5 mm thick.You must see what some cabinet makers do with shutter ply but it takes a lot of sanding to get it right.
Reply With Quote
  #13  
Old Sat 11 December 2010, 02:36
lumberjack_jeff
Just call me: Jeff #31
 
Montesano, WA
United States of America
very nice chairs. Would the cost of 18mm marine ply make the project cost too much?
Reply With Quote
  #14  
Old Sat 11 December 2010, 04:56
Kobus_Joubert
Just call me: Kobus #6
 
Dalview
South Africa
Send a message via Yahoo to Kobus_Joubert Send a message via Skype™ to Kobus_Joubert
Marine ply in SA is VERY expensive...I just came back from town. Paid R 150.00 for pine ply 6mm thick 1.2m x 2.4m.

Marine ply quoted at the same time was R 450.00... 3 x the price
Reply With Quote
  #15  
Old Sat 11 December 2010, 11:56
lumberjack_jeff
Just call me: Jeff #31
 
Montesano, WA
United States of America
Quote:
Originally Posted by Kobus_Joubert View Post
Marine ply in SA is VERY expensive...I just came back from town. Paid R 150.00 for pine ply 6mm thick 1.2m x 2.4m.

Marine ply quoted at the same time was R 450.00... 3 x the price
I guess everyone's economic constraints are different. Here it would probably be worth it to spend somewhat more for materials for each chair if it meant not having to do the second operation to mitigate the unpredictable thickness - or scrapping parts because of core defects, or fielding complaints because an undetected one led to product failure and complaints.

Perhaps the seat surface could be made from shutterply and the legs (since that's where all the stresses will be) made from BS1088.

Those prices are comparable to what I pay here in the states.
Reply With Quote
  #16  
Old Sun 12 December 2010, 00:58
KenC
Just call me: Ken
 
Klang
Malaysia
Plywood here has similar problem, I usually buy exterior grade plywood, so call water proofed plywood mainly used in cement casting form work. When cut, I get voids too...
I eventually resort to glueing up the thinnest available sheets of 3mm & build up the overall thickness. here, 3mm plywood are made out of 3 plies, 2 out of 3 of the plies are visible so we can control of 2/3 of the plies are in good shape. Rather than 18mm plies with 4 out of 6 plies that we can not see. This way the thickness variation is a lot less, +/- 0.5mm thickness variation is possible.
Don't do it very often as the only way to apply pressure for glueing is by placing many 4 gallon water filled buckets all over... but when my vacuum table is operational, I will surely be doing more of this...
Even with this, I'll still have to measure each & reconfigurate the joint dimension for each sheet to ensure good fit.
Just my $0.02
Reply With Quote
  #17  
Old Sun 12 December 2010, 01:17
hennie
Just call me: Hennie #23
 
Roodepoort JHB
South Africa
I am looking into using bamboo ply the thing with the sheets are that the thickness is the same all over the board.It is a bit pricey though.I got a price from a supplier to bring it in,in a container and that brings it down.Ken maybe if you have access since it comes from your side of the world give us some more detail on using bambo vs ply.Also it is a green product
Reply With Quote
  #18  
Old Sun 12 December 2010, 02:11
KenC
Just call me: Ken
 
Klang
Malaysia
Bamboo ply is a rare here.
We export a lot of very high quality plywood but the quality for local market isn't as good as those for export, the local wholesaler told me that the local market can't pay for the quality...
If you are looking for environmantal friendly stuff, I personally love to use rubberwood, they are easier to cut too.
Reply With Quote
  #19  
Old Sun 12 December 2010, 02:44
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by KenC View Post
. . . used in cement casting form work. . . .
That casting form work is also called "shuttering" and that is where the name "shutterply" comes from . . . . plywood made for concrete shuttering construction . . . . often used once for a few days and then thrown away.
Reply With Quote
  #20  
Old Sun 12 December 2010, 03:00
KenC
Just call me: Ken
 
Klang
Malaysia
There is always something to learn
Thanks Gerald
Reply With Quote
Reply

Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
First production job started! - Malvern, UK mphel MechMates already cutting 36 Sun 18 September 2011 06:10
It's time to rock and roll! ddoggett Introduce yourself and start planning 3 Wed 15 September 2010 13:20
Onsrud CNC Production Routing Guide sailfl Cutting various materials - bit selection, feeds, speeds 1 Sun 03 May 2009 00:49
Master CNC - 3D model creation and production Master CNC The Market Place 8 Fri 27 March 2009 08:02
Time to complete devo Archives 15 Thu 15 May 2008 21:56


All times are GMT -6. The time now is 00:49.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.